CHEMICALLY AMPLIFIED POSITIVE RESIST COMPOSITION AND RESIST PATTERN FORMING PROCESS
20260056471 ยท 2026-02-26
Assignee
Inventors
Cpc classification
C08F20/40
CHEMISTRY; METALLURGY
G03F7/0397
PHYSICS
G03F1/50
PHYSICS
G03F7/0005
PHYSICS
G03F7/0392
PHYSICS
G03F7/70383
PHYSICS
G03F7/0045
PHYSICS
International classification
G03F7/039
PHYSICS
C08F20/40
CHEMISTRY; METALLURGY
G03F1/50
PHYSICS
G03F7/00
PHYSICS
Abstract
An onium salt consisting of a sulfonic acid anion having an aromatic sulfonic acid structure substituted with an aromatic ring-containing hydrocarbyl group and a triarylsulfonium cation containing iodine and fluorine generates an acid with limited diffusion. A chemically amplified positive resist composition comprising the onium salt as an acid generator and a polymer adapted to be decomposed under the action of acid to increase its solubility in alkaline developer is processed by lithography to form a pattern of rectangular profile.
Claims
1. A chemically amplified positive resist composition comprising (A) a photoacid generator and (B) a base polymer containing a polymer adapted to be decomposed under the action of acid to increase its solubility in alkaline developer, said photoacid generator (A) containing an onium salt consisting of an anion having the formula (A1) and a cation having the formula (A2): ##STR00887## wherein n1 is 0 or 1, n2 is 0, 1, 2, 3 or 4, n3 is 0, 1, 2, 3 or 4, with the proviso that when n1=0, 0n2+n34, when n1=1, 0n2+n36, and n4 is 0 or 1, W is a C.sub.6-C.sub.40 hydrocarbyl group containing at least one aromatic ring, which may contain a heteroatom, R.sup.F1 is fluorine, a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, C.sub.1-C.sub.6 fluorinated saturated hydrocarbyloxy group, or C.sub.1-C.sub.6 fluorinated saturated hydrocarbylthio group, R.sup.1 is halogen exclusive of fluorine, nitro group, a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbyloxy group which may contain a heteroatom, or C.sub.1-C.sub.20 hydrocarbylthio group which may contain a heteroatom; when n3 is 2, 3 or 4, a plurality of R.sup.1 may be identical or different, and a plurality of R.sup.1 may bond together to form a ring with the carbon atoms to which they are attached, L.sup.A1 and L.sup.B1 are each independently a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond, X.sup.L1 is a single bond or a C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom, ##STR00888## wherein m1 is 0 or 1, m2 is 0 or 1, m3 is 0 or 1, m4 is 0, 1, 2, 3 or 4, m5 is 0, 1, 2, 3 or 4, m6 is 0, 1, 2, 3, 4, 5 or 6, m7 is 0, 1, 2, 3, 4, 5 or 6, m8 is 0, 1 or 2, m9 is 0, 1 or 2, m10 is 0, 1 or 2, m11 is 0 or 1, m12 is 0, 1, 2, 3 or 4, m13 is 0, 1 or 2, m14 is 0, 1 or 2, with the proviso that when m1=0, 0m6+m94, and when m1=1, 0m6+m96; when m2=0, 0m7+m104, and when m2=1, 0m7+m106; when m3=0, 1m4+m5+m8+m144, and when m3=1, 1m4+m5+m8+m146; when m11=0, 0m12+m134, and when m11=1, 0m12+m136; m4+m121, R.sup.F2 to R.sup.F4 are each independently fluorine, a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, C.sub.1-C.sub.6 fluorinated saturated hydrocarbyloxy group, or C.sub.1-C.sub.6 fluorinated saturated hydrocarbylthio group; when m5 is 2 or more, a plurality of R.sup.F2 may be identical or different; when m6 is 2 or more, a plurality of R.sup.F3 may be identical or different; when m7 is 2 or more, a plurality of R.sup.F4 may be identical or different, R.sup.11 to R.sup.14 are each independently halogen exclusive of iodine and fluorine, nitro group, cyano group, a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbyloxy group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbylthio group which may contain a heteroatom; when m8=2, two R.sup.11 may be identical or different and two R.sup.11 may bond together to form a ring with the carbon atoms to which they are attached; when m9=2, two R.sup.12 may be identical or different and two R.sup.12 may bond together to form a ring with the carbon atoms to which they are attached; when m10=2, two R.sup.13 may be identical or different and two R.sup.13 may bond together to form a ring with the carbon atoms to which they are attached; when m13=2, two R.sup.14 may be identical or different and two R.sup.14 may bond together to form a ring with the carbon atoms to which they are attached; the aromatic rings directly bonded to S.sup.+ in the sulfonium cation may bond together to form a ring with S.sup.+, L.sup.A2 and L.sup.B2 are each independently a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond, X.sup.L2 is a single bond or a C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom, said polymer comprising repeat units having the formula (B1): ##STR00889## wherein a1 is 0 or 1, a2 is 0, 1 or 2, a3 is an integer meeting 0a35+2(a2)a4, a4 is 1, 2 or 3, R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl, R.sup.21 is halogen, nitro group, carboxy group, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group, or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group, and A.sup.1 is a single bond or C.sub.1-C.sub.10 saturated hydrocarbylene group in which some CH.sub.2 may be replaced by O.
2. The resist composition of claim 1 wherein W is a group having the formula (W-1) or (W-2): ##STR00890## wherein n5 is 0 or 1, n6 is 0, 1, 2, 3 or 4, n7 is 0, 1, 2, 3 or 4, with the proviso that when n5=0, 1n6+n75, and when n5=1, 1n6+n77, n8 is 0 or 1, n9 is 0 or 1, n10 is 0, 1, 2, 3 or 4, n11 is 0, 1, 2, 3 or 4, R.sup.2 is each independently hydrogen, halogen exclusive of iodine, hydroxy, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, R.sup.3 and R.sup.4 are each independently hydrogen, halogen, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, R.sup.5 to R.sup.9 are each independently hydrogen, halogen, or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom, the broken line designates a point of attachment to L.sup.A1.
3. The resist composition of claim 1 wherein the anion having formula (A1) has the formula (A1-1): ##STR00891## wherein n1 to n4, W, R.sup.F1, R.sup.1, and L.sup.A are as defined above.
4. The resist composition of claim 1 wherein the cation having formula (A2) has the formula (A2-1): ##STR00892## wherein m4 to m10, m12 to m14, R.sup.F2 to R.sup.F4, R.sup.11 to R.sup.14, L.sup.A2, L.sup.B2 and X.sup.L2 are as defined above.
5. The resist composition of claim 4 wherein the cation having formula (A2-1) has the formula (A2-2): ##STR00893## wherein m4 to m10, R.sup.F2 to R.sup.F4, and R.sup.11 to R.sup.13 are as defined above.
6. The resist composition of claim 1 wherein the polymer further comprises repeat units having the formula (B2-1): ##STR00894## wherein R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl, b1 is 0 or 1, b2 is 0, 1 or 2, b3 is an integer meeting 0b35+2(b2)b4, b4 is 1, 2 or 3, b5 is 0 or 1, R.sup.31 is halogen, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group, or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group, A.sup.2 is a single bond or C.sub.1-C.sub.10 saturated hydrocarbylene group in which some CH.sub.2 may be replaced by O, X is an acid labile group when b4=1, and X is hydrogen or an acid labile group, at least one being an acid labile group, when b4=2 or 3.
7. The resist composition of claim 1 wherein the polymer further comprises repeat units having the formula (B2-2): ##STR00895## wherein c1 is 0, 1 or 2, c2 is 0, 1 or 2, c3 is 0, 1, 2, 3, 4 or 5, c4 is 0, 1 or 2, R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl, R.sup.32 and R.sup.33 are each independently a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom, R.sup.32 and R.sup.33 may bond together to form a ring with the carbon atom to which they are attached, R.sup.34 is each independently fluorine, a C.sub.1-C.sub.5 fluorinated alkyl group or C.sub.1-C.sub.5 fluorinated alkoxy group, R.sup.35 is each independently a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom, and A.sup.3 is a single bond, phenylene, naphthylene or *C(O)O-A.sup.31-, A.sup.31 is a C.sub.1-C.sub.20 aliphatic hydrocarbylene group which may contain a hydroxy moiety, ether bond, ester bond or lactone ring, a phenylene group or a naphthylene group, * designates a point of attachment to the carbon atom in the backbone.
8. The resist composition of claim 1 wherein the polymer further comprises repeat units of at least one type selected from repeat units having the formula (B3), repeat units having the formula (B4), and repeat units having the formula (B5): ##STR00896## wherein d is 0, 1, 2, 3, 4, 5 or 6, e is 0, 1, 2, 3 or 4, f1 is 0 or 1, f2 is 0, 1 or 2, f3 is 0, 1, 2, 3, 4 or 5, R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl, R.sup.41 and R.sup.42 are each independently hydroxy, halogen, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group, or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group, R.sup.43 is a C.sub.1-C.sub.20 saturated hydrocarbyl group, C.sub.1-C.sub.20 saturated hydrocarbyloxy group, C.sub.2-C.sub.20 saturated hydrocarbylcarbonyloxy group, C.sub.2-C.sub.20 saturated hydrocarbyloxyhydrocarbyl group, C.sub.2-C.sub.20 saturated hydrocarbylthiohydrocarbyl group, halogen, nitro, or cyano, R.sup.43 may also be hydroxy when f2=1 or 2, and A.sup.4 is a single bond or C.sub.1-C.sub.10 saturated hydrocarbylene group in which some CH.sub.2 may be replaced by O.
9. The resist composition of claim 1 wherein the polymer further comprises repeat units of at least one type selected from repeat units having the formula (B6), repeat units having the formula (B7), repeat units having the formula (B8), repeat units having the formula (B9), and repeat units having the formula (B10): ##STR00897## wherein g1 and g2 are each independently 0, 1, 2 or 3, h1 is 0 or 1, h2 is 0, 1, 2, 3 or 4, h3 is 0, 1, 2, 3 or 4, with the proviso that when h1=0, 0h2+h34, and when h1=1, 0h2+h36, R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl, Z.sup.1 is a single bond or an optionally substituted phenylene group, Z.sup.2 is a single bond, **C(O)OZ.sup.21, **C(O)NHZ.sup.21, or **OZ.sup.21, Z.sup.21 is a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group or a divalent group obtained by combining the foregoing, which may contain halogen, carbonyl moiety, ester bond, ether bond or hydroxy moiety, Z.sup.3 is a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond, Z.sup.4 is a single bond, or a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group or a divalent group obtained by combining the foregoing, which may contain halogen, carbonyl moiety, ester bond, ether bond or hydroxy moiety, Z.sup.5 is each independently a single bond, an optionally substituted phenylene, naphthylene, or *C(O)OZ.sup.5, Z.sup.51 is a C.sub.1-C.sub.10 aliphatic hydrocarbylene group which may contain halogen, hydroxy moiety, ether bond, ester bond or lactone ring, or phenylene or naphthylene group, Z.sup.6 is a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond, Z.sup.7 is each independently a single bond, ***Z.sup.71C(O)O, ***C(O)NHZ.sup.71, or ***OZ.sup.71, Z.sup.71 is a C.sub.1-C.sub.20 hydrocarbylene group which may contain a heteroatom, Z.sup.8 is each independently a single bond, ****Z.sup.81C(O)O, ****C(O)NHZ.sup.81, or ****OZ.sup.81, Z.sup.81 is a C.sub.1-C.sub.20 hydrocarbylene group which may contain a heteroatom, Z.sup.9 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, *C(O)OZ.sup.91, *C(O)N(H)Z.sup.91, or *OZ.sup.91, Z.sup.91 is a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety, * is a point of attachment to the carbon atom in the backbone, ** is a point of attachment to Z.sup.1, *** is a point of attachment to Z.sup.6, **** is a point of attachment to Z.sup.7, L.sup.1 is a single bond, ether bond, ester bond, carbonyl group, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond, Rf.sup.1 and Rf.sup.2 are each independently fluorine or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, Rf.sup.3 and Rf.sup.4 are each independently hydrogen, fluorine, or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, Rf.sup.5 and Rf.sup.6 are each independently hydrogen, fluorine, or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, excluding that all Rf.sup.5 and Rf.sup.6 are hydrogen at the same time, Rf.sup.7 is fluorine, a C.sub.1-C.sub.6 fluorinated alkyl group, C.sub.1-C.sub.6 fluorinated alkoxy group, or C.sub.1-C.sub.6 fluorinated alkylthio group, R.sup.31 and R.sup.32 are each independently a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, R.sup.31 and R.sup.32 may bond together to form a ring with the sulfur atom to which they are attached, R.sup.53 is halogen exclusive of fluorine, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom; when h3 is 2, 3 or 4, a plurality of R.sup.53 may bond together to form a ring with the carbon atoms to which they are attached, M.sup. is a non-nucleophilic counter ion, A.sup.+ is an onium cation.
10. The resist composition of claim 1 wherein repeat units having an aromatic ring structure account for at least 60 mol % of the overall repeat units of the polymer in the base polymer.
11. The resist composition of claim 1, further comprising (C) an organic solvent.
12. The resist composition of claim 1, further comprising (D) a fluorinated polymer comprising repeat units of at least one type selected from repeat units having the formula (D1), repeat units having the formula (D2), repeat units having the formula (D3) and repeat units having the formula (D4) and optionally repeat units of at least one type selected from repeat units having the formula (D5) and repeat units having the formula (D6): ##STR00898## wherein j1 is 1, 2 or 3, j2 is an integer meeting 0j25+2(j3)j1, j3 is 0 or 1, k is 1, 2 or 3, R.sup.B is each independently hydrogen, fluorine, methyl or trifluoromethyl, R.sup.C is each independently hydrogen or methyl, R.sup.101, R.sup.102, R.sup.104 and R.sup.105 are each independently hydrogen or a C.sub.1-C.sub.10 saturated hydrocarbyl group, R.sup.103, R.sup.106, R.sup.107 and R.sup.108 are each independently hydrogen, a C.sub.1-C.sub.15 hydrocarbyl group, C.sub.1-C.sub.15 fluorinated hydrocarbyl group, or acid labile group, and when R.sup.103, R.sup.106, R.sup.107 and R.sup.108 each are a hydrocarbyl or fluorinated hydrocarbyl group, an ether bond or carbonyl moiety may intervene in a carbon-carbon bond, R.sup.109 is hydrogen or a C.sub.1-C.sub.5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond, R.sup.110 is a C.sub.1-C.sub.5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond, R.sup.111 is a C.sub.1-C.sub.20 saturated hydrocarbyl group in which at least one hydrogen is substituted by fluorine, and in which some constituent CH.sub.2 may be replaced by an ester bond or ether bond, X.sup.1 is a C.sub.1-C.sub.20 (k+1)-valent hydrocarbon group or C.sub.1-C.sub.20 (k+1)-valent fluorinated hydrocarbon group, X.sup.2 is a single bond, *C(O)O or *C(O)NH, * designates a point of attachment to the carbon atom in the backbone, X.sup.3 is a single bond, O, *C(O)OX.sup.31X.sup.32 or *C(O)NHX.sup.31X.sup.32, X.sup.31 is a single bond or C.sub.1-C.sub.10 saturated hydrocarbylene group, X.sup.32 is a single bond, ester bond, ether bond, or sulfonamide bond, and * designates a point of attachment to the carbon atom in the backbone.
13. The resist composition of claim 1, further comprising (E) a quencher.
14. The resist composition of claim 13 wherein the photoacid generator (A) and the quencher (E) are present in a weight ratio of less than 3/1.
15. The resist composition of claim 1, further comprising a photoacid generator other than the photoacid generator.
16. A resist pattern forming process comprising the steps of: applying the chemically amplified positive resist composition of claim 1 onto a substrate to form a resist film thereon, exposing the resist film patternwise to high-energy radiation, and developing the exposed resist film in an alkaline developer.
17. The process of claim 16 wherein the high-energy radiation is EUV of wavelength 3 to 15 nm or EB.
18. The process of claim 16 wherein the substrate has the outermost surface of a chromium-containing material.
19. The process of claim 16 wherein the substrate is a photomask blank.
Description
DESCRIPTION OF PREFERRED EMBODIMENTS
[0116] As used herein, the singular forms a, an and the include plural referents unless the context clearly dictates otherwise. Optional or optionally means that the subsequently described event or circumstances may or may not occur, and that description includes instances where the event or circumstance occurs and instances where it does not. The notation (Cn-Cm) means a group containing from n to m carbon atoms per group. In chemical formulae, the broken line (---) and asterisk (*) each designate a point of attachment, namely valence bond. Me stands for methyl and Ac for acetyl. As used herein, the term halogenated refers to a halogen-substituted or halogen-containing compound or group. For example, fluorinated refers to a fluorine-substituted or fluorine-containing compound or group. The terms group and moiety are interchangeable.
[0117] The abbreviations and acronyms have the following meaning. [0118] PAG: photoacid generator [0119] Mw: weight average molecular weight [0120] Mn: number average molecular weight [0121] Mw/Mn: molecular weight distribution or dispersity [0122] GPC: gel permeation chromatography [0123] PEB: post-exposure baking [0124] LER: line edge roughness [0125] CDU: critical dimension uniformity
[0126] It is understood that for some structures represented by chemical formulae, there can exist enantiomers and diastereomers because of the presence of asymmetric carbon atoms. In such a case, a single formula collectively represents all such isomers. The isomers may be used alone or in admixture.
Chemically Amplified Positive Resist Composition
[0127] One embodiment of the invention is a chemically amplified positive resist composition comprising (A) a photoacid generator in the form of an onium salt consisting of a sulfonic acid anion of an aromatic sulfonic acid structure substituted with a hydrocarbyl group containing at least one aromatic ring and a triarylsulfonium cation containing iodine and fluorine and (B) a base polymer containing a specific polymer.
(A) Photoacid Generator
[0128] The photoacid generator (A) is an onium salt containing an anion having the formula (A1).
##STR00013##
[0129] In formula (A1), n1 is 0 or 1. The relevant structure is a benzene ring when n1=0, and a naphthalene ring when n1=1. The benzene ring corresponding to n1=0 is preferred from the aspect of solvent solubility. The subscript n2 is 0, 1, 2, 3 or 4. It is preferred from the aspect of reactant availability that n2 be 4 when n2 is 1 or more. The subscript n3 is 0, 1, 2, 3 or 4. It is provided that when n1=0, 0n2+n34, and when n1=1, 0n2+n36. The subscript n4 is 0 or 1. It is preferred from the aspect of acid diffusion control that n4 be 1.
[0130] In formula (A1), R.sup.F1 is fluorine, a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, C.sub.1-C.sub.6 fluorinated saturated hydrocarbyloxy group, or C.sub.1-C.sub.6 fluorinated saturated hydrocarbylthio group. R.sup.F1 is preferably fluorine, trifluoromethyl, difluoromethyl, trifluoromethoxy, difluoromethoxy, trifluoromethylthio or difluoromethylthio, more preferably fluorine, trifluoromethyl or trifluoromethoxy. Since fluorine or a fluorinated substituent group is contained, the acid strength of the generated acid is so enhanced due to the electron attractive effect that deprotection reaction of acid labile groups such as tertiary ester or tertiary ether groups may smoothly take place. When n2 is 2, 3 or 4, a plurality of R.sup.F1 may be identical or different.
[0131] In formula (A1), R.sup.1 is halogen exclusive of fluorine, nitro group, a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbyloxy group which may contain a heteroatom, or C.sub.1-C.sub.20 hydrocarbylthio group which may contain a heteroatom. Suitable halogen atoms exclusive of fluorine include chlorine, bromine and iodine, with iodine being preferred. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, heptadecyl, octadecyl, nonadecyl, icosyl; C.sub.3-C.sub.20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, adamantyl; C.sub.2-C.sub.20 alkenyl groups such as vinyl, allyl, propenyl, butenyl, hexenyl; C.sub.3-C.sub.20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl; C.sub.6-C.sub.20 aryl groups such as phenyl and naphthyl; C.sub.7-C.sub.20 aralkyl groups such as benzyl, 1-phenylethyl, 2-phenylethyl, and combinations thereof. Inter alia, aryl groups are preferred. In the hydrocarbyl groups, some or all hydrogen may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, cyano, fluorine, chlorine, bromine, iodine, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety. When n3 is 2 or more, a plurality of R.sup.1 may be identical or different. When n3 is 2 or more, a plurality of R.sup.1 may bond together to form a ring with the carbon atoms to which they are attached. The ring is preferably 5 to 8-membered.
[0132] In formula (A1), W is a C.sub.6-C.sub.40 hydrocarbyl group containing at least one aromatic ring, which may contain a heteroatom, preferably a group having the formula (W-1) or (W-2).
##STR00014##
[0133] The broken line designates a point of attachment to L.sup.A1.
[0134] In formula (W-1), n5 is 0 or 1. The relevant structure is a benzene ring when n5=0, and a naphthalene ring when n5=1. The benzene ring corresponding to n5=0 is preferred from the aspect of solvent solubility. The subscript n6 is 0, 1, 2, 3 or 4, and n7 is 0, 1, 2, 3 or 4. It is provided that when n5=0, 1n6+n75, and when n5=1, 1n6+n77. When n5=0, n6 is preferably 2, 3 or 4 and from the aspect of EUV absorption, n6 is more preferably 3 or 4. It is preferred from the aspect of reactant availability that n7 be 1, 2 or 3, and more preferred from the aspect of acid diffusion control that n7 be 2 or 3.
[0135] In formula (W-1), R.sup.2 is each independently hydrogen, halogen exclusive of iodine, hydroxy, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms exclusive of iodine include fluorine, chlorine and bromine, with fluorine being preferred from the aspect of solvent solubility. Examples of the hydrocarbyl group which may contain a heteroatom are as exemplified above for the hydrocarbyl group R.sup.1, but not limited thereto. A group of branched or cyclic structure is preferred as R.sup.2.
[0136] In formula (W-1), it is preferred that at least one selected from R.sup.2 and iodine be attached to the carbon atom adjoining the carbon atom to which L.sup.A is attached. Then, the rotation of the aromatic ring to which R.sup.2 and/or iodine is attached and the aromatic ring to which a sulfo group is attached, about the linking axis: -L.sup.A1-X.sup.L1-L.sup.B1-, is restrained by steric hindrance, leading to a decline of acid diffusion.
[0137] In formula (W-2), n8 is 0 or 1. The relevant structure is a benzene ring when n8=0, and a naphthalene ring when n8=1. The benzene ring corresponding to n8=0 is preferred from the aspect of solvent solubility. The subscript n9 is 0 or 1. The relevant structure is a benzene ring when n9=0, and a naphthalene ring when n9=1. The benzene ring corresponding to n9=0 is preferred from the aspect of solvent solubility. The subscript n10 is 0, 1, 2, 3 or 4. From the aspect of reactant availability, n10 is preferably 0, 1 or 2. The subscript n11 is 0, 1, 2, 3 or 4. From the aspect of reactant availability, n11 is preferably 0, 1 or 2.
[0138] In formula (W-2), R.sup.3 and R.sup.4 are each independently hydrogen, halogen, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine, with fluorine and iodine being preferred. Examples of the hydrocarbyl group which may contain a heteroatom are as exemplified above for the hydrocarbyl group R.sup.1, but not limited thereto. A group of branched or cyclic structure is preferred as R.sup.3 and R.sup.4.
[0139] In formula (W-2), R.sup.5 to R.sup.9 are each independently hydrogen, halogen, or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine, with fluorine and iodine being preferred. Examples of the hydrocarbyl group which may contain a heteroatom are as exemplified above for the hydrocarbyl group R.sup.1, but not limited thereto. A group of branched or cyclic structure is preferred as R.sup.5 to R.sup.9.
[0140] In formula (W-2), any two of R.sup.5 to R.sup.9 may bond together to form a ring with the carbon atoms to which they are attached. The ring is preferably 5 to 8-membered.
[0141] In formula (A1), L.sup.A1 and L.sup.B1 are each independently a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond. L.sup.A1 and L.sup.B1 are preferably a single bond, ether bond or ester bond.
[0142] In formula (A1), X.sup.L1 is a single bond or a C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom. The hydrocarbylene group may be straight, branched or cyclic and examples thereof include alkanediyl groups, cyclic saturated hydrocarbylene groups, and arylene groups. Suitable heteroatoms include oxygen, nitrogen and sulfur.
[0143] Examples of the C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom, represented by X.sup.L1, are shown below, but not limited thereto. Herein, * designates a point of attachment to L.sup.A1 or L.sup.B1.
##STR00015## ##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020##
[0144] Of these, X.sup.L-0 to X.sup.L-22 and X.sup.L-47 to X.sup.L-58 are preferred.
[0145] Of the anions having formula (A1), those having the formula (A1-1) are preferred.
##STR00021##
[0146] Herein n1 to n4, W, R.sup.F1, R.sup.1, and L.sup.A1 are as defined above.
[0147] Examples of the anion having formula (A1) are shown below, but not limited thereto.
##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041##
##STR00042## ##STR00043## ##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052## ##STR00053## ##STR00054## ##STR00055## ##STR00056## ##STR00057## ##STR00058## ##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063##
##STR00064## ##STR00065## ##STR00066## ##STR00067## ##STR00068## ##STR00069## ##STR00070## ##STR00071## ##STR00072## ##STR00073## ##STR00074## ##STR00075## ##STR00076## ##STR00077## ##STR00078## ##STR00079## ##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084## ##STR00085## ##STR00086## ##STR00087## ##STR00088## ##STR00089## ##STR00090## ##STR00091## ##STR00092## ##STR00093## ##STR00094## ##STR00095## ##STR00096## ##STR00097##
##STR00098## ##STR00099## ##STR00100## ##STR00101## ##STR00102## ##STR00103## ##STR00104## ##STR00105## ##STR00106## ##STR00107## ##STR00108## ##STR00109## ##STR00110## ##STR00111## ##STR00112## ##STR00113## ##STR00114## ##STR00115## ##STR00116## ##STR00117## ##STR00118## ##STR00119## ##STR00120## ##STR00121## ##STR00122## ##STR00123## ##STR00124## ##STR00125## ##STR00126## ##STR00127## ##STR00128##
##STR00129## ##STR00130## ##STR00131## ##STR00132## ##STR00133## ##STR00134## ##STR00135## ##STR00136## ##STR00137## ##STR00138## ##STR00139## ##STR00140## ##STR00141## ##STR00142## ##STR00143## ##STR00144## ##STR00145## ##STR00146## ##STR00147## ##STR00148##
##STR00149## ##STR00150## ##STR00151## ##STR00152## ##STR00153## ##STR00154## ##STR00155## ##STR00156## ##STR00157## ##STR00158## ##STR00159## ##STR00160## ##STR00161## ##STR00162## ##STR00163## ##STR00164## ##STR00165## ##STR00166## ##STR00167## ##STR00168## ##STR00169## ##STR00170## ##STR00171## ##STR00172## ##STR00173## ##STR00174## ##STR00175## ##STR00176##
##STR00177## ##STR00178## ##STR00179## ##STR00180## ##STR00181## ##STR00182## ##STR00183## ##STR00184## ##STR00185## ##STR00186## ##STR00187## ##STR00188## ##STR00189## ##STR00190## ##STR00191## ##STR00192## ##STR00193## ##STR00194## ##STR00195## ##STR00196## ##STR00197## ##STR00198## ##STR00199##
##STR00200## ##STR00201## ##STR00202## ##STR00203## ##STR00204## ##STR00205## ##STR00206## ##STR00207## ##STR00208## ##STR00209## ##STR00210## ##STR00211## ##STR00212## ##STR00213## ##STR00214## ##STR00215## ##STR00216## ##STR00217## ##STR00218## ##STR00219## ##STR00220## ##STR00221## ##STR00222## ##STR00223## ##STR00224## ##STR00225## ##STR00226## ##STR00227##
##STR00228## ##STR00229## ##STR00230## ##STR00231## ##STR00232## ##STR00233## ##STR00234## ##STR00235## ##STR00236## ##STR00237## ##STR00238## ##STR00239## ##STR00240## ##STR00241## ##STR00242## ##STR00243## ##STR00244## ##STR00245## ##STR00246## ##STR00247## ##STR00248## ##STR00249##
##STR00250## ##STR00251## ##STR00252## ##STR00253## ##STR00254## ##STR00255## ##STR00256## ##STR00257## ##STR00258## ##STR00259## ##STR00260## ##STR00261## ##STR00262## ##STR00263## ##STR00264## ##STR00265## ##STR00266## ##STR00267## ##STR00268## ##STR00269## ##STR00270## ##STR00271## ##STR00272## ##STR00273## ##STR00274## ##STR00275## ##STR00276## ##STR00277## ##STR00278## ##STR00279##
##STR00280## ##STR00281## ##STR00282## ##STR00283## ##STR00284## ##STR00285## ##STR00286## ##STR00287## ##STR00288## ##STR00289## ##STR00290## ##STR00291## ##STR00292## ##STR00293## ##STR00294## ##STR00295## ##STR00296## ##STR00297## ##STR00298## ##STR00299## ##STR00300## ##STR00301##
##STR00302## ##STR00303## ##STR00304## ##STR00305## ##STR00306## ##STR00307## ##STR00308## ##STR00309## ##STR00310## ##STR00311## ##STR00312## ##STR00313## ##STR00314## ##STR00315## ##STR00316## ##STR00317## ##STR00318## ##STR00319## ##STR00320## ##STR00321## ##STR00322## ##STR00323## ##STR00324## ##STR00325##
##STR00326## ##STR00327## ##STR00328## ##STR00329## ##STR00330## ##STR00331## ##STR00332## ##STR00333## ##STR00334## ##STR00335## ##STR00336## ##STR00337## ##STR00338## ##STR00339## ##STR00340## ##STR00341## ##STR00342## ##STR00343## ##STR00344## ##STR00345## ##STR00346## ##STR00347## ##STR00348## ##STR00349## ##STR00350## ##STR00351## ##STR00352## ##STR00353##
##STR00354## ##STR00355## ##STR00356## ##STR00357## ##STR00358## ##STR00359## ##STR00360## ##STR00361## ##STR00362## ##STR00363## ##STR00364## ##STR00365## ##STR00366## ##STR00367## ##STR00368## ##STR00369## ##STR00370## ##STR00371## ##STR00372## ##STR00373## ##STR00374## ##STR00375##
##STR00376## ##STR00377## ##STR00378## ##STR00379## ##STR00380## ##STR00381## ##STR00382## ##STR00383## ##STR00384## ##STR00385## ##STR00386## ##STR00387## ##STR00388## ##STR00389## ##STR00390## ##STR00391## ##STR00392## ##STR00393## ##STR00394## ##STR00395## ##STR00396## ##STR00397## ##STR00398## ##STR00399## ##STR00400## ##STR00401## ##STR00402## ##STR00403## ##STR00404##
##STR00405## ##STR00406## ##STR00407## ##STR00408## ##STR00409## ##STR00410## ##STR00411## ##STR00412## ##STR00413## ##STR00414## ##STR00415## ##STR00416## ##STR00417## ##STR00418## ##STR00419## ##STR00420## ##STR00421## ##STR00422## ##STR00423## ##STR00424## ##STR00425## ##STR00426## ##STR00427## ##STR00428## ##STR00429## ##STR00430## ##STR00431##
##STR00432## ##STR00433## ##STR00434## ##STR00435## ##STR00436## ##STR00437## ##STR00438## ##STR00439## ##STR00440## ##STR00441## ##STR00442## ##STR00443## ##STR00444## ##STR00445## ##STR00446## ##STR00447## ##STR00448## ##STR00449## ##STR00450## ##STR00451## ##STR00452## ##STR00453## ##STR00454## ##STR00455## ##STR00456## ##STR00457##
##STR00458## ##STR00459## ##STR00460## ##STR00461## ##STR00462## ##STR00463## ##STR00464## ##STR00465## ##STR00466## ##STR00467## ##STR00468## ##STR00469## ##STR00470## ##STR00471## ##STR00472## ##STR00473## ##STR00474## ##STR00475## ##STR00476## ##STR00477## ##STR00478## ##STR00479## ##STR00480## ##STR00481## ##STR00482## ##STR00483## ##STR00484##
##STR00485## ##STR00486## ##STR00487## ##STR00488## ##STR00489## ##STR00490## ##STR00491## ##STR00492## ##STR00493## ##STR00494## ##STR00495## ##STR00496## ##STR00497##
##STR00498## ##STR00499## ##STR00500## ##STR00501## ##STR00502## ##STR00503## ##STR00504## ##STR00505## ##STR00506## ##STR00507## ##STR00508## ##STR00509## ##STR00510## ##STR00511## ##STR00512## ##STR00513## ##STR00514## ##STR00515## ##STR00516## ##STR00517## ##STR00518## ##STR00519## ##STR00520## ##STR00521## ##STR00522## ##STR00523## ##STR00524##
##STR00525## ##STR00526## ##STR00527## ##STR00528## ##STR00529## ##STR00530## ##STR00531## ##STR00532## ##STR00533## ##STR00534## ##STR00535## ##STR00536## ##STR00537## ##STR00538## ##STR00539## ##STR00540## ##STR00541## ##STR00542## ##STR00543## ##STR00544## ##STR00545## ##STR00546## ##STR00547## ##STR00548## ##STR00549## ##STR00550## ##STR00551## ##STR00552## ##STR00553## ##STR00554##
##STR00555## ##STR00556## ##STR00557## ##STR00558## ##STR00559## ##STR00560## ##STR00561## ##STR00562## ##STR00563## ##STR00564## ##STR00565## ##STR00566## ##STR00567## ##STR00568## ##STR00569## ##STR00570## ##STR00571## ##STR00572## ##STR00573## ##STR00574## ##STR00575## ##STR00576## ##STR00577## ##STR00578## ##STR00579## ##STR00580##
[0148] The onium salt as photoacid generator (A) contains a cation having the formula (A2).
##STR00581##
[0149] In formula (A2), m1 is 0 or 1. The relevant structure is a benzene ring when m1=0, and a naphthalene ring when m1=1. The benzene ring corresponding to m1=0 is preferred from the aspect of solvent solubility. The subscript m2 is 0 or 1. The relevant structure is a benzene ring when m2=0, and a naphthalene ring when m2=1. The benzene ring corresponding to m2=0 is preferred from the aspect of solvent solubility. The subscript m3 is 0 or 1. The relevant structure is a benzene ring when m3=0, and a naphthalene ring when m3=1. The benzene ring corresponding to m3=0 is preferred from the aspect of solvent solubility.
[0150] In formula (A2), m4 is 0, 1, 2, 3 or 4. As the number of iodine atoms in the cation structure increases, the compound becomes more absorptive to EUV, but so poor in solvent solubility that it may precipitate in a resist composition. For this reason, m4 is preferably 0, 1, 2 or 3, more preferably 0, 1 or 2.
[0151] In formula (A2), m5 is 0, 1, 2, 3 or 4. It is preferred from the aspect of reactant availability that m5 be 0, 1, 2 or 3, more preferably 0, 1 or 2. The subscript m6 is 0, 1, 2, 3, 4, 5 or 6. It is preferred from the aspect of reactant availability that m6 be 0, 1, 2 or 3, more preferably 0, 1 or 2. The subscript m7 is 0, 1, 2, 3, 4, 5 or 6. It is preferred from the aspect of reactant availability that m7 be 0, 1, 2 or 3, more preferably 0, 1 or 2.
[0152] In formula (A2), m8 is 0, 1 or 2. In view of reactant availability, m8 is preferably 0 or 1. The subscript m9 is 0, 1 or 2. In view of reactant availability, m9 is preferably 0 or 1. The subscript m10 is 0, 1 or 2. In view of reactant availability, m10 is preferably 0 or 1.
[0153] In formula (A2), m11 is 0 or 1. The relevant structure is a benzene ring when m11=0, and a naphthalene ring when m11=1. The benzene ring corresponding to m11=0 is preferred from the aspect of solvent solubility.
[0154] In formula (A2), m12 is 0, 1, 2, 3 or 4. As the number of iodine atoms in the cation structure increases, the compound becomes more absorptive to EUV, but so poor in solvent solubility that it may precipitate in a resist composition. For this reason, m12 is preferably 0, 1, 2 or 3, more preferably 0, 1 or 2.
[0155] In formula (A2), m13 is 0, 1 or 2. In view of reactant availability, m13 is preferably 0 or 1. The subscript m14 is 0, 1 or 2. In view of synthesis, m14 is preferably 0 or 1.
[0156] The subscripts m1 to m14 are in the range that when m1=0, 0m6+m94, and when m1=1, 0m6+m96; when m2=0, 0m7+m104, and when m2=1, 0m7+m106; when m3=0, 1m4+m5+m8+m144, and when m3=1, 1m4+m5+m8+m146; when m11=0, 0m12+m134, and when m11=1, 0m12+m136; and m4+m121.
[0157] In formula (A2), R.sup.F2 to R.sup.F4 are each independently fluorine, a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group, C.sub.1-C.sub.6 fluorinated saturated hydrocarbyloxy group, or C.sub.1-C.sub.6 fluorinated saturated hydrocarbylthio group. Of these, trifluoromethyl, trifluoromethoxy, and trifluorothiomethoxy are preferred. When m5 is 2 or more, a plurality of R.sup.F2 may be identical or different. When m6 is 2 or more, a plurality of R.sup.F3 may be identical or different. When m7 is 2 or more, a plurality of R.sup.F4 may be identical or different.
[0158] In formula (A2), R.sup.11 to R.sup.14 are each independently halogen exclusive of iodine and fluorine, nitro group, cyano group, a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbyloxy group which may contain a heteroatom, C.sub.1-C.sub.20 hydrocarbylthio group which may contain a heteroatom. The hydrocarbyl group and hydrocarbyl moiety in the hydrocarbyloxy and hydrocarbylthio groups may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl group R.sup.1 in formula (A1). In the hydrocarbyl group and hydrocarbyl moiety in the hydrocarbyloxy and hydrocarbylthio groups, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, cyano, fluorine, chlorine, bromine, iodine, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety.
[0159] When m8=2, two R.sup.11 may be identical or different and two R.sup.11 may bond together to form a ring with the carbon atoms to which they are attached. When m9=2, two R.sup.12 may be identical or different and two R.sup.12 may bond together to form a ring with the carbon atoms to which they are attached. When m10=2, two R.sup.13 may be identical or different and two R.sup.13 may bond together to form a ring with the carbon atoms to which they are attached. When m13=2, two R.sup.14 may be identical or different and two R.sup.14 may bond together to form a ring with the carbon atoms to which they are attached. Examples of the ring thus formed include cyclopropane, cyclobutane, cyclopentane, cyclohexane, norbornane, and adamantane rings. In the ring, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the ring may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety.
[0160] The aromatic rings directly bonded to S.sup.+ in the sulfonium cation having formula (A2) may bond together to form a ring with S.sup.+. Exemplary structures of the ring are shown below.
##STR00582##
[0161] In formula (A2), L.sup.A2 and L.sup.B2 are each independently a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond. L.sup.A2 is preferably a single bond, ether bond, ester bond or sulfonate ester bond, more preferably an ester bond or sulfonate ester bond. L.sup.B2 is preferably a single bond, ether bond or ester bond, more preferably a single bond.
[0162] In formula (A2), X.sup.L2 is a single bond or a C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom. Examples of the C.sub.1-C.sub.40 hydrocarbylene group which may contain a heteroatom are as exemplified above for the C.sub.1-C.sub.40 hydrocarbylene group X.sup.L1, but not limited thereto.
[0163] Preferably, the sulfonium cation having formula (A2) has the formula (A2-1):
##STR00583##
wherein m4 to m10, m12 to m14, R.sup.F2 to RF.sup.4, R.sup.11 to R.sup.14, L.sup.A2, L.sup.B2, and X.sup.L2 are as defined above.
[0164] More preferably, the sulfonium cation having formula (A2-1) has the formula (A2-2):
##STR00584##
wherein m4 to m10, R.sup.F2 to R.sup.F4, and R.sup.11 to R.sup.13 are as defined above.
[0165] Examples of the sulfonium cation having formula (A2) are shown below, but not limited thereto.
##STR00585## ##STR00586## ##STR00587## ##STR00588## ##STR00589## ##STR00590## ##STR00591## ##STR00592## ##STR00593## ##STR00594## ##STR00595## ##STR00596## ##STR00597## ##STR00598## ##STR00599## ##STR00600##
##STR00601## ##STR00602## ##STR00603## ##STR00604## ##STR00605## ##STR00606## ##STR00607## ##STR00608## ##STR00609## ##STR00610## ##STR00611## ##STR00612## ##STR00613## ##STR00614## ##STR00615## ##STR00616## ##STR00617## ##STR00618## ##STR00619## ##STR00620## ##STR00621## ##STR00622## ##STR00623## ##STR00624## ##STR00625## ##STR00626## ##STR00627## ##STR00628## ##STR00629## ##STR00630## ##STR00631## ##STR00632## ##STR00633## ##STR00634## ##STR00635## ##STR00636## ##STR00637## ##STR00638## ##STR00639## ##STR00640## ##STR00641## ##STR00642## ##STR00643## ##STR00644## ##STR00645## ##STR00646##
##STR00647## ##STR00648## ##STR00649## ##STR00650## ##STR00651## ##STR00652## ##STR00653## ##STR00654## ##STR00655## ##STR00656## ##STR00657## ##STR00658## ##STR00659## ##STR00660## ##STR00661## ##STR00662## ##STR00663## ##STR00664## ##STR00665## ##STR00666## ##STR00667##
[0166] Examples of the onium salt include arbitrary combinations of anions with cations, both as mentioned above.
[0167] For the synthesis of the inventive onium salt, reference should be made to JP-A 2010-155824 and JP 7067271, for example. These preparation methods are merely exemplary and the method of preparing the onium salt is not limited thereto.
[0168] The inventive onium salt is structurally characterized in that it consists of an aromatic sulfonic acid anion substituted with a hydrocarbyl group containing at least one aromatic ring and a triarylsulfonium cation containing iodine and fluorine. The hydrocarbyl group containing at least one aromatic ring has a large excluded volume and thus serves as a bulky substituent to effectively inhibit the generated acid from diffusing. This effect is readily obtained particularly when the hydrocarbyl group containing at least one aromatic ring is an aromatic ring structure having a substituent as represented by formula (W-1) or a fused ring structure having a substituent as represented by formula (W-2). The structure is also enough resistant to alkaline developer to prevent the pattern in unexposed region from losing a film thickness. The aromatic sulfonic acid structure, on the other hand, generates an acid of robust structure, which is effective for restraining acid diffusion. It is preferred that the aromatic ring that forms the aromatic sulfonic acid structure contain fluorine or an electron attractive sulfonate ester bond as a linking group. Then the generated acid has a higher acidity enough to efficiently deprotect the acid labile groups in the base polymer. In the triarylsulfonium cation containing iodine and fluorine, the fluorine atom, which is a substituent for promoting solvent solubility, acts to increase the solvent solubility of the onium salt so that the onium salt may be uniformly dissolved in the solvent. In addition, iodine atom has a moderate dissolution inhibition relative to alkaline developer and prevents the resist pattern from collapsing. By virtue of the synergy of these effects, the positive resist composition comprising the onium salt can form a resist pattern having a high sensitivity, low acid diffusion, and improved LWR of line patterns or improved CDU of hole patterns. The pattern is fully resistant to collapse. The resist composition is effective for forming small-size patterns.
[0169] In the chemically amplified positive resist composition, the amount of the photoacid generator (A) is preferably 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight per 80 parts by weight of a base polymer (B) to be described just below. As long as the amount of photoacid generator (A) is in the range, an acid is generated in an amount necessary for deprotection of acid labile groups so that a pattern of satisfactory profile may be formed. In addition, the composition has storage stability. The photoacid generator (A) may be used alone or in admixture of two or more.
[0170] In the chemically amplified positive resist composition, an acid generator other than the onium salt consisting of an anion having formula (A1) and a cation having formula (A2) may be added for the purpose of correcting the pattern profile or the like. The other acid generator may be selected from well-known acid generators for use in resist compositions. The amount of the other acid generator is preferably 0 to 40 parts by weight, more preferably 0 to 30 parts by weight per 80 parts by weight of base polymer (B). The other acid generator may be used alone or in admixture.
(B) Base Polymer
[0171] The resist composition further comprises (B) a base polymer containing a polymer which is decomposed under the action of acid to increase its solubility in alkaline developer.
[0172] The polymer contains repeat units having the formula (B1), which are also referred to as repeat units B1.
##STR00668##
[0173] In formula (B1), a1 is 0 or 1. The subscript a2 is 0, 1 or 2. The relevant structure is a benzene ring when a2=0, a naphthalene ring when a2=1, and an anthracene ring when a2=2. The subscript a3 is an integer meeting 0a35+2(a2)a4, and a4 is 1, 2 or 3. When a2 is 0, preferably a3 is 0, 1, 2 or 3 and a4 is 1, 2 or 3. When a2 is 1 or 2, preferably a3 is 0, 1, 2, 3 or 4 and a4 is 1, 2 or 3.
[0174] In formula (B1), R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl.
[0175] In formula (B1), R.sup.21 is halogen, nitro, carboxy, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group. The saturated hydrocarbyl group and saturated hydrocarbyl moiety in the saturated hydrocarbyloxy and saturated hydrocarbylcarbonyloxy groups may be straight, branched or cyclic. Examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and structural isomers thereof; cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl; and combinations thereof. A carbon count within the upper limit ensures a satisfactory solubility in alkaline developer. A plurality of R.sup.21 may be identical or different when a3 is 2 or more.
[0176] In formula (B1), A.sup.1 is a single bond or C.sub.1-C.sub.10 saturated hydrocarbylene group in which some constituent CH.sub.2 may be replaced by O. The saturated hydrocarbylene group may be straight, branched or cyclic and examples thereof include C.sub.1-C.sub.10 alkanediyl groups such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, and structural isomers thereof; C.sub.3-C.sub.10 cyclic saturated hydrocarbylene groups such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and combinations thereof. For the saturated hydrocarbylene group containing an ether bond, in case of a1=1 in formula (B1), the ether bond may be incorporated at any position excluding the position between the - and -carbons relative to the ester oxygen. In case of a1=0, the atom bonding to the backbone becomes an ether oxygen atom, and a second ether bond may be incorporated at any position excluding the position between the - and -carbons relative to the ether oxygen. Saturated hydrocarbylene groups having no more than 10 carbon atoms are desirable because of a sufficient solubility in alkaline developer.
[0177] Preferred examples of the repeat units B1 wherein a1=0 and A.sup.1 is a single bond (meaning that the aromatic ring is directly bonded to the backbone of the polymer), that is, repeat units free of a linker: C(O)O-A.sup.1- include units derived from 3-hydroxystyrene, 4-hydroxystyrene, 5-hydroxy-2-vinylnaphthalene, and 6-hydroxy-2-vinylnaphthalene. Exemplary units are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00669## ##STR00670## ##STR00671## ##STR00672## ##STR00673## ##STR00674## ##STR00675##
[0178] Preferred examples of the repeat units B1 wherein a1=1, that is, having a linker: C(O)O-A.sup.1- are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00676## ##STR00677## ##STR00678## ##STR00679## ##STR00680##
[0179] The content of repeat units B1 is preferably 15 to 90 mol %, more preferably 15 to 80 mol % of the overall units of the polymer. When the polymer further comprises repeat units of at least one type selected from repeat units having formula (B3) and repeat units having formula (B4), which provide the polymer with higher etch resistance, the repeat units containing a phenolic hydroxy group as a substituent, the total content of repeat units B1 and repeat units B3 and/or B4 should preferably fall in the range. The repeat units B1 may be of one type or a combination of plural types.
[0180] In a preferred embodiment, the polymer further contains repeat units B2 having an acidic functional group protected with an acid labile group (i.e., repeat units protected with an acid labile group and adapted to turn alkali soluble under the action of acid) in order that the positive resist composition in an exposed region turn soluble in alkaline developer.
[0181] Typical of the repeat unit B2 is a unit having the formula (B2-1), also referred to as repeat unit B2-1.
##STR00681##
[0182] In formula (B2-1), b1 is 0 or 1. The subscript b2 is 0, 1 or 2. The structure represents a benzene skeleton when b2=0, a naphthalene skeleton when b2=1, and an anthracene skeleton when b2=2. The subscript b3 is an integer meeting 0b35+2(b2)b4. The subscript b4 is 1, 2 or 3, and b5 is 0 or 1. When b2=0, preferably b3 is 0, 1, 2 or 3 and b4 is 1, 2 or 3. When b2=1 or 2, preferably b3 is 0, 1, 2, 3 or 4 and b4 is 1, 2 or 3.
[0183] In formula (B2-1), R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl.
[0184] In formula (B2-1), R.sup.31 is halogen, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group. The saturated hydrocarbyl group and saturated hydrocarbyl moiety in the saturated hydrocarbyloxy group and saturated hydrocarbylcarbonyloxy group may be straight, branched or cyclic, and examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, and structural isomers thereof, cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl, and combinations thereof. A carbon count within the upper limit ensures good solubility in alkaline developer. A plurality of R.sup.31 may be identical or different when b3 is 2 or more.
[0185] In formula (B2-1), A.sup.2 is a single bond or a C.sub.1-C.sub.10 saturated hydrocarbylene group in which some constituent CH.sub.2 may be replaced by O. The saturated hydrocarbylene group may be straight, branched or cyclic and examples thereof include C.sub.1-C.sub.10 alkanediyl groups such as methylene, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, and structural isomers thereof; C.sub.3-C.sub.10 cyclic saturated hydrocarbylene groups such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and combinations thereof. For the saturated hydrocarbylene group containing an ether bond, in case of b1=1 in formula (B2-1), the ether bond may be incorporated at any position excluding the position between the -carbon and -carbon relative to the ester oxygen. In case of b1=0, the atom that bonds with the backbone becomes an ethereal oxygen, and a second ether bond may be incorporated at any position excluding the position between the -carbon and -carbon relative to that ethereal oxygen. Saturated hydrocarbylene groups having no more than 10 carbon atoms are desirable because of a sufficient solubility in alkaline developer.
[0186] In formula (B2-1), X is an acid labile group when b4=1, and hydrogen or an acid labile group, at least one X being an acid labile group, when b4=2 or 3. That is, repeat units B2-1 have phenolic hydroxy groups bonded to an aromatic ring, at least one of which is protected with an acid labile group, or repeat units B2-1 have a carboxy group bonded to an aromatic ring, which is protected with an acid labile group. The acid labile group used herein is not particularly limited as long as it is commonly used in a number of well-known chemically amplified resist compositions and eliminated under the action of acid to release an acidic group.
[0187] Typical of the acid labile group is a tertiary saturated hydrocarbyl group. The tertiary saturated hydrocarbyl group is preferably of 4 to 18 carbon atoms because a monomer for use in polymerization is recoverable by distillation.
[0188] The saturated hydrocarbyl group bonded to the tertiary carbon atom in the tertiary saturated hydrocarbyl group is preferably of 1 to 15 carbon atoms. The C.sub.1-C.sub.15 saturated hydrocarbyl group may be straight, branched or cyclic and contain an oxygen-containing functional group such as an ether bond or carbonyl group in its carbon-carbon bond. The saturated hydrocarbyl groups bonded to the tertiary carbon atom may bond together to form a ring with the tertiary carbon atom to which they are attached.
[0189] Examples of the alkyl substituent include methyl, ethyl, propyl, adamantyl, norbornyl, tetrahydrofuran-2-yl, 7-oxanorbornan-2-yl, cyclopentyl, 2-tetrahydrofuryl, tricyclo[5.2.1.0.sup.2,6]decyl, 8-ethyl-8-tricyclo[5.2.1.0.sup.2,6]decyl, 3-methyl-3-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl, tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl, and 3-oxo-1-cyclohexyl.
[0190] Examples of the tertiary saturated hydrocarbyl group include, but are not limited to, tert-butyl, tert-pentyl, 1-ethyl-1-methylpropyl, 1,1-diethylpropyl, 1,1,2-trimethylpropyl, 1-adamantyl-1-methylethyl, 1-methyl-1-(2-norbornyl)ethyl, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl, 1-methyl-1-(7-oxanorbornan-2-yl)ethyl, 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-propylcyclopentyl, 1-cyclopentylcyclopentyl, 1-cyclohexylcyclopentyl, 1-(2-tetrahydrofuryl)cyclopentyl, 1-(7-oxanorbornan-2-yl)cyclopentyl, 1-methylcyclohexyl, 1-ethylcyclohexyl, 1-cyclopentylcyclohexyl, 1-cyclohexylcyclohexyl, 2-methyl-2-norbornyl, 2-ethyl-2-norbornyl, 8-methyl-8-tricyclo[5.2.1.0.sup.2,6]decyl, 8-ethyl-8-tricyclo[5.2.1.0.sup.2,6]decyl, 3-methyl-3-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl, 3-ethyl-3-tetracyclo[4.4.0.1.sup.2,5.1.sup.7,10]dodecyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl, 1-methyl-3-oxo-1-cyclohexyl, 1-methyl-1-(tetrahydrofuran-2-yl)ethyl, 5-hydroxy-2-methyl-2-adamantyl, and 5-hydroxy-2-ethyl-2-adamantyl.
[0191] A group having the following formula (B2-1-1) is also suitable as the acid labile group. The group having formula (B2-1-1) is often used as the acid labile group. It is a good choice of the acid labile group that ensures to form a pattern having a relatively rectangular pattern-substrate interface in a consistent manner. An acetal structure is formed when X is a group having formula (B2-1-1).
##STR00682##
[0192] In formula (B2-1-1), R.sup.L1 is hydrogen or a C.sub.1-C.sub.10 saturated hydrocarbyl group. The saturated hydrocarbyl group may be straight, branched or cyclic.
[0193] A choice of R.sup.L1 may depend on the designed sensitivity of labile group to acid. For example, hydrogen or a group in which the carbon atom bonded to acetal carbon is tertiary is selected when the acid labile group is designed to ensure relatively high stability and to be decomposed with strong acid. Examples of R.sup.L1 bonded to acetal carbon via tertiary carbon include tert-butyl, tert-pentyl, and 1-adamantyl, but are not limited thereto. A straight alkyl group is selected when the acid labile group is designed to have relatively high reactivity and high sensitivity to pH changes. Although the choice varies with a particular combination of acid generator and quencher in the resist composition, R.sup.L1 is preferably a group in which the carbon in bond with acetal carbon is secondary, when R.sup.L2 is a relatively large alkyl group substituted at the end and the acid labile group is designed to undergo a substantial change of solubility by decomposition. Examples of R.sup.L1 bonded to acetal carbon via secondary carbon include isopropyl, sec-butyl, cyclopentyl, and cyclohexyl, but are not limited thereto.
[0194] In formula (B2-1-1), R.sup.L2 is a C.sub.1-C.sub.30 hydrocarbyl group. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Some constituent CH.sub.2-in the hydrocarbyl group may be replaced by a heteroatom such as oxygen or sulfur so that the group may contain an ether bond or sulfide bond. Illustrative are C.sub.1-C.sub.30 saturated hydrocarbyl groups and C.sub.6-C.sub.30 aryl groups. R.sup.L2 is preferably a C.sub.1-C.sub.6 hydrocarbyl group for acquiring a higher resolution in forming small-size patterns. When R.sup.L2 is a C.sub.1-C.sub.6 hydrocarbyl group, the alcohol created after a progress of acid-aided deprotection reaction is water soluble. Then, when a positive pattern is formed using an alkaline developer, the alcohol is dissolved in the developer so that defects remaining in the exposed region are minimized.
[0195] Preferred examples of the group having formula (B2-1-1) are given below, but not limited thereto. Herein R.sup.L1 is as defined above.
##STR00683## ##STR00684##
[0196] Another acid labile group which can be used herein is a phenolic hydroxy group whose hydrogen is substituted by CH.sub.2COO (tertiary saturated hydrocarbyl group). The tertiary saturated hydrocarbyl group may be the same as the foregoing tertiary saturated hydrocarbyl group used for the protection of a phenolic hydroxy group.
[0197] Another example of repeat unit B2 is a repeat unit having the following formula (B2-2), referred to as repeat unit B2-2. The repeat unit B2-2 which enables to increase the dissolution rate in the exposed region is a useful choice of the acid labile group-containing unit which affords satisfactory performance against line width variations during develop loading.
##STR00685##
[0198] In formula (B2-2), c1 is 0, 1 or 2, c2 is 0, 1 or 2, c3 is 0, 1, 2, 3, 4 or 5, and c4 is 0, 1 or 2.
[0199] In formula (B2-2), R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl.
[0200] In formula (B2-2), R.sup.32 and R.sup.33 are each independently a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom. R.sup.32 and R.sup.33 may bond together to form a ring with the carbon atom to which they are attached.
[0201] In formula (B2-2), R.sup.34 is each independently fluorine, C.sub.1-C.sub.5 fluorinated alkyl group or C.sub.1-C.sub.5 fluorinated alkoxy group.
[0202] In formula (B2-2), R.sup.35 is each independently a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom.
[0203] In formula (B2-2), A.sup.3 is a single bond, phenylene group, naphthylene group, or *C(O)O-A.sup.31-. A.sup.31 is a C.sub.1-C.sub.20 aliphatic hydrocarbylene group which may contain hydroxy, ether bond, ester bond or lactone ring, or phenylene or naphthylene group, and * is a point of attachment to the carbon atom in the backbone.
[0204] Preferred examples of the repeat unit B2-2 are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00686## ##STR00687## ##STR00688## ##STR00689##
[0205] The content of repeat units B2 is preferably 5 to 95 mol %, more preferably 20 to 80 mol % based on the overall repeat units of the polymer. Each of repeat units B2 may be of one type or a mixture of two or more types.
[0206] In a preferred embodiment, the polymer further comprises repeat units of at least one type selected from units having the formulae (B3), (B4) and (B5). These repeat units are simply referred to as repeat units B3, B4 and B5, respectively.
##STR00690##
[0207] In formulae (B3) and (B4), d is 0, 1, 2, 3, 4, 5 or 6 and e is 0, 1, 2, 3 or 4.
[0208] In formulae (B3) and (B4), R.sup.41 and R.sup.42 are each independently hydroxy, halogen, an optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyl group, optionally halogenated C.sub.1-C.sub.6 saturated hydrocarbyloxy group, or optionally halogenated C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy group. The saturated hydrocarbyl group, saturated hydrocarbyloxy group and saturated hydrocarbylcarbonyloxy group may be straight, branched or cyclic. When d is 2 or more, a plurality of R.sup.41 may be identical or different. When e is 2 or more, a plurality of R.sup.42 may be identical or different.
[0209] In formula (B5), f1 is 0 or 1. The subscript f2 is 0, 1 or 2. The relevant structure represents a benzene skeleton when f2=0, a naphthalene skeleton when f2=1, and an anthracene skeleton when f2=2. The subscript f3 is 0, 1, 2, 3, 4 or 5. When f2=0, preferably f3 is 0, 1, 2 or 3. When f2=1 or 2, preferably f3 is 0, 1, 2, 3 or 4.
[0210] In formula (B5), R.sup.A is hydrogen, fluorine, methyl or trifluoromethyl.
[0211] In formula (B5), R.sup.43 is a C.sub.1-C.sub.20 saturated hydrocarbyl group, C.sub.1-C.sub.20 saturated hydrocarbyloxy group, C.sub.2-C.sub.20 saturated hydrocarbylcarbonyloxy group, C.sub.2-C.sub.20 saturated hydrocarbyloxyhydrocarbyl group, C.sub.2-C.sub.20 saturated hydrocarbylthiohydrocarbyl group, halogen atom, nitro group, or cyano group. When f2 is 1 or 2, R.sup.43 may also be hydroxy. The saturated hydrocarbyl group, saturated hydrocarbyloxy group, saturated hydrocarbylcarbonyloxy group, saturated hydrocarbyloxyhydrocarbyl group, and saturated hydrocarbylthiohydrocarbyl group may be straight, branched or cyclic. When f3 is 2 or more, a plurality of R.sup.43 may be identical or different.
[0212] In formula (B5), A.sup.4 is a single bond or a C.sub.1-C.sub.10 saturated hydrocarbylene group in which some constituent CH.sub.2 may be replaced by O. The saturated hydrocarbylene group may be straight, branched or cyclic. Examples thereof are as exemplified above for A.sup.1 in formula (B1).
[0213] When repeat units of at least one type selected from repeat units B3 to B5 are incorporated, better performance is obtained because not only the aromatic ring possesses etch resistance, but the cyclic structure incorporated into the backbone also exerts the effect of improving etch resistance and resistance to EB irradiation during pattern inspection step.
[0214] The content of repeat units B3 to B5 is preferably at least 5 mol % based on the overall repeat units of the polymer for obtaining the effect of improving etch resistance. Also, the content of repeat units B3 to B5 is preferably up to 25 mol %, more preferably up to 20 mol % based on the overall repeat units of the polymer. When the relevant units are free of functional groups or have a functional group other than hydroxy, their content of up to 25 mol % is preferred because the risk of forming development defects is eliminated. Each of the repeat units B3 to B5 may be of one type or a combination of plural types.
[0215] It is preferred that the polymer comprise repeat units B1, repeat units B2, and repeat units of at least one type selected from repeat units B3 to B5, because both etch resistance and high resolution are achievable. The total content of these repeat units is preferably at least 60 mol %, more preferably at least 70 mol %, even more preferably at least 80 mol %, most preferably at least 90 mol % based on the overall repeat units of the polymer.
[0216] In another preferred embodiment, the polymer further comprises repeat units of at least one type selected from repeat units having the formula (B6), repeat units having the formula (B7), repeat units having the formula (B8), repeat units having the formula (B9), and repeat units having the formula (B10), shown below. Notably these repeat units are also referred to as repeat units B6 to B10.
##STR00691##
[0217] In formulae (B6) to (B10), R.sup.A is each independently hydrogen, fluorine, methyl or trifluoromethyl. Z.sup.1 is a single bond or an optionally substituted phenylene group. Z.sup.2 is a single bond, **C(O)OZ.sup.2, **C(O)NHZ.sup.2, or **OZ.sup.2, wherein Z.sup.21 is a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group or a divalent group obtained by combining the foregoing, which may contain halogen, carbonyl moiety, ester bond, ether bond or hydroxy moiety. Z.sup.3 is a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond. Z.sup.4 is a single bond, or a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group or a divalent group obtained by combining the foregoing, which may contain halogen, carbonyl moiety, ester bond, ether bond or hydroxy moiety. Z.sup.5 is each independently a single bond, an optionally substituted phenylene, naphthylene, or *C(O)OZ.sup.51, wherein Z.sup.51 is a C.sub.1-C.sub.10 aliphatic hydrocarbylene group which may contain halogen, hydroxy moiety, ether bond, ester bond or lactone ring, or phenylene or naphthylene group. Z.sup.6 is a single bond, ether bond, ester bond, amide bond, sulfonate ester bond, sulfonamide bond, carbonate bond or carbamate bond. Z.sup.7 is each independently a single bond, ***Z.sup.71C(O)O, ***C(O)NHZ.sup.71, or ***OZ.sup.71, wherein Z.sup.71 is a C.sub.1-C.sub.20 hydrocarbylene group which may contain a heteroatom. Z.sup.8 is each independently a single bond, ****Z.sup.81C(O)O, ****C(O)NHZ.sup.81, or ****OZ.sup.81, wherein Z.sup.81 is a C.sub.1-C.sub.20 hydrocarbylene group which may contain a heteroatom. Z.sup.9 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, trifluoromethyl-substituted phenylene, *C(O)OZ.sup.91, *C(O)N(H)Z.sup.91, or *OZ.sup.91, wherein Z.sup.91 is a C.sub.1-C.sub.6 aliphatic hydrocarbylene group, phenylene group, fluorinated phenylene group or trifluoromethyl-substituted phenylene group, which may contain a carbonyl moiety, ester bond, ether bond or hydroxy moiety. The asterisk * designates a point of attachment to the carbon atom in the backbone, ** is a point of attachment to Z.sup.1, *** is a point of attachment to Z.sup.6, and **** is a point of attachment to Z.sup.7.
[0218] The aliphatic hydrocarbylene group represented by Z.sup.21, Z.sup.51 and Z.sup.91 may be straight, branched or cyclic. Examples thereof include alkanediyl groups such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-1,3-diyl, propane-2,2-diyl, butane-1,1-diyl, butane-1,2-diyl, butane-1,3-diyl, butane-2,3-diyl, butane-1,4-diyl, 1,1-dimethylethane-1,2-diyl, pentane-1,5-diyl, 2-methylbutane-1,2-diyl, and hexane-1,6-diyl; cycloalkanediyl groups such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, and cyclohexanediyl; and combinations thereof.
[0219] The hydrocarbylene group represented by Z.sup.71 and Z.sup.81 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are shown below, but not limited thereto.
##STR00692##
[0220] In formula (B6), R.sup.51 and R.sup.52 are each independently a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.20 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; C.sub.3-C.sub.20 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; C.sub.2-C.sub.20 alkenyl groups such as vinyl, 1-propenyl, 2-propenyl, butenyl, and hexenyl; C.sub.3-C.sub.20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl; C.sub.6-C.sub.20 aryl groups such as phenyl, naphthyl and thienyl; C.sub.7-C.sub.20 aralkyl groups such as benzyl, 1-phenylethyl and 2-phenylethyl, and combinations thereof. Inter alia, aryl groups are preferred. In the hydrocarbyl group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen and some constituent CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)), or haloalkyl moiety.
[0221] R.sup.51 and R.sup.52 may bond together to form a ring with the sulfur atom to which they are attached. Examples of the ring are shown below.
##STR00693##
[0222] Herein the broken line designates a point of attachment to Z.sup.4.
[0223] Examples of the cation in repeat units B6 are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00694## ##STR00695## ##STR00696## ##STR00697## ##STR00698## ##STR00699## ##STR00700## ##STR00701## ##STR00702## ##STR00703##
[0224] In formula (B6), M.sup. is a non-nucleophilic counter ion. Halide ions, sulfonate anions, imide anions, and methide anions are preferred. Examples of the non-nucleophilic counter ion include halide ions such as chloride and bromide ions; sulfonate anions, specifically fluoroalkylsulfonate ions such as triflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate, arylsulfonate ions such as tosylate, benzenesulfonate, 4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, alkylsulfonate ions such as mesylate and butanesulfonate; imide ions such as bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide and bis(perfluorobutylsulfonyl)imide; and methide ions such as tris(trifluoromethylsulfonyl)methide and tris(perfluoroethylsulfonyl)methide.
[0225] Anions having the following formulae (B6-1) to (B6-4) are also useful as the non-nucleophilic counter ion.
##STR00704##
[0226] In formula (B6-1), R.sup.fa is fluorine or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as will be exemplified below for the hydrocarbyl group R.sup.fa1 in formula (B6-1-1).
[0227] Of the anions of formula (B6-1), an anion having the formula (B6-1-1) is preferred.
##STR00705##
[0228] In formula (B6-1-1), Q.sup.1 and Q.sup.2 are each independently hydrogen, fluorine or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group. It is preferred for solvent solubility that at least one of Q.sup.1 and Q.sup.2 be trifluoromethyl. The subscript m is 0, 1, 2, 3 or 4, preferably 1.
[0229] R.sup.fa1 is a C.sub.1-C.sub.35 hydrocarbyl group which may contain a heteroatom. As the heteroatom, oxygen, nitrogen, sulfur and halogen atoms are preferred, with oxygen being most preferred. Of the hydrocarbyl groups, those groups of 6 to 30 carbon atoms are preferred from the aspect of achieving a high resolution in forming patterns of small feature size. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.35 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl, heptadecyl, and icosyl; C.sub.3-C.sub.35 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl, norbornylmethyl, tricyclodecyl, tetracyclododecyl, tetracyclododecylmethyl, and dicyclohexylmethyl; C.sub.2-C.sub.35 unsaturated aliphatic hydrocarbyl groups such as 2-propenyl and 3-cyclohexenyl; C.sub.6-C.sub.35 aryl groups such as phenyl, 1-naphthyl, 2-naphthyl and 9-fluorenyl; and C.sub.7-C.sub.35 aralkyl groups such as benzyl and diphenylmethyl, and combinations thereof.
[0230] In the foregoing hydrocarbyl groups, some or all hydrogen may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or some constituent CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, nitro, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety. Examples of the heteroatom-containing hydrocarbyl group include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl.
[0231] In formula (B6-1-1), L.sup.a1 is a single bond, ether bond, ester bond, sulfonate ester bond, carbonate bond or carbamate bond. From the aspect of synthesis, an ether bond or ester bond is preferred, with the ester bond being more preferred.
[0232] Examples of the anion having formula (B6-1) are shown below, but not limited thereto. Herein Q.sup.1 is as defined above.
##STR00706## ##STR00707## ##STR00708## ##STR00709## ##STR00710## ##STR00711## ##STR00712## ##STR00713## ##STR00714## ##STR00715## ##STR00716## ##STR00717## ##STR00718## ##STR00719## ##STR00720## ##STR00721##
[0233] In formula (B6-2), R.sup.fb1 and R.sup.fb2 are each independently fluorine or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for R.sup.fa1 in formula (B6-1-1). Preferably R.sup.fb1 and R.sup.fb2 are fluorine or C.sub.1-C.sub.4 straight fluorinated alkyl groups. Also, R.sup.fb1 and R.sup.fb2 may bond together to form a ring with the linkage: CF.sub.2SO.sub.2NSO.sub.2CF.sub.2 to which they are attached. It is preferred that a combination of R.sup.fb1 and R.sup.fb2 be a fluorinated ethylene or fluorinated propylene group.
[0234] In formula (B6-3), R.sup.fc1, R.sup.fc2 and R.sup.fc3 are each independently fluorine or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified for R.sup.fa1 in formula (B6-1-1). Preferably R.sup.fc1, R.sup.fc2 and R.sup.fc3 are fluorine or C.sub.1-C.sub.4 straight fluorinated alkyl groups. Also, R.sup.fc1 and R.sup.fc2 may bond together to form a ring with the linkage: CF.sub.2SO.sub.2CSO.sub.2CF.sub.2 to which they are attached. It is preferred that a combination of R.sup.fc1 and R.sup.fc2 be a fluorinated ethylene or fluorinated propylene group.
[0235] In formula (B6-4), R.sup.fd is a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for R.sup.fa1 in formula (B6-1-1).
[0236] Examples of the anion having formula (B6-4) are shown below, but not limited thereto.
##STR00722## ##STR00723##
[0237] Anions having an iodized or brominated aromatic ring are also useful as the non-nucleophilic counter ion. These anions have the formula (B6-5).
##STR00724##
[0238] In formula (B6-5), x is 1, 2 or 3, y is 1, 2, 3, 4 or 5, z is 0, 1, 2 or 3, and y+z is from 1 to 5. Preferably, y is 1, 2 or 3, more preferably 2 or 3, and z is 0, 1 or 2.
[0239] In formula (B6-5), X.sup.BI is iodine or bromine. A plurality of X.sup.BI may be identical or different when x and/or y is 2 or more.
[0240] In formula (B6-5), L.sup.11 is a single bond, ether bond, ester bond, or a C.sub.1-C.sub.6 saturated hydrocarbylene group which may contain an ether bond or ester bond. The saturated hydrocarbylene group may be straight, branched or cyclic.
[0241] In formula (B6-5), L.sup.12 is a single bond or a C.sub.1-C.sub.20 divalent linking group when x=1, or a C.sub.1-C.sub.20 (x+1)-valent linking group when x=2 or 3. The linking group may contain an oxygen, sulfur or nitrogen atom.
[0242] In formula (B6-5), R.sup.fe is hydroxy, carboxy, fluorine, chlorine, bromine, amino group, or a C.sub.1-C.sub.20 hydrocarbyl, C.sub.1-C.sub.20 hydrocarbyloxy, C.sub.2-C.sub.20 hydrocarbylcarbonyl, C.sub.2-C.sub.20 hydrocarbyloxycarbonyl, C.sub.2-C.sub.20 hydrocarbylcarbonyloxy, or C.sub.1-C.sub.20 hydrocarbylsulfonyloxy group, which may contain fluorine, chlorine, bromine, hydroxy, amino or ether bond, or N(R.sup.feA)(R.sup.feB)_N(R.sup.feC)C(O)R.sup.feD or N(R.sup.feC)C(O)OR.sup.fcD. R.sup.feA and R.sup.feB are each independently hydrogen or a C.sub.1-C.sub.6 saturated hydrocarbyl group. R.sup.feC is hydrogen, or a C.sub.1-C.sub.6 saturated hydrocarbyl group which may contain halogen, hydroxy, C.sub.1-C.sub.6 saturated hydrocarbyloxy, C.sub.2-C.sub.6 saturated hydrocarbylcarbonyl or C.sub.2-C.sub.6 saturated hydrocarbylcarbonyloxy moiety. R.sup.feD is a C.sub.1-C.sub.16 aliphatic hydrocarbyl group, C.sub.6-C.sub.12 aryl group or C.sub.7-C.sub.15 aralkyl group, which may contain halogen, hydroxy, C.sub.1-C.sub.6 saturated hydrocarbyloxy, C.sub.2-C.sub.6 saturated hydrocarbylcarbonyl or C.sub.2-C.sub.6 saturated hydrocarbylcarbonyloxy moiety. The aliphatic hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. The hydrocarbyl, hydrocarbyloxy, hydrocarbylcarbonyl, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups may be straight, branched or cyclic. A plurality of R.sup.fe may be identical or different when x and/or z is 2 or more.
[0243] Of these, R.sup.fe is preferably hydroxy, N(R.sup.feC)C(O)R.sup.feD, N(R.sup.feC)C(O)OR.sup.feD, fluorine, chlorine, bromine, methyl or methoxy.
[0244] In formula (B6-5), Rf.sup.11 to Rf.sup.14 are each independently hydrogen, fluorine or trifluoromethyl, at least one of Rf.sup.11 to Rf.sup.14 is fluorine or trifluoromethyl. Rf.sup.11 and Rf.sup.12, taken together, may form a carbonyl group. More preferably, both Rf.sup.11 and Rf.sup.14 are fluorine.
[0245] Examples of the anion having formula (B6-5) are shown below, but not limited thereto. X.sup.BI is as defined above.
##STR00725## ##STR00726## ##STR00727## ##STR00728## ##STR00729## ##STR00730## ##STR00731## ##STR00732## ##STR00733##
##STR00734## ##STR00735## ##STR00736## ##STR00737## ##STR00738## ##STR00739## ##STR00740## ##STR00741## ##STR00742## ##STR00743## ##STR00744## ##STR00745## ##STR00746## ##STR00747## ##STR00748## ##STR00749## ##STR00750## ##STR00751## ##STR00752## ##STR00753## ##STR00754## ##STR00755##
##STR00756## ##STR00757## ##STR00758## ##STR00759## ##STR00760## ##STR00761## ##STR00762## ##STR00763## ##STR00764## ##STR00765## ##STR00766## ##STR00767## ##STR00768## ##STR00769## ##STR00770##
##STR00771## ##STR00772## ##STR00773## ##STR00774## ##STR00775## ##STR00776## ##STR00777##
[0246] Other useful examples of the non-nucleophilic counter ion include fluorobenzenesulfonic acid anions having an iodized aromatic ring bonded thereto as described in JP 6648726, anions having an acid-catalyzed decomposition mechanism as described in WO 2021/200056 and JP-A 2021-070692, anions having a cyclic ether group as described in JP-A 2018-180525 and JP-A 2021-035935, and anions as described in JP-A 2018-092159.
[0247] Further useful examples of the non-nucleophilic counter ion include fluorine-free bulky benzenesulfonic acid anions as described in JP-A 2006-276759, JP-A 2015-117200, JP-A 2016-065016, and JP-A 2019-202974; fluorine-free benzenesulfonic acid or alkylsulfonic acid anions having an iodized aromatic group bonded thereto as described in JP 6645464.
[0248] Also useful are bissulfonic acid anions as described in JP-A 2015-206932, sulfonamide or sulfonimide anions having sulfonic acid side and different side as described in WO 2020/158366, and anions having a sulfonic acid side and a carboxylic acid side as described in JP-A 2015-024989.
[0249] In formulae (B7) and (B8), g1 and g2 are each independently 0, 1, 2 or 3, preferably 1.
[0250] In formula (B9), h1 is 0 or 1, h2 is 0, 1, 2, 3 or 4, h3 is 0, 1, 2, 3 or 4, with the proviso that when h1=0, 0h2+h34, and when h1=1, 0h2+h36.
[0251] In formulae (B7), (B8) and (B9), L.sup.1 is a single bond, ether bond, ester bond, carbonyl, sulfonate ester bond, carbonate bond or carbamate bond. From the aspect of synthesis, an ether bond, ester bond or carbonyl is preferred, with the ester bond or carbonyl being more preferred.
[0252] In formula (B7), Rf.sup.1 and Rf.sup.2 are each independently fluorine or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group. It is preferred that both Rf.sup.1 and Rf.sup.2 be fluorine because the generated acid has a higher acid strength. Rf.sup.3 and Rf.sup.4 are each independently hydrogen, fluorine or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group. It is preferred for solvent solubility that at least one of Rf.sup.3 and Rf.sup.4 be trifluoromethyl.
[0253] In formula (B8), Rf.sup.5 and Rf.sup.6 are each independently hydrogen, fluorine or a C.sub.1-C.sub.6 fluorinated saturated hydrocarbyl group. It is excluded that all Rf.sup.5 and Rf.sup.6 are hydrogen at the same time. It is preferred for solvent solubility that at least one of Rf.sup.5 and Rf.sup.6 be trifluoromethyl.
[0254] In formula (B9), Rf.sup.7 is fluorine, a C.sub.1-C.sub.6 fluorinated alkyl group, C.sub.1-C.sub.6 fluorinated alkoxy group, or C.sub.1-C.sub.6 fluorinated alkylthio group. Rf.sup.7 is preferably fluorine, trifluoromethyl, difluoromethyl, trifluoromethoxy, difluoromethoxy, trifluoromethylthio or difluoromethylthio, more preferably fluorine, trifluoromethyl or trifluoromethoxy. When h2 is 2, 3 or 4, a plurality of Rf.sup.7 may be identical or different.
[0255] In formula (B9), R.sup.53 is a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof are as exemplified above for the hydrocarbyl group R.sup.1 in formula (A1), but not limited thereto. When h3 is 2, 3 or 4, a plurality of R.sup.53 may be identical or different.
[0256] When h3 is 2, 3 or 4, a plurality of R.sup.53 may bond together to form a ring with the carbon atom to which they are attached. Examples of the ring thus formed include cyclopropane, cyclobutane, cyclopentane, cyclohexane, norbornane, and adamantane rings. In the ring, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the ring may contain a hydroxy, fluorine, chlorine, bromine, iodine, cyano, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety.
[0257] Examples of the anion in repeat unit B7 are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00778## ##STR00779## ##STR00780## ##STR00781## ##STR00782## ##STR00783## ##STR00784## ##STR00785## ##STR00786## ##STR00787## ##STR00788## ##STR00789## ##STR00790## ##STR00791## ##STR00792## ##STR00793## ##STR00794## ##STR00795## ##STR00796## ##STR00797## ##STR00798## ##STR00799## ##STR00800## ##STR00801## ##STR00802##
[0258] Examples of the anion in repeat unit B8 are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00803## ##STR00804## ##STR00805## ##STR00806## ##STR00807## ##STR00808## ##STR00809## ##STR00810## ##STR00811## ##STR00812## ##STR00813## ##STR00814## ##STR00815## ##STR00816## ##STR00817## ##STR00818## ##STR00819## ##STR00820## ##STR00821## ##STR00822## ##STR00823## ##STR00824## ##STR00825##
[0259] Examples of the anion in repeat unit B9 are shown below, but not limited thereto. Herein R.sup.A is as defined above.
##STR00826## ##STR00827## ##STR00828## ##STR00829## ##STR00830## ##STR00831## ##STR00832## ##STR00833## ##STR00834## ##STR00835## ##STR00836## ##STR00837## ##STR00838## ##STR00839## ##STR00840## ##STR00841## ##STR00842## ##STR00843## ##STR00844## ##STR00845## ##STR00846## ##STR00847## ##STR00848##
[0260] Examples of the anion in repeat unit B10 are shown below, but not limited thereto. Herein R.sup.1 is as defined above.
##STR00849## ##STR00850##
[0261] In formulae (B7) to (B10), A.sup.+ is an onium cation. Suitable onium cations include sulfonium, iodonium and ammonium cations, with the sulfonium and iodonium cations being preferred. Examples of the sulfonium cation include those described in JP-A 2024-003744, paragraphs [0102]-[0125], and JP-A 2023-169812, paragraphs [0070]-[0085], and those having formula (A2), but are not limited thereto. Examples of the iodonium cation include those described in JP-A 2024-000259, paragraph [0181], but are not limited thereto. Examples of the ammonium cation are as will be exemplified later as the ammonium cation having formula (am-1), but not limited thereto.
[0262] Illustrative structures of repeat units B6 to B10 include arbitrary combinations of anions with cations, both as mentioned above.
[0263] The repeat units B6 to B10 are capable of generating an acid upon exposure to high-energy radiation. It is believed that binding of the relevant units to a polymer enables to appropriately control acid diffusion and to form a pattern with reduced LER. Since the acid-generating unit is bound to a polymer, the phenomenon that acid volatilizes from the exposed region and re-deposits on the unexposed region during bake in vacuum is suppressed. This is effective for reducing LER and for suppressing profile degradation due to unwanted film thickness loss in the unexposed region.
[0264] Of repeat units B6 to B10, repeat units B7 to B10 are preferred for the processing of photomask blanks because an optimum acid strength is available for the suppression of acid diffusion and the design of an acid labile group on the polymer. The repeat units B7, B8 and B9 are more preferred
[0265] When repeat units B6 to B10 are included, their content is preferably 0.1 to 30 mol %, more preferably 0.5 to 20 mol % based on the overall repeat units of the polymer. Each of repeat units B6 to B10 may be of one type or a combination of plural types.
[0266] The content of repeat units having an aromatic ring structure is preferably at least 65 mol %, more preferably at least 75 mol %, even more preferably at least 85 mol % based on the overall repeat units of the polymer. When the polymer does not contain repeat units B6 to B10, it is preferred that all units have an aromatic ring structure.
[0267] The polymer may further comprise (meth)acrylate units protected with an acid labile group or (meth)acrylate units having an adhesive group such as lactone structure or hydroxy group other than phenolic hydroxy as commonly used in the art. These repeat units are effective for fine adjustment of properties of a resist film, but not essential.
[0268] Examples of the (meth)acrylate unit having an adhesive group include repeat units having the following formulae (B11) to (B13), which are also referred to as repeat units B11 to B13. While these units do not exhibit acidity, they may be used as auxiliary units for providing adhesion to substrates or adjusting solubility.
##STR00851##
[0269] In formulae (B11) to (B13), R.sup.A is each independently hydrogen, fluorine, methyl or trifluoromethyl. R.sup.61 is O or methylene. R.sup.62 is hydrogen or hydroxy. R.sup.63 is a C.sub.1-C.sub.4 saturated hydrocarbyl group, and h is 0, 1, 2 or 3.
[0270] When repeat units B11 to B13 are included, their content is preferably 0 to 20 mol %, more preferably 0 to 10 mol % based on the overall repeat units of the polymer. Each of repeat units B11 to B13 may be of one type or a combination of plural types.
[0271] The polymer may be synthesized by combining suitable monomers optionally protected with a protective group, copolymerizing them in the standard way, and effecting deprotection reaction if necessary. The copolymerization reaction is preferably radical or anionic polymerization though not limited thereto. For the polymerization reaction, reference may be made to JP-A 2004-115630, for example.
[0272] The polymer should preferably have a Mw of 1,000 to 50,000, and more preferably 2,000 to 20,000. A Mw of at least 1,000 eliminates the risk that pattern features are rounded at their top to invite degradations of resolution and LER. A Mw of up to 50,000 eliminates the risk that LER is degraded when a pattern with a line width of up to 100 nm is formed. As used herein, Mw is measured by GPC versus polystyrene standards using tetrahydrofuran (THF) or dimethylformamide (DMF) solvent.
[0273] The polymer preferably has a narrow molecular weight distribution or dispersity (Mw/Mn) of 1.0 to 2.0, more preferably 1.0 to 1.9. A polymer with such a narrow dispersity eliminates the risk that foreign particles are left on the pattern after development and the pattern profile is aggravated.
[0274] The base polymer is designed such that the dissolution rate in alkaline developer is preferably up to 10 nm/min, more preferably up to 7 nm/min, even more preferably up to 5 nm/min. In the advanced generation of lithography wherein the coating film on the substrate is in a thin film range of up to 100 nm, the influence of pattern film thickness loss during alkaline development becomes strong. When the polymer has an alkaline dissolution rate of greater than 10 nm/min, pattern collapse occurs, i.e., a small-size pattern cannot be formed. The problem becomes outstanding in the fabrication of photomasks requiring to be defect less and having a tendency of strong development process. It is noted that the dissolution rate of a base polymer in alkaline developer is computed by spin coating a 16.7 wt % solution of a polymer in propylene glycol monomethyl ether acetate (PGMEA) solvent onto a 8-inch silicon wafer, baking at 100 C. for 90 seconds to form a film of 1,000 nm thick, developing the film in a 2.38 wt % aqueous solution of tetramethylammonium hydroxide (TMAH) at 23 C. for 100 seconds, and measuring a loss of film thickness.
[0275] In addition to the polymer defined above, the base polymer (B) may contain another polymer. The other polymer may be any of prior art well-known base polymers used in resist compositions. The content of the other polymer is not particularly limited as long as the benefits of the invention are not impaired.
(C) Organic Solvent
[0276] The chemically amplified positive resist composition may comprise an organic solvent as component (C). The organic solvent used herein is not particularly limited as long as the components are soluble therein. Examples of the organic solvent are described in JP-A 2008-111103, paragraphs [0144] to [0145](U.S. Pat. No. 7,537,880). Specifically, exemplary solvents include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and diacetone alcohol (DAA); ethers such as propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate (EL), ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as -butyrolactone (GBL), and mixtures thereof. Where an acid labile group of acetal form is used, a high boiling alcohol solvent such as diethylene glycol, propylene glycol, glycerol, 1,4-butanediol or 1,3-butanediol may be added to accelerate deprotection reaction of acetal.
[0277] Of the above organic solvents, it is recommended to use 1-ethoxy-2-propanol, PGMEA, PGME, cyclohexanone, EL, GBL, and mixtures thereof.
[0278] In the resist composition, the organic solvent (C) is preferably used in an amount of 200 to 10,000 parts, more preferably 400 to 5,000 parts by weight per 80 parts by weight of the base polymer (B). The organic solvent may be used alone or in admixture.
(D) Fluorinated Polymer
[0279] The chemically amplified positive resist composition may further comprise a fluorinated polymer for the purposes of enhancing contrast, preventing chemical flare of acid upon exposure to high-energy radiation, preventing mixing of acid from an anti-charging film in the step of coating an anti-charging film-forming material on a resist film, and suppressing unexpected unnecessary pattern degradation. The fluorinated polymer contains repeat units of at least one type selected from repeat units having the formula (D1), repeat units having the formula (D2), repeat units having the formula (D3), and repeat units having the formula (D4), and may contain repeat units of at least one type selected from repeat units having the formula (D5) and repeat units having the formula (D6). It is noted that repeat units having formulae (D1), (D2), (D3), (D4), (D5), and (D6) are also referred to as repeat units D1, D2, D3, D4, D5, and D6, respectively, hereinafter. Since the fluorinated polymer also has a surface-active function, it can prevent insoluble residues from re-depositing onto the substrate during the development step and is thus effective for preventing development defects.
##STR00852##
[0280] In formulae (D1) to (D6), j1 is 1, 2 or 3, j2 is an integer meeting: 0j25+2(j3)j1, j3 is 0 or 1, and k is 1, 2 or 3. R.sup.B is each independently hydrogen, fluorine, methyl or trifluoromethyl. R.sup.C is each independently hydrogen or methyl. R.sup.101, R.sup.102, R.sup.104 and R.sup.105 are each independently hydrogen or a C.sub.1-C.sub.10 saturated hydrocarbyl group. R.sup.103, R.sup.106, R.sup.107 and R.sup.108 are each independently hydrogen, a C.sub.1-C.sub.15 hydrocarbyl group or fluorinated hydrocarbyl group, or an acid labile group. An ether bond or carbonyl moiety may intervene in a carbon-carbon bond in the hydrocarbyl groups or fluorinated hydrocarbyl groups represented by R.sup.103, R.sup.106, R.sup.107 and R.sup.108. R.sup.109 is hydrogen or a C.sub.1-C.sub.5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond. R.sup.110 is a C.sub.1-C.sub.5 straight or branched hydrocarbyl group in which a heteroatom-containing moiety may intervene in a carbon-carbon bond. R.sup.111 is a C.sub.1-C.sub.20 saturated hydrocarbyl group in which at least one hydrogen is substituted by fluorine and some constituent CH.sub.2 may be replaced by an ester bond or ether bond. X.sup.1 is a C.sub.1-C.sub.20 (k+1)-valent hydrocarbon group or C.sub.1-C.sub.20 (k+1)-valent fluorinated hydrocarbon group. X.sup.2 is a single bond, *C(O)O or *C(O)NH wherein * designates a point of attachment to the carbon atom in the backbone. X.sup.3 is a single bond, O, *C(O)OX.sup.31X.sup.32 or *C(O)NHX.sup.31X.sup.32, wherein X.sup.31 is a single bond or a C.sub.1-C.sub.10 saturated hydrocarbylene group, X.sup.32 is a single bond, ester bond, ether bond or sulfonamide bond, and * designates a point of attachment to the carbon atom in the backbone.
[0281] In formulae (D1) and (D2), the C.sub.1-C.sub.10 saturated hydrocarbyl group represented by R.sup.101, R.sup.102, R.sup.104 and R.sup.105 may be straight, branched or cyclic and examples thereof include C.sub.1-C.sub.10 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl, and C.sub.3-C.sub.10 cyclic saturated hydrocarbyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Inter alia, C.sub.1-C.sub.6 saturated hydrocarbyl groups are preferred.
[0282] In formulae (D1) to (D4), the C.sub.1-C.sub.15 hydrocarbyl group represented by R.sup.103, R.sup.106, R.sup.107 and R.sup.108 may be straight, branched or cyclic and examples thereof include C.sub.1-C.sub.15 alkyl, C.sub.2-C.sub.15 alkenyl and C.sub.2-C.sub.15 alkynyl groups, with the alkyl groups being preferred. Suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl and n-pentadecyl. The fluorinated hydrocarbyl groups correspond to the foregoing hydrocarbyl groups in which some or all carbon-bonded hydrogen atoms are substituted by fluorine atoms.
[0283] In formula (D4), examples of the C.sub.1-C.sub.20 (k+1)-valent hydrocarbon group X.sup.1 include the foregoing C.sub.1-C.sub.20 alkyl groups and C.sub.3-C.sub.20 cyclic saturated hydrocarbyl groups, with k number of hydrogen atoms being eliminated. Examples of the C.sub.1-C.sub.20 (k+1)-valent fluorinated hydrocarbon group X.sup.1 include the foregoing (k+1)-valent hydrocarbon groups in which at least one hydrogen atom is substituted by fluorine.
[0284] Examples of the repeat units D1 to D4 are given below, but not limited thereto. Herein R.sup.B is as defined above.
##STR00853## ##STR00854## ##STR00855##
[0285] In formula (D5), examples of the C.sub.1-C.sub.5 hydrocarbyl groups R.sup.109 and R.sup.110 include alkyl, alkenyl and alkynyl groups, with the alkyl groups being preferred. Suitable alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and n-pentyl. In these groups, a moiety containing a heteroatom such as oxygen, sulfur or nitrogen may intervene in a carbon-carbon bond.
[0286] In formula (D5), OR.sup.109 is preferably a hydrophilic group. In this case, R.sup.109 is preferably hydrogen or a C.sub.1-C.sub.5 alkyl group in which oxygen intervenes in a carbon-carbon bond.
[0287] In formula (D5), X.sup.2 is preferably *C(O)O or *C(O)NH. Also preferably R.sup.C is methyl. The inclusion of carbonyl in X.sup.2 enhances the ability to trap the acid originating from the anti-charging film. A polymer wherein R.sup.C is methyl is a robust polymer having a high glass transition temperature (Tg) which is effective for suppressing acid diffusion. As a result, the resist film is improved in stability with time, and neither resolution nor pattern profile is degraded.
[0288] Examples of the repeat unit D5 are given below, but not limited thereto. Herein R.sup.C is as defined above.
##STR00856## ##STR00857## ##STR00858##
[0289] In formula (D6), the C.sub.1-C.sub.10 saturated hydrocarbylene group X.sup.3 may be straight, branched or cyclic and examples thereof include methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,1-diyl, propane-1,2-diyl, propane-1,3-diyl, propane-2,2-diyl, butane-1,1-diyl, butane-1,2-diyl, butane-1,3-diyl, butane-2,3-diyl, butane-1,4-diyl, and 1,1-dimethylethane-1,2-diyl.
[0290] The C.sub.1-C.sub.20 saturated hydrocarbyl group having at least one hydrogen substituted by fluorine, represented by R.sup.111, may be straight, branched or cyclic and examples thereof include C.sub.1-C.sub.20 alkyl groups and C.sub.3-C.sub.20 cyclic saturated hydrocarbyl groups in which at least one hydrogen is substituted by fluorine.
[0291] Examples of the repeat unit D6 are given below, but not limited thereto. Herein R.sup.C is as defined above.
##STR00859## ##STR00860## ##STR00861##
[0292] The content of repeat units D1 to D4 is preferably 15 to 95 mol %, more preferably 20 to 85 mol % based on the overall repeat units of the fluorinated polymer. The content of repeat unit D5 and/or D6 is preferably 5 to 85 mol %, more preferably 15 to 80 mol % based on the overall repeat units of the fluorinated polymer. Each of repeat units D1 to D6 may be used alone or in admixture.
[0293] The fluorinated polymer may comprise additional repeat units as well as the repeat units D1 to D6. Suitable additional repeat units include those described in U.S. Pat. No. 9,091,918 (JP-A 2014-177407, paragraphs [0046]-[0078]). When the fluorinated polymer comprises additional repeat units, their content is preferably up to 50 mol % based on the overall repeat units.
[0294] The fluorinated polymer may be synthesized by combining suitable monomers optionally protected with a protective group, copolymerizing them in the standard way, and effecting deprotection reaction if necessary. The copolymerization reaction is preferably radical or anionic polymerization though not limited thereto. For the polymerization reaction, reference may be made to JP-A 2004-115630.
[0295] The fluorinated polymer should preferably have a Mw of 2,000 to 50,000, and more preferably 3,000 to 20,000. A fluorinated polymer with a Mw of less than 2,000 helps acid diffusion, degrading resolution and detracting from age stability. A polymer with too high Mw has a reduced solubility in solvent, with a risk of leaving coating defects. The fluorinated polymer preferably has a dispersity (Mw/Mn) of 1.0 to 2.2, more preferably 1.0 to 1.7.
[0296] In the resist composition, the fluorinated polymer (D) is preferably used in an amount of 0.01 to 30 parts by weight, more preferably 0.1 to 20 parts by weight per 80 parts by weight of the base polymer (B). The fluorinated polymer may be used alone or in admixture.
(E) Quencher
[0297] The chemically amplified positive resist composition preferably comprises a quencher as component (E). As used herein, the quencher refers to a compound capable of trapping an acid generated from the acid generator upon exposure. The quencher is effective for holding down the rate of diffusion of the acid (generated by the acid generator) in the resist film. Even when a substrate whose outermost surface is made of a chromium-containing material is used, the quencher is effective for suppressing the influence of the acid (generated in the resist film) on the chromium-containing material.
[0298] The quencher is typically selected from conventional basic compounds. Conventional basic compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds with carboxy group, nitrogen-containing compounds with sulfonyl group, nitrogen-containing compounds with hydroxy group, nitrogen-containing compounds with hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives, imide derivatives, and carbamate derivatives. Also included are primary, secondary, and tertiary amine compounds, specifically amine compounds having a hydroxy, ether bond, ester bond, lactone ring, cyano, or sulfonate ester group as described in JP-A 2008-111103, paragraphs [0146]-[0164], and compounds having a carbamate group as described in JP 3790649. Inter alia, tris[2-(methoxymethoxy)ethyl]amine, tris[2-(methoxymethoxy)ethyl]amine-N-oxide, dibutylaminobenzoic acid, morpholine derivatives, and imidazole derivatives are preferred. Addition of a basic compound may be effective for further suppressing the diffusion rate of acid in the resist film or correcting the pattern profile.
[0299] Onium salts such as sulfonium, iodonium and ammonium salts of carboxylic acids which are not fluorinated at -position as described in U.S. Pat. No. 8,795,942 (JP-A 2008-158339) may also be used as the quencher. While an -fluorinated sulfonic acid, imide acid, and methide acid are necessary to deprotect the acid labile group, an -non-fluorinated carboxylic acid is released by salt exchange with an -non-fluorinated onium salt. The -non-fluorinated carboxylic acid functions as a quencher because it does not induce substantial deprotection reaction.
[0300] Examples of the onium salt of -non-fluorinated carboxylic acid include compounds having the formula (E1).
##STR00862##
[0301] In formula (E1), R.sup.201 is hydrogen or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom, exclusive of the hydrocarbyl group in which the hydrogen bonded to the carbon atom at -position of the carboxy group is substituted by fluorine or fluoroalkyl.
[0302] The hydrocarbyl group R.sup.201 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.40 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl; C.sub.3-C.sub.40 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0.sup.2,6]decyl, adamantyl, and adamantylmethyl; C.sub.2-C.sub.40 alkenyl groups such as vinyl, allyl, propenyl, butenyl and hexenyl; C.sub.3-C.sub.40 cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl; C.sub.6-C.sub.40 aryl groups such as phenyl, naphthyl, alkylphenyl groups (e.g., 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 4-ethylphenyl, 4-tert-butylphenyl, 4-n-butylphenyl), di- or trialkylphenyl groups (e.g., 2,4-dimethylphenyl and 2,4,6-triisopropylphenyl), alkylnaphthyl groups (e.g., methylnaphthyl and ethylnaphthyl), dialkylnaphthyl groups (e.g., dimethylnaphthyl and diethylnaphthyl); and C.sub.7-C.sub.40 aralkyl groups such as benzyl, 1-phenylethyl and 2-phenylethyl.
[0303] In the hydrocarbyl groups, some or all hydrogen may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some CH.sub.2 may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxy moiety, cyano moiety, carbonyl moiety, ether bond, thioether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)), or haloalkyl moiety. Suitable heteroatom-containing hydrocarbyl groups include heteroaryl groups such as thienyl; alkoxyphenyl groups such as 4-hydroxyphenyl, 4-methoxyphenyl, 3-methoxyphenyl, 2-methoxyphenyl, 4-ethoxyphenyl, 4-tert-butoxyphenyl, 3-tert-butoxyphenyl; alkoxynaphthyl groups such as methoxynaphthyl, ethoxynaphthyl, n-propoxynaphthyl and n-butoxynaphthyl; dialkoxynaphthyl groups such as dimethoxynaphthyl and diethoxynaphthyl; and aryloxoalkyl groups, typically 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl, 2-(1-naphthyl)-2-oxoethyl and 2-(2-naphthyl)-2-oxoethyl.
[0304] In formula (E1), Mq.sub.A.sup.+ is an onium cation. The onium cation is preferably selected from sulfonium, iodonium and ammonium cations, more preferably sulfonium and iodonium cations. Exemplary sulfonium cations include those described in JP-A 2024-003744, paragraphs [0102]-[0125] and JP-A 2023-169812, paragraphs [0070]-[0085], and those having formula (A2), but are not limited thereto. Exemplary iodonium cations include those described in JP-A 2024-000259, paragraph [0181], but are not limited thereto.
[0305] The ammonium cation preferably has the formula (am-1).
##STR00863##
[0306] In formula (am-1), R.sup.q11 to R.sup.q14 are each independently a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. Any two of R.sup.q11 to R.sup.q14 may bond together to form a ring with the nitrogen atom to which they are attached. Examples of the hydrocarbyl group are as exemplified above for the hydrocarbyl group R.sup.1 in formula (A1).
[0307] Examples of the ammonium cation having formula (am-1) are shown below, but not limited thereto.
##STR00864##
[0308] Examples of the anion in the onium salt having formula (E1) are shown below, but not limited thereto.
##STR00865## ##STR00866## ##STR00867## ##STR00868##
[0309] A sulfonium salt of iodized benzene ring-containing carboxylic acid having the formula (E2) is also useful as the quencher.
##STR00869##
[0310] In formula (E2), s is 1, 2, 3, 4 or 5, t is 0, 1, 2 or 3, s+t is from 1 to 5, and u is 1, 2 or 3.
[0311] In formula (E2), R.sup.211 is hydroxy, fluorine, chlorine, bromine, amino, nitro, cyano, or a C.sub.1-C.sub.6 saturated hydrocarbyl, C.sub.1-C.sub.6 saturated hydrocarbyloxy, C.sub.2-C.sub.6 saturated hydrocarbylcarbonyloxy or C.sub.1-C.sub.4 saturated hydrocarbylsulfonyloxy group, in which some or all hydrogen may be substituted by halogen, or N(R.sup.211A)C(O)R.sup.211B, or N(R.sup.211A)C(O)OR.sup.211B. R.sup.211A is hydrogen or a C.sub.1-C.sub.6 saturated hydrocarbyl group. R.sup.211B is a C.sub.1-C.sub.6 saturated hydrocarbyl or C.sub.2-C.sub.8 unsaturated aliphatic hydrocarbyl group. A plurality of R.sup.211 may be identical or different when t and/or u is 2 or 3.
[0312] In formula (E2), L.sup.21 is a single bond or a C.sub.1-C.sub.20 (u+1)-valent linking group which may contain at least one moiety selected from ether bond, carbonyl moiety, ester bond, amide bond, sultone ring, lactam ring, carbonate bond, halogen, hydroxy moiety, and carboxy moiety. The saturated hydrocarbyl, saturated hydrocarbyloxy, saturated hydrocarbylcarbonyloxy, and saturated hydrocarbylsulfonyloxy groups may be straight, branched or cyclic.
[0313] In formula (E2), R.sup.212, R.sup.213 and R.sup.214 are each independently halogen, or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.20 alkyl, C.sub.2-C.sub.20 alkenyl, C.sub.6-C.sub.20 aryl, and C.sub.7-C.sub.20 aralkyl groups. In these groups, some or all hydrogen may be substituted by hydroxy, carboxy, halogen, oxo, cyano, nitro, sultone ring, sulfo, or sulfonium salt-containing moiety, or some CH.sub.2 may be replaced by an ether bond, ester bond, carbonyl moiety, amide bond, carbonate bond or sulfonate ester bond. Also, R.sup.212 and R.sup.213 may bond together to form a ring with the sulfur atom to which they are attached.
[0314] Examples of the compound having formula (E2) include those described in U.S. Pat. No. 10,295,904 (JP-A 2017-219836). These compounds exert a sensitizing effect due to remarkable absorption and an acid diffusion-controlling effect.
[0315] A nitrogen-containing carboxylic acid salt compound having the formula (E3) is also useful as the quencher.
##STR00870##
[0316] In formula (E3), R.sup.221 to R.sup.224 are each independently hydrogen, -L.sup.22-CO.sub.2.sup., or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom. R.sup.221 and R.sup.222, R.sup.222 and R.sup.223, or R.sup.223 and R.sup.224 may bond together to form a ring with the carbon atom to which they are attached. L.sup.22 is a single bond or a C.sub.1-C.sub.20 hydrocarbylene group which may contain a heteroatom. R.sup.225 is hydrogen or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom.
[0317] In formula (E3), the ring R.sup.r is a C.sub.2-C.sub.6 ring containing the carbon and nitrogen atoms in the formula, in which some or all of the carbon-bonded hydrogen atoms may be substituted by a C.sub.1-C.sub.20 hydrocarbyl group or -L.sup.22-CO.sub.2.sup. and in which some carbon may be replaced by sulfur, oxygen or nitrogen. The ring may be alicyclic or aromatic and is preferably a 5- or 6-membered ring. Suitable rings include pyridine, pyrrole, pyrrolidine, piperidine, pyrazole, imidazoline, pyridazine, pyrimidine, pyrazine, imidazoline, oxazole, thiazole, morpholine, thiazine, and triazole rings.
[0318] The carboxylic onium salt having formula (E3) has at least one -L.sup.22-CO.sub.2.sup.. That is, at least one of R.sup.221 to R.sup.224 is -L.sup.22-CO.sub.2.sup., and/or at least one of hydrogen atoms bonded to carbon atoms in the ring R.sup.r is substituted by -L.sup.22-CO.sub.2.sup..
[0319] In formula (E3), Mq.sub.B.sup.+ is a sulfonium, iodonium or ammonium cation, with the sulfonium cation being preferred. Examples of the sulfonium cation include those described in JP-A 2024-003744, paragraphs [0102]-[0125], and JP-A 2023-169812, paragraphs [0070]-[0085], and those having formula (A2), but are not limited thereto.
[0320] Examples of the anion in the compound having formula (E3) are shown below, but not limited thereto.
##STR00871## ##STR00872## ##STR00873## ##STR00874## ##STR00875##
[0321] Weak acid betaine compounds are also useful as the quencher. Non-limiting examples thereof are shown below.
##STR00876##
[0322] Also useful are quenchers of polymer type as described in U.S. Pat. No. 7,598,016 (JP-A 2008-239918). The polymeric quencher segregates at the resist surface after coating and thus enhances the rectangularity of resist pattern. When a protective film is applied as is often the case in the immersion lithography, the polymeric quencher is also effective for preventing a film thickness loss of resist pattern or rounding of pattern top.
[0323] When used, the quencher (E) is preferably added in an amount of 0 to 50 parts, more preferably 0.1 to 40 parts by weight per 80 parts by weight of the base polymer (B). The quencher may be used alone or in admixture.
[0324] When the chemically amplified positive resist composition contains both the PAG (A) and the quencher (E), the weight ratio of the PAG to the quencher, (A)/(E) is preferably less than 3/1, more preferably less than 2.5/l, even more preferably less than 2/l. As long as the weight ratio of the PAG to the quencher is in the range, the resist composition is able to fully suppress acid diffusion, leading to improved resolution and dimensional uniformity.
(F) Surfactant
[0325] The resist composition may contain any conventional surfactants for facilitating to coat the composition to the substrate. A number of surfactants are known in the art as described in WO 2006/121096, JP-A 2008-102383, JP-A 2008-304590, JP-A 2004-115630, and JP-A 2005-008766, and any suitable one may be chosen therefrom.
[0326] When the resist composition contains the surfactant (G), the amount of the surfactant (G) added is preferably up to 2 parts by weight, more preferably up to 1 part by weight and preferably at least 0.01 part by weight per 80 parts by weight of the base polymer (B).
Process
[0327] A further embodiment of the invention is a process of forming a pattern from the chemically amplified positive resist composition defined above by lithography. The preferred process includes the steps of applying the resist composition onto a substrate to form a resist film thereon, exposing the resist film to high-energy radiation, and developing the exposed resist film in a developer. Any desired steps may be added to the process if necessary.
[0328] The substrate used herein may be a substrate for integrated circuitry fabrication, e.g., Si, SiO.sub.2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective film, etc. or a substrate for mask circuitry fabrication, e.g., Cr, CrO, CrON, MoSi.sub.2, SiO.sub.2, etc.
[0329] The resist composition is applied onto a substrate by a suitable coating technique such as spin coating. The coating is prebaked on a hot plate preferably at a temperature of 60 to 150 C. for 1 to 20 minutes, more preferably at 80 to 140 C. for 1 to 10 minutes. The resulting resist film preferably has a thickness of 0.03 to 2 m.
[0330] Then the resist film is exposed to a pattern of high-energy radiation, typically UV, deep UV, excimer (KrF or ArF) laser, EUV of wavelength 3 to 15 nm, EB, X-ray, -ray or synchrotron radiation. On use of UV, deep UV, excimer laser, EUV, X-ray, -ray or synchrotron radiation, the resist film is exposed through a mask having a desired pattern, preferably in a dose of 1 to 300 mJ/cm.sup.2, more preferably 10 to 200 mJ/cm.sup.2. On use of EB, a pattern may be written directly, preferably in a dose of 1 to 300 C/cm.sup.2, more preferably 10 to 200 C/cm.sup.2. The inventive resist composition is quite effective in the EUV and EB lithography.
[0331] The exposure may be performed by conventional lithography whereas the immersion lithography of holding a liquid between the resist film and the mask may be employed if desired. The liquid is typically water, and in this case, a protective film which is insoluble in water may be formed on the resist film.
[0332] After the exposure, the resist film may be baked (PEB), for example, on a hotplate preferably at 60 to 150 C. for 1 to 20 minutes, more preferably at 80 to 140 C. for 1 to 10 minutes.
[0333] The resist film is then developed with a developer in the form of an aqueous base solution, for example, 0.1 to 5 wt %, preferably 2 to 3 wt % aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1 to 3 minutes, preferably 0.5 to 2 minutes by conventional techniques such as dip, puddle and spray techniques. In this way, the exposed region of the resist film is dissolved away, and a desired resist pattern is formed on the substrate.
[0334] The chemically amplified positive resist composition has high etch resistance and is useful when used to meet the requirement that even when the duration from exposure to PEB is prolonged, the pattern experiences little changes of line width and has reduced LER. The resist composition is effectively applicable to a substrate, specifically a substrate having a surface layer of material to which a resist film is less adherent and which is likely to invite pattern stripping or pattern collapse, and particularly a substrate having sputter deposited on its outermost surface metallic chromium or a chromium compound containing at least one light element selected from oxygen, nitrogen and carbon. The resist composition is useful particularly when a photomask blank is used as the substrate.
EXAMPLES
[0335] Examples of the invention are given below by way of illustration and not by way of limitation. The abbreviation pbw is parts by weight. Analysis is made by time-of-flight mass spectrometry (TOF-MS) using MALDI TOF-MS S3000 (JEOL Ltd.).
[1] Synthesis of Onium Salts
Synthesis Example 1-1
Synthesis of Onium Salt PAG-1
##STR00877##
(1) Synthesis of Intermediate In-1
[0336] In nitrogen atmosphere, a reactor was charged with 6.3 g of reactant SM-1, 9.8 g of reactant SM-2, 0.3 g of DMAP, and 50 g of methylene chloride and cooled in an ice bath. While the internal temperature of the reactor was kept below 20 C., 5.8 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride in powder form was added. Thereafter, the reactor was allowed to reach room temperature, at which the reaction solution was aged for 12 hours. At the end of aging, water was added to quench the reaction, followed by ordinary aqueous work-up. The subsequent steps of distilling off the solvent and washing the residue with diisopropyl ether gave 13.9 g of Intermediate In-1 as oily matter (yield 92%).
(2) Synthesis of Onium Salt PAG-1
[0337] In nitrogen atmosphere, a reactor was charged with 13.9 g of Intermediate In-1, 12.6 g of reactant SM-3, 50 g of methylene chloride, and 30 g of water, which were stirred for 15 minutes. The organic layer was taken out, washed with water, and concentrated under reduced pressure. To the concentrate, 50 g of methyl isobutyl ketone was added, followed by azeotropic dewatering. Diisopropyl ether was then added for recrystallization, obtaining 20.0 g of the target onium salt, PAG-1 as white crystals (yield 95%).
[0338] PAG-1 was analyzed by TOF-MS, with the data shown below.
MALDI TOF-MS:
[0339] positive M.sup.+ 461 (corresponding to C.sub.15H.sub.10F.sub.4IS.sup.+) [0340] negative M.sup. 455 (corresponding to C.sub.27H.sub.19O.sub.5S.sup.)
Synthesis Examples 1-2 to 1-10
Synthesis of Onium Salts PAG-2 to PAG-10
[0341] Onium salts PAG-2 to PAG-10 shown below were synthesized using corresponding reactants and well-known organic synthesis reactions.
##STR00878## ##STR00879## ##STR00880## ##STR00881##
[2] Synthesis of base polymers
Synthesis Examples 2-1 to 2-6
Synthesis of Base Polymers P-1 to P-6
[0342] Base polymers P-1 to P-6 were synthesized in a standard way by combining monomers, performing copolymerization reaction in a solvent, pouring the reaction solution to hexane for precipitation, washing the solid precipitate with hexane, isolation and drying. The polymer was analyzed for composition by .sup.1H-NMR and .sup.13C-NMR spectroscopy and for Mw and Mw/Mn by GPC versus polystyrene standards using THF solvent.
##STR00882##
[3] Preparation of Chemically Amplified Positive Resist Compositions
Examples 1-1 to 1-53 and Comparative Examples 1-1 to 1-28
[0343] A chemically amplified positive resist composition was prepared by dissolving selected components in an organic solvent in accordance with the formulation shown in Tables 1 to 3, and filtering the solution through a nylon filter with a pore size of 5 nm and a UPE filter with a pore size of 1 nm. The organic solvent was a mixture of 940 pbw of PGMEA, 1,870 pbw of EL and 1,870 pbw of PGME.
TABLE-US-00001 TABLE 1 Resist Polymer 1 Polymer 2 Photoacid Quencher Fluorinated composition (pbw) (pbw) generator (pbw) (pbw) polymer (pbw) Example 1-1 R-1 P-1 (80) PAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-2 R-2 P-1 (80) PAG-1 (12) Q-1 (7.0) 1-3 R-3 P-1 (80) PAG-2 (12) Q-1 (7.0) FP-1 (1.5) 1-4 R-4 P-1 (80) PAG-3 (12) Q-1 (7.0) FP-1 (1.5) 1-5 R-5 P-1 (80) PAG-4 (12) Q-1 (7.0) FP-1 (1.5) 1-6 R-6 P-1 (80) PAG-5 (12) Q-1 (7.0) FP-1 (1.5) 1-7 R-7 P-1 (80) PAG-6 (12) Q-1 (7.0) FP-1 (1.5) 1-8 R-8 P-1 (80) PAG-7 (12) Q-1 (7.0) FP-1 (1.5) 1-9 R-9 P-1 (80) PAG-8 (12) Q-1 (7.0) FP-1 (1.5) 1-10 R-10 P-1 (80) PAG-9 (12) Q-1 (7.0) FP-1 (1.5) 1-11 R-11 P-1 (80) PAG-10 (12) Q-1 (7.0) FP-1 (1.5) 1-12 R-12 P-1 (80) PAG-1 (8) Q-2 (7.0) FP-1 (1.5) PAG-A (4) 1-13 R-13 P-1 (80) PAG-2 (8) Q-4 (7.0) FP-2 (1.5) PAG-B (4) 1-14 R-14 P-1 (80) PAG-3 (12) Q-3 (7.0) FP-3 (1.5) 1-15 R-15 P-1 (80) PAG-6 (12) Q-2 (7.0) FP-4 (1.5) 1-16 R-16 P-2 (80) PAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-17 R-17 P-2 (80) PAG-2 (12) Q-3 (7.0) FP-1 (1.5) 1-18 R-18 P-2 (80) PAG-3 (12) Q-1 (7.0) FP-1 (1.5) 1-19 R-19 P-2 (80) PAG-4 (12) Q-4 (7.0) FP-5 (1.5) 1-20 R-20 P-2 (80) PAG-6 (12) Q-1 (7.0) FP-1 (1.5) 1-21 R-21 P-2 (80) PAG-8 (12) Q-2 (7.0) FP-2 (1.5) 1-22 R-22 P-2 (80) PAG-10 (12) Q-1 (7.0) FP-1 (1.5) 1-23 R-23 P-2 (80) PAG-1 (8) Q-1 (7.0) FP-1 (1.5) PAG-A (4) 1-24 R-24 P-2 (80) PAG-2 (8) Q-3 (7.0) FP-2 (1.5) PAG-B (4) 1-25 R-25 P-2 (80) PAG-6 (10) Q-1 (6.8) FP-1 (1.5) PAG-B (2) 1-26 R-26 P-3 (80) PAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-27 R-27 P-3 (80) PAG-2 (12) Q-2 (6.8) FP-1 (1.5) 1-28 R-28 P-3 (80) PAG-3 (12) Q-1 (7.0) FP-1 (1.5) 1-29 R-29 P-3 (80) PAG-6 (12) Q-4 (7.0) FP-3 (1.5) 1-30 R-30 P-3 (80) PAG-10 (12) Q-1 (7.0) FP-1 (1.5)
TABLE-US-00002 TABLE 2 Resist Polymer 1 Polymer 2 Photoacid Quencher Fluorinated composition (pbw) (pbw) generator (pbw) (pbw) polymer (pbw) Example 1-31 R-31 P-3 (80) PAG-1 (8) Q-1 (7.0) FP-4 (1.5) PAG-A (4) 1-32 R-32 P-4 (80) PAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-33 R-33 P-4 (80) PAG-2 (12) Q-2 (6.8) FP-1 (1.5) 1-34 R-34 P-4 (80) PAG-4 (12) Q-1 (7.0) FP-1 (1.5) 1-35 R-35 P-4 (80) PAG-5 (12) Q-4 (7.0) FP-3 (1.5) 1-36 R-36 P-4 (80) PAG-9 (12) Q-1 (7.0) FP-1 (1.5) 1-37 R-37 P-4 (80) PAG-3 (8) Q-1 (7.0) FP-4 (1.5) PAG-B (4) 1-38 R-38 P-5 (80) PAG-1 (4) Q-1 (7.0) FP-1 (1.5) 1-39 R-39 P-5 (80) PAG-2 (4) Q-2 (7.2) FP-1 (1.5) 1-40 R-40 P-5 (80) PAG-6 (4) Q-1 (7.0) FP-1 (1.5) 1-41 R-41 P-5 (80) PAG-8 (4) Q-3 (7.0) FP-1 (1.5) 1-42 R-42 P-5 (80) PAG-10 (4) Q-4 (7.4) FP-2 (1.5) 1-43 R-43 P-5 (80) PAG-1 (3) Q-1 (7.2) FP-1 (1.5) PAG-A (1) 1-44 R-44 P-6 (80) PAG-1 (4) Q-1 (7.0) FP-3 (1.5) 1-45 R-45 P-6 (80) PAG-2 (4) Q-2 (7.0) FP-1 (1.5) 1-46 R-46 P-6 (80) PAG-4 (4) Q-4 (7.2) FP-4 (1.5) 1-47 R-47 P-6 (80) PAG-7 (4) Q-1 (7.0) FP-1 (1.5) 1-48 R-48 P-6 (80) PAG-9 (4) Q-2 (7.0) FP-1 (1.5) 1-49 R-49 P-6 (80) PAG-1 (3) Q-1 (7.0) FP-1 (1.5) PAG-B (1) 1-50 R-50 P-1 (40) P-5 (40) PAG-1 (4) Q-1 (7.0) FP-1 (1.5) 1-51 R-51 P-1 (40) P-6 (40) PAG-2 (4) Q-1 (7.0) FP-1 (1.5) 1-52 R-52 P-2 (40) P-5 (40) PAG-6 (4) Q-2 (7.0) FP-1 (1.5) 1-53 R-53 P-3 (40) P-6 (40) PAG-10 (4) Q-3 (7.0) FP-1 (1.5)
TABLE-US-00003 TABLE 3 Resist Polymer 1 Polymer 2 Photoacid Quencher Fluorinated composition (pbw) (pbw) generator (pbw) (pbw) polymer (pbw) Comparative 1-1 CR-1 P-1 (80) cPAG-1 (12) Q-1 (7.0) FP-1 (1.5) Example 1-2 CR-2 P-1 (80) cPAG-1 (12) Q-1 (7.0) 1-3 CR-3 P-1 (80) cPAG-2 (12) Q-1 (7.0) FP-1 (1.5) 1-4 CR-4 P-1 (80) cPAG-4 (12) Q-1 (7.0) FP-1 (1.5) 1-5 CR-5 P-1 (80) cPAG-1 (8) Q-2 (7.0) FP-1 (1.5) PAG-A (4) 1-6 CR-6 P-2 (80) cPAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-7 CR-7 P-2 (80) cPAG-2 (12) Q-3 (7.0) FP-1 (1.5) 1-8 CR-8 P-2 (80) cPAG-3 (12) Q-2 (7.0) FP-4 (1.5) 1-9 CR-9 P-2 (80) cPAG-2 (8) Q-3 (7.0) FP-2 (1.5) PAG-B (4) 1-10 CR-10 P-3 (80) cPAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-11 CR-11 P-3 (80) cPAG-2 (12) Q-2 (6.8) FP-1 (1.5) 1-12 CR-12 P-3 (80) cPAG-4 (12) Q-4 (7.0) FP-3 (1.5) 1-13 CR-13 P-3 (80) cPAG-1 (8) Q-1 (7.0) FP-4 (1.5) PAG-A (4) 1-14 CR-14 P-4 (80) cPAG-1 (12) Q-1 (7.0) FP-1 (1.5) 1-15 CR-15 P-4 (80) cPAG-2 (12) Q-4 (7.0) FP-3 (1.5) 1-16 CR-16 P-4 (80) cPAG-4 (12) Q-1 (7.0) FP-1 (1.5) 1-17 CR-17 P-4 (80) cPAG-3 (8) Q-1 (7.0) FP-4 (1.5) PAG-B (4) 1-18 CR-18 P-5 (40) cPAG-1 (4) Q-1 (7.0) FP-1 (1.5) 1-19 CR-19 P-5 (40) cPAG-2 (4) Q-2 (7.2) FP-5 (1.5) 1-20 CR-20 P-5 (40) cPAG-3 (4) Q-1 (7.0) FP-1 (1.5) 1-21 CR-21 P-5 (40) cPAG-1 (3) Q-1 (7.2) FP-1 (1.5) PAG-A (1) 1-22 CR-22 P-6 (40) cPAG-1 (4) Q-1 (7.0) FP-3 (1.5) 1-23 CR-23 P-6 (40) cPAG-2 (4) Q-2 (7.0) FP-1 (1.5) 1-24 CR-24 P-6 (40) PAG-1 (3) Q-1 (7.0) FP-1 (1.5) PAG-B (1) 1-25 CR-25 P-6 (40) Q-2 (7.0) FP-5 (1.5) 1-26 CR-26 P-1 (40) P-5 (40) cPAG-1 (4) Q-1 (7.0) FP-1 (1.5) 1-27 CR-27 P-2 (40) P-5 (40) cPAG-3 (4) Q-2 (7.0) FP-1 (1.5) 1-28 CR-28 P-1 (40) P-6 (40) cPAG-2 (2) Q-1 (7.0) FP-1 (1.5)
[0344] Comparative photoacid generators cPAG-1 to cPAG-4, photoacid generators PAG-A and PAG-B, Quenchers Q-1 to Q-4, and Fluorinated Polymers FP-1 to FP-5 in Tables 1 to 3 are identified below.
##STR00883## ##STR00884## ##STR00885## ##STR00886##
[4] EB Lithography Test
Examples 2-1 to 2-53 and Comparative Examples 2-1 to 2-28
[0345] A photomask blank of reflection type for an EUV lithography mask was furnished by starting with a low-coefficient-of-thermal-expansion glass substrate of 6 inches squares and depositing thereon a multilayer reflective film of 40 Mo/Si layers with a thickness of 284 nm, a Ru film of 3.5 nm thick as protective film, a TaN film of 70 nm thick as absorbing layer, and a CrN film of 6 nm thick as hard mask. Using a coater/developer system ACT-M (Tokyo Electron Ltd.), each of the resist compositions (R-1 to R-53, CR-1 to CR-28) was spin coated onto the photomask blank, and prebaked on a hotplate at 110 C. for 600 seconds to form a resist film of 80 nm thick. The thickness of the resist film was measured by an optical film thickness measurement system Nanospec (Nanometrics Inc.). Measurement was made at 81 points in the plane of the blank substrate excluding a peripheral band extending 10 mm inward from the blank periphery, and an average film thickness and a film thickness range were computed therefrom.
[0346] The resist film was exposed to EB using an EB writer system EBM-5000Plus (NuFlare Technology Inc., accelerating voltage 50 kV), then baked (PEB) at 110 C. for 600 seconds, and developed in a 2.38 wt % TMAH aqueous solution, thereby yielding a positive pattern.
[0347] The resist pattern was evaluated as follows. The patterned mask blank was observed under a top-down scanning electron microscope (TD-SEM). The optimum dose (Eop) was defined as the exposure dose (C/cm.sup.2) which provided a 1:1 resolution at the top and bottom of a 200-nm 1:1 line-and-space (LS) pattern. The resolution (or maximum IS resolution) was defined as the minimum size at the dose which provided a 9:1 resolution for an isolated space (IS) of 200 nm. The edge roughness (LER) of a 200-nm LS pattern was measured under SEM. The pattern was visually observed to judge whether or not the profile was rectangular. The results are shown in Tables 4 to 6.
TABLE-US-00004 TABLE 4 Resist Optimum dose Maximum IS LER Pattern composition (C/cm.sup.2) resolution (nm) (nm) profile Example 2-1 R-1 210 15 4.0 rectangular 2-2 R-2 200 16 4.2 rectangular 2-3 R-3 205 15 4.1 rectangular 2-4 R-4 210 16 4.2 rectangular 2-5 R-5 215 15 4.3 rectangular 2-6 R-6 210 17 4.3 rectangular 2-7 R-7 215 16 4.1 rectangular 2-8 R-8 220 17 4.2 rectangular 2-9 R-9 210 16 4.2 rectangular 2-10 R-10 215 15 4.3 rectangular 2-11 R-11 215 15 4.4 rectangular 2-12 R-12 210 16 4.2 rectangular 2-13 R-13 215 17 4.3 rectangular 2-14 R-14 210 16 4.1 rectangular 2-15 R-15 215 16 4.3 rectangular 2-16 R-16 210 17 4.2 rectangular 2-17 R-17 215 16 4.1 rectangular 2-18 R-18 210 15 4.4 rectangular 2-19 R-19 210 16 4.2 rectangular 2-20 R-20 200 16 4.3 rectangular 2-21 R-21 210 18 4.3 rectangular 2-22 R-22 215 15 4.3 rectangular 2-23 R-23 210 17 4.5 rectangular 2-24 R-24 215 17 4.3 rectangular 2-25 R-25 210 16 4.2 rectangular 2-26 R-26 215 16 4.2 rectangular 2-27 R-27 215 16 4.2 rectangular 2-28 R-28 205 15 4.2 rectangular 2-29 R-29 200 16 4.1 rectangular 2-30 R-30 205 17 4.4 rectangular
TABLE-US-00005 TABLE 5 Resist Optimum dose Maximum IS LER Pattern composition (C/cm.sup.2) resolution (nm) (nm) profile Example 2-31 R-31 210 15 4.2 rectangular 2-32 R-32 215 16 4.1 rectangular 2-33 R-33 210 15 4.2 rectangular 2-34 R-34 215 16 4.2 rectangular 2-35 R-35 220 16 4.3 rectangular 2-36 R-36 215 15 4.1 rectangular 2-37 R-37 210 17 4.2 rectangular 2-38 R-38 205 16 4.1 rectangular 2-39 R-39 215 17 4.0 rectangular 2-40 R-40 210 16 4.2 rectangular 2-41 R-41 215 17 4.2 rectangular 2-42 R-42 205 17 4.1 rectangular 2-43 R-43 200 15 4.2 rectangular 2-44 R-44 215 16 4.3 rectangular 2-45 R-45 215 16 4.4 rectangular 2-46 R-46 210 17 4.2 rectangular 2-47 R-47 215 16 4.1 rectangular 2-48 R-48 205 16 4.2 rectangular 2-49 R-49 215 17 4.3 rectangular 2-50 R-50 210 15 4.1 rectangular 2-51 R-51 215 16 4.3 rectangular 2-52 R-52 200 16 4.2 rectangular 2-53 R-53 215 16 4.1 rectangular
TABLE-US-00006 TABLE 6 Resist Optimum dose Maximum IS LER Pattern composition (C/cm.sup.2) resolution (nm) (nm) profile Comparative 2-1 CR-1 215 19 4.9 rectangular Example 2-2 CR-2 200 20 4.9 footing 2-3 CR-3 200 22 5.1 rectangular 2-4 CR-4 215 20 4.8 rectangular 2-5 CR-5 205 18 5.1 footing 2-6 CR-6 210 22 5 rectangular 2-7 CR-7 200 21 4.9 footing 2-8 CR-8 210 22 4.7 rectangular 2-9 CR-9 210 21 4.8 rectangular 2-10 CR-10 210 21 4.9 rectangular 2-11 CR-11 215 20 5 rectangular 2-12 CR-12 210 20 4.9 footing 2-13 CR-13 210 22 4.7 rectangular 2-14 CR-14 210 21 4.8 rectangular 2-15 CR-15 215 22 5 footing 2-16 CR-16 210 22 4.8 rectangular 2-17 CR-17 215 20 4.7 rectangular 2-18 CR-18 200 21 4.9 footing 2-19 CR-19 210 21 4.8 rectangular 2-20 CR-20 215 21 5 rectangular 2-21 CR-21 200 20 4.9 rectangular 2-22 CR-22 205 23 5 footing 2-23 CR-23 215 22 4.8 rectangular 2-24 CR-24 200 23 4.7 rectangular 2-25 CR-25 205 22 5 footing 2-26 CR-26 215 20 4.8 rectangular 2-27 CR-27 200 19 4.9 footing 2-28 CR-28 205 20 4.7 rectangular
[0348] As is evident from Tables 4 to 6, the chemically amplified positive resist composition comprising the onium salt consisting of an anion having formula (A1) and a cation having formula (A2) as a photoacid generator and the resist pattern forming process within the scope of the invention are effective in photolithography for the fabrication of semiconductor devices and the processing of photomask blanks of transmission and reflection types.
[0349] Japanese Patent Application No. 2024-107164 is incorporated herein by reference.
[0350] Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.