RESIST COMPOSITION AND PATTERN FORMING PROCESS

Abstract

A resist composition comprising a base polymer possessing a sulfonium or iodonium salt structure having an iodized arylsulfonic acid anion attached to its backbone is provided. It exhibits a high sensitivity and forms a pattern with reduced LWR or improved CDU independent of whether it is of positive or negative type.

Claims

1. A resist composition comprising a base polymer possessing a sulfonium or iodonium salt structure having an iodized arylsulfonic acid anion attached to its backbone.

2. The resist composition of claim 1 wherein the base polymer comprises repeat units having the formula (a): ##STR00200## wherein p is an integer of 0 to 10, q is an integer of 1 to 5, R.sup.A is hydrogen or methyl, R.sup.B is hydrogen or may form a ring with X.sup.1, X.sup.1 is a single bond, ester bond, phenylene group or naphthylene group, X.sup.2 is a single bond or a C.sub.1-C.sub.20 hydrocarbylene group which may contain at least one moiety selected from oxygen, nitrogen, sulfur and halogen, X.sup.3 is a single bond, ether bond, ester bond, sulfonate ester bond, sulfonyl group or carbonyl group, R.sup.1 is hydrogen, hydroxy, carboxy, fluorine, chlorine, bromine, amino, nitro, cyano, a C.sub.1-C.sub.20 hydrocarbyl group, C.sub.1-C.sub.20 hydrocarbyloxy group, C.sub.2-C.sub.20 hydrocarbyloxycarbonyl group, C.sub.2-C.sub.20 hydrocarbylcarbonyloxy group, C.sub.1-C.sub.20 hydrocarbylsulfonyloxy group, N(R.sup.1A)C(O)R.sup.1B, N(R.sup.1A)C(O)OR.sup.1B, or N(R.sup.1A)S(O).sub.2R.sup.1B, the hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups may contain at least one moiety selected from fluorine, chlorine, bromine, iodine, hydroxy, amino, ester bond, ether bond, urethane bond, urea bond, carbonate bond, amide bond, sulfonate ester bond, carbonyl, sulfide, and sulfonyl, R.sup.1A 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.1B is a C.sub.1-C.sub.16 aliphatic hydrocarbyl group or C.sub.6-C.sub.12 aryl 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, Ar is a C.sub.6-C.sub.16 (p+q+1)-valent aromatic hydrocarbon group, and M.sup.+ is a sulfonium or iodonium cation.

3. The resist composition of claim 2 wherein q is 2, 3 or 4.

4. The resist composition of claim 1 wherein the base polymer further comprises repeat units having the formula (b1) or (b2): ##STR00201## wherein R.sup.A is each independently hydrogen or methyl, Y.sup.1 is a single bond, phenylene group, naphthylene group or a C.sub.1-C.sub.12 linking group which contains at least one moiety selected from an ester bond, ether bond and lactone ring, the phenylene group, naphthylene group and linking group may contain at least one moiety selected from hydroxy, C.sub.1-C.sub.8 saturated hydrocarbyloxy moiety and C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy moiety, Y.sup.2 is a single bond or ester bond, Y.sup.3 is a single bond, ether bond or ester bond, R.sup.11 and R.sup.12 are each independently an acid labile group, R.sup.13 is a C.sub.1-C.sub.4 saturated hydrocarbyl group, halogen, C.sub.2-C.sub.5 saturated hydrocarbylcarbonyl group, cyano, or C.sub.2-C.sub.5 saturated hydrocarbyloxycarbonyl group, R.sup.14 is a single bond or a C.sub.1-C.sub.6 alkanediyl group which may contain at least one moiety selected from hydroxy, C.sub.1-C.sub.8 saturated hydrocarbyloxy moiety, C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy moiety, ether bond, and ester bond, a is an integer of 0 to 4.

5. The resist composition of claim 4 which is a chemically amplified positive resist composition.

6. The resist composition of claim 1 wherein the base polymer is free of an acid labile group.

7. The resist composition of claim 6 which is a chemically amplified negative resist composition.

8. The resist composition of claim 1, further comprising an organic solvent.

9. The resist composition of claim 1, further comprising a quencher.

10. The resist composition of claim 1, further comprising a surfactant.

11. A pattern forming process comprising the steps of applying the resist composition of claim 1 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.

12. The process of claim 11 wherein the high-energy radiation is ArF excimer laser of wavelength 193 nm, KrF excimer laser of wavelength 248 nm, EB or EUV of wavelength 3 to 15 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0038] 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. As used herein, the term fluorinated refers to a fluorine-substituted or fluorine-containing compound or group, and the term iodized refers to an iodine-substituted or iodine-containing compound or group. The terms group and moiety are interchangeable.

[0039] The abbreviations and acronyms have the following meaning. [0040] EB: electron beam [0041] EUV: extreme ultraviolet [0042] Mw: weight average molecular weight [0043] Mn: number average molecular weight [0044] Mw/Mn: molecular weight distribution or dispersity [0045] GPC: gel permeation chromatography [0046] PEB: post-exposure bake [0047] PAG: photoacid generator [0048] LWR: line width roughness [0049] CDU: critical dimension uniformity

[Resist Composition]

[0050] One embodiment of the invention is a resist composition comprising a base polymer possessing a sulfonium or iodonium salt structure having an iodized arylsulfonic acid anion attached to its backbone. Due to the cooperation of the high absorption of iodine, the high acid strength of sulfonic acid, and the bulkiness of arylsulfonic acid, the salt structure achieves a high contrast. The attachment of the salt structure to the polymer backbone ensures low acid diffusion. Then LWR or CDU is improved.

[0051] The acid generator exerts the effect of improving LWR or CDU, which is valid in positive or negative tone pattern formation by aqueous alkaline development or in negative tone pattern formation by organic solvent development.

[Base Polymer]

[0052] In a preferred embodiment, the base polymer comprises repeat units having the formula (a). The repeat units are also referred to as repeat units (a).

##STR00003##

[0053] In formula (a), p is an integer of 0 to 10, and q is an integer of 1 to 5, preferably 2, 3 or 4.

[0054] In formula (a), R.sup.A is hydrogen or methyl. R.sup.B is hydrogen or may bond with X.sup.1 to form a ring.

[0055] In formula (a), X.sup.1 is a single bond, ester bond, phenylene group or naphthylene group.

[0056] In formula (a), X.sup.2 is a single bond or a C.sub.1-C.sub.20 hydrocarbylene group which may contain at least one moiety selected from oxygen, nitrogen, sulfur and halogen.

[0057] The hydrocarbylene group X.sup.2 may be saturated or unsaturated and straight, branched or cyclic. Examples of the C.sub.1-C.sub.20 hydrocarbylene group include C.sub.1-C.sub.20 alkanediyl groups such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl, tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl, octadecane-1,18-diyl, nonadecane-1,19-diyl, and eicosane-1,20-diyl; C.sub.3-C.sub.20 cyclic saturated hydrocarbylene groups such as cyclopropanediyl, cyclobutanediyl, cyclopentanediyl, methylcyclopentanediyl, dimethylcyclopentanediyl, trimethylcyclopentanediyl, tetramethylcyclopentanediyl, cyclohexanediyl, methylcyclohexanediyl, dimethylcyclohexanediyl, trimethylcyclohexanediyl, tetramethylcyclohexanediyl, norbornanediyl and adamantanediyl; C.sub.2-C.sub.20 alkenediyl groups such as ethenediyl, propenediyl and butenediyl; C.sub.2-C.sub.20 alkynediyl groups such as ethynediyl, propynediyl and butynediyl; C.sub.6-C.sub.20 arylene groups such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, tert-butylnaphthylene, tetrahydronaphthylene, biphenyldiyl, methylbiphenyldiyl and dimethylbiphenyldiyl; and combinations thereof. In the hydrocarbylene group, some or all of the hydrogen atoms may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or 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, ester bond, ether bond, amide bond, carbamate bond or urea bond.

[0058] In formula (a), X.sup.3 is a single bond, ether bond, ester bond, sulfonate ester bond, sulfonyl group or carbonyl group.

[0059] In formula (a), R.sup.1 is hydrogen, hydroxy, carboxy, fluorine, chlorine, bromine, amino, nitro, cyano, a C.sub.1-C.sub.20 hydrocarbyl group, C.sub.1-C.sub.20 hydrocarbyloxy group, C.sub.2-C.sub.20 hydrocarbyloxycarbonyl group, C.sub.2-C.sub.20 hydrocarbylcarbonyloxy group, C.sub.1-C.sub.20 hydrocarbylsulfonyloxy group, N(R.sup.1A)C(O)R.sup.1B, N(R.sup.1A)C(O)OR.sup.1B, or N(R.sup.1A)S(O).sub.2R.sup.1B. The hydrocarbyl, hydrocarbyloxy, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups may contain at least one moiety selected from fluorine, chlorine, bromine, iodine, hydroxy, amino, ester bond, ether bond, urethane bond, urea bond, carbonate bond, amide bond, sulfonate ester bond, carbonyl, sulfide, and sulfonyl. R.sup.1A 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.1B is a C.sub.1-C.sub.16 aliphatic hydrocarbyl group or C.sub.6-C.sub.12 aryl 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.

[0060] The hydrocarbyl group and hydrocarbyl moiety in the hydrocarbyloxy, hydrocarbyloxycarbonyl, hydrocarbylcarbonyloxy, and hydrocarbylsulfonyloxy groups, represented by R.sup.1, 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, and icosyl; 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, propenyl, butenyl and hexenyl; C.sub.2-C.sub.20 alkynyl groups such as ethynyl, propynyl and butynyl; C.sub.3-C.sub.20 Cyclic unsaturated aliphatic hydrocarbyl groups such as cyclohexenyl and norbornenyl; C.sub.6-C.sub.20 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; C.sub.7-C.sub.20 aralkyl groups such as benzyl and phenethyl; and combinations thereof.

[0061] In formula (a), Ar is a C.sub.6-C.sub.16 (p+q+1)-valent aromatic hydrocarbon group. Examples of the aromatic hydrocarbon group include groups obtained by eliminating (p+q+1) number of hydrogen atoms from aromatic hydrocarbons such as benzene, naphthalene, anthracene, and pyrene.

[0062] Examples of the anion in the monomer from which repeat units (a) are derived are shown below, but not limited thereto. Herein R.sup.A is as defined above.

##STR00004## ##STR00005## ##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010##

##STR00011## ##STR00012## ##STR00013## ##STR00014## ##STR00015## ##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020## ##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025## ##STR00026## ##STR00027## ##STR00028## ##STR00029## ##STR00030## ##STR00031## ##STR00032## ##STR00033## ##STR00034##

##STR00035## ##STR00036## ##STR00037## ##STR00038## ##STR00039## ##STR00040## ##STR00041## ##STR00042##

[0063] In formula (a), M.sup.+ is a sulfonium or iodonium cation, preferably a sulfonium cation having the formula (a1) or iodonium cation having the formula (a2).

##STR00043##

[0064] In formulae (a1) and (a2), R.sup.2 to R.sup.6 are each independently 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.

[0065] The C.sub.1-C.sub.20 hydrocarbyl group represented by R.sup.2 to R.sup.6 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, and icosyl; 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, propenyl, butenyl, and hexenyl; C.sub.2-C.sub.20 alkynyl groups such as ethynyl, propynyl and butynyl; C.sub.3-C.sub.20 cyclic unsaturated hydrocarbyl groups such as cyclohexenyl and norbornenyl; C.sub.6-C.sub.20 aryl groups such as phenyl, methylphenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, n-butylphenyl, isobutylphenyl, sec-butylphenyl, tert-butylphenyl, naphthyl, methylnaphthyl, ethylnaphthyl, n-propylnaphthyl, isopropylnaphthyl, n-butylnaphthyl, isobutylnaphthyl, sec-butylnaphthyl, and tert-butylnaphthyl; C.sub.7-C.sub.20 aralkyl groups such as benzyl and phenethyl, and combinations thereof.

[0066] 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 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, mercapto, carbonyl, ether bond, ester bond, sulfonate ester bond, carbonate bond, lactone ring, sultone ring, carboxylic anhydride (C(O)OC(O)) or haloalkyl moiety.

[0067] Also, R.sup.2 and R.sup.3 may bond together to form a ring with the sulfur atom to which they are attached. Exemplary structures of the ring are shown below.

##STR00044##

[0068] Examples of the sulfonium cation M+ are shown below, but not limited thereto.

##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##

[0069] Examples of the iodonium cation M+ are shown below, but not limited thereto.

##STR00124## ##STR00125## ##STR00126##

[0070] The monomer from which repeat units (a) are derived can be synthesized, for example, by reacting an iodized aromatic compound with fuming sulfuric acid to synthesize an iodized aromatic sulfonic acid, and performing salt exchange between an ammonium or alkali metal salt of the aromatic sulfonic acid and a sulfonium or iodonium salt containing a halide anion.

[0071] The repeat units (a) may be of one type or a mixture of plural types.

[0072] In the case of a positive resist composition, the base polymer typically comprises repeat units containing an acid labile group. The preferred repeat units containing an acid labile group are repeat units having the formula (b1) or repeat units having the formula (b2). These repeat units are also referred to as repeat units (b1) and (b2).

##STR00127##

[0073] In formulae (b1) and (b2), R.sup.A is each independently hydrogen or methyl. Y.sup.1 is a single bond, phenylene group, naphthylene group, or a C.sub.1-C.sub.12 linking group containing at least one moiety selected from ester bond, ether bond and lactone ring. The phenylene group, naphthylene group, and linking group may contain at least one moiety selected from hydroxy, C.sub.1-C.sub.8 saturated hydrocarbyloxy moiety, and C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy moiety. Y.sup.2 is a single bond or ester bond. Y.sup.3 is a single bond, ether bond or ester bond. R.sup.11 and R.sup.12 are each independently an acid labile group. R.sup.13 is a C.sub.1-C.sub.4 saturated hydrocarbyl group, halogen, C.sub.2-C.sub.5 saturated hydrocarbylcarbonyl group, cyano, or C.sub.2-C.sub.5 saturated hydrocarbyloxycarbonyl group. R.sup.14 is a single bond or C.sub.1-C.sub.6 alkanediyl group which may contain at least one moiety selected from hydroxy, C.sub.1-C.sub.8 saturated hydrocarbyloxy moiety, C.sub.2-C.sub.8 saturated hydrocarbylcarbonyloxy moiety, ether bond, and ester bond. The subscript a is an integer of 0 to 4.

[0074] Examples of the monomer from which repeat units (b1) are derived are shown below, but not limited thereto. Herein R.sup.A and R.sup.11 are as defined above.

##STR00128## ##STR00129## ##STR00130##

[0075] Examples of the monomer from which repeat units (b2) are derived are shown below, but not limited thereto. Herein R.sup.A and R.sup.12 are as defined above.

##STR00131## ##STR00132##

[0076] In formulae (b1) and (b2), R.sup.11 and R.sup.12 are each independently an acid labile group. The acid labile group may be selected from a variety of such groups, for example, groups having the following formulae (AL-1) to (AL-3).

##STR00133##

[0077] In formula (AL-1), b is an integer of 0 to 6. R.sup.L1 is a C.sub.4-C.sub.20, preferably C.sub.4-C.sub.15 tertiary hydrocarbyl group, a trihydrocarbylsilyl group in which each hydrocarbyl moiety is a C.sub.1-C.sub.6 saturated hydrocarbyl moiety, a C.sub.4-C.sub.20 saturated hydrocarbyl group containing a carbonyl moiety, ether bond or ester bond, or a group having formula (AL-3). It is noted that the tertiary hydrocarbyl group refers to a group obtained by eliminating hydrogen on tertiary carbon from a hydrocarbon.

[0078] Of the groups represented by R.sup.L1, the tertiary hydrocarbyl group may be saturated or unsaturated and branched or cyclic, and examples thereof include tert-butyl, tert-pentyl, 1,1-diethylpropyl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and 2-methyl-2-adamantyl. Examples of the trihydrocarbylsilyl group include trimethylsilyl, triethylsilyl and dimethyl-tert-butylsilyl. The saturated hydrocarbyl group containing a carbonyl moiety, ether bond or ester bond may be straight, branched or cyclic, preferably cyclic, and examples thereof include 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, 5-methyl-2-oxooxolan-5-yl, 2-tetrahydropyranyl and 2-tetrahydrofuranyl.

[0079] Examples of the acid labile group having formula (AL-1) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-pentyloxycarbonyl, tert-pentyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl.

[0080] Other examples of the acid labile group having formula (AL-1) include groups having the formulae (AL-1)-1 to (AL-1)-10.

##STR00134##

[0081] In formulae (AL-1)-1 to (AL-1)-10, b is as defined above. R.sup.L8 is each independently a C.sub.1-C.sub.10 saturated hydrocarbyl group or C.sub.6-C.sub.20 aryl group. R.sup.L9 is hydrogen or a C.sub.1-C.sub.10 saturated hydrocarbyl group. R.sup.L10 is a C.sub.2-C.sub.10 saturated hydrocarbyl group or C.sub.6-C.sub.20 aryl group. The saturated hydrocarbyl group may be straight, branched or cyclic.

[0082] In formula (AL-2), R.sup.12 and R.sub.13 are each independently hydrogen or a C.sub.1-C.sub.18, preferably C.sub.1-C.sub.10 saturated hydrocarbyl group. The saturated hydrocarbyl group may be straight, branched or cyclic and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl and n-octyl.

[0083] In formula (AL-2), R.sup.L4 is a C.sub.1-C.sub.18, preferably C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. Inter alia, C.sub.1-C.sub.18 saturated hydrocarbyl groups are preferred, in which some hydrogen may be substituted by hydroxy, alkoxy, oxo, amino or alkylamino. Examples of the substituted saturated hydrocarbyl group are shown below.

##STR00135##

[0084] A pair of R.sup.L2 and R.sup.L3, R.sup.L2 and RIA, or R.sup.L3 and R.sup.L4 may bond together to form a ring with the carbon atom or carbon and oxygen atoms to which they are attached. R.sup.L2 and R.sup.L3, R.sup.L2 and R.sup.L4, or R.sup.L3 and R.sup.L4 which form a ring are each independently a C.sub.1-C.sub.18, preferably C.sub.1-C.sub.10 alkanediyl group. The ring thus formed is preferably of 3 to 10, more preferably 4 to 10 carbon atoms.

[0085] Of the acid labile groups having formula (AL-2), suitable straight or branched groups include those having formulae (AL-2)-1 to (AL-2)-69, but are not limited thereto.

##STR00136## ##STR00137## ##STR00138## ##STR00139## ##STR00140## ##STR00141## ##STR00142##

[0086] Of the acid labile groups having formula (AL-2), suitable cyclic groups include tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-ethyltetrahydropyran-2-yl.

[0087] Also included are acid labile groups having the following formulae (AL-2a) and (AL-2b). With these acid labile groups, the base polymer may be crosslinked within the molecule or between molecules.

##STR00143##

[0088] In formulae (AL-2a) and (AL-2b), R.sup.L11 and R.sup.L12 are each independently hydrogen or a C.sub.1-C.sub.8 saturated hydrocarbyl group which may be straight, branched or cyclic. Also, R.sup.L11 and R.sup.L12 may bond together to form a ring with the carbon atom to which they are attached, and in this case, R.sup.L11 and R.sup.L12 are each independently a C.sub.1-C.sub.8 alkanediyl group. R.sup.L13 is each independently a C.sub.1-C.sub.10 saturated hydrocarbylene group which may be straight, branched or cyclic. The subscripts c and d are each independently an integer of 0 to 10, preferably 0 to 5, and e is an integer of 1 to 7, preferably 1 to 3.

[0089] In formulae (AL-2a) and (AL-2b), LA is a C.sub.1-C.sub.50 (e+1)-valent aliphatic saturated hydrocarbon group, C.sub.3-C.sub.50 (e+1)-valent alicyclic saturated hydrocarbon group, C.sub.6-C.sub.50 (e+1)-valent aromatic hydrocarbon group or C.sub.3-C.sub.50 (e+1)-valent heterocyclic group. In these groups, some constituent CH.sub.2 may be replaced by a heteroatom-containing moiety, or some carbon-bonded hydrogen may be substituted by a hydroxy, carboxy, acyl moiety or fluorine. LA is preferably a C.sub.1-C.sub.20 saturated hydrocarbon group (e.g., saturated hydrocarbylene group, trivalent saturated hydrocarbon group or tetravalent saturated hydrocarbon group), or C.sub.6-C.sub.30 arylene group. The saturated hydrocarbon group may be straight, branched or cyclic. L.sup.B is C(O)O, NHC(O)O or NHC(O)NH.

[0090] Examples of the crosslinking acetal groups having formulae (AL-2a) and (AL-2b) include groups having the formulae (AL-2)-70 to (AL-2)-77.

##STR00144##

[0091] In formula (AL-3), R.sup.L5 is hydrogen or a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. R.sup.L6 and R.sup.L7 are each independently a C.sub.1-C.sub.20 hydrocarbyl group which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. The hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic and examples thereof include C.sub.1-C.sub.20 alkyl groups, C.sub.3-C.sub.20 cyclic saturated hydrocarbyl groups, C.sub.2-C.sub.20 alkenyl groups, C.sub.3-C.sub.20 cyclic unsaturated hydrocarbyl groups, and C.sub.6-C.sub.10 aryl groups. A pair of R.sup.L5 and R.sup.L6, R.sup.L5 and R.sup.L7, or R.sup.L6 and R.sup.L7 may bond together to form a C.sub.3-C.sub.20 aliphatic ring with the carbon atom to which they are attached.

[0092] Examples of the group having formula (AL-3) include tert-butyl, 1,1-diethylpropyl, 1-ethylnorbornyl, 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-isopropylcyclopentyl, 1-ethylcyclohexyl, 2-(2-methyl) adamantyl, 2-(2-ethyl) adamantyl, and tert-pentyl.

[0093] Examples of the group having formula (AL-3) also include groups having the formulae (AL-3)-1 to (AL-3)-22.

##STR00145## ##STR00146## ##STR00147##

[0094] In formulae (AL-3)-1 to (AL-3)-22, R.sup.L14 is each independently hydrogen, a C.sub.1-C.sub.8 aliphatic hydrocarbyl group or C.sub.6-C.sub.20 aryl group. R.sup.L15 and R.sup.L17 are each independently hydrogen or a C.sub.1-C.sub.20 saturated hydrocarbyl group. R.sup.L16 is a C.sub.6-C.sub.20 aryl group. The saturated hydrocarbyl group may be straight, branched or cyclic. Typical of the aryl group is phenyl. R.sup.L18 is fluorine, iodine, nitro or trifluoromethyl. R.sup.L19 is each independently hydrogen, fluorine, iodine, nitro, C.sub.1-C.sub.8 saturated hydrocarbyl group, or C.sub.1-C.sub.8 saturated hydrocarbyloxy group. The subscript f is an integer of 1 to 5.

[0095] Other examples of the group having formula (AL-3) include groups having the formulae (AL-3)-23 and (AL-3)-24. With these acid labile groups, the base polymer may be crosslinked within the molecule or between molecules.

##STR00148##

[0096] In formulae (AL-3)-23 and (AL-3)-24, R.sup.L14 is as defined above. R.sup.L20 is a C.sub.1-C.sub.20 (g+1)-valent saturated or unsaturated hydrocarbylene group or C.sub.6-C.sub.20 (g+1)-valent arylene group, which may contain a heteroatom such as oxygen, sulfur or nitrogen. The saturated or unsaturated hydrocarbylene group may be straight, branched or cyclic, and g is an integer of 1 to 3.

[0097] Also included in the acid labile group represented by R.sup.11 and R.sup.12 are acid labile groups containing an aromatic group as described in JP 5407941, JP 5434983, JP 5565293, JP 5655755, and JP 5655756.

[0098] The base polymer may comprise repeat units (c) having a phenolic hydroxy group as an adhesive group. Examples of suitable monomers from which repeat units (c) are derived are given below, but not limited thereto. Herein R.sup.A is as defined above.

##STR00149## ##STR00150##

[0099] The base polymer may further comprise repeat units (d) having another adhesive group selected from hydroxy group (other than the foregoing phenolic hydroxy), lactone ring, sultone ring, ether bond, ester bond, sulfonate ester bond, carbonyl group, sulfonyl group, cyano group, and carboxy group. Examples of suitable monomers from which repeat units (d) are derived are given below, but not limited thereto. Herein R.sup.A is as defined above.

##STR00151## ##STR00152## ##STR00153## ##STR00154## ##STR00155## ##STR00156## ##STR00157## ##STR00158## ##STR00159## ##STR00160## ##STR00161## ##STR00162## ##STR00163##

##STR00164## ##STR00165## ##STR00166## ##STR00167## ##STR00168## ##STR00169##

[0100] In another preferred embodiment, the base polymer may further comprise repeat units (e) derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, and norbornadiene, or derivatives thereof. Suitable monomers are exemplified below.

##STR00170##

[0101] The base polymer may further comprise repeat units (f) which are derived from styrene, vinylnaphthalene, vinylanthracene, vinylpyrene, methyleneindene, vinylpyridine, vinylcarbazole, or derivatives thereof.

[0102] The base polymer for formulating the positive resist composition comprises repeat units (a) and repeat units (b1) or (b2) having an acid labile group as essential component and additional repeat units (c), (d), (e), and (f) as optional components. A fraction of units (a), (b1), (b2), (c), (d), (e), and (f) is: preferably 0<a0.5, 0b1<1.0, 0b2<1.0, 0<b1+b2<1.0, 0c0.9, 0d0.9, 0e0.8, and 0f0.8; more preferably 0.02a 0.4, 0b10.9, 0b20.9, 0.1b1+b20.9, 0c0.8, 0d0.8, 0e0.7, and 0f0.7; and even more preferably 0.05a0.35, 0b10.8, 0b20.8, 0.1b1+b2 0.8, 0c0.75, 0d0.75, 0e0.6, and 0f0.6. Notably, a+b1+b2+c+d+e+f=1.0.

[0103] For the base polymer for formulating the negative resist composition, an acid labile group is not necessarily essential. The base polymer comprises repeat units (a) and (c), and optionally repeat units (d), (e), and/or (f). A fraction of these units is: preferably 0<a0.5, 0<c1.0, 0d0.9, 0e0.8, and 0f0.8; more preferably 0.02a0.4, 0.2c 1.0, 0d0.8, 0e0.7, and 0f0.7; and even more preferably 0.05a0.35, 0.3c1.0, 0d0.75, 0e0.6, and 0f0.6. Notably, a+c+d+e+f=1.0.

[0104] The base polymer may be synthesized by any desired methods, for example, by dissolving one or more monomers selected from the monomers corresponding to the foregoing repeat units in an organic solvent, adding a radical polymerization initiator thereto, and heating for polymerization. Examples of the organic solvent which can be used for polymerization include toluene, benzene, tetrahydrofuran (THF), diethyl ether, and dioxane. Examples of the polymerization initiator used herein include 2,2-azobisisobutyronitrile (AIBN), 2,2-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. Preferably, the reaction temperature is 50 to 80 C. and the reaction time is 2 to 100 hours, more preferably 5 to 20 hours.

[0105] Where a monomer having a hydroxy group is copolymerized, the hydroxy group may be replaced by an acetal group susceptible to deprotection with acid, typically ethoxyethoxy, prior to polymerization, and the polymerization be followed by deprotection with weak acid and water. Alternatively, the hydroxy group may be replaced by an acetyl, formyl, pivaloyl or similar group prior to polymerization, and the polymerization be followed by alkaline hydrolysis.

[0106] When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, an alternative method is possible. Specifically, acetoxystyrene or acetoxyvinylnaphthalene is used instead of hydroxystyrene or hydroxyvinylnaphthalene, and after polymerization, the acetoxy group is deprotected by alkaline hydrolysis, for thereby converting the polymer product to hydroxystyrene or hydroxyvinylnaphthalene. For alkaline hydrolysis, a base such as aqueous ammonia or triethylamine may be used. Preferably the reaction temperature is 0 C. to 100 C., more preferably 0 C. to 60 C., and the reaction time is 0.2 to 100 hours, more preferably 0.5 to 20 hours.

[0107] The base polymer should preferably have a weight average molecular weight (Mw) in the range of 1,000 to 500,000, and more preferably 2,000 to 30,000, as measured by GPC versus polystyrene standards using tetrahydrofuran (THF) solvent. A Mw in the range ensures that the resist film has heat resistance and high solubility in alkaline developer.

[0108] If a base polymer has a wide molecular weight distribution or dispersity (Mw/Mn), which indicates the presence of lower and higher molecular weight polymer fractions, there is a possibility that foreign matter is left on the pattern or the pattern profile is degraded. The influences of Mw and Mw/Mn become stronger as the pattern rule becomes finer. Therefore, the base polymer should preferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially 1.0 to 1.5, in order to provide a resist composition suitable for micropatterning to a small feature size.

[0109] It is understood that a blend of two or more polymers which differ in compositional ratio, Mw or Mw/Mn is acceptable.

[Organic Solvent]

[0110] An organic solvent may be added to the resist composition. The organic solvent used herein is not particularly limited as long as the foregoing and other components are soluble therein. Examples of the organic solvent are described in JP-A 2008-111103, paragraphs [0144]-[0145] (U.S. Pat. No. 7,537,880). 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, ethyl pyruvate, butyl acetate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as -butyrolactone, which may be used alone or in admixture.

[0111] The organic solvent is preferably added in an amount of 100 to 10,000 parts, and more preferably 200 to 8,000 parts by weight per 100 parts by weight of the base polymer.

[Quencher]

[0112] The resist composition may comprise a quencher. As used herein, the quencher refers to a compound capable of trapping the acid generated from the acid generator for thereby preventing the acid from diffusing to the unexposed region.

[0113] 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 group, ether bond, ester bond, lactone ring, cyano group, or sulfonic ester bond as described in U.S. Pat. No. 7,537,880 (JP-A 2008-111103, paragraphs [0146]-[0164]), and compounds having a carbamate bond as described in JP 3790649. Addition of a basic compound is effective for further suppressing the diffusion rate of acid in the resist film or correcting the pattern profile.

[0114] Suitable quenchers also include onium salts such as sulfonium salts, iodonium salts and ammonium salts of sulfonic acids which are not fluorinated at -position, carboxylic acids or fluorinated alkoxides, as described in U.S. Pat. No. 8,795,942 (JP-A 2008-158339). While an -fluorinated sulfonic acid, imide acid, and methide acid are necessary to deprotect the acid labile group of carboxylic acid ester, an -non-fluorinated sulfonic acid, carboxylic acid or fluorinated alcohol is released by salt exchange with an -non-fluorinated onium salt. The -non-fluorinated sulfonic acid, carboxylic acid and fluorinated alcohol function as a quencher because they do not induce deprotection reaction.

[0115] Exemplary such quenchers include a compound (onium salt of -non-fluorinated sulfonic acid) having the formula (1), a compound (onium salt of carboxylic acid) having the formula (2), and a compound (onium salt of alkoxide) having the formula (3).

##STR00171##

[0116] In formula (1), R.sup.101 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 sulfo group is substituted by fluorine or fluoroalkyl moiety.

[0117] The C.sub.1-C.sub.40 hydrocarbyl group 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, isobutyl, 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, 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.

[0118] 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 moiety, cyano moiety, carbonyl moiety, ether bond, ester bond, sulfonic 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, 4-hydroxyphenyl, alkoxyphenyl groups such as 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.

[0119] In formula (2), R.sup.102 is a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. Examples of the hydrocarbyl group R.sup.102 are as exemplified above for the hydrocarbyl group R.sup.101. Also included are fluorinated alkyl groups such as trifluoromethyl, trifluoroethyl, 2,2,2-trifluoro-1-methyl-1-hydroxyethyl, 2,2,2-trifluoro-1-(trifluoromethyl)-1-hydroxyethyl, and fluorinated aryl groups such as pentafluorophenyl and 4-trifluoromethylphenyl.

[0120] In formula (3), R.sup.103 is a C.sub.1-C.sub.8 saturated hydrocarbyl group containing at least 3 fluorine atoms or a C.sub.6-C.sub.10 aryl group containing at least 3 fluorine atoms, the hydrocarbyl and aryl groups optionally containing a nitro moiety.

[0121] In formulae (1), (2) and (3), Mq.sup.+ is an onium cation. The onium cation is preferably a sulfonium, iodonium or ammonium cation, with the sulfonium cation being more preferred. Suitable sulfonium cations are as exemplified for the sulfonium cation M.sup.+ in formula (a).

[0122] A sulfonium salt of iodized benzene ring-containing carboxylic acid having the formula (4) is also useful as the quencher.

##STR00172##

[0123] In formula (4), x is an integer of 1 to 5, y is an integer of 0 to 3, and z is an integer of 1 to 3.

[0124] In formula (4), R.sup.111 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.111A)C(O)R.sup.111B, or N(R.sup.111A)C(O)OR.sup.111B. R.sup.111A is hydrogen or a C.sub.1-C.sub.6 saturated hydrocarbyl group. R.sup.111B 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.111 may be identical or different when y and/or z is 2 or 3.

[0125] In formula (4), L.sup.1 is a single bond, or a C.sub.1-C.sub.20 (z+1)-valent linking group which may contain an ether bond, carbonyl, ester bond, amide bond, sultone ring, lactam ring, carbonate bond, halogen, hydroxy or carboxy moiety or a mixture thereof. The saturated hydrocarbyl, saturated hydrocarbyloxy, saturated hydrocarbylcarbonyloxy and saturated hydrocarbylsulfonyloxy groups may be straight, branched or cyclic.

[0126] In formula (4), R.sup.112, R.sup.113 and R.sup.114 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 are as exemplified for the hydrocarbyl groups R.sup.2 to R.sup.6 in formulae (a1) and (a2).

[0127] Examples of the compound having formula (4) include those described in U.S. Pat. No. 10,295,904 (JP-A 2017-219836) and US20210188770 (JP-A 2021-091666).

[0128] 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 film surface 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.

[0129] Other useful quenchers include sulfonium salts of betaine structure as described in JP 6848776 and JP-A 2020-037544, fluorine-free methide acids as described in JP-A 2020-055797, sulfonium salts of sulfonamide as described in JP 5807552, and sulfonium salts of iodized sulfonamide, phenols, halogens or acid generators capable of generating carbonic acid as described in JP-A 2019-211751.

[0130] The quencher is preferably added in an amount of 0 to 5 parts, more preferably 0 to 4 parts by weight per 100 parts by weight of the base polymer. The quencher may be used alone or in admixture.

Other Components

[0131] In addition to the foregoing components, the resist composition may contain other components such as an acid generator, surfactant, dissolution inhibitor, crosslinker, water repellency improver and acetylene alcohol. Each of the other components may be used alone or in admixture.

[0132] The acid generator is typically a compound (PAG) capable of generating an acid upon exposure to actinic ray or radiation. Although the PAG used herein may be any compound capable of generating an acid upon exposure to high-energy radiation, those compounds capable of generating sulfonic acid, imide acid (imidic acid) or methide acid are preferred. Suitable PAGs include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acid generators. Exemplary PAGs are described in JP-A 2008-111103, paragraphs [0122]-[0142] (U.S. Pat. No. 7,537,880), JP-A 2018-005224, and JP-A 2018-025789. The acid generator is preferably used in an amount of 0 to 200 parts, more preferably 0.1 to 100 parts by weight per 100 parts by weight of the base polymer.

[0133] Exemplary surfactants are described in JP-A 2008-111103, paragraphs [0165]-[0166]. Inclusion of a surfactant may improve or control the coating characteristics of the resist composition. The surfactant is preferably added in an amount of 0.0001 to 10 parts by weight per 100 parts by weight of the base polymer.

[0134] In the embodiment wherein the resist composition is of positive tone, the inclusion of a dissolution inhibitor may lead to an increased difference in dissolution rate between exposed and unexposed areas and a further improvement in resolution. The dissolution inhibitor is typically a compound having at least two phenolic hydroxy groups on the molecule, in which an average of from 0 to 100 mol % of all the hydrogen atoms on the phenolic hydroxy groups are replaced by acid labile groups or a compound having at least one carboxy group on the molecule, in which an average of 50 to 100 mol % of all the hydrogen atoms on the carboxy groups are replaced by acid labile groups, both the compounds having a molecular weight of 100 to 1,000, and preferably 150 to 800. Typical are bisphenol A, trisphenol, phenolphthalein, cresol novolac, naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic acid derivatives in which the hydrogen atom on the hydroxy or carboxy group is replaced by an acid labile group, as described in U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs [0155]-[0178]).

[0135] The dissolution inhibitor is preferably added in an amount of 0 to 50 parts, more preferably 5 to 40 parts by weight per 100 parts by weight of the base polymer.

[0136] In the case of negative resist compositions, a negative pattern may be formed by adding a crosslinker to reduce the dissolution rate of exposed area. Suitable crosslinkers which can be used herein include epoxy compounds, melamine compounds, guanamine compounds, glycoluril compounds and urea compounds having substituted thereon at least one group selected from among methylol, alkoxymethyl and acyloxymethyl groups, isocyanate compounds, azide compounds, and compounds having a double bond such as an alkenyloxy group. These compounds may be used as an additive or introduced into a polymer side chain as a pendant. Hydroxy-containing compounds may also be used as the crosslinker.

[0137] Suitable epoxy compounds include tris(2,3-epoxypropyl) isocyanurate, trimethylolmethane triglycidyl ether, trimethylolpropane triglycidyl ether, and triethylolethane triglycidyl ether. Examples of the melamine compound include hexamethylol melamine, hexamethoxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups methoxymethylated and mixtures thereof, hexamethoxyethyl melamine, hexaacyloxymethyl melamine, hexamethylol melamine compounds having 1 to 6 methylol groups acyloxymethylated and mixtures thereof. Examples of the guanamine compound include tetramethylol guanamine, tetramethoxymethyl guanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethoxyethyl guanamine, tetraacyloxyguanamine, tetramethylol guanamine compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the glycoluril compound include tetramethylol glycoluril, tetramethoxyglycoluril, tetramethoxymethyl glycoluril, tetramethylol glycoluril compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, tetramethylol glycoluril compounds having 1 to 4 methylol groups acyloxymethylated and mixtures thereof. Examples of the urea compound include tetramethylol urea, tetramethoxymethyl urea, tetramethylol urea compounds having 1 to 4 methylol groups methoxymethylated and mixtures thereof, and tetramethoxyethyl urea.

[0138] Suitable isocyanate compounds include tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate and cyclohexane diisocyanate. Suitable azide compounds include 1,1-biphenyl-4,4-bisazide, 4,4-methylidenebisazide, and 4,4-oxybisazide. Examples of the alkenyloxy group-containing compound include ethylene glycol divinyl ether, triethylene glycol divinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol divinyl ether, tetramethylene glycol divinyl ether, neopentyl glycol divinyl ether, trimethylol propane trivinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, sorbitol tetravinyl ether, sorbitol pentavinyl ether, and trimethylol propane trivinyl ether.

[0139] In the negative resist composition, the crosslinker is preferably added in an amount of 0.1 to 50 parts, more preferably 1 to 40 parts by weight per 100 parts by weight of the base polymer.

[0140] To the resist composition, a water repellency improver may also be added for improving the water repellency on surface of a resist film. The water repellency improver may be used in the topcoatless immersion lithography. Suitable water repellency improvers include polymers having a fluoroalkyl group and polymers having a specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue and are described in JP-A 2007-297590 and JP-A 2008-111103, for example. The water repellency improver to be added to the resist composition should be soluble in alkaline developers and organic solvent developers. The water repellency improver of specific structure with a 1,1,1,3,3,3-hexafluoro-2-propanol residue is well soluble in the developer. A polymer having an amino group or amine salt copolymerized as repeat units may serve as the water repellent additive and is effective for preventing evaporation of acid during PEB, thus preventing any hole pattern opening failure after development. An appropriate amount of the water repellency improver is 0 to 20 parts, preferably 0.5 to 10 parts by weight per 100 parts by weight of the base polymer.

[0141] Also, an acetylene alcohol may be blended in the resist composition. Suitable acetylene alcohols are described in JP-A 2008-122932, paragraphs [0179]-[0182]. An appropriate amount of the acetylene alcohol blended is 0 to 5 parts by weight per 100 parts by weight of the base polymer.

[Process]

[0142] The resist composition is used in the fabrication of various integrated circuits. Pattern formation using the resist composition may be performed by well-known lithography processes. The process generally involves 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. If necessary, any additional steps may be added.

[0143] Specifically, the resist composition is first applied onto a substrate on which an integrated circuit is to be formed (e.g., Si, SiO.sub.2, SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrate on which a mask circuit is to be formed (e.g., Cr, CrO, CrON, MoSi.sub.2, or SiO.sub.2) by a suitable coating technique such as spin coating, roll coating, flow coating, dipping, spraying or doctor coating. The coating is prebaked on a hotplate preferably at a temperature of 60 to 150 C. for 10 seconds to 30 minutes, more preferably at 80 to 120 C. for 30 seconds to 20 minutes. The resulting resist film is generally 0.01 to 2 m thick.

[0144] The resist film is then exposed to a desired pattern of high-energy radiation such as UV, deep-UV, EB, EUV of wavelength 3 to 15 nm, x-ray, soft x-ray, excimer laser light, -ray or synchrotron radiation. When UV, deep-UV, EUV, x-ray, soft x-ray, excimer laser light, -ray or synchrotron radiation is used as the high-energy radiation, the resist film is exposed thereto through a mask having a desired pattern in a dose of preferably about 1 to 200 mJ/cm.sup.2, more preferably about 10 to 100 mJ/cm.sup.2. When EB is used as the high-energy radiation, the resist film is exposed thereto directly or through a mask having a desired pattern in a dose of preferably about 0.1 to 300 C/cm.sup.2, more preferably about 0.5 to 200 C/cm.sup.2. It is appreciated that the inventive resist composition is suited in micropatterning using KrF excimer laser, ArF excimer laser, EB, EUV, x-ray, soft x-ray, -ray or synchrotron radiation, especially in micropatterning using EB or EUV.

[0145] After the exposure, the resist film may be baked (PEB) on a hotplate or in an oven preferably at 30 to 150 C. for 10 seconds to 30 minutes, more preferably at 50 to 120 C. for 30 seconds to 20 minutes.

[0146] After the exposure or PEB, the resist film is developed in a developer in the form of an aqueous base solution for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes by conventional techniques such as dip, puddle and spray techniques. A typical developer is a 0.1 to 10 wt %, preferably 2 to 5 wt % aqueous solution of tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), or tetrabutylammonium hydroxide (TBAH). In the case of positive tone, the resist film in the exposed area is dissolved in the developer whereas the resist film in the unexposed area is not dissolved. In this way, the desired positive pattern is formed on the substrate. In the case of negative tone, inversely the resist film in the exposed area is insolubilized whereas the resist film in the unexposed area is dissolved away.

[0147] In an alternative embodiment, a negative pattern can be obtained from the positive resist composition comprising a base polymer containing acid labile groups by effecting organic solvent development. The developer used herein is preferably selected from among 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, methyl propionate, ethyl propionate, ethyl 3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and 2-phenylethyl acetate, and mixtures thereof.

[0148] At the end of development, the resist film is rinsed. As the rinsing liquid, a solvent which is miscible with the developer and does not dissolve the resist film is preferred. Suitable solvents include alcohols of 3 to 10 carbon atoms, ether compounds of 8 to 12 carbon atoms, alkanes, alkenes, and alkynes of 6 to 12 carbon atoms, and aromatic solvents. Specifically, suitable alcohols of 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, t-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and 1-octanol. Suitable ether compounds of 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-s-butyl ether, di-n-pentyl ether, diisopentyl ether, di-s-pentyl ether, di-t-pentyl ether, and di-n-hexyl ether. Suitable alkanes of 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, and cyclononane. Suitable alkenes of 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, and cyclooctene. Suitable alkynes of 6 to 12 carbon atoms include hexyne, heptyne, and octyne. Suitable aromatic solvents include toluene, xylene, ethylbenzene, isopropylbenzene, t-butylbenzene and mesitylene.

[0149] Rinsing is effective for minimizing the risks of resist pattern collapse and defect formation. However, rinsing is not essential. If rinsing is omitted, the amount of solvent used may be reduced.

[0150] A hole or trench pattern after development may be shrunk by the thermal flow, RELACS or DSA process. A hole pattern is shrunk by coating a shrink agent thereto, and baking such that the shrink agent may undergo crosslinking at the resist surface as a result of the acid catalyst diffusing from the resist layer during bake, and the shrink agent may attach to the sidewall of the hole pattern. The bake is preferably at a temperature of 70 to 180 C., more preferably 80 to 170 C., for a time of 10 to 300 seconds. The extra shrink agent is stripped and the hole pattern is shrunk.

EXAMPLES

[0151] Examples of the invention are given below by way of illustration and not by way of limitation. All parts are by weight (pbw). THF stands for tetrahydrofuran.

[0152] Monomers PM-1 to PM-16, cPM-1, cPM-2, AM-1 to AM-5, and FM-1 as shown below were used in the synthesis of base polymers. It is noted that Monomers PM-1 to PM-16 were synthesized by ion exchange between an ammonium salt of an iodized benzenesulfonic acid providing the anion shown below and a sulfonium chloride providing the cation shown below. It is noted that Mw of a polymer is measured versus polystyrene standard by GPC using THF.

##STR00173## ##STR00174## ##STR00175## ##STR00176## ##STR00177## ##STR00178## ##STR00179##

[Synthesis Example 1] Synthesis of Polymer P-1

[0153] A 2-L flask was charged with 8.4 g of 1-methyl-1-cyclopentyl methacrylate, 4.8 g of 4-hydroxystyrene, 8.1 g of Monomer PM-1, and 40 g of THF solvent. The reactor was cooled at 70 C. in nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of azobisisobutyronitrile (AIBN) as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of isopropyl alcohol (IPA) for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-1. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00180##

[Synthesis Example 2] Synthesis of Polymer P-2

[0154] A 2-L flask was charged with 9.0 g of 1-vinyl-1-cyclopentyl methacrylate, 4.8 g of 3-hydroxystyrene, 9.8 g of Monomer PM-2, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-2. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00181##

[Synthesis Example 3] Synthesis of Polymer P-3

[0155] A 2-L flask was charged with 11.1 g of Monomer AM-1, 4.8 g of 3-hydroxystyrene, 11.3 g of Monomer PM-3, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-3. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00182##

[Synthesis Example 4] Synthesis of Polymer P-4

[0156] A 2-L flask was charged with 8.1 g of Monomer AM-2, 2.7 g of Monomer AM-4, 4.8 g of 3-hydroxystyrene, 10.4 g of Monomer PM-4, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-4. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00183##

[Synthesis Example 5] Synthesis of Polymer P-5

[0157] A 2-L flask was charged with 11.6 g of Monomer AM-3, 5.2 g of 3-hydroxystyrene, 8.7 g of Monomer PM-5, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-5. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00184##

[Synthesis Example 6] Synthesis of Polymer P-6

[0158] A 2-L flask was charged with 8.3 g of Monomer AM-5, 4.8 g of 3-hydroxystyrene, 10.2 g of Monomer PM-6, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-6. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00185##

[Synthesis Example 7] Synthesis of Polymer P-7

[0159] A 2-L flask was charged with 11.1 g of Monomer AM-1, 3.4 g of 3-hydroxystyrene, 3.2 g of Monomer FM-1, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-7. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00186##

[Synthesis Example 8] Synthesis of Polymer P-8

[0160] A 2-L flask was charged with 11.1 g of Monomer AM-1, 4.8 g of 3-hydroxystyrene, 9.9 g of Monomer PM-8, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-8. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00187##

[Synthesis Example 9] Synthesis of Polymer P-9

[0161] A 2-L flask was charged with 12.1 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 10.5 g of Monomer PM-9, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-9. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00188##

[Synthesis Example 10] Synthesis of Polymer P-10

[0162] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 10.4 g of Monomer PM-10, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-10. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00189##

[Synthesis Example 11] Synthesis of Polymer P-11

[0163] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 11.0 g of Monomer PM-11, and 40 g of THE solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-11. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00190##

[Synthesis Example 12] Synthesis of Polymer P-12

[0164] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 10.2 g of Monomer PM-12, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-12. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00191##

[Synthesis Example 13] Synthesis of Polymer P-13

[0165] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 10.5 g of Monomer PM-13, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-13. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00192##

[Synthesis Example 14] Synthesis of Polymer P-14

[0166] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 4-hydroxystyrene, 10.7 g of Monomer PM-14, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-14. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00193##

[Synthesis Example 15] Synthesis of Polymer P-15

[0167] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 3-hydroxystyrene, 7.2 g of Monomer PM-15, and 40 g of THF solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-15. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00194##

[Synthesis Example 16] Synthesis of Polymer P-16

[0168] A 2-L flask was charged with 12.0 g of Monomer AM-1, 4.8 g of 3-hydroxystyrene, 6.8 g of Monomer PM-16, and 40 g of THE solvent. The reactor was cooled at 70 C. in a nitrogen atmosphere, after which vacuum pumping and nitrogen blow were repeated three times. The reactor was warmed up to room temperature, whereupon 1.2 g of AIBN as polymerization initiator was added. The reactor was heated at 60 C. and held at the temperature for 15 hours for reaction. The reaction solution was poured into 1 L of IPA for precipitation. The resulting white solid was collected by filtration and dried in vacuum at 60 C., obtaining Polymer P-16. The polymer was analyzed for composition by .sup.13C- and .sup.1H-NMR spectroscopy and for Mw and Mw/Mn by GPC.

##STR00195##

[Comparative Synthesis Example 1] Synthesis of Comparative Polymer cP-1

[0169] Comparative Polymer cP-1 was synthesized by the same procedure as in Synthesis Example 1 aside from using Monomer cPM-1 instead of Monomer PM-1.

##STR00196##

[Comparative Synthesis Example 2] Synthesis of Comparative Polymer cP-2

[0170] Comparative Polymer cP-2 was synthesized by the same procedure as in Synthesis Example 1 aside from using Monomer cPM-2 instead of Monomer PM-1.

##STR00197##

[Examples 1 to 18 and Comparative Examples 1 and 2] Preparation and Evaluation of Resist Compositions

(1) Preparation of Resist Compositions

[0171] Resist compositions were prepared by dissolving the selected components in a solvent in accordance with the recipe shown in Table 1, and filtering through a filter having a pore size of 0.2 m.

[0172] The components in Table 1 are as identified below.

Organic Solvents:

[0173] PGMEA (propylene glycol monomethyl ether acetate) [0174] EL (ethyl lactate) [0175] DAA (diacetone alcohol)

Acid Generators: PAG-1 and PAG-2

##STR00198##

Quenchers: Q-1 to Q-5

##STR00199##

(2) EUV Lithography Test

[0176] Each of the resist compositions in Table 1 was spin coated on a silicon substrate having a 20-nm coating of silicon-containing spin-on hard mask SHB-A940 (Shin-Etsu Chemical Co., Ltd., silicon content 43 wt %) and prebaked on a hotplate at 105 C. for 60 seconds to form a resist film of 60 nm thick. Using an EUV scanner NXE3400 (ASML, NA 0.33, 0.9/0.6, quadrupole illumination), the resist film was exposed to EUV through a mask bearing a hole pattern having a pitch (on-wafer size) of 40 nm+20% bias. The resist film was baked (PEB) on a hotplate at the temperature shown in Table 1 for 60 seconds and developed in a 2.38 wt % TMAH aqueous solution for 30 seconds to form a hole pattern having a size of 20 nm.

[0177] The resist pattern was observed under CD-SEM (CG-6300, Hitachi High-Technologies Corp.). The exposure dose that provides a hole pattern of 20 nm size is reported as sensitivity. The size of 50 holes was measured, from which a 3-fold value (36) of the standard deviation (o) was computed and reported as CDU.

[0178] The resist composition is shown in Table 1 together with the sensitivity and CDU of EUV lithography.

TABLE-US-00001 TABLE 1 Polymer Acid generator Quencher Organic solvent PEB temp. Sensitivity CDU (pbw) (pbw) (pbw) (pbw) ( C.) (mJ/cm.sup.2) (nm) Example 1 P-1 (100) Q-1 (5.38) PGMEA (500) 100 27 2.7 EL (2000) 2 P-2 (100) Q-1 (5.38) PGMEA (500) 95 26 2.6 EL (2000) 3 P-3 (100) Q-1 (5.38) PGMEA (500) 95 27 2.6 EL (2000) 4 P-4 (100) Q-2 (4.54) PGMEA (2000) 100 24 2.6 DAA (500) 5 P-5 (100) Q-3 (7.06) PGMEA (2000) 100 24 2.5 DAA (500) 6 P-6 (100) Q-4 (5.26) PGMEA (2000) 95 26 2.6 DAA (500) 7 P-7 (100) Q-4 (5.26) PGMEA (2000) 95 28 2.6 DAA (500) 8 P-8 (100) Q-4 (5.26) PGMEA (2000) 95 27 2.7 DAA (500) 9 P-9 (100) Q-4 (5.26) PGMEA (2000) 95 23 2.8 DAA (500) 10 P-10 (100) Q-4 (5.26) PGMEA (2000) 95 25 2.7 DAA (500) 11 P-11 (100) Q-4 (5.26) PGMEA (2000) 95 28 2.8 DAA (500) 12 P-12 (100) Q-4 (5.26) PGMEA (2000) 95 25 2.7 DAA (500) 13 P-13 (100) Q-4 (5.26) PGMEA (2000) 95 28 2.8 DAA (500) 14 P-14 (100) Q-4 (5.26) PGMEA (2000) 95 29 2.7 DAA (500) 15 P-15 (100) Q-4 (5.26) PGMEA (2000) 95 29 2.8 DAA (500) 16 P-16 (100) Q-4 (5.26) PGMEA (2000) 95 30 2.8 DAA (500) 17 P-1 (100) PAG-1 (9.72) Q-4 (5.26) PGMEA (2000) 90 22 2.8 DAA (500) 18 P-1 (100) PAG-2 (9.88) Q-5 (5.43) PGMEA (2000) 90 22 2.7 DAA (500) Comparative 1 cP-1 (100) Q-1 (5.28) PGMEA (2000) 95 32 3.2 Example DAA (500) 2 cP-2 (100) Q-1 (5.28) PGMEA (2000) 95 30 3.0 DAA (500)

[0179] It is demonstrated in Table 1 that resist compositions comprising a base polymer possessing a sulfonium or iodonium salt structure having an iodized arylsulfonic acid anion attached to its backbone have a high sensitivity and form patterns with improved CDU.

[0180] Japanese Patent Application Nos. 2023-182957 and 2024-063766 are incorporated herein by reference. 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.