RESIST PATTERN FORMING PROCESS

Abstract

A resist pattern is formed by (i) applying a resist composition comprising a hypervalent iodine compound, a carboxylic acid, and a solvent onto a substrate or an underlying film to form a resist film, (ii) exposing the resist film to high-energy radiation, (iii) baking the exposed resist film, and (iv) dry etching the baked resist film for development.

Claims

1. A resist pattern forming process comprising the steps of: (i) applying a resist composition onto a substrate or a substrate having an underlying film deposited thereon to form a resist film thereon, the resist composition comprising at least one hypervalent iodine compound selected from a hypervalent iodine compound having the formula (1) and a hypervalent iodine compound having the formula (2), a carboxylic acid, and a solvent, (ii) exposing the resist film to high-energy radiation, (iii) baking the exposed resist film, and (iv) dry etching the baked resist film for development to form a resist pattern, ##STR00089## wherein m is 0 or 1, n is an integer of 0 to 4 when m=0 and an integer of 0 to 6 when m=1, k is an integer of 0 to 5, R.sup.1 is halogen or a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom, R.sup.2 is halogen or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom; when n is 2 or more, a plurality of R.sup.2 may be identical or different and a plurality of R.sup.2 may bond together to form a ring with the carbon atoms on the aromatic ring to which they are attached, R.sup.3 is carbonyl or a C.sub.1-C.sub.10 hydrocarbylene group which may contain a heteroatom, *1 and *2 each designate a point of attachment to the carbon atom on the aromatic ring in the formula, *1 and *2 are attached to vicinal carbon atoms on the aromatic ring, R.sup.4 and R.sup.5 are each independently halogen or a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom, R.sup.4 and R.sup.5 may bond together to form a ring with the carbon atoms to which they are attached and the intervenient atoms, and R.sup.6 is halogen or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom; when k is 2, 3, 4 or 5, a plurality of R.sup.6 may be identical or different and a plurality of R.sup.6 may bond together to form a ring with the carbon atoms on the aromatic ring to which they are attached.

2. The process of claim 1 wherein the carboxylic acid has the formula (3): ##STR00090## wherein p is an integer of 1 to 4, R.sup.11 is a C.sub.1-C.sub.40 p-valent hydrocarbon group or C.sub.2-C.sub.40 p-valent heterocyclic group, R.sup.11 may also be an ether bond, carbonyl group, azo group, thioether bond, carbonate bond, carbamate bond, sulfinyl group or sulfonyl group when p=2, some or all of the hydrogen atoms in the p-valent hydrocarbon group or p-valent heterocyclic group may be substituted by a heteroatom-containing moiety, and some CH.sub.2 in the p-valent hydrocarbon group may be replaced by a heteroatom-containing moiety, R.sup.12 is a single bond or C.sub.1-C.sub.20 hydrocarbylene group, some or all of the hydrogen atoms in the hydrocarbylene group may be substituted by a heteroatom-containing moiety, some CH.sub.2 in the hydrocarbylene group may be replaced by a heteroatom-containing moiety, and a plurality of R.sup.12 may be identical or different when p=2, 3 or 4.

3. The process of claim 1 wherein the high-energy radiation is i-line, KrF excimer laser, ArF excimer laser, EB or EUV.

4. The process of claim 1 wherein the dry etching step (iv) is carried out using a gas containing at least one of oxygen and tetrafluoromethane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0040] The terms a and an herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. As used herein, the notation (C.sub.n-C.sub.m) means a group containing from n to m carbon atoms per group. Me stands for methyl.

[0041] The abbreviations and acronyms have the following meaning. [0042] UV: ultraviolet radiation [0043] EUV: extreme ultraviolet [0044] EB: electron beam [0045] Mw: weight average molecular weight [0046] Mw/Mn: polydispersity index [0047] GPC: gel permeation chromatography [0048] PAB: post-apply bake [0049] PEB: post-exposure bake [0050] LWR: line width roughness [0051] CDU: critical dimension uniformity

[Resist Composition]

[0052] The resist pattern forming process of the invention uses a resist composition comprising a specific hypervalent iodine compound, a carboxylic acid, and a solvent.

[Hypervalent Iodine Compound]

[0053] The hypervalent iodine compound is a three-coordinate hypervalent iodine compound having the formula (1) or (2).

##STR00003##

[0054] In formula (1), m is 0 or 1. The subscript n is an integer of 0 to 4 when m=0 and an integer of 0 to 6 when m=1. The subscript n is preferably 0, 1, 2, 3 or 4, more preferably 0, 1, 2 or 3, even more preferably 0, 1 or 2, most preferably 0 or 1.

[0055] In formula (1), R.sup.1 is halogen or a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The C.sub.1-C.sub.10 hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. 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, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl, C.sub.3-C.sub.10 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0.sup.2,6]decanyl, and adamantyl, C.sub.2-C.sub.10 alkenyl groups such as vinyl and allyl, C.sub.6-C.sub.10 aryl groups such as phenyl and naphthyl, and combinations thereof. Also included are hydrocarbyl groups in which some or all of the hydrogen atoms are substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain hydroxy, cyano, halogen, carbonyl, ether bond, thioether bond, ester bond, sulfonic ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)). R.sup.1 is preferably a C.sub.1-C.sub.4 hydrocarbyl group or C.sub.1-C.sub.4 fluorinated hydrocarbyl group, more preferably a C.sub.1-C.sub.4 hydrocarbyl group.

[0056] In formula (1), R.sup.2 is 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. 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, and 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]decanyl, adamantyl, and adamantylmethyl, and C.sub.6-C.sub.40 aryl groups such as phenyl, naphthyl, and anthracenyl. Also included are hydrocarbyl groups in which some or all of the hydrogen atoms are substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain hydroxy, cyano, halogen, carbonyl, ether bond, thioether bond, ester bond, sulfonic ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)). When n is 2 or more, a plurality of R.sup.2 may be identical or different and a plurality of R.sup.2 may bond together to form a ring with the carbon atoms on the aromatic ring to which they are attached.

[0057] In formula (1), R.sup.3 is carbonyl or a C.sub.1-C.sub.10 hydrocarbylene group which may contain a heteroatom. The C.sub.1-C.sub.10 hydrocarbylene group may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.10 alkylene 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, 2-methylpropane-1,2-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, and decane-1,10-diyl; C.sub.3-C.sub.10 cyclic saturated hydrocarbylene groups such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, adamantanediyl, and tricyclo[5.2.1.0.sup.2,6]decanediyl; C.sub.2-C.sub.10 alkenylene groups such as vinylene and propynylene; C.sub.6-C.sub.10 arylene groups such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, and naphthylene; 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, 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, haloalkyl, halogen, carbonyl moiety, ether bond, thioether bond, ester bond, sulfonate ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)). R.sup.3 is preferably carbonyl, a C.sub.1-C.sub.4 hydrocarbylene group or C.sub.1-C.sub.4 fluorinated hydrocarbylene group.

[0058] In formula (1), *1 and *2 each designate a point of attachment to the carbon atom on the aromatic ring in the formula, with the proviso that *1 and *2 are attached to vicinal carbon atoms on the aromatic ring. It is contemplated that the combination of *1 and *2 with m includes the following four patterns.

##STR00004##

[0059] Herein n, R.sup.2 and R.sup.3 are as defined above. The broken line designates a point of attachment to R.sup.1C(O)O.

[0060] In formula (2), k is an integer of 0 to 5.

[0061] In formula (2), R.sup.4 and R.sup.5 are each independently halogen or a C.sub.1-C.sub.10 hydrocarbyl group which may contain a heteroatom. R.sup.4 and R.sup.5 may bond together to form a ring with the carbon atoms to which they are attached and the intervenient atoms. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. The C.sub.1-C.sub.10 hydrocarbyl group may be saturated or unsaturated and straight, branched or cyclic. 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, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl, C.sub.3-C.sub.10 cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, tricyclo[5.2.1.0.sup.2,6]decanyl, and adamantyl, C.sub.2-C.sub.10 alkenyl groups such as vinyl and allyl, C.sub.6-C.sub.10 aryl groups such as phenyl and naphthyl, and combinations thereof. Also included are hydrocarbyl groups in which some or all of the hydrogen atoms are substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain hydroxy, cyano, halogen, carbonyl, ether bond, thioether bond, ester bond, sulfonic ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)). R.sup.4 and R.sup.5 each are preferably a C.sub.1-C.sub.4 hydrocarbyl group or C.sub.1-C.sub.4 fluorinated hydrocarbyl group, more preferably a C.sub.1-C.sub.4 hydrocarbyl group.

[0062] In formula (2), R.sup.6 is halogen or a C.sub.1-C.sub.40 hydrocarbyl group which may contain a heteroatom. When k is 2, 3, 4 or 5, a plurality of R.sup.6 may be identical or different and a plurality of R.sup.6 may bond together to form a ring with the carbon atoms on the aromatic ring to which they are attached. Suitable halogen atoms include fluorine, chlorine, bromine and iodine. 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, and 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]decanyl, and adamantyl, C.sub.2-C.sub.40 alkenyl groups such as vinyl and allyl, C.sub.6-C.sub.40 aryl groups such as phenyl and naphthyl, and combinations thereof. Also included are hydrocarbyl groups in which some or all of the hydrogen atoms are substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, and some constituent CH.sub.2 is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain hydroxy, cyano, halogen, carbonyl, ether bond, thioether bond, ester bond, sulfonic ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)). R.sup.6 is preferably a C.sub.1-C.sub.4 hydrocarbyl group.

[0063] Examples of the hypervalent iodine compound having formula (1) are shown below, but not limited thereto.

##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## ##STR00043## ##STR00044##

##STR00045## ##STR00046## ##STR00047## ##STR00048## ##STR00049## ##STR00050## ##STR00051## ##STR00052## ##STR00053## ##STR00054## ##STR00055## ##STR00056##

[0064] Examples of the hypervalent iodine compound having formula (2) are shown below, but not limited thereto.

##STR00057## ##STR00058## ##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063## ##STR00064## ##STR00065## ##STR00066## ##STR00067## ##STR00068## ##STR00069## ##STR00070## ##STR00071## ##STR00072## ##STR00073## ##STR00074## ##STR00075## ##STR00076## ##STR00077## ##STR00078##

[Carboxylic Acid]

[0065] The carboxylic acid may be any of compounds generally defined as carboxylic acids in the organic chemistry, preferably a carboxylic acid having the formula (3).

##STR00079##

[0066] In formula (3), p is an integer of 1 to 4. R.sup.11 is a C.sub.1-C.sub.40 p-valent hydrocarbon group or C.sub.2-C.sub.40 p-valent heterocyclic group, R.sup.11 may also be an ether bond, carbonyl group, azo group, thioether bond, carbonate bond, carbamate bond, sulfinyl group or sulfonyl group when p=2. Some or all of the hydrogen atoms in the p-valent hydrocarbon group or p-valent heterocyclic group may be substituted by a heteroatom-containing moiety, and some CH.sub.2 in the p-valent hydrocarbon group may be replaced by a heteroatom-containing moiety. R.sup.12 is a single bond or C.sub.1-C.sub.20 hydrocarbylene group, some or all of the hydrogen atoms in the hydrocarbylene group may be substituted by a heteroatom-containing moiety, and some CH.sub.2 in the hydrocarbylene group may be replaced by a heteroatom-containing moiety. A plurality of R.sup.12 may be identical or different when p=2, 3 or 4.

[0067] The p-valent hydrocarbon group R.sup.11 may be saturated or unsaturated and straight, branched or cyclic. The p-valent hydrocarbon group is obtained by eliminating p number of hydrogen from a hydrocarbon. Examples of the hydrocarbon include C.sub.1-C.sub.40 alkanes, C.sub.2-C.sub.40 alkenes, C.sub.2-C.sub.40 alkynes, C.sub.3-C.sub.40 cyclic saturated hydrocarbons, C.sub.3-C.sub.40 cyclic unsaturated hydrocarbons, and C.sub.6-C.sub.40 aromatic hydrocarbons.

[0068] Exemplary of the C.sub.1-C.sub.40 alkanes are methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, and structural isomers thereof. Exemplary of the C.sub.2-C.sub.40 alkenes are ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, decene, and structural isomers thereof. Exemplary of the C.sub.2-C.sub.40 alkynes are acetylene, propyne, butyne, pentyne, hexyne, heptyne, octyne, nonyne, decyne, and structural isomers thereof. Exemplary of the C.sub.3-C.sub.40 cyclic saturated hydrocarbons are cyclopropane, cyclobutane, cyclohexane, cycloheptane, cyclooctane, adamantane, and norbornane. Exemplary of the C.sub.3-C.sub.40 cyclic unsaturated hydrocarbons are cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and norbornene. Exemplary of the C.sub.6-C.sub.40 aromatic hydrocarbons are benzene, naphthalene, and biphenyl.

[0069] The p-valent heterocyclic group R.sup.11 are obtained by eliminating p number of hydrogen from a heterocyclic compound. Suitable heterocyclic compounds include furans, pyridines, pyrazoles, and thiazolidines.

[0070] Some or all of the hydrogen atoms in the p-valent hydrocarbon group or p-valent heterocyclic group may be substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, so that the group may contain a hydroxy, cyano, fluorine, chlorine, bromine or iodine. Also, some CH.sub.2 in the p-valent hydrocarbon group may be replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a carbonyl moiety, ether bond, thioether bond, ester bond, sulfonate ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)).

[0071] The hydrocarbylene group R.sup.12 may be saturated or unsaturated and straight, branched or cyclic. Examples thereof include C.sub.1-C.sub.20 alkanediyl groups such as methanediyl, ethane-1,1-diyl, ethane-1,2-diyl, propane-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 and dodecane-1,12-diyl; C.sub.3-C.sub.20 cyclic saturated hydrocarbylene groups such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; C.sub.2-C.sub.20 unsaturated aliphatic hydrocarbylene groups such as vinylene and propene-1,3-diyl; C.sub.6-C.sub.20 arylene groups such as phenylene and naphthylene; 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, 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, fluorine, chlorine, bromine, iodine, carbonyl moiety, ether bond, thioether bond, ester bond, sulfonate ester bond, carbonate bond, carbamate bond, lactone ring, sultone ring, or carboxylic anhydride (C(O)OC(O)).

[0072] Of the carboxylic acids having formula (3), those wherein p is 2, 3 or 4 are preferred. When mixed with the hypervalent iodine compound, such a carboxylic acid is likely to form a robust resist film having a high molecular weight, which is preferred from the aspects of etch resistance and developer resistance.

[0073] Examples of the carboxylic acid are shown below.

##STR00080## ##STR00081## ##STR00082## ##STR00083## ##STR00084## ##STR00085##

[0074] In the resist composition, the hypervalent iodine compound and the carboxylic acid are preferably present such that the molar ratio of the hypervalent iodine compound to the carboxylic acid may range from 10:90 to 90:10, more preferably from 20:80 to 80:20, even more preferably from 30:70 to 70:30. The hypervalent iodine compound may be used alone or as a mixture of two or more. The carboxylic acid may be used alone or as a mixture of two or more.

[Organic Solvent]

[0075] The resist composition further contains a solvent. The solvent is not particularly limited as long as the hypervalent iodine compound, the carboxylic acid and other components are dissolvable therein and a film can be formed from the resulting solution. Organic solvents are preferred. Suitable organic solvents include ketones such as cyclohexanone, methyl 2-n-pentyl ketone, and methyl isoamyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, diacetone alcohol, and 4-methyl-2-pentanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monomethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, propylene glycol mono-tert-butyl ether acetate, and methyl 2-hydroxyisobutyrate; carboxylic acids such as formic acid, acetic acid, and propionic acid; lactones such as -butyrolactone, and mixtures thereof.

[0076] The solvent is preferably present in such amounts that the resist composition may have a solids concentration of 0.1 to 20% by weight, more preferably 0.1 to 15% by weight, even more preferably 0.1 to 10% by weight. As used herein, the term solids is a general term for all components in the resist composition excluding the solvent. The solvent may be used alone or in admixture of two or more.

[Other Components]

[0077] The resist composition may further contain a surfactant as another component. The surfactant is preferably selected from fluorochemical and silicon-based surfactants. Exemplary surfactants are described, for example, in US 2008/0248425, paragraph [0276]. Also useful are surfactants other than the fluorochemical and silicon-based surfactants, as described, for example, in US 2008/0248425, paragraph [0280]. When used, the surfactant is preferably present in an amount of 0.0001 to 2% by weight based on the overall solids. The surfactant may be used alone or in admixture.

[0078] The resist composition may further contain a radical scavenger (or radical trapping agent) as an additional component. When added, the radical scavenger is effective for controlling photo-reaction and adjusting sensitivity during photolithography.

[0079] Suitable radical scavengers include hindered phenols, quinones, hindered amines, and thiol compounds. Exemplary hindered phenols include dibutylhydroxytoluene (BHT) and 2,2-methylenebis(4-methyl-6-tert-butylphenol). Exemplary quinones include 4-methoxyphenol (or methoquinone) and hydroquinone. Exemplary hindered amines include 2,2,6,6-tetramethylpyperidine and 2,2,6,6-tetramethylpyperidine-N-oxy radical. Exemplary thiol compounds include dodecanethiol and hexadecanethiol. When used, the radical scavenger is preferably present in an amount of 0.01 to 10% by weight based on the overall solids. The radical scavenger may be used alone or in admixture.

[0080] The resist composition may contain a crosslinker. The crosslinker serves to promote crosslinking reaction in the photolithography to eventually reduce an etching rate.

[0081] Suitable crosslinkers are compounds having an unsaturated carbon-carbon bond such as vinyl, (meth)acrylate, allyl, alkynyl or aromatic ring as a functional group. Suitable compounds having a vinyl group include linear alkenes, branched alkenes, and cyclic alkenes, which may have a substituent. Suitable compounds having a (meth)acryloyl group include acrylic acids, methacrylic acids, acrylates, and methacrylates, which may have a substituent. Suitable compounds having an allyl group include allyl alcohols, allyl ethers, allyl esters, allyl amides, allyl amines, and allyl-containing isocyanurates, which may have a substituent. Suitable compounds having an alkynyl group include straight alkynes, branched alkynes, cyclic alkynes, alkynyl alcohols, alkynyl ethers, alkynyl esters, alkynyl amides, alkynyl amines, alkynyl-containing isocyanurates, which may have a substituent. Suitable compounds having an aromatic ring include arenes, heteroarenes, styrenes, stilbenes, phenylacethylenes, acenaphthylenes, and chalcones, which may have a substituent. The crosslinker may have one or more of the foregoing functional groups. The number of functional groups in the crosslinker is preferably from 1 to 10, more preferably from 2 to 8.

[0082] When the resist composition contains the crosslinker, the amount of the crosslinker is preferably 0.01 to 50% by weight of the overall solids. The crosslinker may be used alone or in admixture.

[0083] When the resist composition contains the crosslinker, it may further contain a photopolymerization initiator. Upon receipt of high-energy radiation, the photopolymerization initiator generates radicals to promote crosslinking of the crosslinker.

[0084] Examples of the photopolymerization initiator include benzophenone derivatives such as benzophenone, methyl O-benzoylbenzoate, 4-benzyol-4-methyl diphenyl ketone, dibenzyl ketone, and fluorenone; acetophenone derivatives such as 2,2-diethoxyacetophenone, 2-hydroxy-2-methylpropiophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, and methyl phenylglyoxylate; thioxanthone derivatives such as thioxanthone, 2-methylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, and diethylthioxanthone; benzyl derivatives such as benzyl, benzyl dimethyl ketal, and benzyl--methoxyethylacetal; benzoin derivatives such as benzoin, benzoin methyl ether, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; oxime compounds such as 1-phenyl-1,2-butanedione-2-(O-methoxycarbonyl) oxime, 1-phenyl-1,2-propanedione-2-(O-methoxycarbonyl) oxime, 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl) oxime, 1-phenyl-1,2-propanedione-2-(O-benzoyl) oxime, 1,3-diphenylpropanetrione-2-(O-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxypropanetrione-2-(O-benzoyl) oxime 1,2-octanedione, 1-{4-(phenylthio)-2-(O-benzoyl) oxime ethanone, and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime); -hydroxyketone compounds such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropane; -aminoalkylphenone compounds such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) butanone-1 and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-ylphenyl) butan-1-one; phosphine oxide compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide; and titanocene compounds such as bis(5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium.

[0085] When the resist composition contains the photopolymerization initiator, the amount of the initiator is preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, even more preferably 0.1 to 1% by weight of the overall solids. A sufficient effect is available as long as the amount is 0.1% by weight or more.

[0086] The resist composition contains the hypervalent iodine compound and the carboxylic acid as main components, but not a polymer containing an acid labile group and a photoacid generator as used in conventional chemically amplified resist compositions. Nevertheless, this resist composition works such that the region thereof exposed to EB or EUV is removed by dry process development to form a positive tone pattern, or the unexposed region thereof is removed by dry process development to form a negative tone pattern. Although its mechanism is not well understood, the following mechanism is presumed.

[0087] The hypervalent iodine compound is a three-coordinate compound having carboxylate ligands as represented by formula (1) or (2). When such a three-coordinate iodine compound is mixed with a carboxylic acid, replacement of carboxylate ligands takes place as equilibration reaction. If the original carboxylate ligands are removed by any suitable means, a hypervalent iodine compound having new ligands is created. For example, if iodobenzene diacetate which is relatively readily available as the hypervalent iodine compound is mixed with a carboxylic acid having a high molecular weight, and the resulting low-boiling acetic acid is removed, then ligand exchange is completed. If the ligand has a fully high molecular weight, then a robust resist film is formed. Particularly when the carboxylic acid has a plurality of carboxy groups, for example, a dicarboxylic acid is used, a high molecular weight compound of polyester structure having the hypervalent iodine compound is formed. This ensures film formability.

[0088] The combined form of hypervalent iodine compound and carboxylic acid is formed during film preparation. That is, by removing a low-molecular-weight carboxylic acid formed during film formation and subsequent bake step, ligand exchange reaction is completed and a resist film is formed.

[0089] The resist composition may become of either positive or negative tone depending on a choice of components. The resist film obtained from the positive resist composition contains the polymer to which the hypervalent iodine compound is bonded during film formation. However, upon receipt of light, the hypervalent iodine compound is decomposed into a monovalent iodine compound. At the same time, the crosslink between the hypervalent iodine compound and the carboxylic acid is canceled and the molecular weight is reduced. As a result, a difference in etching rate is established between the exposed and unexposed regions. Through the dry process development, a pattern of positive tone wherein the film in the unexposed region is left is formed.

[0090] In contrast, the resist film obtained from the negative resist composition contains the polymer crosslinked with the hypervalent iodine compound, which is formed during film formation. Upon receipt of light, the hypervalent iodine compound is decomposed (whereby the crosslink or bond is changed) and converted into a chemical species having a lower etching rate than the unexposed region. As a result, a difference in etching rate is established between the exposed and unexposed regions. Through the dry process development, a pattern of negative tone wherein the film in the exposed region is left is formed.

[0091] It is unknown what component should be selected in order that the resist composition become of positive or negative tone. When the resist film obtained from the resist composition is of positive tone, the exposed region becomes soluble in an organic solvent. When the resist film obtained from the resist composition is of negative tone, the exposed region becomes insoluble in an alkaline aqueous solution. This gives the criterion of judgment.

[0092] From the foregoing presumption, the inventive resist composition is regarded as falling in the concept of non-chemically-amplified resist composition. There is no need for an acid labile group-containing polymer and a photoacid generator as used in conventional chemically amplified resist compositions. Using the inventive resist composition, a small size pattern can be resolved without any adverse effect (e.g., image blur) due to acid diffusion.

[0093] The inventive resist composition is quite effective in the EUV lithography. This is because an iodine atom having a high absorptivity to EUV radiation is included. That is, shot noise is reduced, and higher resolution and lower LWR are achievable.

[0094] As the EUV lithography resist composition capable of forming a small size pattern, a metal resist composition based on a metal (specifically tin) compound having a high absorptivity to EUV radiation like iodine atom is known, for example, from Patent Document 2. However, the metal resist composition suffers from many problems including a lack of solvent solubility, poor shelf stability, and defects in the form of post-etching residues due to the containment of metal elements, as discussed previously. In contrast, the inventive resist composition which does not use metal elements is advantageous in defectiveness over the metal resist and eliminates the problem of solvent solubility. The inventive resist composition has a wide range of application because it becomes of both positive and negative tones. In the step of forming contact holes, for example, although a metal resist composition subject to negative tone development requires the reversal processing step after pillar pattern formation, the positive resist composition does not require the reversal step. From the aspect of process simplicity, the inventive resist composition is regarded more useful than the metal resist composition.

[0095] JP-A 2015-180928 and JP-A 2018-095853 describe a resist composition comprising a hypervalent iodine compound as an additive and a resist composition comprising a base polymer having a hypervalent iodine compound incorporated in its framework. It is described in these patent documents that these resist compositions are successful only in improving line edge roughness. They refer nowhere to a possibility of photo-decomposition of the hypervalent iodine compound and an ability to function as a non-chemically amplified resist. In these resist compositions, the hypervalent iodine compound is not a main component. It is then believed that a material capable of reducing shot noise during the EUV lithography and forming a small size pattern as the non-chemically amplified resist is not conceivable from these patent documents. That is, the present invention provides a definitely novel resist composition and pattern forming process.

[Resist Pattern Forming Process]

[0096] One embodiment of the invention is a resist pattern forming process comprising the steps of: [0097] (i) applying a resist composition as defined above onto a substrate or a substrate having an underlying film deposited thereon to form a resist film on the substrate or the underlying film, [0098] (ii) exposing the resist film to high-energy radiation, [0099] (iii) baking the exposed resist film, and [0100] (iv) dry etching the baked resist film for development to form a resist pattern.
[Step (i)]

[0101] Step (i) is to apply the resist composition onto a substrate or a substrate having an underlying film thereon to form a resist film on the substrate or underlying film. Specifically, the resist composition is applied onto a substrate for integrated circuit fabrication (e.g., Si, SiO.sub.2, SiN, SiON, TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrate having an underlying film thereon, or a substrate for mask circuit fabrication (e.g., Cr, CrO, CrON, MoSi.sub.2, or SiO.sub.2) or a substrate having an underlying film thereon by any suitable technique such as spin coating, roll coating, flow coating, dip coating, spray coating or doctor coating. The coating is prebaked (PAB) on a hot plate at a temperature of preferably 60 to 200 C. for 10 seconds to 30 minutes, more preferably at 80 to 160 C. for 30 seconds to 20 minutes to form a resist film having a thickness of 0.01 to 2 m. Notably, the underlying film refers to a film formed between a substrate and a resist film in the multilayer resist process. The underlying film is not particularly limited and any of well-known films may be used.

[Step (ii)]

[0102] Step (ii) is to expose the resist film to high-energy radiation. The radiation is selected from among UV, deep UV, EB at accelerating voltage 1 to 150 kV, EUV of wavelength 3 to 15 nm, X-ray, soft X-ray, excimer laser radiation, -ray, and synchrotron radiation. On use of UV, deep UV, EUV, X-ray, soft X-ray, excimer laser radiation, -ray, and synchrotron radiation as the high-energy radiation, the resist film is exposed thereto directly or through a mask having the desired pattern so as to reach a dose of preferably about 1 to 300 mJ/cm.sup.2, more preferably about 10 to 200 mJ/cm.sup.2. On use of EB as the high-energy radiation, imagewise writing is performed directly or through a mask having the desired pattern so as to reach a dose of preferably about 0.1 to 5,000 C/cm.sup.2, more preferably about 0.5 to 3,000 C/cm.sup.2. The resist composition is best suited in micropatterning using EB or EUV as the high-energy radiation.

[Step (iii)]

[0103] Step (iii) is to bake (or heat treat) the exposed resist film. This step is also referred to as post-exposure bake (PEB). PEB may be performed on a hot plate or by IR irradiation, laser irradiation, or hot air blowing. PEB may also be performed by inserting the wafer into an atmosphere at the baking temperature. Most of the currently used heating means use a hot plate. Once the substrate on which a resist film is formed is rested on a hot plate, the resist film is heated by heat conduction through the substrate. By temperature control of the hot plate, the temperature at which the resist film is heated is adjustable.

[0104] The PEB temperature is preferably 30 to 170 C., more preferably 40 to 160 C., even more preferably 50 to 150 C. The PEB time is preferably 10 seconds to 30 minutes, more preferably 10 seconds to 20 minutes.

[0105] Flood exposure of the resist film after the PEB may be included. During flood exposure, crosslinking takes place in the resist film whereby the resist film has higher etching resistance. For the flood exposure, high-energy radiation, especially UV, deep UV, X-ray and soft X-ray may be used.

[Step (iv)]

[0106] Step (iv) is to dry etch the baked resist film for development to form a resist pattern. On use of a positive resist composition, the exposed region is scraped off to open the space region. On use of a negative resist composition, the unexposed region is scraped off to open the space region.

[0107] Dry etching may be carried out in a conventional dry etching system. Reactive ion etching (RIE) is performed in the chamber with a dry etching gas-containing plasma. As the dry etching gas, use may be made of gas mixtures of oxygen, hydrogen, ammonia, fluorocarbon, chlorine or bromine diluted with nitrogen, argon, helium, carbon dioxide, carbon monoxide, or sulfur dioxide. Gas mixtures containing at least one of oxygen and tetrafluoromethane are preferably used. It is preferred from the aspect of easy control of an etching rate to use a mixture of oxygen and nitrogen or a mixture of tetrafluoromethane and nitrogen.

[0108] Suitable dry etching conditions are described below. On use of a gas mixture of oxygen and nitrogen, for example, the pressure in the chamber is preferably 0.01 to 100 Pa, more preferably 0.1 to 30 Pa. The radio frequency (RF) power is preferably 50 to 1,500 W, more preferably 150 to 1,000 W. The bias power is preferably 0 to 300 W, more preferably 30 to 200 W. The flow rate of oxygen gas is preferably 3 to 300 sccm, more preferably 5 to 150 sccm. The flow rate of nitrogen gas is preferably 5 to 600 sccm, more preferably 10 to 500 sccm. The treating temperature during development is preferably 20 C. to 30 C., more preferably 10 C. to 30 C.

[0109] On use of a gas mixture of tetrafluoromethane and nitrogen, the chamber pressure is preferably 0.01 to 100 Pa, more preferably 0.1 to 30 Pa. The RF power is preferably 50 to 1,500 W, more preferably 150 to 1,000 W. The bias power is preferably 0 to 300 W, more preferably 30 to 200 W. The flow rate of tetrafluoromethane gas is preferably 3 to 300 sccm, more preferably 5 to 150 sccm. The flow rate of nitrogen gas is preferably 5 to 500 sccm, more preferably 10 to 300 sccm. The treating temperature during development is preferably 20 C. to 30 C., more preferably 10 C. to 30 C.

[0110] The dry etching time may be set as appropriate, preferably in the range of 30 to 300 seconds, more preferably 30 to 120 seconds.

[0111] A hole or trench pattern after development may be shrunk by the thermal flow, RELACS or DSA process.

EXAMPLES

[0112] Examples of the invention are given below by way of illustration and not by way of limitation. The abbreviation pbw is parts by weight.

[1] Preparation of Resist Composition

Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-3

[0113] Resist compositions (R-01 to R-10) were prepared by dissolving a hypervalent iodine compound and a carboxylic acid in a solvent in accordance with the recipe shown in Table 1, and filtering the solution through a Teflon filter having a pore size of 0.2 m. Also, resist compositions (CR-01 to CR-03) were prepared by dissolving a base polymer, a photoacid generator, and a sensitivity modifier in a solvent containing 0.01 wt % of a surfactant (PF-636, Omnova Solutions, Inc.) in accordance with the recipe shown in Table 2, and filtering the solution through a Teflon filter having a pore size of 0.2 m.

TABLE-US-00001 TABLE 1 Hypervalent Hypervalent iodine iodine Carboxylic Resist compound 1 compound 2 acid Solvent 1 Solvent 2 composition (pbw) (pbw) (pbw) (pbw) (pbw) Example 1-1 R-01 I-1-1 (10) CA-1 (7.3) PGMEA (800) AcOH (200) 1-2 R-02 I-1-2 (10) CA-1 (7.3) PGMEA (800) AcOH (200) 1-3 R-03 I-1-3 (14) CA-1 (7.3) PGMEA (800) AcOH (200) 1-4 R-04 I-2-1 (10) CA-2 (3.5) PGMEA (800) AcOH (200) 1-5 R-05 I-2-1 (10) CA-3 (7.2) PGMEA (800) AcOH (200) 1-6 R-06 I-2-1 (10) CA-4 (50) PGMEA (800) AcOH (200) 1-7 R-07 I-2-1 (10) CA-5 (6.5) PGMEA (800) AcOH (200) 1-8 R-08 I-2-1 (10) CA-6 (9.9) PGMEA (800) AcOH (200) 1-9 R-09 I-1-1 (10) CA-7 (7.6) PGMEA (800) AcOH (200) 1-10 R-10 I-1-1 (10) CA-8 (5.9) PGMEA (800) AcOH (200)

TABLE-US-00002 TABLE 2 Photoacid Sensitivity Resist Polymer generator modifier Solvent 1 Solvent 2 composition (pbw) (pbw) (pbw) (pbw) (pbw) Comparative 1-1 CR-01 P-1 (80) PAG-1 (19) Q-1 (6) PGMEA (1890) GBL (210) Example 1-2 CR-02 P-1 (80) PAG-2 (21) Q-1 (6) PGMEA (1890) GBL (210) 1-3 CR-03 P-1 (80) PAG-1 (19) Q-2 (9) PGMEA (1890) GBL (210)

[0114] In Table 1, the hypervalent iodine compound (I-1-1 to I-1-3, I-2-1), carboxylic acid (CA-1 to CA-8) and solvent are identified below.

##STR00086## ##STR00087##

Solvent:

[0115] PGMEA (propylene glycol monomethyl ether acetate) [0116] AcOH (acetic acid) [0117] GBL (-butyrolactone)

[0118] In Table 2, the base polymer (P-1), photoacid generator (PAG-1 and PAG-2), and sensitivity modifier (Q-1 and Q-2) are identified below. It is noted that the Mw of the base polymer is as measured by GPC versus polystyrene standards using THF solvent.

##STR00088##

[2] EUV Lithography Test

Examples 2-1 to 2-10 and Comparative Examples 2-1 to 2-3

[0119] Each of the resist compositions (R-01 to R-10, CR-01 to CR-03) was spin coated on a silicon substrate having an antireflective film of 60 nm thick (DUV-42 by Nissan Chemical Co., Ltd.) and baked (PAB) on a hotplate at the temperature shown in Table 3 for 60 seconds to form a resist film of 140 nm thick. Using an EUV scanner NXE3400 (ASML, NA 0.33, 0.9, 90 dipole illumination), the resist film was exposed to EUV through a mask bearing a 40-nm 1:1 line-and-space (LS) pattern. The resist film was baked (PEB) on a hotplate at the temperature shown in Table 3 for 60 seconds.

[0120] After the PEB, dry etching was carried out in a dry etching system Telius (Tokyo Electron) under the following conditions. [0121] Chamber pressure: 12.0 Pa [0122] RF power: 600 W [0123] Bias power: 50 W [0124] Stage temperature: 25 C. [0125] O.sub.2 gas flow rate: 20 sccm [0126] N.sub.2 gas flow rate: 400 sccm [0127] Time: 30 sec

[0128] The resist film and the antireflective film in the exposed region were etched or reduced in thickness by dry etching until the silicon substrate surface was exposed.

[0129] The 40-nm LS pattern was observed under CD-SEM (CG-6300, Hitachi High-Technologies Corp.). The optimum dose (Eop, mJ/cm.sup.2) which provided a 40-nm 1:1 LS pattern was determined and reported as sensitivity. After the wafer was sectioned, the cross-sectional profile of the 40-nm LS pattern was observed under SEM (S-4800, Hitachi High-Technologies Corp.). The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Resist PAB/PEB temp. Sensitivity composition ( C.) (mJ/cm.sup.2) Pattern tone Cross-sectional profile Example 2-1 R-01 100/100 45 negative rectangular 2-2 R-02 100/100 50 negative rectangular 2-3 R-03 100/100 45 negative rectangular 2-4 R-04 100/100 50 negative rectangular 2-5 R-05 100/100 55 negative rectangular 2-6 R-06 100/100 60 negative rectangular 2-7 R-07 100/100 60 positive rectangular 2-8 R-08 100/100 60 positive rectangular 2-9 R-09 100/100 45 positive rectangular 2-10 R-10 100/100 50 positive rectangular Comparative 2-1 CR-01 105/90 72 positive line pattern vanished Example 2-2 CR-02 105/90 75 positive line pattern vanished 2-3 CR-03 105/90 75 positive line pattern vanished

[0130] It is evident from Table 3 that the resist compositions comprising a hypervalent iodine compound and a carboxylic acid within the scope of the invention form patterns through development by dry etching. In contrast, when the chemically amplified resist compositions of Comparative Examples were used, the patterns vanished after dry etching, indicating a failure to establish a substantial difference in etching rate between exposed and unexposed regions. In the case of the resist compositions comprising a hypervalent iodine compound and a carboxylic acid, either positive or negative tone patterns may be formed by a proper choice of the carboxylic acid. The development by dry etching enables to form patterns having a high aspect ratio and high resolution because the pattern collapse which is caused by the stress generated during spin drying in solution development is avoided.

[0131] Japanese Patent Application No. 2024-059982 is 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.