Positive resist material and pattern-forming method

Abstract

The present disclosure provides: a positive resist material that exhibits good transmittance for an energy ray used for patterning and that provides a good pattern shape after being exposed; and a pattern-forming method. A positive resist material according to the present disclosure contains a resin (A). The resin (A) is a copolymer including a structural unit (a-1) represented by formula (1) and a structural unit (a-2) represented by formula (2). (In formulae (1) and (2), RA and RB are each a hydrogen atom or a methyl group. R1 represents an alkanediyl group having 1-6 carbon atoms, and a portion of said carbon atoms is optionally substituted with an ether bond or an ester bond. R2 represents a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1-6 carbon atoms. a represents 1 or 2. b represents an integer of 0-4. Here, 1≤a+b≤5 is satisfied. R4 represents an acid unstable group.)

Description

Positive resist material and pattern forming method

[0001] The present disclosure relates to a positive resist material and a pattern formation method. This application claims priority to Japanese Patent Application No. 2024-082450, filed May 21, 2024, the contents of which are incorporated herein by reference.

[0002] As LSIs become more highly integrated and faster, pattern rules are becoming increasingly finer. This is because the widespread use of 5G high-speed communications and artificial intelligence (AI) requires high-performance devices to process them. As cutting-edge miniaturization technology, studies are being conducted using photolithography techniques and positive resist materials. For example, Patent Document 1 discloses a positive resist material containing a compound having a nitrobenzyl ester group bonded to an aromatic ring substituted with an iodine atom.

[0003] JP 2024-10654 A

[0004] The present disclosure has been made in consideration of the above circumstances, and aims to provide a positive resist material and a pattern formation method that have good transmittance to energy rays used for patterning and that produce a good pattern shape after exposure.

[0005] The present disclosure includes the following aspects: [1] A positive resist material containing a resin (A) and a photoacid generator (B), wherein the resin (A) is a copolymer containing a structural unit (a-1) represented by the following formula (1) and a structural unit (a-2) represented by the following formula (2): (In formula (1), R Ａ is a hydrogen atom or a methyl group. １ R is an alkanediyl group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether bond or an ester bond. ２ is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms; a is 1 or 2; and b is an integer of 0 to 4, provided that 1≦a+b≦5. (In formula (2), RＢ is a hydrogen atom or a methyl group. ４ is an acid labile group.) [2] In the formula (1), R １ [3] The positive resist material according to [1], wherein R is an alkanediyl group having 1 to 3 carbon atoms, and a is 1. ４ is a group represented by the following formula (A-3): (R of the acid labile group represented by formula (A-3) ３４ , R ３５ , R ３６ is a monovalent hydrocarbon group such as a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, or a linear, branched or cyclic alkenyl group having 2 to 20 carbon atoms, which may contain heteroatoms such as oxygen, sulfur, nitrogen or fluorine; R ３４ and R ３５ , R ３４ and R ３６ , R ３５ and R ３６and may be bonded to each other and, together with the carbon atom to which they are bonded, form an alicyclic ring having 3 to 20 carbon atoms.) [4] The positive resist material according to any one of [1] to [3], wherein the resin (A) further contains another structural unit (a-3). [5] The positive resist material according to any one of [1] to [4], wherein, of all the structural units constituting the resin (A), the structural unit (a-1) represented by the above formula (1) accounts for 30 to 90 mol %, the structural unit (a-2) represented by the above formula (2) accounts for 1 to 40 mol %, and the other structural unit (a-3) accounts for 0 to 40 mol %. [6] The positive resist material according to any one of [1] to [5], further containing a solvent (C). [7] The positive resist material according to any one of [1] to [6], wherein the KrF light transmittance is 45% or higher. [8] The positive resist material according to any one of [1] to [5] and [7], further comprising a solvent (C), wherein the content of the resin (A) is 5 to 40 mass% relative to the total of the resin (A) and the solvent (C), and the content of the photoacid generator (B) is 0.1 to 30 mass parts, based on 100 mass parts of the resin (A). [9] A cured resin film consisting of a cured product of the positive resist material according to any one of [1] to [8].

[10] A pattern formation method comprising the steps of: forming a resist film on a substrate using the positive resist material according to any one of [1] to [8]; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.

[11] The pattern forming method according to

[10] , wherein the high-energy radiation is i-ray, KrF excimer laser light, ArF excimer laser light, an electron beam, or extreme ultraviolet light having a wavelength of 3 to 15 nm.

[12] A copolymer containing a structural unit (a-1) represented by the following formula (1), and a structural unit (a-2) represented by the following formula (2): (In formula (1), R Ａ is a hydrogen atom or a methyl group. １ R is an alkanediyl group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether bond or an ester bond. ２is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms; a is 1 or 2; and b is an integer of 0 to 4, provided that 1≦a+b≦5. (In formula (2), R Ｂ is a hydrogen atom or a methyl group. ４ is an acid labile group.

[0006] According to the present disclosure, it is possible to provide a positive resist material and a pattern formation method that have good transmittance of energy rays used for patterning and that produce a good pattern shape after exposure.

[0007] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments described below.

[0008] In this specification, when "to" is used to describe a numerical range, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the numerical range. When multiple upper or lower limits are listed, numerical ranges can be created using all combinations of the upper and lower limits. Similarly, when multiple numerical ranges are listed, separate numerical ranges can be created by individually selecting and combining the upper and lower limits from those numerical ranges.

[0009] In this specification, "(meth)acrylic acid" means methacrylic acid or acrylic acid, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy. In this specification, "(poly)alkylene glycol" means alkylene glycol or polyalkylene glycol.

[0010] As used herein, the term "ethylenically unsaturated bond" refers to a double bond formed between carbon atoms excluding carbon atoms forming an aromatic ring. The term "ethylenically unsaturated group" refers to a group having an ethylenically unsaturated bond. The term "ethylenically unsaturated compound" refers to a compound having an ethylenically unsaturated bond.

[0011] In this specification, the term "structural unit" refers to a unit derived from the polymerizable compound itself used as a monomer, or a unit obtained by further modifying a unit derived from the polymerizable compound itself used as a monomer after polymerization.

[0012] (Positive Resist Material) A positive resist material of one embodiment contains a resin (A) and a photoacid generator (B). The resin (A) is a copolymer containing a structural unit (a-1) represented by the following formula (1) and a structural unit (a-2) represented by the following formula (2). The resin (A) may further contain another structural unit (a-3) as necessary. The positive resist material of one embodiment may also contain a solvent (C).

[0013] [Resin (A)] Resin (A) is a copolymer containing a structural unit (a-1) represented by the following formula (1) and a structural unit (a-2) represented by the following formula (2): Resin (A) (the copolymer) may further contain another structural unit (a-3) as necessary.

[0014]

[0015] (In formula (1), R Ａ is a hydrogen atom or a methyl group. １ R is an alkanediyl group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether bond or an ester bond. ２ is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms; a is 1 or 2; and b is an integer of 0 to 4, provided that 1≦a+b≦5.

[0016]

[0017] (In formula (2), R Ｂ is a hydrogen atom or a methyl group. ４ is an acid labile group.

[0018] The weight average molecular weight (Mw) of the resin (A) is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more. The weight average molecular weight of the resin (A) is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 25,000 or less. When the weight average molecular weight of the resin (A) is 5,000 or more, it is possible to prevent the high-energy ray unexposed portion of the resist from dissolving during alkaline washing. When the weight average molecular weight of the resin (A) is 50,000 or less, the high-energy ray exposed portion of the resist has good alkaline solubility.

[0019] The molecular weight distribution (Mw / Mn) of the resin (A) is preferably 1.1 or more, more preferably 1.5 or more, and even more preferably 1.7 or more. The molecular weight distribution (Mw / Mn) of the resin (A) is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. When the molecular weight distribution (Mw / Mn) of the resin (A) is 1.1 or more, it is easy to control the production conditions during synthesis of the resin (A). When the molecular weight distribution (Mw / Mn) of the resin (A) is 5.0 or less, it is possible to suppress variations in alkali solubility due to variations in the molecular weight distribution of the polymer.

[0020] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​measured using gel permeation chromatography (GPC) under the following conditions and determined using a standard polystyrene calibration curve. Column: Two Showdex (trademark) LF-804 (Resonac Corporation) connected in series. Column temperature: 40°C. Sample: 0.2% by mass solution of the object to be measured in tetrahydrofuran. Developing solvent: tetrahydrofuran. Detector: differential refractometer (Shodex (trademark) RI-71S) (Resonac Corporation). Flow rate: 1 mL / min.

[0021] The content of resin (A) in the positive resist material is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, based on the total of resin (A) and solvent (C). The content of resin (A) is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, based on the total of resin (A) and solvent (C). When the content of resin (A) is within the above range, the resist has an appropriate viscosity, improving workability when applied to a wafer.

[0022] "Structural unit (a-1) represented by formula (1)" The structural unit (a-1) is a structural unit represented by formula (1). The structural unit (a-1) may be of one type, or may be of two or more types. When the resin (A) contains the structural unit (a-1), the positive resist material has good energy ray transmittance, and a cured product having a good pattern shape can be obtained. In the formula (1), R １ is preferably an alkanediyl group having 1 to 6 carbon atoms, more preferably an alkanediyl group having 1 to 3 carbon atoms, and even more preferably an alkanediyl group having 2 to 3 carbon atoms. １ Examples of R include an ethanediyl group and a propanediyl group. ２ is preferably a saturated hydrocarbyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group. In the formula (1), at least a portion of the H atoms of the phenolic hydroxyl groups contained in the resin (A) may be replaced with acid labile groups. The amount of replacement is not particularly limited, but the ratio (molar ratio) of the amount of phenolic hydroxyl groups to the amount of acid labile groups contained in the resin (A) may be 50:50 to 90:10, 60:40 to 90:10, or 60:40 to 80:20. By replacing at least a portion of the H atoms of the phenolic hydroxyl groups with acid labile groups, the solubility of the unexposed areas during development of the cured resin film can be further reduced, thereby reducing unintended dissolution and film loss. a is preferably 1, and it is more preferable that OH is in the 4-position, i.e., the para-position. b is preferably 0 to 2, more preferably 0. R ２ is preferably at the 3-position or 5-position, i.e., the meta-position.

[0023] [Acid Labile Group] The "acid labile group" of the present disclosure is not particularly limited as long as it is a substituent that can be eliminated by reacting with an acid generated by an acid generator described below. Examples of acid labile groups include those described in JP-A Nos. 2013-80033 and 2013-83821. Various acid labile groups are selected, which may be the same or different, and particularly include those represented by the following formulae (A-1) to (A-3). Among these, those represented by the following formulae (A-1) or (A-3) are preferred.

[0024]

[0025] In formula (A-1), R ３０ represents a tertiary alkyl group having 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in which each alkyl group has 1 to 6 carbon atoms, an oxoalkyl group having 4 to 20 carbon atoms, or a group represented by the above general formula (A-3). Specific examples of the tertiary alkyl group include a tert-butyl group, a tert-amyl group, a 1,1-diethylpropyl group, a 1-ethylcyclopentyl group, a 1-butylcyclopentyl group, a 1-ethylcyclohexyl group, a 1-butylcyclohexyl group, a 1-ethyl-2-cyclopentenyl group, a 1-ethyl-2-cyclohexenyl group, and a 2-methyl-2-adamantyl group. Specific examples of the trialkylsilyl group include a trimethylsilyl group, a triethylsilyl group, and a dimethyl-tert-butylsilyl group. Specific examples of the oxoalkyl group include a 3-oxocyclohexyl group, a 4-methyl-2-oxooxan-4-yl group, a 5-methyl-2-oxooxolan-5-yl group, etc. n1 is an integer of 0 to 6.

[0026] In formula (A-2), R ３１ , R ３２ represents a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. ３１ , R ３２Specific examples of R include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a cyclopentyl group, a cyclohexyl group, a 2-ethylhexyl group, and an n-octyl group. ３３ R represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may have a heteroatom such as an oxygen atom. ３３ can be a linear, branched or cyclic alkyl group, or an alkyl group in which some of the hydrogen atoms have been substituted with a hydroxyl group, an alkoxy group, an oxo group, an amino group, an alkylamino group or the like, and specific examples thereof include the following substituted alkyl groups.

[0027]

[0028] R ３１ and R ３２ , R ３１ and R ３３ , R ３２ and R ３３ may be bonded to form a ring together with the carbon atom to which they are attached. When a ring is formed, R ３１ , R ３２ , R ３３ represents a linear or branched alkylene group having 1 to 18, preferably 1 to 10, carbon atoms, and the ring preferably has 3 to 10, particularly preferably 4 to 10, carbon atoms.

[0029] Specific examples of the acid labile group represented by the above formula (A-1) include a tert-butoxycarbonyl group, a tert-butoxycarbonylmethyl group, a tert-amyloxycarbonyl group, a tert-amyloxycarbonylmethyl group, a 1,1-diethylpropyloxycarbonyl group, a 1,1-diethylpropyloxycarbonylmethyl group, a 1-ethylcyclopentyloxycarbonyl group, a 1-ethylcyclopentyloxycarbonylmethyl group, a 1-ethyl-2-cyclopentenyloxycarbonyl group, a 1-ethyl-2-cyclopentenyloxycarbonylmethyl group, a 1-ethoxyethoxycarbonylmethyl group, a 2-tetrahydropyranyloxycarbonylmethyl group, and a 2-tetrahydrofuranyloxycarbonylmethyl group.

[0030] Further examples include substituents represented by the following formulae (A-1)-1 to (A-1)-10.

[0031] Here, R ３７ are the same or different linear, branched or cyclic alkyl groups having 1 to 10 carbon atoms, or aryl groups having 6 to 20 carbon atoms; R ３８ is a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. ３９ are the same or different linear, branched or cyclic alkyl groups having 2 to 10 carbon atoms, or aryl groups having 6 to 20 carbon atoms. n1 is as defined above.

[0032] Of the acid labile groups represented by formula (A-2) above, examples of linear or branched groups include those represented by formulas (A-2)-1 to (A-2)-15 below.

[0033]

[0034] Next, R of the acid labile group represented by formula (A-3) ３４ , R ３５ , R ３６ R is a monovalent hydrocarbon group such as a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms, or a linear, branched, or cyclic alkenyl group having 2 to 20 carbon atoms. ３４ , R ３５ , R ３６ may contain heteroatoms such as oxygen, sulfur, nitrogen, and fluorine. ３４ and R ３５ , R ３４ and R ３６ , R ３５ and R ３６ may be bonded to each other to form an alicyclic ring having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.

[0035] Examples of the tertiary alkyl group of the acid labile group represented by formula (A-3) include a tert-butyl group, a triethylcarbyl group, a 1-ethylnorbornyl group, a 1-methylcyclohexyl group, a 1-ethylcyclopentyl group, a 2-(2-methyl)adamantyl group, a 2-(2-ethyl)adamantyl group, and a tert-amyl group.

[0036] Examples of monomers that provide the structural unit (a-1) include hydroxyphenylmethyl (meth)acrylate, hydroxyphenylethyl (meth)acrylate, hydroxyphenylpropyl (meth)acrylate, 3,5-dimethyl-hydroxyphenylmethyl (meth)acrylate, etc. Of these, hydroxyphenylmethyl (meth)acrylate, hydroxyphenylethyl (meth)acrylate, and hydroxyphenylpropyl (meth)acrylate are preferred, and hydroxyphenylethyl (meth)acrylate is more preferred.

[0037] The content of the structural unit (a-1) in the structural units of the resin (A) is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more. The content of the structural unit (a-1) in the structural units of the resin (A) is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. When the content of the structural unit (a-1) is 30 mol% or more, the dry etching resistance of the resist is good. When the content of the structural unit (a-1) is 90 mol% or less, the proportion of (a-2) in the structural units of the resin (A) is sufficient, and the alkali solubility of the high-energy ray-exposed areas of the resist is good.

[0038] "Structural unit (a-2) represented by formula (2)" The structural unit (a-2) is a structural unit represented by formula (2). The structural unit (a-2) may be of one type, or may be of two or more types. By including the structural unit (a-2) in the resin (A), the developability of the positive resist material is excellent, and a cured product having a favorable pattern shape can be obtained.

[0039] Examples of monomers that provide the structural unit (a-2) include, but are not limited to, those shown below. Ｂ and R ４ is the same as above.

[0040]

[0041] Examples of acid labile groups include those described in JP-A Nos. 2013-80033 and 2013-83821. Various acid labile groups may be selected, which may be the same or different, and particularly include those represented by the above formulae (A-1) to (A-3). Of these, those represented by the above formulae (A-1) and (A-3) are preferred. Preferred examples of formulae (A-1) to (A-3) are the same as those described above in [Acid Labile Group].

[0042] The content of the structural unit (a-2) in the structural units of the resin (A) is preferably 1 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more. The content of the structural unit (a-1) in the structural units of the resin (A) is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less. When the content of the structural unit (a-2) is 1 mol% or more, the alkali solubility of the high-energy ray-exposed areas of the resist is good. When the content of the structural unit (a-2) is 40 mol% or less, the proportion of (a-1) in the structural units of the resin (A) is sufficient, and the dry etching resistance of the resist is good.

[0043] "Other structural units (a-3)" Examples of the other structural units (a-3) include aromatic vinyl compounds, aromatic allyl compounds, vinyl carboxylates, dienes, (meth)acrylic acid esters, vinyl compounds, unsaturated dicarboxylic acid diesters, monomaleimides, etc. The other structural units (a-3) are structural units that do not belong to the structural units (a-1) and structural units (a-2).

[0044] Specific examples of aromatic vinyl compounds include styrene, α-methylstyrene, α-chloromethylstyrene, vinyltoluene, and divinylbenzene.

[0045] Specific examples of aromatic allyl compounds include diallyl phthalate and diallyl benzene phosphonate.

[0046] Specific examples of vinyl carboxylate include vinyl carboxylates such as vinyl acetate and vinyl adipate.

[0047] Examples of the diene include butadiene, isoprene, and chloroprene. Examples of the (meth)acrylic acid ester include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, and cyclohexyl (meth)acrylate; 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, and 2-methyl-3-methylpropanol; p) 2-[2-[2-(2-hydroxyethoxy)ethoxy]ethoxy]ethyl acrylate, hexaethylene glycol mono(meth)acrylate, octaethylene glycol mono(meth)acrylate, rosin (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 1,1,1-trifluoroethyl (meth)acrylate, perfluoroethyl (meth)acrylate, perfluoro-n-propyl (meth)acrylate, 3-(N,N-dimethylamino)propyl (meth)acrylate, and the like.

[0048] Examples of the vinyl compound include vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, N-vinylpyrrolidone, vinylpyridine, vinyl acetate, and vinyltoluene.

[0049] Examples of the unsaturated dicarboxylic acid diester include diethyl citraconate, diethyl maleate, diethyl fumarate, and diethyl itaconate.

[0050] Examples of monomaleimides include N-phenylmaleimide, N-cyclohexylmaleimide, and N-laurylmaleimide.

[0051] The content of the structural unit (a-3) in the structural units of the resin (A) is preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 20 mol% or less. The content of the structural unit (a-3) in the structural units of the resin (A) may be 1 mol% or more, 5 mol% or more, or even 10 mol% or more. If the content of the structural unit (a-2) is 40 mol% or more, the proportions of (a-1) and (a-2) in the structural units of the resin (A) decrease, thereby deteriorating the etching resistance of the resist and the alkali solubility of the areas exposed to high-energy radiation. Of all the structural units constituting the resin (A), it is preferred that the structural unit (a-1) represented by the above formula (1) accounts for 30 to 90 mol%, the structural unit (a-2) represented by the above formula (2) accounts for 1 to 40 mol%, and the other structural unit (a-3) accounts for 0 to 40 mol%. Of all the structural units constituting the resin (A), it is more preferable that the structural unit (a-1) represented by the above formula (1) accounts for 40 to 80 mol%, the structural unit (a-2) represented by the above formula (2) accounts for 10 to 35 mol%, and the other structural unit (a-3) accounts for 5 to 30 mol%. Of all the structural units constituting the resin (A), it is even more preferable that the structural unit (a-1) represented by the above formula (1) accounts for 50 to 70 mol%, the structural unit (a-2) represented by the above formula (2) accounts for 15 to 30 mol%, and the other structural unit (a-3) accounts for 10 to 25 mol%.

[0052] <Method for producing resin (A)> In one embodiment, resin (A) can be produced by copolymerizing monomer (ma-1), monomer (ma-2), and, if necessary, other monomer (ma-3). The proportions of structural units (a-1), (a-2), and (a-3) contained in the copolymer are the same as the proportions of each of monomers (ma-1), (ma-2), and (ma-3) in the total of all monomers used as raw materials for the copolymer.

[0053] The proportions of each monomer used in the copolymerization reaction to form the copolymer precursor are not particularly limited. Preferably, the proportions are 30 to 90 mol% of monomer (ma-1), 1 to 40 mol% of monomer (ma-2), and 0 to 40 mol% of monomer (ma-3). More preferably, the proportions are 40 to 80 mol% of monomer (ma-1), 10 to 35 mol% of monomer (ma-2), and 5 to 30 mol% of monomer (ma-3). Even more preferably, the proportions are 50 to 70 mol% of monomer (ma-1), 15 to 30 mol% of monomer (ma-2), and 10 to 25 mol% of monomer (ma-3).

[0054] The copolymerization reaction can be carried out in the presence or absence of a solvent according to a radical polymerization method known in the art. For example, the above-mentioned monomers may be dissolved in an organic solvent, a polymerization initiator may be added to the solution, and the polymerization reaction may be carried out at 50 to 100°C for 1 to 20 hours.

[0055] The solvent used in the copolymerization reaction can be the same as the solvent (C) described below. Other examples include hydroxyl group-containing organic solvents such as propylene glycol monoaryl ether, 1,3-propanediol monoalkyl ether, 1,3-butanediol monoalkyl ether, 1,4-butanediol monoalkyl ether, glycerin monoalkyl ether, glycerin dialkyl ether, methanol, ethanol, propanol, C5-6 cycloalkanediol, C5-6 cycloalkane dimethanol, ethyl lactate, and diacetone alcohol. Note that "C5-6 cycloalkane" refers to a cycloalkyl group having 5 to 6 carbon atoms. From the viewpoint of preventing abnormal polymerization and ensuring stable polymerization, the copolymerization reaction is preferably carried out in the presence of a hydroxyl group-containing organic solvent. The solvents may be used alone or in combination of two or more.

[0056] The polymerization initiator that can be used in the copolymerization reaction is not particularly limited, but examples thereof include azobisisobutyronitrile, azobisisovaleronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), benzoyl peroxide, and t-butylperoxy-2-ethylhexanoate. The polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is generally 0.5 to 20 parts by mass, and preferably 1.0 to 18 parts by mass, per 100 parts by mass of the total amount of monomers charged.

[0057] [Photoacid Generator (B)] The positive resist material of the present disclosure contains an acid generator that generates a strong acid (hereinafter also referred to as an additive-type acid generator). The strong acid here refers to a compound that has sufficient acidity to cause a deprotection reaction of the acid labile groups of the base polymer.

[0058] Examples of the acid generator include compounds (photoacid generators) that generate acid in response to actinic rays or radiation. The photoacid generator is not particularly limited as long as it is a compound that generates an acid upon irradiation with high-energy rays, but those that generate sulfonic acid, imide acid, or methide acid are preferred. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate-type acid generators. Specific examples of photoacid generators include those described in paragraphs

[0122] to

[0142] of JP 2008-111103 A.

[0059] Furthermore, as the photoacid generator, a sulfonium salt represented by the following formula (2-1) or an iodonium salt represented by the following formula (2-2) can also be suitably used.

[0060] In formulas (2-1) and (2-2), R １０１ ~R １０５ R are each independently a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. １０１ ~R １０５Specific examples of the hydrocarbyl group having 1 to 20 carbon atoms represented by the formula (2-1) include those described in paragraphs

[0154] to

[0156] of JP-A No. 2024-010654. Examples of the cation of the sulfonium salt represented by the formula (2-1) include those described in paragraphs

[0157] to

[0180] of JP-A No. 2024-010654. Examples of the cation of the iodonium salt represented by the formula (2-2) include those described in paragraphs

[0181] to

[0182] of JP-A No. 2024-010654. In the formulas (2-1) and (2-2), Xa － Examples of such a compound include those described in paragraphs

[0183] to

[0196] of JP-A No. 2024-010654.

[0061] Furthermore, as the photoacid generator, an onium salt having high solubility in a suitable solvent is preferred. Specific examples of onium salts include diazonium salts, ammonium salts, iodonium salts, sulfonium salts, phosphonium salts, and oxonium salts. Specific examples include diphenyliodonium triflate, diphenyliodonium pyrenesulfonate, diphenyliodonium dodecylbenzenesulfonate, triphenylsulfonium triflate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium naphthalenesulfonate, and (hydroxyphenyl)benzylmethylsulfonium toluenesulfonate. Commercially available products include the CPI-210 series and IK-1 series (San-Apro Co., Ltd.), which are suitable for use. These thermal acid generators and photoacid generators may be used alone or in combination of two or more.

[0062] The content of the photoacid generator (B) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more, based on 100 parts by mass of the resin (A). The content of the photoacid generator (B) is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, based on 100 parts by mass of the resin (A). When the content of the photoacid generator (B) is 0.1 parts by mass or more, the alkali solubility of the high-energy ray-exposed portion of the resist is good. When the content of the photoacid generator (B) is 30 mol% or less, sufficient solubility in the solvent (C) can be ensured, and affinity with the developer can also be ensured.

[0063] [Solvent (C)] Examples of the solvent (C) include ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; diethylene glycol monoalkyl ethers such as diethylene glycol monomethyl ether and diethylene glycol mono-n-butyl ether; propylene glycol monoalkyl ethers such as triethylene glycol monomethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether; dipropylene glycol monoalkyl ethers such as dipropylene glycol monomethyl ether; tripropylene glycol monoalkyl ethers such as tripropylene glycol monoethyl ether; (poly)alkylene glycol monoalkyl ethers such as 3-methoxy-1-butanol; hydroxy group-containing carboxylic acid esters such as methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl hydroxyacetate, and methyl 2-hydroxy-3-methylbutyrate; and diethylene glycol hydroxy group-containing organic solvents such as ethanol; and (poly)alkylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, and tetrahydrofuran; methyl ethyl ketone, cyclohexanone, Ketones such as 2-heptanone and 3-heptanone; esters such as methyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl ethoxyacetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutylpropionate, ethyl acetate, n-butyl acetate, i-propyl acetate, i-butyl acetate, n-amyl acetate, i-amyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, i-propyl butyrate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, and ethyl 2-oxobutyrate;Examples of the solvent (D) include hydroxyl-free organic solvents such as aromatic hydrocarbons such as toluene and xylene. The solvent (D) may be used alone or in combination of two or more thereof.

[0064] Among these solvents (C), it is preferable to use a compound having an ether structure from the viewpoints of availability, cost, and stability during resist preparation. Specifically, it is more preferable to use at least one selected from propylene glycol monomethyl ether acetate, diethylene glycol methyl ethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, and 3-methoxy-1-butanol.

[0065] [Other Components] In addition to the components described above, the resist composition of the present invention may also contain a surfactant, a dissolution inhibitor, a crosslinking agent, a quencher other than the onium salt of the present invention (hereinafter referred to as "other quenchers"), a water repellency improver, an acetylene alcohol, etc.

[0066] (Method for Producing Positive Resist Material) A positive resist material of one embodiment can be produced by a method of mixing a resin (A), a photoacid generator (B), and a solvent (C) using a known mixing device. A positive resist material of one embodiment can be produced by a method of mixing a resin (A), a photoacid generator (B), and a solvent (C) using a known mixing device.

[0067] When producing a positive resist material, the reaction solution used to produce resin (A) can be used as is as a raw material. In this case, the solvent contained in the reaction solution can be used as part or all of the solvent (C) contained in the positive resist material.

[0068] When producing a positive resist material, the resin (A) may be isolated from a reaction solution containing the resin (A) by a known method and used as a raw material.

[0069] (Cured Resin Film) In one embodiment, the cured resin film is a cured product of the positive resist material of the present embodiment. The cured resin film of the present embodiment can be produced, for example, by applying a liquid containing the positive resist material to form a film, and then evaporating the solvent using a hot plate or the like.

[0070] (Pattern Forming Method) When the resist composition of the present invention is used in the manufacture of various integrated circuits, known lithography techniques can be applied. For example, the pattern forming method of the present invention includes a method comprising the following steps: (i) forming a resist film on a substrate using the resist composition (chemically amplified resist material) of the present invention described above; (ii) exposing the resist film to high-energy radiation; and (iii) developing the exposed resist film using a developer.

[0071] An example of the pattern forming method of the present invention will be described below.

[0072] First, the resist composition of the present invention is applied to a substrate for integrated circuit production (e.g., Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic antireflective coating, etc.) or a substrate for mask circuit production (e.g., Cr, CrO, CrON, MoSi2, SiO2, etc.) by an appropriate coating method so as to give a coating film thickness of 0.01 to 10 μm. Examples of the coating method include spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc. This is then pre-baked on a hot plate, preferably at 60 to 150°C for 10 seconds to 30 minutes, more preferably at 80 to 120°C for 30 seconds to 20 minutes, to form a resist film.

[0073] Next, the resist film is exposed to high-energy radiation. Examples of the high-energy radiation include ultraviolet radiation, far ultraviolet radiation, electron beam (EB), extreme ultraviolet radiation (EUV) with a wavelength of 3 to 15 nm, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation. When ultraviolet radiation, far ultraviolet radiation, EUV, X-rays, soft X-rays, excimer laser light, gamma rays, and synchrotron radiation are used as the high-energy radiation, the radiation is carried out directly or through a mask for forming a desired pattern. The exposure dose at this time is preferably 1 to 500 mJ / cm. ２ approximately, more preferably 10 to 300 mJ / cm ２ When EB is used as the high energy beam, the exposure dose is preferably about 0.1 to 300 μC / cm2, more preferably 0.5 to 200 μC / cm2. ２ The resist composition of the present invention is preferably used for fine patterning using high-energy radiation such as KrF excimer laser light, ArF excimer laser light, EB, EUV, X-rays, soft X-rays, γ-rays, and synchrotron radiation. Of these, it is preferable to use KrF excimer laser light, ArF excimer laser light, EB, or EUV with a wavelength of 3 to 15 nm. It is particularly suitable for fine patterning using EB or EUV.

[0074] After exposure, PEB may or may not be performed on a hot plate 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.

[0075] After exposure or PEB, the exposed resist film is developed by a conventional development method using a 0.1 to 10% by weight, preferably 2 to 5% by weight, aqueous alkaline developer, to form the desired pattern. Examples of the aqueous alkaline solution include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. Examples of the development method include a dip method, a puddle method, and a spray method for 3 seconds to 3 minutes, preferably 5 seconds to 2 minutes. In the case of a positive resist composition, the irradiated portion dissolves in the developer, while the unexposed portion remains insoluble, forming the desired positive pattern on the substrate. In the case of a negative resist composition, the opposite occurs: the irradiated portion becomes insoluble in the developer, while the unexposed portion dissolves.

[0076] A negative pattern can also be obtained by organic solvent development using a positive resist composition containing a base polymer having an acid labile group. Examples of developers that can be used in this case include 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, and ethyl crotonate. Examples of organic solvents include 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. These organic solvents may be used alone or in combination of two or more.

[0077] Upon completion of development, it is preferable to perform rinsing. As a rinsing liquid, a solvent that is miscible with the developer but does not dissolve the resist film is preferable. Examples of such solvents that are preferably used include alcohols having 3 to 10 carbon atoms, ether compounds having 8 to 12 carbon atoms, alkanes, alkenes, alkynes, and aromatic solvents having 6 to 12 carbon atoms.

[0078] Examples of the alcohol having 3 to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-pentyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, and 3-hexanol. Examples thereof include 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.

[0079] Examples of the ether compound having 8 to 12 carbon atoms include di-n-butyl ether, diisobutyl ether, di-sec-butyl ether, di-n-pentyl ether, diisopentyl ether, di-sec-pentyl ether, di-tert-pentyl ether, and di-n-hexyl ether.

[0080] Examples of the alkanes having 6 to 12 carbon atoms include hexane, heptane, octane, nonane, decane, undecane, dodecane, methylcyclopentane, dimethylcyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane, cyclononane, etc. Examples of the alkenes having 6 to 12 carbon atoms include hexene, heptene, octene, cyclohexene, methylcyclohexene, dimethylcyclohexene, cycloheptene, cyclooctene, etc. Examples of the alkynes having 6 to 12 carbon atoms include hexyne, heptine, octyne, etc.

[0081] Examples of the aromatic solvent include toluene, xylene, ethylbenzene, isopropylbenzene, tert-butylbenzene, and mesitylene.

[0082] Rinsing can reduce the occurrence of resist pattern collapse and defects. Rinsing is not always necessary, and not performing rinsing can reduce the amount of solvent used.

[0083] The developed hole or trench pattern can also be shrunk using thermal flow, RELACS, or DSA techniques. A shrink agent is applied to the hole pattern, and the diffusion of an acid catalyst from the resist film during baking causes crosslinking of the shrink agent on the surface of the resist film, resulting in adhesion of the shrink agent to the sidewalls of the hole pattern. The baking temperature is preferably 70 to 180°C, more preferably 80 to 170°C, and the baking time is preferably 10 to 300 seconds. Excess shrink agent is removed, and the hole pattern is shrunk.

[0084] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0085] A synthesis example of resin (A) is shown below. [Raw Materials] 4-Hydroxyphenylmethyl methacrylate (manufactured by Resonac) 2-Hydroxyphenylethyl methacrylate (manufactured by Resonac) 4-Hydroxyphenylethyl methacrylate (manufactured by Resonac) 4-Hydroxyphenylpropyl methacrylate (manufactured by Resonac) 3,5-Dimethyl-4-hydroxyphenylethyl methacrylate (manufactured by Resonac) p-Acetoxystyrene (manufactured by Sanwa Chemifa) 4-Hydroxyphenyl methacrylate (manufactured by Resonac) t-Butyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 1-Ethylcyclopentyl (meth)acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 1-Ethylcyclohexyl (meth)acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Methyl-2-adamantyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Styrene (manufactured by Idemitsu Kosan Co., Ltd.) p-Methylstyrene (manufactured by Tokyo Chemical Industry Co., Ltd.) Cyclohexyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 2,2'-Azobis(2-methylpropionate)dimethyl (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0086] Synthesis Example 1 Into a flask equipped with a stirrer, a dropping funnel, a condenser, a thermometer, and a gas inlet tube, 80 g of propylene glycol monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed as a solvent (C), and the mixture was stirred while being purged with nitrogen gas and heated to 90°C.

[0087] Next, 73 g (60 mol%) of 4-hydroxyphenylethyl methacrylate as monomer (ma-1), 12 g (20 mol%) of tert-butyl acrylate as monomer (ma-2), 15 g (20 mol%) of styrene as monomer (ma-3), 20 g (20 parts by mass relative to 100 parts by mass of the total of the monomer components) of propylene glycol monomethyl ether as solvent (C), and 2.5 g (2.5 parts by mass relative to 100 parts by mass of the total of the monomer components) of 2,2'-azobis(2-methylpropionate)dimethyl (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as a polymerization initiator were mixed to prepare a raw material monomer solution.

[0088] The entire amount of the prepared raw material monomer solution was added dropwise over 2 hours using a dropping funnel to solvent (C) in a flask under nitrogen gas atmosphere and normal pressure. After the addition was completed, the solution in the flask was cooled to 85°C with stirring, and a polymerization reaction was carried out for 4 hours to obtain a liquid containing the copolymer and solvent (C). The weight average molecular weight and molecular weight distribution of resin (A) were measured using the methods described above and are shown in Tables 1 and 2.

[0089] [Synthesis Examples 2 to 12] Liquids containing resin (A) of Synthesis Examples 2 to 12 were obtained in the same manner as Synthesis Example 1 using the raw materials and blending ratios shown in Table 1. The weight average molecular weight and molecular weight distribution of each resin (A) were measured by the methods described above and are shown in Table 1.

[0090] Comparative Synthesis Examples 1 to 4 Liquids containing copolymers (cA) of Comparative Synthesis Examples 1 to 4 were obtained in the same manner as in Synthesis Example 1 using the raw materials and blending ratios shown in Table 2. The weight average molecular weight and molecular weight distribution of each copolymer (cA) were measured by the methods described above and are shown in Table 2.

[0091]

[0092]

[0093] In Tables 1 and 2, the abbreviations have the following meanings: 4HPMM: 4-hydroxyphenylmethyl methacrylate 2HPEM: 2-hydroxyphenylethyl methacrylate 4HPEM: 4-hydroxyphenylethyl methacrylate 4HPPM: 4-hydroxyphenylpropyl methacrylate DHPEM: 3,5-dimethyl-4-hydroxyphenylethyl methacrylate 4HSt: 4-hydroxystyrene 4HPM: 4-hydroxyphenyl methacrylate BA: t-butyl acrylate ECPM: 1-ethylcyclopentyl (meth)acrylate ECHM: 1-ethylcyclohexyl (meth)acrylate MAM: 2-methyl-2-adamantyl methacrylate St: styrene MSt: p-methylstyrene CHA: cyclohexyl acrylate

[0094] [Examples 1 to 12, Comparative Examples 1 to 4] Resin (A) of Synthesis Examples 1 to 12 shown in Tables 3 and 4, or copolymer (cA) of Comparative Synthesis Examples 1 to 4, CPI-210S (manufactured by San-Apro) as the photoacid generator (B), and propylene glycol monomethyl ether (PGME) as the solvent (C) were mixed in the proportions shown in Tables 3 and 4, respectively, to prepare resist compositions of Examples 1 to 12 and Comparative Examples 1 to 4. The blending amount of resin (A) or (cA) shown in Tables 3 and 4 does not include the amount of solvent. The concentrations shown in Tables 3 and 4 indicate the content of resin (A) relative to the total of resin (A) and solvent (C) in the resist composition.

[0095] (Film Thickness Measurement) The resist compositions of Examples 1 to 12 and Comparative Examples 1 to 4 were each applied by spin coating onto a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) so that the thickness after pre-baking was 2 μm, forming a coating film. The coating film was then heated at 90° C. for 90 seconds to volatilize and remove the solvent (C) in the coating film. The thickness of the prepared resist film was measured using a step gauge. The results are shown in Tables 3 and 4.

[0096] (KrF Light Transmittance Measurement) The resist compositions of Examples 1 to 12 and Comparative Examples 1 to 4 were each applied by spin coating to a square non-alkali glass substrate measuring 5 cm in length and 5 cm in width in plan view, to form a coating film with a thickness of 3 μm after exposure. The coating film was then heated at 90° C. for 90 seconds to volatilize and remove the solvent (C) in the coating film. The resist films thus prepared were measured using a spectrophotometer to measure the transmittance at 248 nm, which corresponds to KrF light. The results are shown in Tables 3 and 4.

[0097] (Evaluation of Pattern Shape) The pattern shape was evaluated by measuring Eop and Bottom CD.

[0098] "Preparation of Pattern-Forming Samples" Each of the resist compositions of Examples 1 to 12 and Comparative Examples 1 to 4 was applied by spin coating onto a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd.) so that the thickness after pre-baking would be 2 μm, forming a coating film. Next, the coating film was heated at 90° C. for 90 seconds to volatilize and remove the solvent (C) in the coating film.

[0099] "Eop Measurement" The prepared resist film was exposed using a KrF stepper (FPA 300-EX5, CANON). The wafer was baked (PEB) on a hot plate at 90°C for 90 seconds and then puddle developed with a 2.38% by mass TMAH aqueous solution for 60 seconds. The obtained resist pattern was confirmed using a CD-SEM S9200 (Hitachi High-Tech). The exposure dose that formed 16 nm lines / 32 nm pitch (line and space (L / S = 1 / 1)) was defined as the optimal exposure dose, and the exposure dose at this time was defined as Eop. The results are shown in Tables 3 and 4.

[0100] "Bottom CD measurement" The resist film was exposed to an exposure dose of 300 mJ / cm ２ Exposure was performed using a KrF stepper (FPA 300-EX5, CANON) so that the wafer was exposed to light at 90°C for 90 seconds (PEB). The wafer was then baked on a hot plate at 90°C for 90 seconds and puddle developed with a 2.38% by mass TMAH aqueous solution for 60 seconds. The resist pattern, masked so that the lowest part of the resist pattern was approximately 2,000 nm, was confirmed using a CD-SEM S9200 (Hitachi High-Tech). The lowest part of the resist pattern was measured, and its length was taken as the Bottom CD. The results are shown in Tables 3 and 4.

[0101]

[0102]

[0103] (Discussion) From the results in Tables 3 and 4, it can be seen that in Examples 1 to 12, a resist resin containing the structural unit (a-1) was used, resulting in good transmittance and a good pattern shape after exposure. On the other hand, in Comparative Examples 1 to 4, a resist resin not containing the structural unit (a-1) was used, resulting in poor transmittance and an unsatisfactory pattern shape after exposure. In Comparative Examples 1 and 2, the phenol structure, as in hydroxystyrene, is connected to the polymer chain without an ester structure. In this case, the phenol structures are arranged in close proximity, which leads to absorption of energy rays when the positive resist material is exposed, thereby reducing transmittance and presumably preventing a good pattern shape from being obtained. Furthermore, in Comparative Examples 3 and 4, in the formula (1) of the structural unit (a-1), R １was a single bond, not an alkanediyl group having 1 to 6 carbon atoms. In this case, it is presumed that resonance between the ester structure and the phenol structure resulted in the absorption of energy rays when exposing the positive resist material, resulting in a decrease in transmittance and making it impossible to obtain a good pattern shape.

Claims

1. A positive resist material containing a resin (A) and a photoacid generator (B), wherein the resin (A) is a copolymer containing a structural unit (a-1) represented by the following formula (1) and a structural unit (a-2) represented by the following formula (2): (In formula (1), R Ａ is a hydrogen atom or a methyl group. １ R is an alkanediyl group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether bond or an ester bond. ２ is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms; a is 1 or 2; and b is an integer of 0 to 4, provided that 1≦a+b≦5. (In formula (2), R Ｂ is a hydrogen atom or a methyl group. ４ is an acid labile group.

2. In the formula (1), R １ 2. The positive resist material according to claim 1, wherein is an alkanediyl group having 1 to 3 carbon atoms, and a is 1.

3. In the formula (2), R ４ 2. A positive resist material according to claim 1, wherein the acid labile group represented by the formula (A-3) below is a group represented by the formula (A-3): (R of the acid labile group represented by formula (A-3) ３４ , R ３５ , R ３６ is a monovalent hydrocarbon group such as a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, or a linear, branched or cyclic alkenyl group having 2 to 20 carbon atoms, which may contain heteroatoms such as oxygen, sulfur, nitrogen or fluorine, and R ３４ and R ３５ , R ３４ and R ３６ , R ３５ and R ３６ may be bonded to each other to form an alicyclic ring having 3 to 20 carbon atoms together with the carbon atom to which they are bonded.

4. The positive resist material according to claim 1, wherein the resin (A) further contains another structural unit (a-3).

5. The positive resist material according to claim 1, wherein, of all the structural units constituting said resin (A), the structural unit (a-1) represented by the above formula (1) accounts for 30 to 90 mol %, the structural unit (a-2) represented by the above formula (2) accounts for 1 to 40 mol %, and the other structural unit (a-3) accounts for 0 to 40 mol %.

6. The positive resist material according to claim 1, further comprising a solvent (C).

7. The positive resist material according to claim 1, which has a KrF light transmittance of 45% or more.

8. The positive resist material according to claim 1, further comprising a solvent (C), wherein the content of the resin (A) is 5 to 40 mass % relative to the total of the resin (A) and the solvent (C), and the content of the photoacid generator (B) is 0.1 to 30 mass parts per 100 mass parts of the resin (A).

9. A cured resin film comprising a cured product of the positive resist material according to any one of claims 1 to 8.

10. A pattern formation method comprising the steps of: forming a resist film on a substrate using the positive resist material according to any one of claims 1 to 8; exposing the resist film to high-energy rays; and developing the exposed resist film using a developer.

11. The pattern forming method according to claim 10, wherein the high-energy beam is i-line, KrF excimer laser light, ArF excimer laser light, electron beam, or extreme ultraviolet light having a wavelength of 3 to 15 nm.

12. A copolymer containing a structural unit (a-1) represented by the following formula (1) and a structural unit (a-2) represented by the following formula (2): (In formula (1), R Ａ is a hydrogen atom or a methyl group. １ is an alkanediyl group having 1 to 6 carbon atoms, some of the carbon atoms of which may be substituted with an ether bond or an ester bond. ２ is a fluorine atom, a trifluoromethyl group, a cyano group, or a saturated hydrocarbyl group having 1 to 6 carbon atoms; a is 1 or 2; and b is an integer of 0 to 4, provided that 1≦a+b≦5. (In formula (2), R Ｂ is a hydrogen atom or a methyl group. ４ is an acid labile group.

Images