Resist composition and pattern forming method

Abstract

To provide a resist composition that exhibits a high contrast, improved maximum resolution, and excellent sensitivity and line width roughness (LWR) in lithography using high-energy radiation, and a pattern forming method using the resist composition.SOLUTION: A resist composition comprises (A) a base polymer containing a polymer comprising repeat units having an acid labile group and repeat units having a carboxy group, (B) an organic solvent, and (C) a hypervalent iodine compound represented by formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resist composition and a pattern forming method. [Background technology]

[0002] As LSIs become more highly integrated and faster, pattern rules are becoming increasingly miniaturized. This is due to the increasing popularity of 5G high-speed communications and artificial intelligence (AI), which require high-performance devices to process these. The most advanced miniaturization technology is extreme ultraviolet (EUV) lithography with a wavelength of 13.5 nm, which is currently used to mass-produce 5 nm node devices. Furthermore, the use of EUV lithography is being considered for next-generation 3 nm node devices and the next-generation 2 nm node devices.

[0003] As miniaturization progresses, image blurring due to acid diffusion has become a problem. To ensure resolution in fine patterns with processing dimensions of 45 nm and below, it has been proposed that controlling acid diffusion is important in addition to improving dissolution contrast, as has been proposed in the past (Non-Patent Document 1). However, because chemically amplified resist compositions increase sensitivity and contrast through acid diffusion, attempts to minimize acid diffusion by lowering the post-exposure bake (PEB) temperature or shortening the time result in significant decreases in sensitivity and contrast.

[0004] In response to this, adding an acid generator that generates an acid with a bulky structure is an effective method for controlling acid diffusion. Furthermore, a design that further suppresses acid diffusion has been proposed in which a repeating unit derived from an onium salt having a polymerizable unsaturated bond is incorporated into the polymer. In this case, the polymer also functions as an acid generator (polymer-bound acid generator). Patent Document 1 proposes a polymer-bound acid generator that generates a specific fluorosulfonic acid from a base polymer.

[0005] However, for 3-nm and 2-nm node devices, fine pattern formation technology using EUV lithography is required, and in such areas, sufficient resolution can no longer be ensured by acid diffusion control alone. For example, in line and space patterns, pattern defects such as bridges between patterns and scum at the bottom are an issue, and one of the causes is said to be insufficient contrast.

[0006] As a method for increasing contrast, attempts have been made to crosslink polymer chains with acid-decomposable crosslinking groups. Crosslinking can increase the molecular weight in advance, and the crosslinks in exposed areas can be decomposed by the acid generated during exposure. Patent Document 2 discloses a crosslinked polymer obtained by reacting a unit having a carboxyl group or a hydroxyl group with a divinyl ether unit.

[0007] On the other hand, crosslinked polymers formed by crosslinking between polymer chains have very large molecular weights, and when stored for a long period of time as a resist solution, the polymers aggregate, causing problems such as an increase in the number of defects. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-133448 [Patent Document 2] Patent No. 5562651 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-180928 [Patent Document 4] Japanese Patent Application Publication No. 2018-095853 [Non-patent literature]

[0009] [Non-Patent Document 1] SPIE Vol. 6520 65203L-1 (2007) Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resist composition that achieves high contrast and improved limiting resolution, as well as excellent sensitivity and line width roughness (LWR), in lithography using high-energy rays, particularly in EB lithography and EUV lithography, and a pattern formation method that uses the resist composition. [Means for solving the problem]

[0011] As a result of extensive research into achieving the above-mentioned object, the present inventors have discovered that a resist composition comprising a base polymer including a polymer containing a repeating unit having an acid labile group and a repeating unit having a carboxy group, an organic solvent, and a specific hypervalent iodine compound enhances contrast, and as a result, has excellent limiting resolution and is extremely effective for precise microfabrication, which has led to the completion of the present invention.

[0012] That is, the present invention provides the following resist composition and pattern forming method. 1. A resist composition comprising: (A) a base polymer including a polymer containing a repeating unit having an acid labile group and a repeating unit having a carboxy group; (B) an organic solvent; and (C) a hypervalent iodine compound represented by the following formula (1): [ka] (In the formula, n is an integer of 0 to 5. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. 2. The resist composition of 1, wherein the repeating unit having an acid labile group is represented by the following formula (a1) or (a2): [ka] (In the formula, a is an integer of 0 to 4. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -X 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group or a naphthylene group, and the saturated hydrocarbylene group may contain at least one selected from a hydroxy group, an ether bond, an ester bond and a lactone ring. X 2 is a single bond or *-C(=O)-O-. * indicates a bond to a carbon atom in the main chain. R 11 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. AL 1 and AL 2 are each independently an acid labile group. 3. The resist composition of 1 or 2, wherein the repeating unit having a carboxy group is represented by the following formula (b): [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OY 11 -It is. Y 11is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. 4. The resist composition of any one of 1 to 3, wherein the polymer further comprises at least one repeating unit selected from the group consisting of repeating units represented by the following formulae (c1) and (c2): [ka] (In the formula, b is 1 or 2, and c is an integer of 0 to 4. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 is a group having 1 to 20 carbon atoms and containing at least one selected from a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic anhydride (—C(═O)—OC(═O)—). R 22 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. 5. The resist composition of any one of 1 to 4, wherein the polymer further comprises a repeating unit having a photoacid generating group. 6. The resist composition according to any one of 1 to 5, further comprising (D) a photoacid generator. 7. The resist composition according to any one of 1 to 6, further comprising (E) a quencher. 8. The resist composition according to any one of 1 to 7, further comprising (F) a surfactant. 9. A pattern forming method comprising the steps of forming a resist film on a substrate using the resist composition of any one of 1 to 8; exposing the resist film to a KrF excimer laser, an ArF excimer laser, an electron beam, or extreme ultraviolet light; and developing the exposed resist film using a developer. [Effects of the Invention]

[0013] The resist composition of the present invention has high contrast and therefore has small LWR, making it possible to construct a high-resolution pattern profile. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Resist composition] The resist composition of the present invention comprises (A) a base polymer including a polymer containing a repeating unit having an acid labile group and a repeating unit having a carboxy group, (B) an organic solvent, and (C) a predetermined hypervalent iodine compound.

[0015] [(A) Base polymer] The base polymer of component (A) includes a polymer containing a repeating unit having an acid labile group. The unit having an acid labile group is preferably a repeating unit represented by the following formula (a1) (hereinafter also referred to as repeating unit a1) or a repeating unit represented by the following formula (a2) (hereinafter also referred to as repeating unit a2). [ka]

[0016] In formulas (a1) and (a2), a is an integer of 0 to 4, preferably 0 or 1. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OX 11 -X 11is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. 2 is a single bond or *-C(=O)-O-. * is a bond to a carbon atom in the main chain. R 11 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. 1 and AL 2 are each independently an acid labile group.

[0017] X 11 The saturated hydrocarbylene group represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include alkanediyl groups having 1 to 10 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; and cyclic saturated hydrocarbylene groups having 3 to 10 carbon atoms, such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group.

[0018] R 11 Specific examples of the halogen atom represented by R include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. 11The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0019] X in formula (a1) 1 Examples of structures in which R is changed include, but are not limited to, those shown below. A and AL 1 is the same as above. [ka]

[0020] [ka]

[0021] A polymer containing the repeating unit a1 is decomposed by the action of an acid to produce a carboxyl group, and becomes alkali-soluble.

[0022] AL 1 and AL 2 The acid labile group represented by the formula (I) is not particularly limited, but preferred examples include a group represented by any one of the following formulae (L1) to (L4), a tertiary hydrocarbyl group having 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trihydrocarbylsilyl group in which each hydrocarbyl group has 1 to 6 carbon atoms, a carbonyl group, or a hydrocarbyl group having 4 to 20 carbon atoms and containing an ether bond or an ester bond. [ka] (In the formula, the dashed lines represent bonds.)

[0023] In formula (L1), R L01 and R L02 is a hydrogen atom or a saturated hydrocarbyl group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. The saturated hydrocarbyl group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-octyl group, and 2-ethylhexyl group; and cyclic saturated hydrocarbyl groups such as a cyclopentyl group, cyclohexyl group, norbornyl group, tricyclodecanyl group, tetracyclododecanyl group, and adamantyl group.

[0024] In formula (L1), R L03is a hydrocarbyl group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic, but is preferably a saturated hydrocarbyl group. In addition, some or all of the hydrogen atoms of the saturated hydrocarbyl group may be substituted with a hydroxy group, a saturated hydrocarbyloxy group, an oxo group, an amino group, a saturated hydrocarbylamino group, or the like, and some of the -CH2- of the saturated hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom. Examples of the saturated hydrocarbyl group include R L01 and R L02 Examples of the saturated hydrocarbyl group represented by the formula (I) include the same as those mentioned above. Examples of the substituted saturated hydrocarbyl group include the groups shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0025] R L01 , R L02 and R L03 Any two of the R may be bonded to each other to form a ring together with the carbon atom or carbon atom and oxygen atom to which they are bonded. L01 , R L02 and R L03 It is preferred that any two of these are each independently an alkanediyl group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms.

[0026] In formula (L2), R L04 is a tertiary hydrocarbyl 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, a carbonyl group, a saturated hydrocarbyl group having 4 to 20 carbon atoms and containing an ether bond or an ester bond, or a group represented by formula (L1): x is an integer of 0 to 6.

[0027] R L04The tertiary hydrocarbyl group represented by the formula (I) may be branched or cyclic, and specific examples thereof include tert-butyl, tert-pentyl, 1,1-diethylpropyl, 2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl, 2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Examples of the trialkylsilyl group include trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Examples of the saturated hydrocarbyl group containing a carbonyl group, an ether bond, or an ester bond include a 3-oxocyclohexyl group, a 4-methyl-2-oxooxan-4-yl group, and a 5-methyl-2-oxooxolan-5-yl group.

[0028] In formula (L3), R L05is an optionally substituted saturated hydrocarbyl group having 1 to 8 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms. The optionally substituted saturated hydrocarbyl group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, and n-hexyl; cyclic saturated hydrocarbyl groups such as cyclopentyl and cyclohexyl; and groups in which some or all of the hydrogen atoms have been substituted with a hydroxy group, a saturated hydrocarbyloxy group having 1 to 8 carbon atoms, a carboxy group, a saturated hydrocarbylcarbonyl group having 1 to 8 carbon atoms, an oxo group, an amino group, a saturated hydrocarbylamino group having 1 to 8 carbon atoms, a cyano group, a mercapto group, a saturated hydrocarbylthio group having 1 to 8 carbon atoms, a sulfo group, or the like. Examples of the optionally substituted aryl group include a phenyl group, a methylphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, and groups in which some or all of the hydrogen atoms of these groups have been substituted with a hydroxy group, a saturated hydrocarbyloxy group having 1 to 8 carbon atoms, a carboxy group, a saturated hydrocarbylcarbonyl group having 1 to 8 carbon atoms, an oxo group, an amino group, a saturated hydrocarbylamino group having 1 to 8 carbon atoms, a cyano group, a mercapto group, a saturated hydrocarbylthio group having 1 to 8 carbon atoms, a sulfo group, or the like.

[0029] In formula (L3), y is 0 or 1, z is an integer of 0 to 3, and 2y+z=2 or 3.

[0030] In formula (L4), R L06 is an optionally substituted saturated hydrocarbyl group having 1 to 8 carbon atoms or an optionally substituted aryl group having 6 to 20 carbon atoms. Specific examples of the optionally substituted saturated hydrocarbyl group and the optionally substituted aryl group include R L05 Examples of the compound represented by the formula (I) include the same compounds as those exemplified above.

[0031] In formula (L4), R L07 ~R L16are each independently a hydrogen atom or an optionally substituted hydrocarbyl group having 1 to 15 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic, but is preferably a saturated hydrocarbyl group. Examples of the hydrocarbyl group include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-pentyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, and n-decyl; cyclic saturated hydrocarbyl groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, and cyclohexylbutyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with hydroxy, saturated hydrocarbyloxy groups having 1 to 8 carbon atoms, carboxy, saturated hydrocarbyloxycarbonyl groups having 1 to 8 carbon atoms, oxo, amino, saturated hydrocarbylamino groups having 1 to 8 carbon atoms, cyano, mercapto, saturated hydrocarbylthio groups having 1 to 8 carbon atoms, sulfo, or the like. L07 ~R L16 Two selected from these may be bonded to each other to form a ring together with the carbon atoms to which they are bonded (for example, R L07 and R L08 , R L07 and R L09 , R L07 and R L10 , R L08 and R L10 , R L09 and R L10 , R L11 and R L12 , R L13 and R L14 In this case, the group participating in the ring formation is a hydrocarbylene group having 1 to 15 carbon atoms. Examples of the hydrocarbylene group include those obtained by removing one hydrogen atom from the above-mentioned examples of the hydrocarbyl group. L07 ~R L16 may bond to adjacent carbon atoms without any intervening bond to form a double bond (for example, R L07 and R L09 , RL09 and R L15 , R L13 and R L15 , R L14 and R L15 etc.).

[0032] Among the acid labile groups represented by formula (L1), linear or branched groups include, but are not limited to, the groups shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0033] Among the acid labile groups represented by formula (L1), examples of cyclic groups include a tetrahydrofuran-2-yl group, a 2-methyltetrahydrofuran-2-yl group, a tetrahydropyran-2-yl group, and a 2-methyltetrahydropyran-2-yl group.

[0034] Examples of the acid labile group represented by formula (L2) include a tert-butoxycarbonyl group, a tert-butoxycarbonylmethyl group, a tert-pentyloxycarbonyl group, a tert-pentyloxycarbonylmethyl 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.

[0035] Examples of the acid labile group represented by formula (L3) include a 1-methylcyclopentyl group, a 1-ethylcyclopentyl group, a 1-n-propylcyclopentyl group, a 1-isopropylcyclopentyl group, a 1-n-butylcyclopentyl group, a 1-sec-butylcyclopentyl group, a 1-cyclohexylcyclopentyl group, a 1-(4-methoxy-n-butyl)cyclopentyl group, a 1-methylcyclohexyl group, a 1-ethylcyclohexyl group, a 3-methyl-1-cyclopenten-3-yl group, a 3-ethyl-1-cyclopenten-3-yl group, a 3-methyl-1-cyclohexen-3-yl group, and a 3-ethyl-1-cyclohexen-3-yl group.

[0036] As the acid labile group represented by formula (L4), groups represented by the following formulae (L4-1) to (L4-4) are particularly preferred. [ka]

[0037] In formulas (L4-1) to (L4-4), the dashed lines represent the bond positions and bond directions. L41 are each independently a hydrocarbyl group having 1 to 10 carbon atoms. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic, but is preferably a saturated hydrocarbyl group. Examples of the hydrocarbyl group include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, and n-hexyl; and cyclic saturated hydrocarbyl groups such as cyclopentyl and cyclohexyl.

[0038] The groups represented by formulae (L4-1) to (L4-4) may have stereoisomers (enantiomers or diastereomers), and formulae (L4-1) to (L4-4) represent all of these stereoisomers. When the acid labile group is a group represented by formula (L4), multiple stereoisomers may be included.

[0039] For example, formula (L4-3) represents a mixture of one or two types selected from groups represented by the following formulae (L4-3-1) and (L4-3-2). [ka] (In the formula, R L41 The dashed lines represent the bond positions and bond directions.

[0040] Furthermore, formula (L4-4) represents one or a mixture of two or more selected from groups represented by the following formulae (L4-4-1) to (L4-4-4). [ka] (In the formula, R L41 The dashed lines represent the bond positions and bond directions.

[0041] Formulas (L4-1) to (L4-4), (L4-3-1), (L4-3-2), and formulas (L4-4-1) to (L4-4-4) also represent their enantiomers and mixtures of enantiomers.

[0042] The bonds in formulae (L4-1) to (L4-4), (L4-3-1), (L4-3-2), and (L4-4-1) to (L4-4-4) are exo-oriented relative to the bicyclo[2.2.1]heptane ring, thereby achieving high reactivity in acid-catalyzed elimination reactions (see JP 2000-336121 A). In the production of monomers containing a tertiary exo-saturated hydrocarbyl group as a substituent having a bicyclo[2.2.1]heptane skeleton, monomers substituted with endo-alkyl groups represented by the following formulae (L4-1-endo) to (L4-4-endo) may be included. To achieve good reactivity, the exo-alkyl ratio is preferably 50 mol% or more, and more preferably 80 mol% or more. [ka] (In the formula, R L41The dashed lines represent the bond positions and bond directions.

[0043] Examples of the acid labile group represented by formula (L4) include, but are not limited to, the groups shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0044] Also, AL 1 and AL 2 Among the acid labile groups represented by the formula (I), the tertiary hydrocarbyl group having 4 to 20 carbon atoms, the trihydrocarbylsilyl group in which each hydrocarbyl group has 1 to 6 carbon atoms, and the saturated hydrocarbyl group having 4 to 20 carbon atoms and containing a carbonyl group, an ether bond or an ester bond are each represented by the formula (I), (II), (III), (IV ... L04 Examples of the above-mentioned examples are the same as those given in the explanation of the above.

[0045] Specific examples of the repeating unit a1 include, but are not limited to, the following: A is the same as above. [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] [ka]

[0050] These specific examples are X 1 is a single bond, but X 1 When X is other than a single bond, it can be combined with a similar acid labile group. 1 Specific examples of when is other than a single bond are as described above.

[0051] Polymers containing the repeating unit a2 are decomposed by the action of an acid, similar to the repeating unit a1, to produce hydroxyl groups and become alkali-soluble. Specific examples of the repeating unit a2 include, but are not limited to, the following. In the following formula, R A is the same as above. [ka]

[0052] [ka]

[0053] The polymer is characterized in that it contains a repeating unit having a carboxy group (hereinafter also referred to as repeating unit b) in addition to a repeating unit having an acid labile group. As the repeating unit b, one represented by the following formula (b) is preferred. [ka]

[0054] In formula (b), R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OY 11 -It is. Y 11represents a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain. Y 1 The saturated hydrocarbylene group represented by the formula (a1) may be linear, branched, or cyclic. 11 Specific examples of the saturated hydrocarbylene group represented by the formula: include the same as those exemplified above.

[0055] Specific examples of the repeating unit b include, but are not limited to, those shown below. A is the same as above. [ka]

[0056] [ka]

[0057] The polymer preferably further contains at least one repeating unit selected from the group consisting of a repeating unit represented by the following formula (c1) (hereinafter also referred to as repeating unit c1) and a repeating unit represented by the following formula (c2) (hereinafter also referred to as repeating unit c2): [ka]

[0058] In formulas (c1) and (c2), b is 1 or 2. c is an integer of 0 to 4, preferably 0 or 1. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21R is a group having 1 to 20 carbon atoms and containing at least one selected from a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-OC(=O)-). 22 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom.

[0059] R 22 Specific examples of halogen atoms represented by R 11 Specific examples of halogen atoms represented by the formula R include those exemplified above. 22 The hydrocarbyl group represented by may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 11 Specific examples of the hydrocarbyl group represented by the formula:

[0060] Specific examples of the repeating unit c1 include, but are not limited to, those shown below. A is the same as above. [ka]

[0061] [ka]

[0062] [ka]

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] Specific examples of the repeating unit c2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] As the repeating units c1 and c2, those having a lactone ring as a polar group are particularly preferred for ArF lithography, and those having a phenolic hydroxy group are preferred for KrF lithography, EB lithography and EUV lithography.

[0075] The polymer preferably further contains a repeating unit having a photoacid generating group. This allows for strong control of the diffusion of the generated acid, thereby improving LWR and dimensional uniformity (CDU). Specific examples of such a repeating unit having a photoacid generating group include a repeating unit represented by the following formula (d1) (hereinafter also referred to as repeating unit d1), a repeating unit represented by the following formula (d2) (hereinafter also referred to as repeating unit d2), a repeating unit represented by the following formula (d3) (hereinafter also referred to as repeating unit d3), and a repeating unit represented by the following formula (d4) (hereinafter also referred to as repeating unit d4). [ka]

[0076] In formulas (d1) to (d4), R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is a single bond or a phenylene group. 2 is **-C(=O)-OZ 21 -, **-C(=O)-NH-Z 21 -or **-OZ 21 -It is. Z 21 Z is an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, or a divalent group obtained by combining these, and may contain at least one selected from a carbonyl group, an ester bond, an ether bond, and a hydroxy group. 3 are each independently a single bond, a phenylene group, a naphthylene group, or *-C(=O)-OZ 31 -It is. Z 31is an aliphatic hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the aliphatic hydrocarbylene group may contain at least one selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. 4 is a single bond or ***-Z 41 -C(=O)-O-. Z 41 is a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. 5 represents a single bond, a methylene group, an ethylene group, a phenylene group, a fluorinated phenylene group, a phenylene group substituted with a trifluoromethyl group, *-C(=O)-OZ 51 -, *-C(=O)-N(H)-Z 51 -or*-OZ 51 -It is. Z 51 represents an aliphatic hydrocarbylene group having 1 to 6 carbon atoms, a phenylene group, a fluorinated phenylene group, or a phenylene group substituted with a trifluoromethyl group, and may contain at least one selected from a carbonyl group, an ester bond, an ether bond, and a hydroxy group. * represents a bond to a carbon atom in the main chain. ** represents a bond to a carbon atom in the main chain. Z 1 *** represents a bond with Z 3 Represents a bond with .

[0077] Z 21 , Z 31 and Z 51The aliphatic hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,1-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane- Examples of the alkyl group include alkanediyl groups such as a 2,3-diyl group, a butane-1,4-diyl group, a 1,1-dimethylethane-1,2-diyl group, a pentane-1,5-diyl group, a 2-methylbutane-1,2-diyl group, and a hexane-1,6-diyl group; cycloalkanediyl groups such as a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, and a cyclohexanediyl group; and groups obtained by combining these groups.

[0078] Z 41 The hydrocarbylene group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include, but are not limited to, those shown below. [ka] (In the formula, the dashed lines represent bonds.)

[0079] In formula (d1), R 31 and R 32 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 31 and R 32may be bonded to each other to form a ring together with the sulfur atom to which they are attached. The hydrocarbyl groups may be saturated or unsaturated, and may be linear, branched or cyclic. Specific examples thereof include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; saturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, 4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl; unsaturated cyclic hydrocarbyl groups having 3 to 20 carbon atoms, such as cyclohexenyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, naphthyl, and thienyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, 1-phenylethyl, and 2-phenylethyl; and groups obtained by combining these, with aryl groups being preferred. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc.

[0080] Specific examples of the cation of the repeating unit d1 include, but are not limited to, the following: A is the same as above. [ka]

[0081] [ka]

[0082] [ka]

[0083] [ka]

[0084] [ka]

[0085] [ka]

[0086] [ka]

[0087] In formula (d1), M - is a non-nucleophilic counter ion. Examples of the non-nucleophilic counter ion include halide ions such as chloride ion and bromide ion; fluoroalkylsulfonate ions such as triflate ion, 1,1,1-trifluoroethanesulfonate ion and nonafluorobutanesulfonate ion; arylsulfonate ions such as tosylate ion, benzenesulfonate ion, 4-fluorobenzenesulfonate ion and 1,2,3,4,5-pentafluorobenzenesulfonate ion; alkylsulfonate ions such as mesylate ion and butanesulfonate ion; imide ions such as bis(trifluoromethylsulfonyl)imide ion, bis(perfluoroethylsulfonyl)imide ion and bis(perfluorobutylsulfonyl)imide ion; and methide ions such as tris(trifluoromethylsulfonyl)methide ion and tris(perfluoroethylsulfonyl)methide ion.

[0088] Other examples of the non-nucleophilic counter ion include a sulfonate anion represented by the following formula (d1-1) in which the α-position is substituted with a fluorine atom, and a sulfonate anion represented by the following formula (d1-2) in which the α-position is substituted with a fluorine atom and the β-position is substituted with a trifluoromethyl group. [ka]

[0089] In formula (d1-1), R 33 is a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 30 carbon atoms, or a hydrocarbyloxycarbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group may contain a halogen atom, an ether bond, an ester bond, a carbonyl group, or a lactone ring. The hydrocarbyl group and the hydrocarbyl moiety of the hydrocarbylcarbonyloxy group and hydrocarbyloxycarbonyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0090] In formula (d1-2), R 34 R is a hydrogen atom, a hydrocarbyl group having 1 to 30 carbon atoms, or a hydrocarbylcarbonyl group having 2 to 30 carbon atoms, and the hydrocarbyl group and hydrocarbylcarbonyl group may contain a halogen atom, an ether bond, an ester bond, a carbonyl group, or a lactone ring. 35 is a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. The hydrocarbyl moiety of the hydrocarbyl group and the hydrocarbyl carbonyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. 35 As the aryl group, a trifluoromethyl group is preferred.

[0091] Specific examples of the sulfonate anion represented by formula (d1-1) or (d1-2) include, but are not limited to, the following: 35 is the same as above, and Ac is an acetyl group. [ka]

[0092] [ka]

[0093] [ka]

[0094] [ka]

[0095] [ka]

[0096] [ka]

[0097] [ka]

[0098] [ka]

[0099] [ka]

[0100] [ka]

[0101] [ka]

[0102] [ka]

[0103] [ka]

[0104] In formulas (d2) and (d3), L 1 is a single bond, an ether bond, an ester bond, a carbonyl group, a sulfonate ester bond, a carbonate bond, or a carbamate bond. Among these, from the viewpoint of synthesis, an ether bond, an ester bond, or a carbonyl group is preferred, and an ester bond or a carbonyl group is more preferred.

[0105] In formula (d2), Rf 1 and Rf 2 are each independently a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms. 1 and Rf 2 In order to increase the acid strength of the generated acid, it is preferable that Rf be a fluorine atom. 3 and Rf 4 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms. Of these, Rf 3 and Rf 4 At least one of these is preferably a trifluoromethyl group.

[0106] In formula (d3), Rf 5 and Rf 6 are each independently a hydrogen atom, a fluorine atom, or a fluorinated alkyl group having 1 to 6 carbon atoms, provided that all Rf 5 and Rf 6cannot be simultaneously hydrogen atoms. Among these, Rf 5 and Rf 6 At least one of these is preferably a trifluoromethyl group.

[0107] In the formulas (d2) and (d3), d is an integer of 0 to 3, with 1 being preferred.

[0108] Examples of the anion of the repeating unit d2 include, but are not limited to, those shown below. A is the same as above. [ka]

[0109] [ka]

[0110] [ka]

[0111] [ka]

[0112] [ka]

[0113] [ka]

[0114] Examples of the anion of the repeating unit d3 include, but are not limited to, those shown below. A is the same as above. [ka]

[0115] [ka]

[0116] [ka]

[0117] [ka]

[0118] [ka]

[0119] [ka]

[0120] Specific examples of the anion of the repeating unit d4 include, but are not limited to, those shown below. A is the same as above. [ka]

[0121] In formulas (d2) to (d4), A + is an onium cation. Examples of the onium cation include a sulfonium cation, an iodonium cation, and an ammonium cation, and the sulfonium cation and the iodonium cation are preferred. Specific examples of these cations include the same as those exemplified as the cations represented by formulas (6-1) to (6-3) described below.

[0122] The repeating units d1 to d4 function as a photoacid generator. When a polymer containing the repeating units d1 to d4 (i.e., a polymer-bound photoacid generator) is used, the resist composition of the present invention may or may not contain a photoacid generator (D) described below.

[0123] The polymer may further contain a repeating unit having a structure in which a hydroxy group is protected by an acid labile group (hereinafter also referred to as repeating unit e). The repeating unit e is not particularly limited as long as it has one or more structures in which a hydroxy group is protected and the protecting group is decomposed by the action of an acid to generate a hydroxy group, but is preferably one represented by the following formula (e1): [ka]

[0124] In formula (e1), R A has the same meaning as above. e is an integer of 1 to 4. R 41 R is a hydrocarbon group having 1 to 30 carbon atoms and a valence of (e+1), which may contain a heteroatom. 42 is an acid labile group.

[0125] In formula (e1), R 42 The acid labile group represented by R may be any group that can be deprotected by the action of an acid to generate a hydroxy group. 42 Although the structure is not particularly limited, an acetal structure, a ketal structure, an alkoxycarbonyl group, an alkoxymethyl group represented by the following formula (e2), and the like are preferred, and an alkoxymethyl group represented by the following formula (e2) is particularly preferred. [ka] (In the formula, * represents a bond. R 43 is a hydrocarbyl group having 1 to 15 carbon atoms.

[0126] R 42Examples of the acid-labile group represented by [Formula] and the alkoxymethyl group represented by formula (e2) and the repeating unit e are the same as those exemplified in the description of the repeating unit d described in JP-A-2020-111564.

[0127] The polymer may further contain a repeating unit e derived from indene, benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, norbornadiene or a derivative thereof. Examples of the monomer that provides the repeating unit f include, but are not limited to, the following. [Chemical Formula]

[0128] The polymer may further contain a repeating unit g derived from indane, vinyl pyridine or vinyl carbazole.

[0129] In the polymer, the content ratios of the repeating units a1, a2, b, c1, c2, d1 to d4, e, f and g are preferably 0 < a1 ≤ 0.8, 0 ≤ a2 ≤ 0.8, 0 ≤ b ≤ 0.5, 0 ≤ c1 ≤ 0.6, 0 ≤ c2 ≤ 0.6, 0 ≤ d1 ≤ 0.4, 0 ≤ d2 ≤ 0.4, 0 ≤ d3 ≤ 0.4, 0 ≤ d4 ≤ 0.4, 0 ≤ e ≤ 0.4, 0 ≤ f ≤ 0.3 and 0 ≤ g ≤ 0.3, and more preferably [0 < a1 ≤ 0.7, 0 ≤ a2 ≤ 0.7, 0 ≤ b ≤ 0.3, 0 ≤ c1 ≤ 0.5, 0 ≤ c2 ≤ 0.5, 0 ≤ d1 ≤ 0.3, 0 ≤ d2 ≤ 0.3, 0 ≤ d3 ≤ 0.3, 0 ≤ d4 ≤ 0.3, 0 ≤ e ≤ 0.3, 0 ≤ f ≤ 0.3 and 0 ≤ g ≤ 0.3]. However, a1 + a2 + b + c1 + c2 + d1 + d2 + d3 + d4 + e + f + g ≤ 1.

[0130] The weight-average molecular weight (Mw) of the polymer is preferably 1,000 to 500,000, more preferably 3,000 to 100,000. When Mw is within this range, sufficient etching resistance is obtained, and there is no risk of a decrease in resolution due to an inability to ensure a difference in dissolution rate before and after exposure. In the present invention, Mw is a value measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) or N,N-dimethylformamide (DMF) as a solvent.

[0131] Furthermore, since the influence of Mw / Mn on the molecular weight distribution of the polymer tends to become greater as the pattern rule becomes finer, in order to obtain a resist composition that is suitable for use with fine pattern dimensions, it is preferable that Mw / Mn be a narrow dispersity of 1.0 to 2.0. If it is within this range, there will be little low-molecular-weight or high-molecular-weight polymer, and there will be no risk of foreign matter being observed on the pattern or deterioration of the pattern shape after exposure.

[0132] The polymer can be synthesized, for example, by polymerizing a monomer that provides the repeating unit described above in an organic solvent with the addition of a radical polymerization initiator by heating.

[0133] Examples of organic solvents used during polymerization include toluene, benzene, THF, diethyl ether, dioxane, cyclohexane, cyclopentane, methyl ethyl ketone (MEK), propylene glycol monomethyl ether acetate (PGMEA), and γ-butyrolactone (GBL). Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl-2,2-azobis(2-methylpropionate), 1,1'-azobis(1-acetoxy-1-phenylethane), benzoyl peroxide, and lauroyl peroxide. The amount of these initiators added is preferably 0.01 to 25 mol% based on the total amount of monomers to be polymerized. The reaction temperature is preferably 50 to 150°C, more preferably 60 to 100°C. The reaction time is preferably 2 to 24 hours, and more preferably 2 to 12 hours from the viewpoint of production efficiency.

[0134] The polymerization initiator may be added to the monomer solution and then fed to the reaction vessel. Alternatively, an initiator solution may be prepared separately from the monomer solution and then fed to the reaction vessel independently. From the perspective of quality control, it is preferable to prepare the monomer solution and the initiator solution independently and then add them dropwise, since radicals generated from the initiator during the waiting time may cause the polymerization reaction to proceed, resulting in the formation of ultra-high molecular weight polymers. The acid labile group may be used as is after being introduced into the monomer, or may be protected or partially protected after polymerization. Furthermore, known chain transfer agents such as dodecyl mercaptan and 2-mercaptoethanol may be used in combination to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 20 mol % of the total amount of monomers to be polymerized.

[0135] In the case of a monomer containing a hydroxy group, the hydroxy group may be substituted with an acetal group, such as an ethoxyethoxy group, which is easily deprotected by an acid, during polymerization, and then deprotected with a weak acid and water after polymerization. Alternatively, the hydroxy group may be substituted with an acetyl group, a formyl group, a pivaloyl group, or the like, and then subjected to alkaline hydrolysis after polymerization.

[0136] When copolymerizing hydroxystyrene or hydroxyvinylnaphthalene, hydroxystyrene or hydroxyvinylnaphthalene and other monomers may be polymerized by heating in an organic solvent with the addition of a radical polymerization initiator. Alternatively, acetoxystyrene or acetoxyvinylnaphthalene may be used, and after polymerization, the acetoxy group may be deprotected by alkaline hydrolysis to form polyhydroxystyrene or hydroxypolyvinylnaphthalene.

[0137] The base that can be used in alkaline hydrolysis includes aqueous ammonia, triethylamine, etc. The reaction temperature is preferably −20 to 100° C., more preferably 0 to 60° C. The reaction time is preferably 0.2 to 100 hours, more preferably 0.5 to 20 hours.

[0138] The amount of each monomer in the monomer solution may be appropriately set so as to achieve the preferred content ratio of the repeating units described above.

[0139] The polymer obtained by the above-described production method may be a reaction solution obtained by a polymerization reaction as a final product, or a powder obtained through a purification step such as a reprecipitation method in which a polymerization solution is added to a poor solvent to obtain a powder, and the resulting powder may be handled as a final product. However, from the viewpoint of work efficiency and quality stability, it is preferable to handle a polymer solution obtained by dissolving the powder obtained through the purification step in a solvent as a final product.

[0140] Specific examples of the solvent used in this case include ketones such as cyclohexanone and methyl-2-n-pentyl ketone, as described in paragraphs

[0144] to

[0145] of JP-A No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; propylene glycol monomethyl ether (PGME), ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether. esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono tert-butyl ether acetate; lactones such as GBL; alcohols such as diacetone alcohol (DAA); high-boiling alcohol solvents such as diethylene glycol, propylene glycol, glycerin, 1,4-butanediol, and 1,3-butanediol; and mixed solvents thereof.

[0141] The concentration of the polymer in the polymer solution is preferably 0.01 to 30% by mass, more preferably 0.1 to 20% by mass.

[0142] The reaction solution and polymer solution are preferably filtered through a filter, which is effective in stabilizing quality by removing foreign matter and gels that may cause defects.

[0143] Examples of filter materials used in the filter filtration include fluorocarbon, cellulose, nylon, polyester, and hydrocarbon-based materials. However, in the filtration process of resist compositions, filters made of fluorocarbons, such as Teflon (registered trademark), hydrocarbons such as polyethylene and polypropylene, or nylon are preferred. The pore size of the filter can be selected appropriately depending on the target cleanliness, but is preferably 100 nm or less, more preferably 20 nm or less. These filters may be used alone or in combination. The filtration method may involve passing the solution through the filter only once, but it is more preferable to circulate the solution and filter it multiple times. The filtration process can be performed in any order and any number of times in the polymer production process. However, it is preferable to filter the reaction solution after the polymerization reaction, the polymer solution, or both.

[0144] The base polymer (A) may be used singly or in combination of two or more different polymers with different composition ratios, Mw, and / or Mw / Mn. The base polymer (A) may also contain, in addition to the above polymer, a hydrogenated ring-opening metathesis polymer, and the polymers described in JP-A-2003-066612 can be used.

[0145] The base polymer (A) of the present invention preferably contains a repeating unit having a photoacid generating group, particularly when forming narrow-pitch patterns using EUV lithography. More preferably, an anionic skeleton that generates acid is bound to the polymer. This minimizes acid diffusion. Additionally, the base polymer (A) of the present invention preferably contains an aromatic ring in the repeating unit having an acid labile group, and more preferably contains a phenolic hydroxy group-containing unit represented by formula (c2). The aromatic group-containing structure improves etching resistance and also improves secondary electron generation efficiency after exposure to EUV light.

[0146] [(B) Organic solvent] The resist composition of the present invention contains an organic solvent as component (B). There are no particular restrictions on the organic solvent, so long as it is capable of dissolving the aforementioned component (A) and the components described below. Examples of the organic solvent include ketones such as cyclohexanone, cyclopentanone, methyl-2-n-pentyl ketone, and 2-heptanone, as described in paragraphs

[0144] and

[0145] of JP-A No. 2008-111103; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and DAA; PGME, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and ethylene glycol monoethyl ether. ethers such as propylene glycol monoethyl ether acetate, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as PGMEA, propylene glycol monoethyl ether acetate, ethyl lactate, methyl 2-hydroxyisobutyrate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as GBL.

[0147] In the resist composition of the present invention, the content of (B) organic solvent is preferably 100 to 10,000 parts by mass, and more preferably 200 to 8,000 parts by mass, relative to 80 parts by mass of (A) base polymer. (B) Organic solvent may be used singly or in combination of two or more types.

[0148] [(C) Hypervalent iodine compounds] The resist composition of the present invention further comprises a hypervalent iodine compound represented by the following formula (1) as component (C). [ka]

[0149] In formula (1), n ​​is an integer of 0 to 5.

[0150] In formula (1), R 1 and R2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between the carbon atoms. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 10 carbon atoms may be saturated or unsaturated and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, and a tricyclo[5.2.1.0 2,6 ] cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms such as decanyl and adamantyl; alkenyl groups such as vinyl and allyl; aryl groups having 6 to 10 carbon atoms such as phenyl and naphthyl; and groups obtained by combining these. In addition, some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen, sulfur, nitrogen, and halogen atoms, and some of the -CH2- in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen, sulfur, and nitrogen atoms, resulting in the hydrocarbyl groups containing hydroxy groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), etc. 1 and R 2 is preferably a hydrocarbyl group having 1 to 4 carbon atoms.

[0151] In formula (1), R 3is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom. When n is 2 to 5, each R 3 may be the same or different. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The hydrocarbyl group having 1 to 40 carbon atoms may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms such as 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 tert-pentyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, and a tricyclo[5.2.1.0 2,6 cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as a ]decanyl group, an adamantyl group, or an adamantylmethyl group; and aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group, or an anthracenyl group. Some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms, or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, or nitrogen atoms, so that the hydrocarbyl groups may contain hydroxy groups, cyano groups, halogen atoms, carbonyl groups, ether bonds, thioether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, carbamate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), or the like.

[0152] Specific examples of the hypervalent iodine compound represented by formula (1) include, but are not limited to, the following: [ka]

[0153] [ka]

[0154] [ka]

[0155] [ka]

[0156] [ka]

[0157] [ka]

[0158] The content of the hypervalent iodine compound represented by formula (1) is preferably 1 to 50 mass %, more preferably 2 to 30 mass %, of the total solid content in the resist composition. When the content is within this range, sufficient sensitivity and resolution can be obtained, and there is no risk of foreign matter or defects appearing during film formation.

[0159] The resist composition of the present invention contains, as essential components, (A) a polymer containing a repeating unit having an acid labile group and a repeating unit having a carboxyl group, (B) an organic solvent, and (C) a hypervalent iodine compound represented by formula (1), which enables the formation of high-contrast images even in fine pattern formation, resulting in improved limiting resolution and LWR. The reason for this is not clearly understood, but is presumed to be, for example, as follows.

[0160] The resist composition of the present invention is a so-called chemically amplified resist composition in which the acid generated from the photoacid generator upon exposure cleaves acid-labile groups in the polymer, generating polar groups, thereby creating a dissolution contrast between exposed and unexposed areas. In addition to this general reaction mechanism of chemically amplified resist compositions, another reaction is thought to occur in the present invention. That is, a reaction involving a carboxy group in the polymer and a hypervalent iodine compound represented by formula (1).

[0161] The hypervalent iodine compound represented by formula (1) is a three-coordinate iodine compound. The iodine-oxygen bond in the hypervalent iodine compound is a relatively weak bond called a three-center four-electron bond, and when a carboxyl group-containing compound is present externally, it is believed that a ligand exchange reaction proceeds in an equilibrium state. In view of this, in the resist composition of the present invention, at the stage of film formation, the hypervalent iodine compound is in a state in which it is partially bonded to the carboxyl groups in the polymer. In other words, it is presumed that the polymers are in a state in which they are crosslinked by the hypervalent iodine compound.

[0162] As mentioned above, the iodine-oxygen bond in hypervalent iodine compounds is weak and is thought to be broken by exposure to light. Therefore, the polymer crosslinked by the hypervalent iodine compounds during film formation is broken by exposure to light, resulting in a significant decrease in molecular weight in the exposed areas.

[0163] Based on the above speculation, it is believed that the dissolution contrast of the resist composition of the present invention is achieved by two factors: a change in polarity and a change in molecular weight. As a result, higher contrast and improved resolution can be achieved compared to conventional chemically amplified resist compositions.

[0164] An example of a resist composition containing a hypervalent iodine compound is that described in Patent Document 3. However, Patent Document 3 only describes that the resist composition improves line edge roughness, and makes no mention of the need for a carboxy group-containing unit in the applied polymer. Therefore, it is believed that it would be difficult to improve resolution by increasing contrast with the resist composition described in Patent Document 3.

[0165] Patent Document 4 describes the use of a resist polymer prepared using a hypervalent iodine compound containing a polymerizable group. The hypervalent iodine compound in Patent Document 4 crosslinks the polymer, but the crosslink density is too high, resulting in poor developer solubility after exposure, and insoluble residues are generated during development, resulting in poor resolution and LWR. In contrast, the resist composition of the present invention is partially crosslinked during film formation, so the exposed areas are easily dissolved in the developer, improving resolution. The idea of ​​improving performance by partial crosslinking through a ligand exchange reaction during film formation is not apparent from Patent Document 4. Therefore, the resist composition of the present invention can be said to be a novel solution to these problems.

[0166] [(D) Photoacid generator] The resist composition of the present invention may contain a photoacid generator as component (D). The photoacid generator for component (D) is not particularly limited as long as it is a compound that generates an acid upon exposure to high-energy rays. Suitable photoacid generators include those represented by the following formula (2): [ka]

[0167] In formula (2), R 101 , R 102 and R 103 are each independently a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. 101 , R 102 and R 103Any two of these may be bonded to each other to form a ring together with the sulfur atom to which they are bonded. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 31 and R 32 Examples of the hydrocarbyl group represented by formula (6-1) include the same as those exemplified above. Examples of the cation of the sulfonium salt represented by formula (2) include the same as those exemplified above as the sulfonium cation represented by formula (6-1) described later.

[0168] In formula (2), Xa - is a non-nucleophilic counter anion. Examples of the non-nucleophilic counter anion include anions selected from the following formulae (2A) to (2D). [ka]

[0169] In formula (2A), R fa is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A') described below. fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0170] The anion represented by formula (2A) is preferably one represented by the following formula (2A'). [ka]

[0171] In formula (2A'), R HF is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group.

[0172] R fa1is a hydrocarbyl group having 1 to 38 carbon atoms which may contain a heteroatom. The heteroatom is preferably an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom, or the like, and more preferably an oxygen atom. In order to obtain high resolution in the formation of a fine pattern, the hydrocarbyl group is particularly preferably one having 6 to 30 carbon atoms.

[0173] R fa1 The hydrocarbyl group having 1 to 38 carbon atoms and represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, pentadecyl, heptadecyl, and icosyl groups; cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, and 1-adamantylmethyl. saturated cyclic hydrocarbyl groups having 3 to 30 carbon atoms such as a norbornyl group, a norbornylmethyl group, a tricyclodecanyl group, a tetracyclododecanyl group, a tetracyclododecanylmethyl group, or a dicyclohexylmethyl group; unsaturated aliphatic hydrocarbyl groups having 2 to 30 carbon atoms such as an allyl group or a 3-cyclohexenyl group; aryl groups having 6 to 30 carbon atoms such as a phenyl group, a 1-naphthyl group, or a 2-naphthyl group; aralkyl groups having 7 to 38 carbon atoms such as a benzyl group or a diphenylmethyl group; and groups obtained by combining these.

[0174] Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. Examples of hydrocarbyl groups containing heteroatoms include tetrahydrofuryl, methoxymethyl, ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl, (2-methoxyethoxy)methyl, acetoxymethyl, 2-carboxy-1-cyclohexyl, 2-oxopropyl, 4-oxo-1-adamantyl, 5-hydroxy-1-adamantyl, 5-tert-butylcarbonyloxy-1-adamantyl, 4-oxatricyclo[4.2.1.0]. 3,7 ]nonan-5-on-2-yl group, 3-oxocyclohexyl group, and the like.

[0175] Synthesis of sulfonium salts containing anions represented by formula (2A') is described in detail in JP-A Nos. 2007-145797, 2008-106045, 2009-7327, and 2009-258695. Sulfonium salts described in JP-A Nos. 2010-215608, 2012-41320, 2012-106986, and 2012-153644 are also suitable.

[0176] Specific examples of the anion represented by formula (2A) include the same as those exemplified as specific examples of the sulfonate anion represented by formula (d1-1) or (d1-2).

[0177] In formula (2B), R fb1 and R fb2are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fb1 and R fb2 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fb1 and R fb2 are bonded to each other and form the bonded group (-CF2-SO2-N - -SO2-CF2-) together may form a ring, in which case R fb1 and R fb2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0178] In formula (2C), R fc1 , R fc2 and R fc3 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a fluorine atom or a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by R include the same as those exemplified above. fc1 , R fc2 and R fc3 is preferably a fluorine atom or a linear fluorinated alkyl group having 1 to 4 carbon atoms. fc1 and R fc2 are bonded to each other and form the bonded group (-CF2-SO2-C - -SO2-CF2-) together may form a ring, in which case R fc1 and R fc2 The group obtained by bonding together is preferably a fluorinated ethylene group or a fluorinated propylene group.

[0179] In formula (2D), R fdis a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group represented by the formula (I) include the same as those exemplified above.

[0180] The synthesis of sulfonium salts containing anions represented by formula (2D) is described in detail in JP-A-2010-215608 and JP-A-2014-133723.

[0181] Specific examples of the anion represented by formula (2D) include, but are not limited to, those shown below. [ka]

[0182] [ka]

[0183] Further examples of the non-nucleophilic counter anion include an anion having an aromatic ring substituted with an iodine atom or a bromine atom, such as an anion represented by the following formula (2E): [ka]

[0184] In formula (2E), x is an integer that satisfies 1≦x≦3. y and z are integers that satisfy 1≦y≦5, 0≦z≦3, and 1≦y+z≦5. y is preferably an integer that satisfies 1≦y≦3, more preferably 2 or 3. z is preferably an integer that satisfies 0≦z≦2.

[0185] In formula (2E), X BI is an iodine atom or a bromine atom, and when x and / or y are 2 or more, they may be the same or different.

[0186] In formula (2E), L 11 is a single bond, an ether bond, an ester bond, or a saturated hydrocarbylene group having 1 to 6 carbon atoms which may contain an ether bond or an ester bond. The saturated hydrocarbylene group may be linear, branched, or cyclic.

[0187] In formula (2E), L 12 represents a single bond or a divalent linking group having 1 to 20 carbon atoms when x is 1, and represents an (x+1)-valent linking group having 1 to 20 carbon atoms when x is 2 or 3, and the linking group may contain an oxygen atom, a sulfur atom, or a nitrogen atom.

[0188] In formula (2E), R fe is a hydroxy group, a carboxy group, a fluorine atom, a chlorine atom, a bromine atom or an amino group, or a hydrocarbyl group having 1 to 20 carbon atoms, a hydrocarbyloxy group having 1 to 20 carbon atoms, a hydrocarbylcarbonyl group having 2 to 20 carbon atoms, a hydrocarbyloxycarbonyl group having 2 to 20 carbon atoms, a hydrocarbylcarbonyloxy group having 2 to 20 carbon atoms or a hydrocarbylsulfonyloxy group having 1 to 20 carbon atoms which may contain a fluorine atom, a chlorine atom, a bromine atom, a hydroxy group, an amino group or an ether bond, or feA )(R feB ), -N(R feC )-C(=O)-R feD or -N(R feC )-C(=O)-OR feD R feA and R feB are each independently a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms. feC is a hydrogen atom or a saturated hydrocarbyl group having 1 to 6 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. feDis an aliphatic hydrocarbyl group having 1 to 16 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 15 carbon atoms, and may contain a halogen atom, a hydroxy group, a saturated hydrocarbyloxy group having 1 to 6 carbon atoms, a saturated hydrocarbylcarbonyl group having 2 to 6 carbon atoms, or a saturated hydrocarbylcarbonyloxy group having 2 to 6 carbon atoms. The aliphatic hydrocarbyl group may be saturated or unsaturated and may be linear, branched, or cyclic. The hydrocarbyl group, hydrocarbyloxy group, hydrocarbylcarbonyl group, hydrocarbyloxycarbonyl group, hydrocarbylcarbonyloxy group, and hydrocarbylsulfonyloxy group may be linear, branched, or cyclic. When x and / or z is 2 or more, each R fe may be the same or different from each other.

[0189] Of these, R fe Examples of the hydroxyl group include -N(R feC )-C(=O)-R feD , -N(R feC )-C(=O)-OR feD fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, etc. are preferred.

[0190] In formula (2E), Rf 11 ~Rf 14 are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, and at least one of them is a fluorine atom or a trifluoromethyl group. 11 and Rf 12 may combine to form a carbonyl group. 13 and Rf 14 are preferably both fluorine atoms.

[0191] Specific examples of the anion represented by formula (2E) include, but are not limited to, the following: BI is the same as above. [ka]

[0192]

change

[0193]

change

[0194]

change

[0195]

change

[0196]

change

[0197]

change

[0198]

change

[0199]

change

[0200]

change

[0201]

change

[0202]

change

[0203]

change

[0204]

change

[0205]

change

[0206]

change

[0207]

change

[0208]

change

[0209]

change

[0210]

change

[0211]

change

[0212]

change

[0213] [ka]

[0214] Examples of the non-nucleophilic anion include a fluorobenzenesulfonate anion bonded to an aromatic group containing an iodine atom as described in Japanese Patent No. 6648726, an anion having a mechanism for decomposing with an acid as described in International Publication No. 2021 / 200056 and Japanese Patent Application Laid-Open No. 2021-070692, an anion having a cyclic ether group as described in Japanese Patent Application Laid-Open No. 2018-180525 and Japanese Patent Application Laid-Open No. 2021-035935, and an anion as described in Japanese Patent Application Laid-Open No. 2018-092159.

[0215] Further, as the non-nucleophilic anion, anions of bulky benzenesulfonic acid derivatives not containing fluorine atoms, as described in JP 2006-276759 A, JP 2015-117200 A, JP 2016-065016 A, and JP 2019-202974 A, and benzenesulfonic acid anions and alkylsulfonic acid anions not containing fluorine atoms bonded to aromatic groups containing iodine atoms, as described in Japanese Patent No. 6645464, can also be used.

[0216] Further examples of the non-nucleophilic anion include the anion of a bissulfonic acid described in JP 2015-206932 A, the anion of a sulfonamide or sulfonimide having a sulfonic acid on one side and a different sulfonic acid on the other side described in WO 2020 / 158366 A, and the anion of a sulfonic acid on one side and a carboxylic acid on the other described in JP 2015-024989 A.

[0217] Furthermore, the photoacid generator of the component (D) is preferably one represented by the following formula (3). [ka]

[0218] In formula (3), R 201 and R 202R are each independently a hydrocarbyl group having 1 to 30 carbon atoms which may contain a heteroatom. 203 is a hydrocarbylene group having 1 to 30 carbon atoms which may contain a heteroatom. 201 , R 202 and R 203 Any two of may be bonded to each other to form a ring together with the sulfur atom to which they are attached.

[0219] R 201 and R 202 The hydrocarbyl group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 30 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl; cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbornyl, oxanorbornyl, and tricyclo[5.2.1.0]. 2,6cyclic saturated hydrocarbyl groups having 3 to 30 carbon atoms such as a phenyl group, a methylphenyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, an isobutylphenyl group, a sec-butylphenyl group, a tert-butylphenyl group, a naphthyl group, a methylnaphthyl group, an ethylnaphthyl group, an n-propylnaphthyl group, an isopropylnaphthyl group, an n-butylnaphthyl group, an isobutylnaphthyl group, a sec-butylnaphthyl group, a tert-butylnaphthyl group, an anthracenyl group, and the like; and groups obtained by combining these. Furthermore, some or all of the hydrogen atoms of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom or a halogen atom, and some of the -CH- groups of the hydrocarbyl group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom or a nitrogen atom, and as a result, the hydrocarbyl group may contain a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, or the like.

[0220] R 203The hydrocarbylene group having 1 to 30 carbon atoms represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkanediyl groups having 1 to 30 carbon atoms, such as methanediyl group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,3-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, decane-1,10-diyl group, undecane-1,11-diyl group, dodecane-1,12-diyl group, tridecane-1,13-diyl group, tetradecane-1,14-diyl group, pentadecane-1,15-diyl group, hexadecane-1,16-diyl group, and heptadecane-1,17-diyl group; cyclopentanediyl group, cyclohexene-1,18-diyl group, and the like. Examples of the alkylene groups include cyclic saturated hydrocarbylene groups having 3 to 30 carbon atoms, such as xanediyl, norbornanediyl, and adamantanediyl; arylene groups having 6 to 30 carbon atoms, such as phenylene, methylphenylene, ethylphenylene, n-propylphenylene, isopropylphenylene, n-butylphenylene, isobutylphenylene, sec-butylphenylene, tert-butylphenylene, naphthylene, methylnaphthylene, ethylnaphthylene, n-propylnaphthylene, isopropylnaphthylene, n-butylnaphthylene, isobutylnaphthylene, sec-butylnaphthylene, and tert-butylnaphthylene; and groups obtained by combining these groups. In addition, some or all of the hydrogen atoms of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, a nitrogen atom, or a halogen atom, and some of the -CH- groups of the hydrocarbylene group may be substituted with a group containing a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom, resulting in the hydrocarbylene group containing a hydroxy group, a cyano group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, a carboxylic anhydride (-C(=O)-OC(=O)-), a haloalkyl group, etc. As the heteroatom, an oxygen atom is preferred.

[0221] In formula (3), LA is a single bond, an ether bond, or a hydrocarbylene group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbylene group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R 203 Examples of the hydrocarbylene group represented by the formula (I) include the same as those exemplified above.

[0222] In formula (3), X a , X b , X c and X d are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that X a , X b , X c and X d At least one of the groups is a fluorine atom or a trifluoromethyl group.

[0223] The photoacid generator represented by formula (3) is preferably one represented by the following formula (3'). [ka]

[0224] In formula (3'), L A is the same as above. X e is a hydrogen atom or a trifluoromethyl group, preferably a trifluoromethyl group. 301 , R 302 and R 303 are each independently a hydrogen atom or a hydrocarbyl group having 1 to 20 carbon atoms which may contain a heteroatom. The hydrocarbyl group may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include R in formula (2A'). fa1 Examples of the hydrocarbyl group include the same as those exemplified above. x' and y' each independently represent an integer of 0 to 5, and z' represents an integer of 0 to 4.

[0225] Examples of the photoacid generator represented by formula (3) include the same compounds as those exemplified as the photoacid generator represented by formula (2) in JP-A-2017-026980.

[0226] Among the photoacid generators, those containing an anion represented by formula (2A') or (2D) are particularly preferred because of their small acid diffusion and excellent solubility in solvents. Also, those represented by formula (3') are particularly preferred because of their extremely small acid diffusion.

[0227] When the resist composition of the present invention contains a photoacid generator (D), the content thereof is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, relative to 80 parts by mass of the base polymer (A). When the amount of the photoacid generator (D) added is within the above range, the resolution is good and there is no risk of problems with foreign matter occurring after development of the resist film or during stripping, which is preferable. The photoacid generator (D) may be used alone, or two or more different types may be used in combination. When the base polymer contains any of the repeating units d1 to d4 and / or when the resist composition contains a photoacid generator (D), the resist composition of the present invention can function as a chemically amplified resist composition.

[0228] [(E) Quencher] The chemically amplified resist composition of the present invention preferably contains a quencher (acid diffusion controller). In the present invention, the quencher refers to a material that traps the acid generated by the photoacid generator in the chemically amplified resist composition, thereby preventing the acid from diffusing to unexposed areas and forming a desired pattern. Examples of such quenchers include onium salts represented by the following formula (4) or (5): [ka]

[0229] In formula (4), R 401represents a hydrogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom, but excludes those in which the hydrogen atom bonded to the carbon atom at the α-position of the sulfo group is substituted with a fluorine atom or a fluoroalkyl group.

[0230] R 401 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 40 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a tert-pentyl group, an n-hexyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, and an n-decyl group; a cyclopentyl group, a cyclohexyl group, a cyclopentylmethyl group, a cyclopentylethyl group, a cyclopentylbutyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a cyclohexylbutyl group, a norbornyl group, an oxanorbornyl group, and a tricyclo[5.2.1.0] 2,6 cyclic saturated hydrocarbyl groups having 3 to 40 carbon atoms, such as a ]decanyl group or an adamantyl group; aryl groups having 6 to 40 carbon atoms, such as a phenyl group, a naphthyl group or an anthracenyl group; and groups obtained by combining these. Some or all of the hydrogen atoms in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms, nitrogen atoms or halogen atoms, and some of the -CH2- groups in the hydrocarbyl groups may be substituted with groups containing heteroatoms such as oxygen atoms, sulfur atoms or nitrogen atoms, so that the hydrocarbyl groups may contain hydroxy groups, cyano groups, fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, carbonyl groups, ether bonds, ester bonds, sulfonate ester bonds, carbonate bonds, lactone rings, sultone rings, carboxylic anhydrides (-C(=O)-OC(=O)-), haloalkyl groups, etc.

[0231] In formula (5), R 402 is a hydrogen atom or a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. Specific examples of the hydrocarbyl group which may contain a heteroatom include R 401In addition to the substituents exemplified as specific examples, examples include fluorinated saturated hydrocarbyl groups such as trifluoromethyl group and trifluoroethyl group, and fluorinated aryl groups such as pentafluorophenyl group and 4-trifluoromethylphenyl group.

[0232] Specific examples of the anion of the onium salt represented by formula (4) include, but are not limited to, those shown below. [ka]

[0233] [ka]

[0234] [ka]

[0235] Specific examples of the anion of the onium salt represented by formula (5) include, but are not limited to, those shown below. [ka]

[0236] [ka]

[0237] [ka]

[0238] In equations (3) and (4), Mq + is an onium cation. The onium cation is preferably a sulfonium cation represented by the following formula (6-1), an iodonium cation represented by the following formula (6-2), or an ammonium cation represented by the following formula (6-3). [ka]

[0239] In formulas (6-1) to (6-3), R 411 ~R 419 are each independently a hydrocarbyl group having 1 to 40 carbon atoms which may contain a heteroatom. 411 and R 412 may be bonded to each other to form a ring together with the sulfur atom to which they are attached, and R 416 and R 417 and may be bonded to each other to form a ring together with the nitrogen atom to which they are bonded. 401 Examples of the above-mentioned methods are the same as those described above.

[0240] Specific examples of the sulfonium cation represented by formula (6-1) include, but are not limited to, the following: [ka]

[0241] Specific examples of the iodonium cation represented by formula (6-2) include, but are not limited to, the following: [ka]

[0242] Specific examples of the ammonium cation represented by formula (6-3) include, but are not limited to, the following: [ka]

[0243] Specific examples of the onium salts represented by formula (4) or (5) include any combination of the anions and cations described above. These onium salts can be easily prepared by ion exchange reactions using known organic chemistry methods. For details on ion exchange reactions, see, for example, JP 2007-145797 A.

[0244] The onium salt represented by formula (4) or (5) functions as a quencher in the chemically amplified resist composition of the present invention. This is because the counter anion of each onium salt is the conjugate base of a weak acid. The term "weak acid" as used herein refers to an acidity that is insufficient to deprotect the acid labile group in the acid labile group-containing unit contained in the base polymer. The onium salt represented by formula (4) or (5) functions as a quencher when used in combination with an onium salt-type photoacid generator having a counter anion that is the conjugate base of a strong acid, such as a sulfonic acid fluorinated at the α-position. Specifically, when an onium salt that generates a strong acid, such as a sulfonic acid fluorinated at the α-position, is mixed with an onium salt that generates a weak acid, such as a non-fluorinated sulfonic acid or carboxylic acid, the strong acid generated from the photoacid generator upon irradiation with high-energy radiation collides with an onium salt having an unreacted weak acid anion, releasing the weak acid through salt exchange and generating an onium salt having a strong acid anion. In this process, the strong acid is exchanged for a weak acid with a lower catalytic activity, and the acid appears to be deactivated, allowing for control of acid diffusion.

[0245] Here, when the photoacid generator that generates a strong acid is an onium salt, the strong acid generated by irradiation with high-energy rays can be exchanged for a weak acid as described above, but on the other hand, it is thought that the weak acid generated by irradiation with high-energy rays collides with the unreacted onium salt that generates the strong acid, making it difficult to carry out salt exchange. This is due to the phenomenon that the onium cation is more likely to form an ion pair with the anion of the strong acid.

[0246] When the resist composition of the present invention contains an onium salt represented by formula (4) or (5) as the (E) quencher, the content thereof is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 80 parts by mass of the (A) base polymer.

[0247] The quencher of component (E) may be a nitrogen-containing compound. Examples of such nitrogen-containing compounds include primary, secondary, or tertiary amine compounds described in paragraphs

[0146] to

[0164] of JP 2008-111103 A, particularly amine compounds having a hydroxy group, an ether bond, an ester bond, a lactone ring, a cyano group, or a sulfonate ester bond. Other examples include compounds in which a primary or secondary amine is protected with a carbamate group, such as the compounds described in JP 3790649 A.

[0248] Alternatively, a sulfonate sulfonium salt having a nitrogen-containing substituent may be used as the nitrogen-containing compound. Such a compound functions as a quencher in the unexposed area and loses its quenching ability in the exposed area by neutralizing with the acid generated by the compound itself, functioning as a so-called photodegradable base. The use of a photodegradable base can further enhance the contrast between the exposed and unexposed areas. For example, JP-A Nos. 2009-109595 and 2012-046501 can be used as references for the photodegradable base.

[0249] When the resist composition of the present invention contains a nitrogen-containing compound as a quencher, the content thereof is preferably 0.001 to 12 parts by mass, and more preferably 0.01 to 8 parts by mass, relative to 80 parts by mass of the (A) base polymer. The nitrogen-containing compound may be used alone or in combination of two or more types.

[0250] [(F) Surfactant] The resist composition of the present invention may further comprise a surfactant as component (F). The surfactant (F) is preferably a surfactant that is insoluble or slightly soluble in water but soluble in an alkaline developer, or a surfactant that is insoluble or slightly soluble in both water and an alkaline developer. Examples of such surfactants include those described in JP-A-2010-215608 and JP-A-2011-016746.

[0251] Among the surfactants described in the above publications, preferred surfactants that are insoluble or slightly soluble in water and alkaline developers include FC-4430 (manufactured by 3M), Surflon (registered trademark) S-381 (manufactured by AGC Seimi Chemical Co., Ltd.), Olfine (registered trademark) E1004 (manufactured by Nissin Chemical Industry Co., Ltd.), KH-20, KH-30 (manufactured by AGC Seimi Chemical Co., Ltd.), and oxetane ring-opening polymers represented by the following formula (surf-1): [ka]

[0252] Here, R, Rf, A, B, C, m, and n apply only to formula (surf-1), regardless of the above descriptions. R is a divalent to tetravalent aliphatic group having 2 to 5 carbon atoms. Examples of the divalent aliphatic group include an ethylene group, a 1,4-butylene group, a 1,2-propylene group, a 2,2-dimethyl-1,3-propylene group, and a 1,5-pentylene group, and examples of the trivalent or tetravalent aliphatic group include the following: [ka] (In the formula, the dashed lines represent bonds and are partial structures derived from glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol, respectively.)

[0253] Among these, a 1,4-butylene group, a 2,2-dimethyl-1,3-propylene group, and the like are preferred.

[0254] Rf is a trifluoromethyl group or a pentafluoroethyl group, preferably a trifluoromethyl group. m is an integer of 0 to 3, n is an integer of 1 to 4, and the sum of n and m is the valence of R, which is an integer of 2 to 4. A is 1. B is an integer of 2 to 25, preferably an integer of 4 to 20. C is an integer of 0 to 10, preferably 0 or 1. The order of the structural units in formula (surf-1) is not specified, and they may be bonded in blocks or randomly. The production of surfactants based on partially fluorinated oxetane ring-opening polymers is described in detail in the specification of U.S. Pat. No. 5,650,483, etc.

[0255] Surfactants that are insoluble or slightly soluble in water but soluble in alkaline developers have the function of reducing water penetration and leaching by orienting themselves on the surface of the resist film when a resist protective film is not used in ArF immersion lithography. Therefore, they are useful for suppressing the elution of water-soluble components from the resist film and reducing damage to the exposure equipment. They are also useful because they become soluble during alkaline aqueous development after exposure or post-exposure bake (PEB), making them less likely to become contaminants that cause defects. Such surfactants are insoluble or slightly soluble in water but soluble in alkaline developers. They are polymeric surfactants, also known as hydrophobic resins, and are particularly preferred because they have high water repellency and improve water slippage.

[0256] Specific examples of such polymer surfactants include those containing at least one repeating unit selected from those represented by any of the following formulae (7A) to (7E). [ka]

[0257] In formulas (7A) to (7E), R B is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 1 is -CH2-, -CH2CH2-, -O- or two -H groups separated from each other. s1are each independently a hydrogen atom or a hydrocarbyl group having 1 to 10 carbon atoms. s2 R is a single bond or a linear or branched hydrocarbylene group having 1 to 5 carbon atoms. s3 R are each independently a hydrogen atom, a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, or an acid labile group. s3 When R is a hydrocarbyl group or a fluorinated hydrocarbyl group, an ether bond or a carbonyl group may be present between the carbon-carbon bonds. s4 is a hydrocarbon group or a fluorinated hydrocarbon group having 1 to 20 carbon atoms and a valence of (u+1). u is an integer of 1 to 3. R s5 are each independently a hydrogen atom or -C(=O)-OR sa R is a group represented by sa is a fluorinated hydrocarbyl group having 1 to 20 carbon atoms. s6 is a hydrocarbyl group or a fluorinated hydrocarbyl group having 1 to 15 carbon atoms, and an ether bond or a carbonyl group may be present between the carbon-carbon bonds.

[0258] R s1 The hydrocarbyl group represented by the formula (I) is preferably a saturated hydrocarbyl group, and may be linear, branched, or cyclic. Specific examples thereof include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl; and cyclic saturated hydrocarbyl groups having 3 to 10 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, adamantyl, and norbornyl. Of these, those having 1 to 6 carbon atoms are preferred.

[0259] R s2 The hydrocarbylene group represented by the formula (I) is preferably a saturated hydrocarbylene group, which may be linear, branched, or cyclic. Specific examples thereof include a methylene group, an ethylene group, a propylene group, a butylene group, and a pentylene group.

[0260] R s3 or R s6 The hydrocarbyl group represented by the formula (I) may be saturated or unsaturated, and may be linear, branched, or cyclic. Specific examples thereof include saturated hydrocarbyl groups, and aliphatic unsaturated hydrocarbyl groups such as alkenyl groups and alkynyl groups, with saturated hydrocarbyl groups being preferred. As the saturated hydrocarbyl group, R s1 In addition to the examples of the hydrocarbyl group represented by the formula (R), examples include an n-undecyl group, an n-dodecyl group, a tridecyl group, a tetradecyl group, and a pentadecyl group. s3 or R s6 Examples of the fluorinated hydrocarbyl group represented by the formula (I) include groups in which some or all of the hydrogen atoms bonded to the carbon atoms of the aforementioned hydrocarbyl group have been substituted with fluorine atoms. As mentioned above, an ether bond or a carbonyl group may be present between these carbon-carbon bonds.

[0261] R s3 Specific examples of the acid labile group represented by the formula (AL-3) to (AL-5) include the groups represented by the formulas (AL-3) to (AL-5) above, trialkylsilyl groups in which each alkyl group has 1 to 6 carbon atoms, and oxo group-containing alkyl groups having 4 to 20 carbon atoms.

[0262] R s4 The (u+1)-valent hydrocarbon group or fluorinated hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic, and specific examples thereof include groups in which u hydrogen atoms have been further removed from the aforementioned hydrocarbyl group or fluorinated hydrocarbyl group.

[0263] R saThe fluorinated hydrocarbyl group represented by the formula (I) is preferably saturated and may be linear, branched or cyclic. Specific examples thereof include those in which some or all of the hydrogen atoms of the hydrocarbyl groups have been substituted with fluorine atoms, such as a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoro-1-propyl group, a 3,3,3-trifluoro-2-propyl group, a 2,2,3,3-tetrafluoropropyl group, a 1,1,1,3,3,3-hexafluoroisopropyl group, a 2,2,3,3,4,4,4-heptafluorobutyl group, a 2,2,3,3,4,4,5,5-octafluoropentyl group, a 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl group, a 2-(perfluorobutyl)ethyl group, a 2-(perfluorohexyl)ethyl group, a 2-(perfluorooctyl)ethyl group, and a 2-(perfluorodecyl)ethyl group.

[0264] Examples of the repeating unit represented by any one of formulas (7A) to (7E) include, but are not limited to, those shown below. B is the same as above. [ka]

[0265] [ka]

[0266] [ka]

[0267] [ka]

[0268] [ka]

[0269] [ka]

[0270] The polymer surfactant may further contain other repeating units in addition to the repeating units represented by formulae (7A) to (7E). Examples of such other repeating units include repeating units obtained from methacrylic acid and α-trifluoromethylacrylic acid derivatives. In the polymer surfactant, the content of the repeating units represented by formulae (7A) to (7E) is preferably 20 mol % or more, more preferably 60 mol % or more, and even more preferably 100 mol %, of all repeating units.

[0271] The Mw of the polymer surfactant is preferably from 1,000 to 500,000, and more preferably from 3,000 to 100,000. The Mw / Mn is preferably from 1.0 to 2.0, and more preferably from 1.0 to 1.6.

[0272] The polymer surfactant can be synthesized by heating a monomer containing an unsaturated bond that provides the repeating units represented by formulas (7A) to (7E) and, if necessary, other repeating units, in an organic solvent with the addition of a radical initiator to polymerize the monomer. Examples of organic solvents used in polymerization include toluene, benzene, THF, diethyl ether, and dioxane. Examples of polymerization initiators include AIBN, 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide. The reaction temperature is preferably 50 to 100°C. The reaction time is preferably 4 to 24 hours. The acid labile group introduced into the monomer may be used as is, or may be protected or partially protected after polymerization.

[0273] When synthesizing the polymer surfactant, a known chain transfer agent such as dodecyl mercaptan or 2-mercaptoethanol may be used to adjust the molecular weight. In this case, the amount of the chain transfer agent added is preferably 0.01 to 10 mol % based on the total number of moles of the monomers to be polymerized.

[0274] When the resist composition of the present invention contains a surfactant (F), the content thereof is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 10 parts by mass, relative to 80 parts by mass of the base polymer (A). When the surfactant (F) content is 0.1 part by mass or more, the receding contact angle between the resist film surface and water is sufficiently improved, while when the surfactant content is 50 parts by mass or less, the dissolution rate of the resist film surface in the developer is low, and the height of the formed fine pattern is sufficiently maintained. The surfactant (F) may be used alone or in combination of two or more types.

[0275] [(G) Other ingredients] The resist composition of the present invention may contain, as other components (G), a compound that decomposes in the presence of acid to generate acid (acid amplifying compound), an organic acid derivative, a fluorine-substituted alcohol, or a compound with a Mw of 3000 or less whose solubility in a developer changes upon the action of acid (dissolution inhibitor). Examples of the acid amplifying compound include the compounds described in JP-A-2009-269953 and JP-A-2010-215608. When the acid amplifying compound is contained, its content is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, relative to 80 parts by mass of the (A) base polymer. If the content is too high, it may be difficult to control acid diffusion, resulting in degradation of resolution and pattern shape. Examples of the organic acid derivative, fluorine-substituted alcohol, and dissolution inhibitor include the compounds described in JP-A-2009-269953 and JP-A-2010-215608.

[0276] [Pattern formation method] The pattern forming method of the present invention includes the steps of forming a resist film on a substrate using the resist composition described above, exposing the resist film to high-energy rays, and developing the exposed resist film using a developer.

[0277] The substrate may be, for example, a substrate for integrated circuit manufacturing (Si, SiO2, SiN, SiON, TiN, WSi, BPSG, SOG, organic anti-reflective coating, etc.) or a substrate for mask circuit manufacturing (Cr, CrO, CrON, MoSi2, SiO2, etc.).

[0278] The resist film can be formed, for example, by applying the resist composition onto a substrate by a method such as spin coating so that the film thickness is preferably 0.05 to 2 μm, and then pre-baking the applied resist composition on a hot plate preferably at 60 to 150°C for 1 to 10 minutes, more preferably at 80 to 140°C for 1 to 5 minutes.

[0279] Examples of high-energy rays used to expose the resist film include KrF excimer laser light, ArF excimer laser light, EB, EUV, etc. When KrF excimer laser light, ArF excimer laser light, or EUV is used for exposure, a mask for forming a desired pattern is used, and the exposure dose is preferably 1 to 200 mJ / cm. 2 , more preferably 10 to 100 mJ / cm 2 When EB is used, the exposure dose is preferably 1 to 300 μC / cm 2 , either directly or through a mask for forming a desired pattern. 2 , more preferably 10 to 200 μC / cm 2 Irradiate so that

[0280] In addition to the usual exposure method, the immersion method can also be used, in which a liquid with a refractive index of 1.0 or higher is placed between the resist film and the projection lens. In this case, a water-insoluble protective film can also be used.

[0281] The water-insoluble protective film is used to prevent elution from the resist film and increase the water sliding property of the film surface. It can be broadly divided into two types. One is an organic solvent-removable type that requires stripping before alkaline aqueous development using an organic solvent that does not dissolve the resist film. The other is an alkaline aqueous solution-soluble type that is soluble in alkaline developer and removes the protective film along with removing the soluble portion of the resist film. The latter is particularly based on a polymer containing 1,1,1,3,3,3-hexafluoro-2-propanol residues that is insoluble in water but soluble in alkaline developer, and is preferably dissolved in an alcohol solvent with 4 or more carbon atoms, an ether solvent with 8 to 12 carbon atoms, or a mixed solvent thereof. Materials can also be prepared by dissolving the water-insoluble, alkaline developer-soluble surfactant described above in an alcohol solvent with 4 or more carbon atoms, an ether solvent with 8 to 12 carbon atoms, or a mixed solvent thereof.

[0282] After the exposure, PEB may be performed by heating on a hot plate, for example, preferably at 60 to 150° C. for 1 to 5 minutes, more preferably at 80 to 140° C. for 1 to 3 minutes.

[0283] The development is carried out using a developer, for example, an alkaline aqueous solution of tetramethylammonium hydroxide (TMAH) or the like, preferably at 0.1 to 5 mass %, more preferably 2 to 3 mass %, for preferably 0.1 to 3 minutes, more preferably 0.5 to 2 minutes, by a conventional method such as dipping, puddling, or spraying, whereby the exposed areas are dissolved and the desired pattern is formed on the substrate.

[0284] After forming the resist film, the resist film may be rinsed with pure water to extract the acid generator and the like from the film surface or to wash away particles, or the resist film may be rinsed after exposure to remove water remaining on the film.

[0285] Furthermore, the pattern may be formed by a double patterning method, such as a trench method in which a first exposure and etching process is performed to process an underlayer with a 1:3 trench pattern, and then a second exposure process is performed with a shifted position to form a 1:3 trench pattern, thereby forming a 1:1 pattern, or a line method in which a first underlayer with a 1:3 isolated leave pattern is processed by a first exposure and etching process, and then a second exposure process is performed with a shifted position to process a second underlayer with a 1:3 isolated leave pattern formed below the first underlayer, thereby forming a 1:1 pattern with half the pitch.

[0286] In the pattern forming method of the present invention, a negative tone development method may be used in which an organic solvent is used as a developer instead of the alkaline aqueous solution to dissolve unexposed areas. For the organic solvent development, the developer may be 2-octanone, 2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone, diisobutyl ketone, methylcyclohexanone, acetophenone, methylacetophenone, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, methyl valerate, methyl pentenoate, methyl crotonate, ethyl crotonate, propyl cyclohexanone ... Examples of organic solvents that can be used 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, ethyl phenylacetate, benzyl formate, phenylethyl formate, methyl 3-phenylpropionate, benzyl propionate, and 2-phenylethyl acetate. These organic solvents may be used alone or in combination of two or more. [Example]

[0287] The present invention will be specifically explained below by showing synthesis examples, examples and comparative examples, but the present invention is not limited to the following examples.

[0288] [1] Synthesis of base polymer The monomers used in the synthesis of the base polymer are as follows: [ka]

[0289] [ka]

[0290] [ka]

[0291] [ka] (Synthesized with reference to JP 2018-095853 A)

[0292] [Synthesis Example 1] Synthesis of Polymer P-1 Under a nitrogen atmosphere, a flask was charged with 1.9 g of monomer a1-0, 50.1 g of monomer a1-1, 16.2 g of monomer b2-1, 49.7 g of monomer c1, 3.96 g of V-601 (Fujifilm Wako Pure Chemical Industries, Ltd.), and 127 g of MEK to prepare a monomer-polymerization initiator solution. 46 g of MEK was charged to a separate flask under a nitrogen atmosphere and heated to 80°C with stirring, after which the monomer-polymerization initiator solution was added dropwise over 4 hours. After completion of the dropwise addition, stirring was continued for 2 hours while maintaining the temperature of the polymerization solution at 80°C, and then the polymerization solution was cooled to room temperature. The resulting polymerization solution was added dropwise to 2,000 g of vigorously stirred hexane, and the precipitated polymer was filtered off. The resulting polymer was washed twice with 600 g of hexane and then vacuum dried at 50°C for 20 hours to obtain polymer P-1 as a white powder (yield: 119.4 g, 98%). The Mw of polymer P-1 was 10,900, and the Mw / Mn ratio was 1.82. The Mw was measured using GPC in DMF as a solvent, converted into polystyrene equivalents. [ka]

[0293] [Synthesis Examples 2 to 14] Synthesis of polymers P-2 to P-14 The polymers shown in Table 1 below were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of the respective monomers were changed.

[0294] [Table 1]

[0295] [2] Preparation of resist composition [Examples 1-1 to 1-14, Comparative Examples 1-1 to 1-6] Resist compositions (R-01 to R-14) were prepared by dissolving polymers (P-1 to P-14), hypervalent iodine compounds (I-1 to I-3), photoacid generator (PAG-1), and quenchers (Q-1 and Q-2) in a solvent containing 0.01 wt% surfactant (PF-636, Omnova) according to the compositions shown in Table 2. The resulting solution was then filtered through a 0.2 μm Teflon filter to prepare resist compositions (R-01 to R-14). Comparative resist compositions (CR-01 to CR-06) were also prepared by mixing polymers, photoacid generators, sensitivity modifiers, hypervalent iodine compounds, solvents, and 0.01 wt% surfactant (PF-636, Omnova) according to the compositions shown in Table 3. The resulting mixture was then filtered through a 0.2 μm Teflon filter.

[0296] [Table 2]

[0297] [Table 3]

[0298] In Tables 2 and 3, the components are as follows: Organic solvent: PGMEA (propylene glycol monomethyl ether acetate) DAA (diacetone alcohol) HBM (2-hydroxyisobutyric acid methyl ester)

[0299] Photoacid generator: PAG-1 [ka]

[0300] Quencher: Q-1, Q-2 [ka]

[0301] Hypervalent iodine compounds: I-1, I-2, I-3 [ka]

[0302] [4] EUV lithography evaluation [Examples 2-1 to 2-14, Comparative Examples 2-1 to 2-6] Each resist composition (R-01 to R-14, CR-01 to CR-06) was spin-coated onto a Si substrate on which a 20 nm thick silicon-containing spin-on hard mask SHB-A940 (43% silicon by mass) manufactured by Shin-Etsu Chemical Co., Ltd. had been formed, and the substrate was pre-baked at 100°C for 60 seconds using a hot plate to produce a 50 nm thick resist film. An ASML EUV scanner NXE3300 (NA 0.33, σ 0.9 / 0.6, dipole illumination) was used to expose an LS pattern with an on-wafer dimension of 18 nm and a pitch of 36 nm, varying the exposure dose and focus (exposure dose pitch: 1 mJ / cm). 2 The resist film was exposed to light while being scanned with a focus pitch of 0.020 μm. After exposure, PEB was performed for 60 seconds at the temperatures shown in Tables 4 and 5 below. Paddle development was then performed for 30 seconds with a 2.38% by mass aqueous solution of TMAH, followed by rinsing with a surfactant-containing rinse solution and spin drying to obtain a positive pattern. The developed LS pattern was observed with a Hitachi High-Technologies Corporation critical dimension SEM (CG6300), and the sensitivity, LWR, DOF, and collapse limit were evaluated according to the methods described below. The results are shown in Tables 4 and 5.

[0303] [Sensitivity evaluation] The optimum exposure dose Eop (mJ / cm) to obtain an LS pattern with a line width of 18 nm and a pitch of 36 nm 2 ) was calculated and used as the sensitivity.

[0304] [LWR rating] The LS pattern obtained by irradiation with Eop was measured at 10 points along the line length, and the LWR was calculated as three times the standard deviation (σ) (3σ). The smaller this value, the less roughness and the more uniform the line width pattern obtained.

[0305] [DOF evaluation] For the DOF evaluation, the focus range formed within a range of ±10% (16.2 to 19.8 nm) of the 18 nm dimension in the LS pattern was determined. The larger this value, the wider the depth of focus.

[0306] [Line pattern collapse limit evaluation] The line dimension of the LS pattern at each exposure dose at the optimum focus was measured at 10 points in the longitudinal direction. The thinnest line dimension obtained without collapse was defined as the collapse limit dimension. The smaller this value, the better the collapse limit.

[0307] [Table 4]

[0308] [Table 5]

[0309] The results shown in Tables 4 and 5 confirm that the resist composition of the present invention has high resolution and is excellent in various lithography performances.

Claims

1. A resist composition comprising: (A) a base polymer including a polymer having a repeating unit having an acid labile group and a repeating unit having a carboxy group; (B) an organic solvent; and (C) a hypervalent iodine compound represented by the following formula (1): 【Chemical 1】 (wherein n is an integer from 0 to 5. R 1 and R 2 are each independently a halogen atom or a hydrocarbyl group having 1 to 10 carbon atoms which may contain a heteroatom. 1 and R 2 may be bonded to each other to form a ring together with the carbon atoms to which they are bonded and the atoms between said carbon atoms. R 3 is a hydrocarbyl group having 1 to 40 carbon atoms which may contain a halogen atom or a heteroatom.

2. 2. The resist composition according to claim 1, wherein the repeating unit having an acid labile group is represented by the following formula (a1) or (a2): 【Chemistry 2】 (In the formula, a is an integer of 0 to 4. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. X 1 is a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-X 11 - is. X 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. X 2 is a single bond or *-C(=O)-O-. * indicates a bond to a carbon atom in the main chain. R 11 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom. AL 1 and AL 2 are each independently an acid labile group.

3. 2. The resist composition according to claim 1, wherein the repeating unit having a carboxy group is represented by the following formula (b): 【Chemistry 3】 (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 1 represents a single bond, a phenylene group, a naphthylene group, or *-C(=O)-O-Y 11 - is. Y 11 is a saturated hydrocarbylene group having 1 to 10 carbon atoms, a phenylene group, or a naphthylene group, and the saturated hydrocarbylene group may contain at least one bond selected from a hydroxy group, an ether bond, an ester bond, and a lactone ring. * represents a bond to a carbon atom in the main chain.

4. 2. The resist composition according to claim 1, wherein the polymer further comprises at least one repeating unit selected from the group consisting of repeating units represented by the following formulas (c1) and (c2): 【Chemistry 4】 (In the formula, b is 1 or 2, and c is an integer of 0 to 4. R A are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y 2 is a single bond or *-C(=O)-O-. * represents a bond to a carbon atom in the main chain. R 21 is a group having 1 to 20 carbon atoms and containing at least one selected from a hydroxy group, a cyano group, a carbonyl group, an ether bond, an ester bond, a sulfonate ester bond, a carbonate bond, a lactone ring, a sultone ring, and a carboxylic acid anhydride (-C(=O)-O-C(=O)-). R 22 is a hydrocarbyl group having 1 to 20 carbon atoms which may contain a halogen atom or a heteroatom.

5. 2. The resist composition according to claim 1, wherein the polymer further comprises a repeating unit having a photoacid generating group.

6. 2. The resist composition according to claim 1, further comprising (D) a photoacid generator.

7. 2. The resist composition according to claim 1, further comprising (E) a quencher.

8. 2. The resist composition according to claim 1, further comprising (F) a surfactant.

9. 9. A pattern forming method comprising the steps of: forming a resist film on a substrate using the resist composition according to claim 1; exposing the resist film to a KrF excimer laser, an ArF excimer laser, an electron beam, or extreme ultraviolet light; and developing the exposed resist film using a developer.

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