Radiation-sensitive composition, pattern formation method, polymer, and compound

Abstract

Provided are: a radiation-sensitive composition which can exhibit sensitivity, CDU, development defect suppression properties, EL, LWR, MEEF, and pattern squareness to a sufficient level at the time of pattern formation; a pattern formation method; and a compound. The radiation-sensitive composition contains: a polymer that includes a structural unit (I) derived from a compound represented by formula (1) and a structural unit (II) having an acid-dissociable group; and a solvent. In the formula, A is a polymerizable group-containing monovalent organic group having 2-40 carbon atoms. R1 and R2 are each a hydrogen atom, -CN, -NO2, -F, -CF2Ra, -SO2Rb, -CORc, or a monovalent organic group (a) having 1–20 carbon atoms other than -CF2Ra, -SO2Rb, -CORc or -CF3. However, when R1 is -F, R2 bonded to a carbon atom to which R1 is bonded is a group other than -F. At least one selected from the group consisting of R1 and R2 is a group other than a hydrogen atom. Z+ is a monovalent organic cation.

Description

Radiation-sensitive compositions, pattern-forming methods, polymers, and compounds

[0001] The present invention relates to radiation-sensitive compositions, pattern-forming methods, polymers, and compounds.

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic solvent-based developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, or combine this radiation with liquid immersion lithography to advance pattern miniaturization. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] As pattern miniaturization progresses, a technology has been proposed to introduce an acid-generating structure into polymers for the purpose of controlling excessive acid diffusion, etc. (Japanese Patent Publication No. 2023-094359).

[0005] Japanese Patent Publication No. 2023-094359

[0006] In recent years, with the growing environmental awareness, there has been a strong demand for fluorine reduction in the components that make up resist compositions. Even in resist compositions with reduced fluorine content, various resist performance characteristics such as sensitivity, CDU (Critical Dimension Uniformity), development defect suppression, exposure margin (EL), LWR (Line Width Roughness), MEEF (Mask Error Enhancement Factor), and pattern rectangularity are required to be equivalent to or better than those of conventional resists.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern forming method, and a compound that can achieve a sufficient level of sensitivity, CDU, development defect suppression, EL, LWR, MEEF, and pattern rectangularity during pattern formation while reducing the fluorine content in the polymer.

[0008] As a result of intensive studies to solve this problem, the inventors of the present invention have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition containing a polymer containing a structural unit (I) derived from a compound represented by the following formula (1) and a structural unit (II) having an acid dissociable group, and a solvent. (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms containing a polymerizable group. R １ and R ２ are each independently a hydrogen atom, -CN, -NO ２ , -F, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ other than a monovalent organic group (a) having 1 to 20 carbon atoms. R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. R １ and R ２ When there are a plurality of R １ and R ２ are the same or different from each other. However, when R １ is -F, R １ The R bonded to the carbon atom to which ２ is bonded is a group other than -F. At least one selected from the group consisting of R １ and R ２ is a group other than a hydrogen atom. n１ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ and R ２ However, if each is independently a hydrogen atom or the above-mentioned monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ It is 1. Z ＋ (This is a monovalent organic cation.)

[0010] According to this radiation-sensitive composition, excellent sensitivity, CDU, development defect suppression, EL, LWR, MEEF, and pattern rectangularity can be achieved during resist pattern formation. Although the reason for this is not entirely clear, it is presumed to be as follows.

[0011] The above polymer (hereinafter also referred to as the "base polymer") contains structural unit (I). The sulfonate anion and organic cation in structural unit (I) form an onium salt structure, and function as a radiation-sensitive acid generation structure that generates an acid that dissociates the above-mentioned acid-dissociable group upon exposure. Since the sulfonate anion in the radiation-sensitive acid generation structure is covalently incorporated into structural unit (I), the acid diffusion length can be appropriately controlled, and roughness can be improved. Furthermore, instead of the fluoro group or perfluoroalkyl group near the sulfonate anion that is frequently used in conventional radiation-sensitive acid generation structures, a predetermined electron-withdrawing group is introduced. As a result, the solubility and dispersibility of the entire polymer are improved, allowing for good film homogeneity and suppression of roughness. In addition, the base polymer becomes less hydrophobic, resulting in good developer solubility, which can improve pattern shape and development defect suppression. It is presumed that the above-mentioned resist performance can be achieved through the combined effects of these factors.

[0012] In another embodiment, the present invention relates to a pattern forming method comprising the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

[0013] In this pattern formation method, since the above-mentioned radiation-sensitive composition is used during resist pattern formation, which exhibits excellent sensitivity, CDU, development defect suppression, EL, LWR, MEEF, and pattern rectangularity, high-quality resist patterns can be efficiently formed.

[0014] In another embodiment, the present invention relates to a polymer comprising a structural unit (I) derived from a compound represented by the following formula (1) and a structural unit (II) having an acid-dissociable group. (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. １ and R ２ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If multiple R １ and R ２ They are either the same or different. However, R １ However, if -F, R １ R bonded to the carbon atom to which it is attached. ２ R is a group other than -F. １ and R ２ At least one of the groups selected from the group consisting of is a group other than a hydrogen atom. １ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ and R ２When each is independently a hydrogen atom or the monovalent organic group (a) having 1 to 20 carbon atoms, n ２ is 1. Z ＋ is a monovalent organic cation.)

[0015] In the polymer, since the structural unit (I) adopting a predetermined electron-withdrawing group in the radiation-sensitive acid-generating structure is incorporated, when applied to a radiation-sensitive composition, it can exhibit acid diffusion controllability, film quality homogeneity, and developer solubility as described above, and can improve resist performance.

[0016] The present invention further relates to a compound (hereinafter also referred to as "compound (1a)") represented by the following formula (1a) in another embodiment. (In formula (1a), A is a monovalent organic group having 2 to 40 carbon atoms containing a polymerizable group. R １ａ and R ２ａ are each independently a hydrogen atom, -CN, -NO ２ , -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or a monovalent organic group (a) having 1 to 20 carbon atoms other than -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ outside. R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. R １ａ and R ２ａ When there are a plurality of R １ａ and R ２ａ , the plurality of R １ａ and R ２ａ are each the same or different. However, at least one selected from the group consisting of R １ is an integer of 1 to 4. n ２ is 0 or 1. However, R １ａ and R２ａ is, independently, a hydrogen atom or the monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ is 1. Z ＋ is a monovalent organic cation.)

[0017] In another embodiment, the present invention relates to a compound represented by the following formula (1b) (hereinafter also referred to as "compound (1b)"). (In formula (1b), the number of carbon atoms in the organic acid anion is 7 or more, and A is a monovalent organic group having 2 to 40 carbon atoms containing a polymerizable group. R １ｂ and R ２ｂ are, independently, a hydrogen atom, -CN, -NO ２ , -F, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ other than a monovalent organic group (a) having 1 to 20 carbon atoms. R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are, independently, monovalent organic groups having 1 to 20 carbon atoms. When there are a plurality of R １ｂ and R ２ｂ , the plurality of R １ｂ and R ２ｂ are each the same or different. However, one of the one or more R １ｂ is -F, and the R １ｂ bonded to the carbon atom to which -F is bonded is a group other than -F. At least one selected from the group consisting of R ２ｂ is a group other than a hydrogen atom. n １ｂ and R ２ｂ is an integer of 1 to 4. n １ is 0 or 1. Z ２ is a monovalent organic cation.) ＋ is a monovalent organic cation.)

[0018] Compounds (1a) and (1b) have a structure in which fluoro groups and the like are reduced by introducing a predetermined electron-withdrawing group into the radiation-sensitive acid generation structure. Therefore, they are suitable as monomers for polymers that serve as the main components of radiation-sensitive compositions where acid diffusion controllability, film homogeneity, and developer solubility are required.

[0019] In this specification, "organic group" means a group having at least one carbon atom. In the structural formula, "Me" represents a methyl group.

[0020] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Preferred combinations of embodiments are also preferred.

[0021] Radiation-sensitive composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer and a solvent. The above composition may contain other optional components as long as they do not impair the effects of the present invention.

[0022] <Polymers> A polymer (i.e., a base polymer) is an aggregate of polymer chains having the above-mentioned structural units (I) and (II). In addition to structural units (I) and (II), the base polymer may also contain structural units having phenolic hydroxyl groups (hereinafter also referred to as "structural unit (III)"), structural units including onium salt structures that function as acid diffusion control structures (IV), structural units including lactone structures, etc. (hereinafter also referred to as "structural unit (V)"), structural units including polar groups (hereinafter also referred to as "structural unit (VI)"), etc.

[0023] The above base polymer preferably contains an iodine group. By including an iodine group in the base polymer, the radiation absorption efficiency is increased and the secondary electron generation efficiency is enhanced, thereby improving sensitivity. The iodine group may be contained in structural unit (I) or in other structural units. In particular, it is preferable that the iodine group is contained in the onium salt structure of structural unit (I) or in the acid-dissociable group of structural unit (II).

[0024] When introducing an iodine group into the above-mentioned base polymer, it is preferable that the iodine group be in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by iodine groups.

[0025] The aromatic ring in the iodine group-containing aromatic ring structure is not particularly limited as long as it is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, perylene rings, and coronene rings; aromatic heterocycles such as furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, carbazole rings, and dibenzofuran rings; or combinations thereof. Among these, the benzene ring is preferred as the aromatic ring.

[0026] The number of iodine atoms in the above-described iodine group-containing aromatic ring structure is not particularly limited, but it is preferably 1 to 4, more preferably 1, 2, or 3, and even more preferably 1 or 2.

[0027] (Structural Unit (I)) Structural unit (I) is a structural unit derived from the compound represented by the following formula (1). (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. １ and R ２ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and Rｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If multiple R １ and R ２ They are either the same or different. However, R １ However, if -F, R １ R bonded to the carbon atom to which it is attached. ２ n is a group other than -F. １ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ and R ２ However, if each is independently a hydrogen atom or the above-mentioned monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ It is 1. Z ＋ (This is a monovalent organic cation.)

[0028] Examples of monovalent organic groups having 2 to 40 carbon atoms that contain a polymerizable group represented by A include the polymerizable group alone, or a group formed by combining the polymerizable group with a monovalent organic group having 1 to 40 carbon atoms, resulting in a total of 2 to 40 carbon atoms.

[0029] Examples of polymerizable groups include ethylenically unsaturated double bonds, or structures containing ethylenically unsaturated double bonds as a substructure constituting a ring. Examples of ring structures containing ethylenically unsaturated double bonds include cycloalkene structures, structures in which the methylene group of a cycloalken is replaced with a divalent heteroatom-containing group, and polymerizable aromatic heterocyclic structures such as furan.

[0030] Examples of the above-mentioned cycloalkene structures include cyclopropene structures, cyclopentene structures, cyclohexene structures, and other cycloalkene structures; as well as bridged ring unsaturated hydrocarbon groups such as norbornene structures and tricyclodecene structures.

[0031] Examples of the above-mentioned divalent heteroatom-containing groups include -CO-, -CS-, -NR'-, -O-, -S-, and combinations thereof. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0032] The polymerizable group may have substituents. Examples of substituents include halogen atoms, monovalent organic groups having 1 to 20 carbon atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, and oxo groups (=O).

[0033] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms. Hereafter, unless otherwise specified, "halogen atom" refers to these atoms.

[0034] Examples of the monovalent organic groups having 1 to 20 carbon atoms include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups (a) having a divalent heteroatom-containing group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with monovalent heteroatom-containing groups, or combinations thereof.

[0035] Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof.

[0036] Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, and t-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0037] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl groups; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and bridged ring unsaturated hydrocarbon groups such as norbornyl and tricyclodecenyl groups.

[0038] Examples of monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0039] Examples of heteroatoms that constitute a divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, and the like.

[0040] The divalent heteroatom-containing groups are as described above.

[0041] Examples of monovalent heteroatom-containing groups include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0042] Specific examples of the polymerizable group mentioned above include, but are not limited to, structures represented by the following formula.

[0043] (In the formula, * represents a connection with other structures in A of formula (1) above.)

[0044] As the monovalent organic group having 1 to 40 carbon atoms that can be combined with the polymerizable group, it is preferable to use a group that is an extension of the monovalent organic group having 1 to 20 carbon atoms shown as a substituent of the polymerizable group, extending the number of carbon atoms from 2 to 40.

[0045] A is preferably a monovalent organic group having 5 to 40 carbon atoms that includes a polymerizable group and a cyclic structure.

[0046] The above cyclic structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be alicyclic, aromatic, heterocyclic, or a combination thereof. In the case of a combination, the cyclic structures may be linked by a chain structure, and two or more cyclic structures may form a fused ring structure, a bridged ring structure, or a spiro-ring structure. Divalent heteroatom-containing groups may be present between carbon atoms forming the skeleton of the cyclic or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure may be substituted with other substituents. Among these, polycyclic cycloalkane structures, polycyclic lactone structures, and aromatic hydrocarbon structures are preferred as the above cyclic structure, and norbornane structures, adamantane structures, norbornane lactone structures, adamantane lactone structures, and benzene ring structures are more preferred.

[0047] The chain structure described above is preferably a chain hydrocarbon structure having 1 to 20 carbon atoms, a divalent heteroatom-containing group, or a combination thereof. The chain hydrocarbon structure having 1 to 20 carbon atoms is a structure corresponding to the monovalent chain hydrocarbon group having 1 to 20 carbon atoms shown in the polymerizable group of formula (1) above.

[0048] Substituents that the above-mentioned cyclic or chain-like structures may have include, for example, halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino groups; alkoxy groups; alkoxycarbonyl groups; cycloalkoxycarbonyl groups; alkoxycarbonylalkyloxy groups; cycloalkoxycarbonylalkyloxy groups; acyl groups; acyloxy groups or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; or groups that combine these; oxo groups (=O), etc.

[0049] R ａ , R ｂ and R ｃ As the monovalent organic group having 1 to 20 carbon atoms represented by the formula (1) above, the monovalent organic group having 1 to 20 carbon atoms shown in the polymerizable group of formula (1) above can be suitably adopted. Among them, R ａ , R ｂ and R ｃThe organic group is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, a group having an ether bond on the bonding side of the hydrocarbon group, more preferably an alkyl group or alkoxy group, and even more preferably a methyl group, ethyl group, methoxy group, or ethoxy group.

[0050] R ａ R is preferably a hydrogen atom. ｃ It is preferable that it does not contain polymerizable groups.

[0051] R １ and R ２ The monovalent organic group (a) having 1 to 20 carbon atoms, represented by -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ or -CF ３ It is an organic group other than the above. The above organic group (a) is preferably a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, more preferably a substituted or unsubstituted alkyl group, and even more preferably a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, or a group in which some or all of the hydrogen atoms of these groups are substituted. As substituents in organic group (a), substituents that the above cyclic structure and the like may have can be suitably adopted.

[0052] R bonded to the α-carbon of the sulfur atom in formula (1) above １ and R ２ At least one selected from the group consisting of -CN, -F, and -CF ２ H, or -SO ２ R ａ It is preferable that it be -CN, and more preferably -CN.

[0053] n １ It is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0054] The organic acid anion of the compound that gives structural unit (I) preferably has the structure represented by the following formula (1-1). (In formula (1-1), W is a polymerizable group. L) ｘ This is a single bond or a divalent heteroatom-containing group. Cy１１ and Cy １２ These are, independently, substituted or unsubstituted cyclic structures. １２ If there are multiple Cy １２ They are either identical or different from each other. ｙ and L ｚ Each of these is independently a single bond, a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent heteroatom-containing group, or a combination thereof. ｙ If there are multiple L ｙ They are either identical or different from each other. ２ R is an integer between 0 and 4. １ , R ２ and n １ This is equivalent to the higher-level formula (1).

[0055] The polymerizable group represented by W can preferably be the polymerizable group of formula (1) above.

[0056] L ｘ ~L ｚ As the divalent heteroatom-containing group represented by the above formula (1), the divalent heteroatom-containing group shown in the polymerizable group of formula (1) can be suitably adopted.

[0057] Cy １１ and Cy １２ As the cyclic structure represented by the above formula (1), the cyclic structure shown in A can be suitably adopted. As the substituents that the cyclic structure may have, the substituents that the above cyclic structure may have can be suitably adopted.

[0058] L ｙ and L ｚ As the divalent hydrocarbon group having 1 to 10 carbon atoms in the above formula (1), it is preferable to use a group obtained by removing one hydrogen atom from the monovalent hydrocarbon group having 1 to 20 carbon atoms that corresponds to the group having 1 to 10 carbon atoms, as shown in the polymerizable group of formula (1) above. As the substituents that the hydrocarbon group may have, it is preferable to use substituents that the above cyclic structure may have.

[0059] n ２ It is preferably an integer between 0 and 2, and more preferably 0 or 1.

[0060] Specific examples of organic acid anions of monomeric compounds that give structural unit (I) include, but are not limited to, structures represented by the following formulas (1-1-1) to (1-1-66) (including the structure represented by formula (1-1) above).

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] Z ＋ The monovalent organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, and ammonium cations.

[0069] Z ＋ It is preferable that the onium cation is a monovalent radiation-sensitive onium cation. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0070] The above organic cation preferably has at least one selected from the group consisting of an iodine group and a fluoro group. The above organic cation preferably contains the above iodine group-containing aromatic ring structure as the form of the iodine group. In the organic cation, the fluoro group is preferably in the form of a fluoro group-containing aromatic ring structure. The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced by a fluoro group. As the aromatic ring in the fluoro group-containing aromatic ring structure, the aromatic ring in the iodine group-containing aromatic ring structure can be suitably adopted. By introducing an iodine group or a fluoro group, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0071] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0072]

[0073] In the above equation (X-1), R ａ１ , R ａ２ and R ａ３ Each of these independently comprises a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom, or -OSO ２ -R Ｐ , -SO ２ -R Ｑ , -S-R Ｔ R represents a ring structure consisting of -O-, -CO-, or a combination thereof, or two or more of these groups combined with each other. This ring structure may contain heteroatoms such as O or S between the carbon-carbon bonds forming the skeleton. Ｐ , R Ｑ and R ＴEach of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently integers from 0 to 5. R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ If each of them is multiple, then multiple R ａ１ ~R ａ３ And R Ｐ , R Ｑ and R Ｔ These may be the same or different.

[0074] In the above equation (X-2), R ｂ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. ｋ n is either 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O and S between the carbon-carbon bonds that form the skeleton.

[0075] In the above equation (X-3), R ｃ１ , R ｃ２ and R ｃ３ Each of these is independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0076] In the above equation (X-4), R ｇ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, halogen atom, or hydroxyl group having 6 to 8 carbon atoms. ｋ２ n is either 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0077] In the above equation (X-5), R ｄ１ and R ｄ２Each of these independently represents a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by two or more of these groups combined. k6 and k7 are each independently integers from 0 to 5. R ｄ１ and R ｄ２ If each of them is multiple, then multiple R ｄ１ and R ｄ２ These may be the same or different.

[0078] In the above formula (X-6), R ｅ１ and R ｅ２ k8 and k9 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0079] Specific examples of organic cations used as the above-mentioned radiation-sensitive onium cation include, but are not limited to, the structures shown in formulas (1-2-1) to (1-2-59) below.

[0080]

[0081]

[0082]

[0083] The monomeric compound that gives structural unit (I) is obtained by combining the above-mentioned organic acid anion (sulfonic acid anion) and the above-mentioned onium cation. Specific examples, though not limited to them, include structures represented by the following formulas (A-1) to (A-36). In the formulas, Me is a methyl group.

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] The lower limit of the content of structural unit (I) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By setting the content of structural unit (I) within the above range, it is possible to fully exhibit its function as a radiation-sensitive acid-generating structure and exhibit the above resist properties.

[0090] (Method for producing compounds that give structural unit (I)) Known methods can be used to produce compounds that give structural unit (I). Typically, they can be produced according to the following scheme.

[0091] (In the scheme, R Ａ１ R is a monovalent organic group. １ and Z ＋ This is equivalent to equation (1) above. X - (where is a halide ion; W is a polymerizable group; L is a single or divalent linking group.)

[0092] An ester having a predetermined electron-withdrawing group (cyano group in the scheme) is brominated with a halogenating agent (brominating agent in the scheme), followed by sulfonation, and then salt exchange with the halogenated product of the target organic cation to obtain an onium salt. Subsequently, a reactive group (carboxyl group in the scheme) is generated with an alkali or reducing agent, and finally, the target compound can be produced by reacting it with a polymerizable compound. Other structures can also be produced by appropriately changing the structures of the starting materials and precursors.

[0093] -SO in the sulfonate anion chain ２ If - is present, it can typically be manufactured according to the following scheme.

[0094] (X in scheme) ａ and X ｃL is a halogen atom. L are independently divalent linking groups. ＋ Z is an alkali metal ion. ＋ This is equivalent to equation (1) above. X ｂ - (This is a halide ion. W is a polymerizable group. O is an oxidizing agent.)

[0095] An onium salt is obtained by nucleophilically reacting a thiol with a sulfonate containing an electrophilic group, followed by salt exchange with the halogen of the target organic cation. The desired compound can then be produced by reacting it with a polymerizable compound and finally oxidizing the thioether with an oxidizing agent. Other structures can also be produced by appropriately changing the structures of the starting materials and precursors.

[0096] (Structural Unit (II)) Structural Unit (II) is a structural unit that contains an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (II).

[0097] Structural unit (II) is not particularly limited as long as it has an acid-dissociable group, and examples include structural units having a tertiary alkyl ester moiety, structural units having a secondary alkyl ester moiety to which an aromatic group and an aliphatic group are bonded, structural units having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, structural units having an acetal bond, etc. However, from the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, the structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (II-1)") is preferred.

[0098]

[0099] In the above formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０Each of these independently represents either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0100] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (II-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0101] L １１ａ Examples of alkanediyl groups represented by include methylene groups, ethanediyl groups, 1,3-propanediyl groups, and 2,2-propanediyl groups, which have 1 to 10 carbon atoms. １１ａ Methylene groups and ethanediyl groups are preferred as the base group.

[0102] L １１ａ Examples of allenediyl groups represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the group.

[0103] L １１ａ The substituents that the arenediyl group represented by can have include halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkyl groups, fluorinated alkyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, and alkoxy groups.

[0104] The above R １８ As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (1) above, the monovalent hydrocarbon group having 1 to 20 carbon atoms shown in the polymerizable group of formula (1) above can be suitably adopted.

[0105] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0106] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these atoms with the carbon atoms to which they are bonded, can preferably be a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the polymerizable group of formula (1) above.

[0107] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0108] The above R １８ ~R ２０ The substituents that can be present are L １１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0109] Examples of structural units (II-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (II-1-1) to (II-1-15)").

[0110]

[0111]

[0112] In the above equations (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１R is a halogen atom, hydroxyl group, carboxyl group, cyano group, nitro group, alkyl group, fluorinated alkyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or alkoxy group. i and j are each independently integers from 1 to 4. k and l are 0 or 1. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0113] i and j are preferably 1. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into the structural unit (II).

[0114] Furthermore, the polymer may contain structural units represented by the following formulas (1f) to (2f) as structural units (II).

[0115]

[0116] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0117] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0118] The lower limit of the content of structural unit (II) in relation to the total structural units constituting the polymer (the total content if multiple types are included) is preferably 5 mol%, more preferably 15 mol%, and even more preferably 30 mol% relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 70 mol%, more preferably 65 mol%, and even more preferably 60 mol%. By setting the content of structural unit (II) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0119] (Structural Unit (III)) Structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to structural units (I) to (II)). By including structural unit (III) in the polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the above-mentioned radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, etc. are used as the radiation irradiated in the exposure step in the resist pattern formation method, structural unit (III) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as electron beams and EUV. Structural unit (III) is preferably represented by the following formula (2).

[0120] (In the above formula (2), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ , -O- or -CONH- ＊ * indicates a bond on the aromatic ring side. １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４Each of these is an independent integer between 0 and 8, where 1 ≤ m. ３ +m ４ ≤ 2n ３ (Saves +5.)

[0121] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (III), it is preferable that the atom be a hydrogen atom or a methyl group.

[0122] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0123] R １０２ In this, the halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group, or acyloxy group can preferably be one of the groups listed above as substituents for the cyclic structure, etc. R １０２ In this mixture, iodine or fluorine atoms are preferred as halogen atoms, with iodine atoms being more preferred.

[0124] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0125] The above m ３ The integer is preferably between 1 and 3, and more preferably 1 or 2.

[0126] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0127] The above structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-24) (hereinafter also referred to as "structural unit (III-1) to structural unit (III-24)").

[0128]

[0129]

[0130] In the above equations (2-1) to (2-24), R β This is the same as equation (2) above.

[0131] When the base polymer has structural unit (III), the lower limit of the content of structural unit (III) (total if there are multiple types of structural unit (III)) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the polymer. The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural unit (III) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0132] (Structural Unit (IV)) The base polymer may include structural unit (IV) which has a second organic acid anion and a second onium cation, and which includes a second acid generation structure that generates an acid by exposure without dissociating the above-mentioned acid-dissociable group. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generation structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid generation structure substantially prevents the dissociation of the acid-dissociable group of structural unit (II), and has the function of suppressing the diffusion of acid generated from the above-mentioned radiation-sensitive acid generation structure or radiation-sensitive acid generator (if included) in the unexposed area by salt exchange. The acid generated from the second acid generation structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the above-mentioned radiation-sensitive acid generation structure. Whether an onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable groups of the base polymer, and the acidity of the onium salt structure or the generated acid.

[0133] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (IV) of the base polymer is not particularly limited. The base polymer may have the second organic acid anion as a side chain portion, or it may have the second onium cation as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the second organic acid anion is bonded to the main chain as a side chain structure of the base polymer, the second onium cation is ionically bonded to the second organic acid anion as its counterion. On the other hand, when the second onium cation is bonded to the main chain as a side chain structure of the base polymer, the second organic acid anion is ionically bonded to the second onium cation as its counterion. From the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion.

[0134] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion, and more preferably has a carboxylic acid anion. However, when the above-mentioned second organic acid anion has the above-mentioned sulfonic acid anion, no electron-withdrawing group is bonded to either the α-position or the β-position carbon atom of the sulfur atom in the above-mentioned sulfonic acid anion. Examples of electron-withdrawing groups include electron-withdrawing groups that the above-mentioned first organic acid anion may have in the above-mentioned first acid generation structure. The acid generated by exposure is a carboxylic acid or sulfonic acid, corresponding to the above-mentioned acid anion portion.

[0135] The above-mentioned second organic acid anion preferably includes -O-, -CO-, a cyclic structure, or a combination thereof, as a structure other than the acid anion portion. Such a structure can preferably be the one represented by the sulfonic acid anion of structural unit (I).

[0136] The above-mentioned second organic acid anion preferably has an iodine group or a hydroxyl group. The above-mentioned second organic acid anion preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0137] As the second onium cation mentioned above, the organic cation shown in structural unit (I) can be suitably adopted.

[0138] The above-mentioned second onium cation preferably has an iodine group. The above-mentioned second onium cation preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0139] The secondary onium cation in structural unit (IV) preferably has the above-mentioned fluorogroup-containing aromatic ring structure. This can improve sensitivity by increasing the radiation absorption efficiency.

[0140] The structural unit (IV) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0141] The structural unit (IV) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (IV-1)").

[0142]

[0143] In formula (p1), R A This is either a hydrogen atom or a methyl group.

[0144] In formula (p1), X 1 These are single bonds, ester bonds, ether bonds, phenylene groups, naphthylene groups, or combinations thereof.

[0145] In formula (p1), X ２ This is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may include an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3- Examples include C1-C12 alkanediyl groups such as diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, heptane-1,7-diyl groups, octane-1,8-diyl groups, nonane-1,9-diyl groups, and decane-1,10-diyl groups; C3-C12 cyclic saturated hydrocarbylene groups such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; and groups obtained by combining these.

[0146] In formula (p1), X 3 These are single bonds, ester bonds, or ether bonds.

[0147] In formula (p1), X 1 ~X ２ Some or all of the hydrogen atoms in may be substituted with substituents. The substituents shown in the above-mentioned cyclic structure, etc., can be suitably adopted. 1 ~X ２ If the compound has a phenylene group, it is preferable that some or all of the hydrogen atoms of the phenylene group are substituted with fluorine atoms or iodine atoms.

[0148] In formula (p1), Z ２ ＋ This is Z in equation (1) above. ＋ It is synonymous with [the above].

[0149] In the above formula (p1), an iodonium cation can also be used as the second onium cation. As the iodonium cation, the diaryliodonium cation shown as the onium cation of structural unit (I) can be suitably adopted.

[0150] Examples of the second organic acid anion of the monomer that provides the structural unit (IV) (including the structural unit (IV-1)) include, but are not limited to, those shown below. Although each of the second organic acid anions shown below has an iodine group or a hydroxy group, the structural unit (IV) does not necessarily require an iodine group or a hydroxy group. As the second organic acid anion having no iodine group or hydroxy group, a structure in which the iodine group or hydroxy group in the following formula is substituted with a hydrogen atom or a substituent shown in the above cyclic structure or the like can be preferably adopted. In the following formula, R Ａ is the same as described above. The second organic acid anion preferably has a carboxylic acid anion and a hydroxy group. In this case, it is preferable that the carboxylic acid anion and the hydroxy group are bonded to the same aromatic ring in the second organic acid anion, and in the same aromatic ring, the carbon atom to which the carboxylic acid anion is bonded and the carbon atom to which the hydroxy group is bonded are more preferably directly bonded to each other.

[0151]

[0152]

[0153]

[0154]

[0155] As the second onium cation of the structural unit (IV), the sulfonium cation of the above formula (1) can be preferably adopted.

[0156] As the side chain structure of the base polymer, an aspect in which the second onium cation is bonded to the main chain and the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation can also be adopted. In this case, the second onium cation is bonded to the main chain via a divalent linking group or a single bond, and the structure from X １ to COO - is preferably ionically bonded to the second onium cation as a counter ion. As the divalent linking group, the divalent heteroatom-containing group shown in the above polymerizable group can be preferably adopted.

[0157] When the base polymer contains the structural unit (IV), the lower limit of the content ratio of the structural unit (IV) (the total content ratio in the case of containing a plurality of types) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol% with respect to all the structural units constituting the base polymer. Further, the upper limit of the above content ratio is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content ratio of the structural unit (IV) within the above range, the function as an acid diffusion control structure can be sufficiently exhibited.

[0158] (Structural unit (V)) The structural unit (V) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further having the structural unit (V), the base polymer can adjust the solubility in the developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. Further, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0159] Examples of the structural unit (V) include structural units represented by the following formulas (T-1) to (T-11).

[0160]

[0161] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group. R Ｌ２ to R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. R Ｌ４ and R Ｌ５ may be a divalent alicyclic group having 3 to 8 carbon atoms formed together with the carbon atoms to which they are bonded. L ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0162] The above R Ｌ４ and R Ｌ５When these are combined with each other, the divalent alicyclic group having 3 to 8 carbon atoms, formed together with the carbon atoms to which they are bonded, is R in formula (3) above. １９ and R ２０ Examples include divalent alicyclic groups with 3 to 20 carbon atoms, where these groups are combined with each other and formed together with the carbon atoms to which they are bonded, specifically groups with 3 to 8 carbon atoms. One or more hydrogen atoms on these alicyclic groups may be substituted with hydroxyl groups.

[0163] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0164] Among these, structural units (V) that include a lactone structure are preferred, and structural units that include a γ-butyrolactone structure, norbornane lactone structure, or adamantane lactone structure are more preferred.

[0165] When the base polymer has structural units (V), the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol% relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of structural units (V) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0166] (Structural Unit (VI)) Structural unit (VI) is a structural unit containing a polar group (excluding those corresponding to structural units (I), (III) to (V)). The second polymer can have its solubility in the developer adjusted by further containing structural unit (VI). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0167] Examples of structural units (VI) include structural units represented by the following formula.

[0168]

[0169]

[0170] In the above formula, R Ｋ These are a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0171] When the base polymer has structural units (VI) having the polar group described above, the lower limit of the content of structural units (VI) (total content if multiple types are included) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 20 mol%, more preferably 12 mol%, and even more preferably 8 mol%. By setting the content of structural units (VI) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0172] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0173] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0174] Solvents used in the above polymerization include, for example, alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; and ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone. Examples include ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and 1,4-dioxanes; polyhydric alcohol partial ethers such as propylene glycol monomethyl ether (1-methoxy-2-propanol); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0175] The reaction temperature in the polymerization described above is usually 40°C to 150°C, with 50°C to 120°C being preferred. The reaction time is usually 1 hour to 48 hours, with 1 hour to 24 hours being preferred.

[0176] The molecular weight of the base polymer is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, and even more preferably 18,000. By keeping the Mw of the base polymer within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0177] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0178] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0179] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh) Column temperature: 40°C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0180] The base polymer content is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0181] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having higher hydrophobicity than the above base polymer (hereinafter also referred to as "highly hydrophobic polymer"). The highly hydrophobic polymer is a polymer having a higher mass content ratio of fluorine atoms or a higher introduction rate of hydrocarbon groups as compared with the above base polymer. When the radiation-sensitive composition contains a highly hydrophobic polymer, it can be preferentially distributed in the surface layer of the resist film with respect to the above base polymer. As a result, the water repellency of the surface of the resist film during immersion exposure can be enhanced, or surface modification of the resist film and control of the distribution of the composition within the film during EUV exposure can be achieved.

[0182] As the highly hydrophobic polymer, for example, it may have a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (i)").

[0183]

[0184] In the above formula (5), R １３ is a hydrogen atom, a methyl group or a trifluoromethyl group. G Ｌ is a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, -SONH ２ ONH-, -CONH-, -OCONH- or a combination thereof. R １４ is a monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0185] As the above R １３ from the viewpoint of the copolymerizability of the monomer that gives the structural unit (i), a hydrogen atom and a methyl group are preferable, and a methyl group is more preferable.

[0186] As the above G Ｌ from the viewpoint of the copolymerizability of the monomer that gives the structural unit (i), a single bond and -COO- are preferable, and -COO- is more preferable.

[0187] Examples of the monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms represented by the above R １４ include those in which some or all of the hydrogen atoms of a linear or branched alkyl group having 1 to 20 carbon atoms are substituted by fluorine atoms.

[0188] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0189] The above R １４ Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0190] When the highly hydrophobic polymer has structural unit (i), the lower limit of the content of structural unit (i) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, relative to the total structural units constituting the highly hydrophobic polymer. The upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural unit (i) within the above range, the mass content of fluorine atoms in the highly hydrophobic polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0191] The highly hydrophobic polymer may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (ii)) represented by the following formula (f-2), either together with or in place of structural unit (i). By having structural unit (f-2), the highly hydrophobic polymer can improve its solubility in alkaline developers and suppress the occurrence of development defects.

[0192]

[0193] Structural units (ii) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In both (x) and (y), in the above formula (f-2), R ＣR is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the terminal end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ -A structure to which a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms of this hydrocarbon group are substituted by an organic group having a heteroatom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer from 1 to 3.

[0194] If structural unit (ii) has (x) an alkali-soluble group, R Ｆ A is a hydrogen atom, １ is an oxygen atom, -COO-* or -SO ２ It is O-*. * is R Ｆ This indicates the binding site. １ This is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ If is an oxygen atom, W １ is A １ It is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which it is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. Having an alkali-soluble group (x) in structural unit (ii) increases its affinity for alkaline developer and suppresses development defects. A is an example of a structural unit (ii) having an alkali-soluble group. １ is an oxygen atom and W １ It is particularly preferable that the group is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0195] If structural unit (ii) has an alkali-dissociable group (y), R Ｆ A is a monovalent organic group having 1 to 30 carbon atoms. １ is an oxygen atom, -NR ａａ-, -COO-*, -OCO-*, or -SO ２ It is O-*. ａａ * is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Ｆ This indicates the binding site. １ R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom. １ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in structural unit (ii) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural unit (ii) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0196] R Ｃ From the viewpoint of copolymerizability of monomers that give structural unit (ii), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0197] When the highly hydrophobic polymer has structural unit (ii), the content of structural unit (ii) (total content if multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of structural unit (ii) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers to suppress the occurrence of development defects.

[0198] [Other structural units] The highly hydrophobic polymer may, if necessary, include structural units other than those listed above, such as structural unit (II) and structural unit (VI) in the base polymer.

[0199] When the highly hydrophobic polymer contains structural unit (II), the content of structural unit (II) is preferably 30 mol%, and more preferably 40 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 70 mol%, and more preferably 60 mol%.

[0200] When a highly hydrophobic polymer contains structural units (VI), the content of structural units (VI) is preferably 1 mol%, and more preferably 3 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 15 mol%, and more preferably 8 mol%.

[0201] The highly hydrophobic polymer may have a structural unit having a primary, secondary, or tertiary hydrocarbyl ester structure instead of the above structural units (i) and (ii) (however, this is different from structural unit (II) in the base polymer; hereinafter also referred to as "structural unit (iii)"). In this case, it is preferable that the highly hydrophobic polymer does not contain fluorine atoms. It is preferable that structural unit (iii) has a secondary hydrocarbyl ester structure. It is preferable that structural unit (iii) is a structural unit represented by the following formula (iii-1). (In formula (iii-1), R γ R is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ３１and R ３２ Each of these is independently a monovalent linear hydrocarbon group having 3 to 10 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a group in which some or all of the hydrogen atoms of the alicyclic hydrocarbon group are substituted with alkyl groups, or R ３１ and R ３２ This represents a monovalent alicyclic group having 3 to 20 carbon atoms, which can be combined with the carbon atoms to which they are bonded, or a group in which some or all of the hydrogen atoms of the alicyclic group are replaced with alkyl groups.

[0202] R γ As the C1 to C10 alkyl group represented by the above formula (1), groups corresponding to C1 to C10 from the alkyl groups shown in the polymerizable group A can be suitably adopted.

[0203] R ３１ and R ３２ As the monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by the formula (1) above, groups corresponding to 3 to 10 carbon atoms from the monovalent chain hydrocarbon group having 1 to 20 carbon atoms shown in the polymerizable group A of the formula (1) above can be suitably adopted. Among them, R ３１ and R ３２ The monovalent chain hydrocarbon group having 3 to 10 carbon atoms represented by isopropyl, isobutyl, t-butyl, and n-hexyl groups are preferred.

[0204] R ３１ and R ３２ As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the polymerizable group A can be suitably adopted. As the alkyl group that substitutes some or all of the hydrogen atoms of the alicyclic hydrocarbon group, R γ A C1 to C10 alkyl group represented by [the formula shown] can be preferably used.

[0205] R ３１ and R ３２ As a monovalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups, the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the polymerizable group A of formula (1) above can be suitably adopted. Among them, R ３１ and R３２ As a monovalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups, monocyclic or polycyclic cycloalkyl groups are preferred, and cyclopentyl, cyclohexyl, and norbornyl groups are more preferred. As an alkyl group that substitutes some or all of the hydrogen atoms of the above monovalent alicyclic group, R γ C1 to C10 alkyl groups represented by can be suitably used. In particular, the alkyl group used as a substituent is preferably a methyl group, an ethyl group, an isopropyl group, or a t-butyl group.

[0206] When a highly hydrophobic polymer has structural unit (iii), the content of structural unit (iii) (total content if multiple types are included) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol% relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural unit (iii) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers to suppress the occurrence of development defects.

[0207] If the highly hydrophobic polymer has structural unit (iii), it may optionally include structural unit (V) in the base polymer as a structural unit other than the above structural unit (iii).

[0208] When the highly hydrophobic polymer contains structural unit (V), the content of structural unit (V) is preferably 8 mol%, and more preferably 15 mol%, relative to the total structural units constituting the highly hydrophobic polymer. Furthermore, the upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0209] The lower limit of Mw for the highly hydrophobic polymer is preferably 4,000, more preferably 6,000, and even more preferably 7,000. The upper limit of Mw is preferably 20,000, more preferably 16,000, and even more preferably 14,000.

[0210] The lower limit of Mw / Mn for a highly hydrophobic polymer is usually 1, with 1.1 being more preferred. The upper limit of Mw / Mn is usually 5, with 3 being preferred, and 2 being more preferred.

[0211] If the radiation-sensitive composition contains a highly hydrophobic polymer, the lower limit of the content of the highly hydrophobic polymer is preferably 0.1 parts by mass, more preferably 0.2 parts by mass, and even more preferably 0.3 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass.

[0212] By setting the content of the highly hydrophobic polymer within the above range, the highly hydrophobic polymer can be more effectively localized to the surface layer of the resist film. As a result, it is possible to enhance the water repellency of the surface of the resist film during immersion exposure, and to control the surface modification of the resist film and the distribution of the internal composition during EUV exposure. The radiation-sensitive composition may contain one or more highly hydrophobic polymers.

[0213] (Method for synthesizing highly hydrophobic polymers) Highly hydrophobic polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0214] <Radiation-sensitive acid generator> The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a tertiary organic acid anion and a tertiary onium cation, forming an onium salt structure. The radiation-sensitive acid generator is a component that generates acid upon exposure. The acid generated upon exposure has the function of dissociating the acid-dissociable groups of the base polymer and generating carboxyl groups, etc. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low molecular weight compound (liberated from the polymer), and is different from the radiation-sensitive acid-generating structure in which the sulfonic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer, as in structural unit (I) of the base polymer.

[0215] At least one selected from the group consisting of the above-mentioned third organic acid anion and third onium cation preferably has an iodine group, and more preferably has the above-mentioned iodine group-containing aromatic ring structure.

[0216] The structure of the third organic acid anion in the radiation-sensitive acid generator can preferably be a structure obtained by removing the polymerizable group from the compound that gives the structural unit (I) of the base polymer, or a conventionally known structure. In this case, the sulfonate anion SO ３ - The α-carbon of the sulfur atom has a fluorine atom, CF ３ Alternatively, it is preferable that a cyano group is bonded to it.

[0217] Examples of the third organic acid anion for the radiation-sensitive acid generator are, but are not limited to, those listed below. Furthermore, as a third organic acid anion that does not have an iodine group-containing aromatic ring structure, a structure in which the iodine group in the following formula is replaced with a hydrogen atom or other substituent can be suitably adopted.

[0218]

[0219]

[0220]

[0221]

[0222]

[0223] The structure of the third onium cation in the radiation-sensitive acid generator can suitably adopt the structure of the onium cation of structural unit (I) in the above-mentioned base polymer.

[0224] The above-mentioned radiation-sensitive acid generator can also be synthesized by known methods, particularly by salt exchange reactions. Known radiation-sensitive acid generators can also be used, as long as they do not impair the effects of the present invention.

[0225] These radiation-sensitive acid generators may be used individually or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total in the case of multiple types) is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass. This allows for excellent sensitivity during resist pattern formation.

[0226] <Acid Diffusion Control Agent> The radiation-sensitive composition may contain an acid diffusion control agent. The acid diffusion control agent contains a quaternary organic acid anion and a quaternary onium cation, and generates an acid with a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. Under pattern-forming conditions using the radiation-sensitive composition, the acid diffusion control agent substantially prevents the dissociation of the acid-dissociable groups of the base polymer and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in the unexposed areas by salt exchange.

[0227] By including the above-mentioned acid diffusion control agent in the radiation-sensitive composition, acid diffusion in unexposed areas can be suppressed, and a resist pattern with superior CDU and development contrast can be formed.

[0228] At least one selected from the group consisting of the above-mentioned fourth organic acid anion and fourth onium cation preferably has an iodine group, and more preferably has the above-mentioned iodine group-containing aromatic ring structure.

[0229] Although the structure of the above-mentioned fourth organic acid anion is not specified, it is preferable that it includes -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure of the above-mentioned organic acid anion of structural unit (I) of the base polymer can be suitably adopted.

[0230] In the acid diffusion control agent, it is preferable that the fourth organic anion has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion (however, if the fourth organic acid anion has a sulfonic acid anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to either the α-position or the β-position carbon atom of the sulfur atom of the sulfonic acid anion). This allows the acid diffusion control agent to efficiently perform the above function.

[0231] Examples of acid diffusion control agents include sulfonium salt compounds represented by the following formula (8-1), iodonium salt compounds represented by the following formula (8-2), and so on. Also, examples include compounds containing both a sulfonium cation and anion within the same molecule, represented by the following formula (8-3), and compounds containing both an iodonium cation and anion within the same molecule, represented by the following formula (8-4).

[0232]

[0233] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. - and Q - Each of them is independent of OH - , R α -COO - , R α -SO ３ - It is the fourth organic acid anion represented by the above formulas (8-1) to (8-2). α R is a monovalent organic group having 1 to 30 carbon atoms. In the above formulas (8-3) to (8-4), α This is a single bond or a divalent organic group having 1 to 30 carbon atoms. As the monovalent organic group having 1 to 30 carbon atoms, a group obtained by extending the monovalent organic group having 1 to 20 carbon atoms shown in the polymerizable group of formula (1) above to 1 to 30 carbon atoms can be suitably adopted. As the divalent organic group having 1 to 30 carbon atoms, a group obtained by removing one hydrogen atom from the monovalent organic group having 1 to 30 carbon atoms can be suitably adopted.

[0234] Examples of the fourth organic acid anion for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also examples. As an organic acid anion that does not have an iodine group-containing aromatic ring structure, a structure in which the iodine group in the following formula is replaced with an atom or group other than an iodine group, such as a hydrogen atom or other substituent, can be suitably adopted.

[0235]

[0236]

[0237] As the fourth onium cation in the above-mentioned acid diffusion control agent, the structure of the onium cation of structural unit (I) in the above-mentioned base polymer can be suitably adopted.

[0238] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0239] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 2 parts by mass, more preferably 4 parts by mass, and even more preferably 6 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 50 parts by mass, more preferably 45 parts by mass, and even more preferably 40 parts by mass.

[0240] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the base polymer and any optional components that may be included.

[0241] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0242] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether), in which some of the hydroxyl groups of the above-mentioned polyhydric alcohol solvents have been etherified. In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0243] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0244] Examples of ketone solvents include: linear ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0245] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0246] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[0247] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0248] Among these, alcohol-based solvents and ester-based solvents are preferred, alcoholic acid ester-based solvents, monoalcohol-based solvents having 1 to 18 carbon atoms, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, and lactone-based solvents are more preferred, and methyl 2-hydroxyisobutyrate, diacetone alcohol, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and γ-butyrolactone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0249] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0250] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a base polymer and a solvent with other optional components as needed in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.4 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0251] <Pattern Forming Method> The pattern forming method in this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (1) (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (2) (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with a developer (3) (hereinafter also referred to as the "development step").

[0252] According to the pattern formation method described above, a high-quality resist pattern can be formed because the above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, CDU, development defect suppression, EL, LWR, MEEF, and pattern rectangularity, is used during pattern formation. The following describes each step.

[0253] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the above-mentioned radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film disclosed in, for example, Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0254] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask. The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; electron beams, alpha rays, and other charged particle beams. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and ArF excimer laser or EUV is even more preferred.

[0255] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the radiation-sensitive acid generator during exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 180°C, with 80°C to 150°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0256] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed with a developer. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0257] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0258] In addition, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As for ester solvents, acetic acid ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0259] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0260] 《Polymers》 The polymer according to this embodiment is a polymer comprising a structural unit (I) derived from a compound represented by the following formula (1) and a structural unit (II) having an acid-dissociable group. (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. １ and R ２ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If multiple R １ and R ２ They are either the same or different. However, R １ However, if -F, R １ R bonded to the carbon atom to which it is attached. ２ n is a group other than -F. １ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ and R ２However, if each is independently a hydrogen atom or the above-mentioned monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ It is 1. Z ＋ (This is a monovalent organic cation.)

[0261] As such a polymer, the base polymer in the above-mentioned radiation-sensitive composition can be suitably used.

[0262] R bonded to the α-carbon of the sulfur atom in formula (1) above １ and R ２ At least one selected from the group consisting of -CN, -F, and -CF ２ H, or -SO ２ R ａ It is preferable that this be the case.

[0263] Compound (1a) The compound (1a) according to this embodiment is a compound represented by the following formula (1a). (In formula (1a), A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. R １ａ and R ２ａ These are, independently, a hydrogen atom, -CN, and -NO. ２ , -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ａ and R ２ａ If multiple R １ａ and R ２ａ They are either the same or different. However, R １ａ and R ２ At least one of the groups selected from the group consisting of is a group other than a hydrogen atom.１ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ａ and R ２ａ However, if each is independently a hydrogen atom or the above-mentioned monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ It is 1. Z ＋ (This is a monovalent organic cation.)

[0264] Such compounds include compounds that give structural unit (I) of the base polymer in the above-mentioned radiation-sensitive composition, and which have R in formula (1) above. １ and R ２ Compounds that do not contain -F can be preferably used in this case.

[0265] R bonded to the α-carbon of the sulfur atom in formula (1a) above １ and R ２ At least one selected from the group consisting of -CN, -CF ２ H, or -SO ２ R ａ It is preferable that this be the case.

[0266] Compound (1b) The compound (1b) according to this embodiment is a compound represented by the following formula (1b). (In formula (1b), the number of carbon atoms in the organic acid anion is 7 or more, and A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. R １ｂ and R ２ｂ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃEach of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ｂ and R ２ｂ If multiple R １ｂ and R ２ｂ Each of them may be the same or different. However, one or more R １ｂ One of them is -F, and R is -F. １ｂ R bonded to the carbon atom to which it is attached. ２ｂ n is a group other than -F. １ n is an integer between 1 and 4. ２ Z is either 0 or 1. ＋ (This is a monovalent organic cation.)

[0267] Suitable compounds for this purpose include those that provide the structural unit (I) of the base polymer in the above-mentioned radiation-sensitive composition, and which have seven or more carbon atoms in the organic acid anion.

[0268] R bonded to the α-carbon of the sulfur atom in formula (1b) above １ and R ２ One of them is preferably -F.

[0269] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0270] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0271] [ １３ [C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0272] <Synthesis of Compound (Monomer)> [Example A1] (Synthesis of Monomer (A-1)) Compound (A-1) was synthesized according to the following synthesis scheme.

[0273] 20.0 mmol of ethyl 2-cyanopropionate, 30.0 mmol of N-bromosuccinimide (NBS), and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 12 hours. Then, saturated sodium thiosulfate aqueous solution was added to the reaction solution to terminate the reaction, and dichloromethane was added for extraction, separating the organic layer. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the bromo compound was obtained in good yield by column chromatography.

[0274] The above bromo compound was mixed with acetonitrile and water (1:1 by mass) to make a 1 M solution, then 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added and the mixture was reacted at 70°C for 4 hours. After extraction with acetonitrile and removal of the solvent, a mixture of acetonitrile and water (3:1 by mass) was added to make a 0.5 M solution. 60.0 mmol of hydrogen peroxide and 2.00 mmol of sodium tungstate were added and the mixture was heated and stirred at 50°C for 12 hours. The sodium sulfonate salt compound was obtained by extraction with acetonitrile and removal of the solvent. 20.0 mmol of tris(4-fluorophenyl)sulfonium bromide was added to the above sodium sulfonate salt compound, and a mixture of water and dichloromethane (1:3 by mass) was added to make a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The resulting organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (A-1-a) was purified by column chromatography to obtain compound (A-1-a) in good yield.

[0275] 50 g of 1 M aqueous sodium hydroxide solution and 50 g of ethanol were added to the above compound (A-1-a) and the mixture was stirred at 0°C for 2 hours. Then, dichloromethane was added to the reaction solution for extraction, and the organic layer was separated. The solvent of the resulting organic layer was removed by distillation to obtain the carboxylic acid compound in good yield.

[0276] 20.0 mmol of 4-iodocalicylic acid, 30.0 mmol of 1,1'-carbonylbis-1H-imidazole, and 100 g of dichloromethane were added to the above carboxylic acid mixture and stirred at room temperature for 12 hours. After adding saturated ammonium chloride aqueous solution to terminate the reaction, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (A-1-b) was obtained in good yield by column chromatography.

[0277] To the above compound (A-1-b), 20.0 mmol of oxalyl chloride and 50 g of acetonitrile were added and the mixture was stirred at 50°C for 2 hours. Then, 30.0 mmol of 4-hydroxystyrene, 30.0 mmol of pyridine, and 3.0 mmol of 4-dimethylaminopyridine were added and the mixture was stirred at 50°C for 10 hours. After that, water was added to stop the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (A-1) represented by the above formula (A-1) was purified by column chromatography to obtain compound (A-1) in good yield.

[0278] [Examples A2 to A8] (Synthesis of monomers (A-2) to (A-8)) Monomers represented by the following formulas (A-2) to (A-8) were synthesized in the same manner as in Example A1, except that the raw materials and precursors were appropriately changed.

[0279]

[0280] [Example A9] (Synthesis of monomer (A-9)) Compound (A-9) was synthesized according to the following synthesis scheme.

[0281] 20.0 mmol of the above compound (A-1-a), 40.0 mmol of sodium borohydride, and 50 g of tetrahydrofuran were added to a reaction vessel and stirred at room temperature for 12 hours. Then, saturated aqueous ammonium chloride solution was added to the reaction solution to terminate the reaction, and dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the alcohol compound in good yield.

[0282] 20.0 mmol of 4-hydroxy-3,5-diiodobenzoic acid, 30.0 mmol of 1,1'-carbonylbis-1H-imidazole, and 100 g of dichloromethane were added to the above alcohol mixture and stirred at room temperature for 5 hours. After adding saturated ammonium chloride aqueous solution to terminate the reaction, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (A-9-a) was obtained in good yield by column chromatography.

[0283] To the above compound (A-9-a), 20.0 mmol of methacryloyl chloride, 20.0 mmol of triethylamine, and 50 g of dichloromethane were added and the mixture was stirred at room temperature for 12 hours. After that, water was added to stop the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (A-9) represented by the above formula (A-9) was purified by column chromatography to obtain the compound (A-9) in good yield.

[0284] [Examples A10 to A15] (Synthesis of monomers (A-10) to (A-15)) Monomers represented by the following formulas (A-10) to (A-15) were synthesized in the same manner as in Example A9, except that the raw materials and precursors were appropriately changed.

[0285]

[0286] [Example A16] (Synthesis of monomer (A-16)) Compound (A-16) was synthesized according to the following synthesis scheme.

[0287]

[0288] 20.0 mmol of sodium 2-bromoethanesulfonate, 25.0 mmol of potassium carbonate, 40.0 mmol of 2-mercaptoethanol, and 30 g of dimethylformamide were added to a reaction vessel and stirred at 80°C for 3 hours. Then, 70 g of water was added to dilute the mixture, and 20.0 mmol of diphenyl(p-tolyl)sulfonium bromide and 100 g of methylene chloride were added and the mixture was vigorously stirred at room temperature for 3 hours. Dichloromethane was then added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, and the solvent was removed by distillation to obtain the alcohol compound in good yield.

[0289] 20.0 mmol of methacryloyl chloride, 20.0 mmol of triethylamine, and 50 g of dichloromethane were added to the above alcohol mixture and the mixture was stirred at room temperature for 2 hours. After that, water was added to stop the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the methacrylic compound was obtained in good yield by column chromatography.

[0290] A mixture of acetonitrile and water (3:1 by mass ratio) was added to the above methacrylic compound to make a 0.5 M solution. 60.0 mmol of hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. Acetonitrile was then added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (A-16) represented by the above formula (A-16) was purified by column chromatography to obtain compound (A-16) in good yield.

[0291] (Other Monomers) Among the monomers used in the synthesis of each polymer, monomers other than monomers (A-1) to (A-16) are shown below. Hereinafter, compounds represented by formulas (M-1) to (M-23) may be referred to as "compound (M-1)" to "compound (M-23)" or "monomer (M-1)" to "monomer (M-23)".

[0292]

[0293]

[0294] <Synthesis of Polymers> In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is set to 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is set to 100 mol%.

[0295] [Example P1] (Synthesis of polymer (P-1) for EUV exposure) Monomer (A-1), monomer (M-1), and monomer (M-9) were dissolved in 1-methoxy-2-propanol (200 parts by mass) in a molar ratio of 15 / 40 / 45 (mol%), and AIBN (azobisisobutyronitrile) (4 mol% relative to the total 100 mol% of monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 1-methoxy-2-propanol was placed in an empty reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the completion of the polymerization reaction, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered again, and dried at 50°C for 10 hours to obtain a white powdery polymer (P-1) (yield: 85%). The Mw of polymer (P-1) was 8,700, and the Mw / Mn ratio was 1.50. Furthermore, 13C-NMR analysis revealed that the content percentages of each structural unit derived from monomer (A-1), monomer (M-1), and monomer (M-9) were 17.0 mol%, 40.5 mol%, and 42.5 mol%, respectively.

[0296] [Examples P2-17 and Comparative Examples CP1-3] (Synthesis of polymers (P-2) to (P-17) and polymers (CP-1) to (CP-3) for EUV exposure) Polymers (P-2) to (P-17) and polymers (CP-1) to (CP-3) were synthesized in the same manner as in Example P1, except that monomers of the types and blending ratios shown in Table 2 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 1 below.

[0297]

[0298] [Examples P18-26 and Comparative Examples CP4-7] (Synthesis of polymers (P-18) to (P-26) and polymers (CP-4) to (CP-7) for ArF exposure) Polymers (P-18) to (P-26) and polymers (CP-4) to (CP-7) were synthesized in the same manner as in Example P1, except that monomers of the types and blending ratios shown in Table 2 below were used. The content ratio (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 2 below.

[0299]

[0300] [Synthesis Example F1] (Synthesis of highly hydrophobic polymer (F-1)) Monomers (M-9), (M-17), (M-18), and (M-19) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 50 / 25 / 20 / 5 (mol%), and MAIB (2 mol%) was added as an initiator to prepare monomer solutions. 100 parts by mass of 2-butanone was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solutions were added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The solvent was replaced with acetonitrile (400 parts by mass), and hexane (100 parts by mass) was added and stirred, and the acetonitrile layer was recovered. This process was repeated three times. A solution of the highly hydrophobic polymer (F-1) was obtained by substituting the solvent with propylene glycol monomethyl ether acetate (yield: 80%). The Mw of the highly hydrophobic polymer (F-1) was 12,500, and the Mw / Mn ratio was 1.70. １３ 13C-NMR analysis revealed that the content of each structural unit derived from (M-9), (M-17), (M-18), and (M-19) was 50.2 mol%, 24.9 mol%, 20.6 mol%, and 4.3 mol%, respectively.

[0301] [Synthesis Example F2] (Synthesis of highly hydrophobic polymer (F-2)) Monomers (M-13), (M-21), (M-22), and (M-23) were dissolved in 2-butanone (200 parts by mass) in a molar ratio of 20 / 35 / 35 / 10 (mol%), and MAIB (5 mol%) was added as an initiator to prepare a monomer solution. The subsequent procedure was the same as in Synthesis Example F1 above to obtain a solution of highly hydrophobic polymer (F-2) (yield: 83%). The Mw of highly hydrophobic polymer (F-2) was 7,500, and the Mw / Mn was 1.72. １３ 13C-NMR analysis revealed that the content of each structural unit derived from (M-13), (M-21), (M-22), and (M-23) was 20.2 mol%, 34.0 mol%, 35.4 mol%, and 10.4 mol%, respectively.

[0302] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator, acid diffusion control agent, and solvent that constitute the radiation-sensitive composition are described below.

[0303] [C] Radiation-sensitive acid generators C-1 to C-2: Compounds represented by the following formulas (C-1) to (C-2)

[0304]

[0305] [D] Acid diffusion control agents D-1 to D-4: Compounds represented by the following formulas (D-1) to (D-4)

[0306]

[0307] [Solvents] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Methyl 2-hydroxyisobutyrate E-4: Diacetone alcohol E-5: γ-Butyrolactone

[0308] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 1] Radiation-sensitive composition (J-1) was prepared by mixing 100 parts by mass of (P-1) as polymer (A), 35.0 parts by mass of (D-1) as acid diffusion control agent (D), 5.0 parts by mass (solids) of (F-1) as highly hydrophobic polymer (F), and 7,000 parts by mass of a mixed solvent of (E-1) / (E-2) as solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0309] [Examples 2-21 and Comparative Examples 1-3] Radiation-sensitive compositions (J-2) to (J-21) and (CJ-1) to (CJ-3) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Table 2 below were used.

[0310]

[0311] <Formation of a resist pattern using a positive-type radiation-sensitive composition for EUV exposure> An anti-reflective underlayer film (ARC66 from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 105 nm. The positive-type radiation-sensitive composition for EUV exposure prepared above was applied to this anti-reflective underlayer film using the spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 65 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an EUV lithography system (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (35 nm contact hole pattern).

[0312] <Evaluation> The sensitivity, CDU, number of development defects, and EL (exposure margin) of the resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated according to the following method. The results are shown in Table 4 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0313] [Sensitivity] In forming a resist pattern using the above-mentioned positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 35 nm contact hole pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 50 mJ / cm². ２ The following conditions are considered "good" and 50 mJ / cm². ２ If it exceeded this value, it was rated as "poor."

[0314] [CDU] The mask size was adjusted to form a 35 nm contact hole pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The hole diameter was measured at 16 points in the range of 500 nm and the average value was calculated. This average value was then measured at a total of 500 points at arbitrary points, and the 3-sigma value was calculated from the distribution of the measured values, which was defined as the CDU performance (nm). A smaller CDU performance value indicates less variation in hole diameter over long periods and is therefore better. CDU performance was evaluated as "good" if it was 3.5 nm or less, and as "poor" if it was greater than 3.5 nm.

[0315] [Development Defect Count] A 35 nm contact hole pattern was formed by exposing a resist film with the optimal exposure dose, and this was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were judged to be originating from the resist film, and their number was calculated. After development, the defect count was evaluated as "good" if the number of defects judged to be originating from the resist film was 100 or less, and as "poor" if it exceeded 100.

[0316] [EL (Exposure Margin)] Within the range of exposure amounts including the above optimal exposure amount, the exposure amount is 1 mJ / cm².２ Each resist pattern was formed by varying the exposure dose, and the hole diameter was measured using the scanning electron microscope described above. From the relationship between the obtained hole diameter and exposure dose, the exposure dose E(38.5) that resulted in a hole diameter of 38.5 nm and the exposure dose E(31.5) that resulted in a hole diameter of 31.5 nm were determined, and the exposure margin (EL) was calculated using the formula: EL = {(E(31.5) - E(38.5)) × 100} / (optimal exposure dose). The larger the exposure margin value, the smaller the variation in the dimensions of the pattern obtained when the exposure dose is varied, and the higher the yield during device fabrication. EL performance was evaluated as "good" if it was 10% or more, and "poor" if it was below 10%.

[0317]

[0318] As is clear from the results in Table 4, the radiation-sensitive compositions of the examples showed good sensitivity, CDU, development defect suppression, and EL when used in EUV exposure, whereas the comparative examples did not satisfy all of these characteristics.

[0319] [Preparation of a radiation-sensitive composition for ArF immersion exposure] [Example 22] A radiation-sensitive composition (J-22) was prepared by mixing 100 parts by mass of (P-18) as a polymer (P), 7.0 parts by mass of (D-3) as an acid diffusion control agent (D), 2.0 parts by mass of (F-1) as a highly hydrophobic polymer (F) (solid content), and 2,730 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-5) as a solvent (E), and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0320] [Examples 23-35 and Comparative Examples 4-7] Radiation-sensitive compositions (J-23) to (J-35) and (CJ-4) to (CJ-7) were prepared in the same manner as in Example 22, except that the components of the types and amounts shown in Table 5 below were used.

[0321]

[0322] <Formation of a resist pattern using a radiation-sensitive composition for ArF immersion lithography> An anti-reflective underlayer film formation composition (ARC66 from Brewer Sciences) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 100 nm. The radiation-sensitive composition for ArF lithography prepared above was applied to this anti-reflective underlayer film using the same spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 130 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed to a 60 nm line-and-space pattern using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Dipole (σ = 0.9 / 0.7). After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (60 nm line-and-space pattern).

[0323] <Evaluation> The sensitivity, LWR, MEEF, and pattern rectangularity of the resist patterns formed using the above ArF immersion exposure positive-type radiation-sensitive composition were evaluated according to the following method. The results are shown in Table 6 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0324] [Sensitivity] In forming a resist pattern using the above ArF immersion lithography positive-type radiation-sensitive composition, the exposure amount used to form a 60 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 40 mJ / cm². ２ The following conditions are considered "good": 40 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0325] [LWR] A 60 nm line-and-space resist pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better quality. An LWR of 3.5 nm or less was evaluated as "good," and an LWR greater than 3.5 nm was evaluated as "poor."

[0326] [MEEF] For resist patterns resolved by irradiating with the optimal exposure amount described above, the slope of the straight line was calculated when the line width of the resist pattern formed using mask patterns with line widths of 62 nm, 64 nm, 66 nm, 68 nm, and 70 nm was plotted on the vertical axis and the line width of the mask pattern on the horizontal axis, and this was defined as MEEF. A MEEF value closer to 1 indicates better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​greater than 2 were evaluated as "poor."

[0327] [Pattern Rectangularity] The 60 nm line and space pattern formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above was observed using the scanning electron microscope described above, and the cross-sectional shape of the line and space pattern was evaluated. The rectangularity of the resist pattern was evaluated as follows: if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape of the line portion was 1 or more and 1.05 or less, it was evaluated as "A" (very good); if it was greater than 1.05 and 1.10 or less, it was evaluated as "B" (good); and if it was greater than 1.10, it was evaluated as "C" (poor).

[0328]

[0329] As is clear from the results in Table 6, the radiation-sensitive compositions of the examples showed good sensitivity, LWR, MEEF, and pattern shape when used in ArF exposure, whereas the comparative examples failed to satisfy all of these characteristics simultaneously.

[0330] The radiation-sensitive composition, pattern formation method, polymer, and compound described above enable the formation of resist patterns with good sensitivity to exposure light and excellent CDU, LWR, MEEF, development defect suppression, EL, and pattern shape. Therefore, these can be suitably used in semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

1. A radiation-sensitive composition containing a polymer comprising a structural unit (I) derived from a compound represented by the following formula (1) and a structural unit (II) having an acid dissociable group, and a solvent. (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms and containing a polymerizable group. R １ and R ２ are each independently a hydrogen atom, -CN, -NO ２ , -F, -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or a monovalent organic group (a) having 1 to 20 carbon atoms other than -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ and R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. R １ and R ２ When there are a plurality of R １ and R ２ are each the same or different. However, when R １ is -F, R １ The R ２ bonded to the carbon atom to which it is bonded is a group other than -F. At least one selected from the group consisting of R １ and R ２ is a group other than a hydrogen atom. n １ is an integer of 1 to 4. n ２ is 0 or 1. However, when R １ and R ２ are each independently a hydrogen atom or the above monovalent organic group (a) having 1 to 20 carbon atoms, n ２ is 1. Z ＋ is a monovalent organic cation.) 2. n １ The radiation-sensitive composition according to claim 1, wherein is 1 or 2.

3. R ​​bonded to the α-carbon of the sulfur atom in formula (1) above. １ and R ２ At least one selected from the group consisting of -CN, -F, and -CF ２ H, or -SO ２ R ａ The radiation-sensitive composition according to claim 1.

4. R bonded to the α-carbon of the sulfur atom in formula (1) above. １ and R ２ The radiation-sensitive composition according to claim 1, wherein at least one selected from the group consisting of is -CN.

5. The radiation-sensitive composition according to any one of claims 1 to 4, wherein A is a monovalent organic group having 5 to 40 carbon atoms and containing a polymerizable group and a cyclic structure.

6. Z ＋ The radiation-sensitive composition according to any one of claims 1 to 4, wherein is a monovalent radiation-sensitive onium cation.

7. Z ＋ The radiation-sensitive composition according to claim 6, wherein is a monovalent sulfonium cation or iodonium cation.

8. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the content of the structural unit (I) in relation to the total structural units constituting the polymer is 1 mol% or more and 40 mol% or less.

9. The radioactive composition according to any one of claims 1 to 4, wherein the above-mentioned structural unit (II) having an acid-dissociable group is represented by the following formula (3). (In formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these is independently either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ These elements combine with each other to form a divalent alicyclic group with 3 to 20 carbon atoms, which is then bonded to the carbon atoms. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

10. The radiation-sensitive composition according to claim 9, wherein the content of structural unit (II) in the total structural units constituting the polymer is 5 mol% or more and 70 mol% or less.

11. The radiation-sensitive composition according to any one of claims 1 to 4, further comprising an acid diffusion control agent.

12. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 4 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

13. The pattern formation method according to claim 12, wherein the exposure is performed using an ArF excimer laser or extreme ultraviolet light.

14. A polymer comprising a structural unit (I) derived from a compound represented by the following formula (1) and a structural unit (II) having an acid-dissociable group. (In formula (1), A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. R １ and R ２ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If multiple R １ and R ２ They are either the same or different. However, R １ However, if -F, R １ R bonded to the carbon atom to which it is attached. ２ R is a group other than -F. １ and R ２ At least one of the groups selected from the group consisting of is a group other than a hydrogen atom. １ n is an integer between 1 and 4. ２ is 0 or 1. However, R １ and R ２ However, if each is independently a hydrogen atom or the above-mentioned monovalent organic group (a) having 1 to 20 carbon atoms, then n ２ It is 1. Z ＋ (This is a monovalent organic cation.) 15. R bonded to the α-position carbon of the sulfur atom in the above formula (1) １ and R ２ At least one selected from the group consisting of -CN, -F, -CF ２ H, or -SO ２ R ａ is the polymer according to claim 14.

16. A compound represented by the following formula (1a). (In formula (1a), A is a monovalent organic group having 2 to 40 carbon atoms and containing a polymerizable group. R １ａ and R ２ａ are each independently a hydrogen atom, -CN, -NO ２ , -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ , or a monovalent organic group (a) having 1 to 20 carbon atoms other than -CF ２ R ａ , -SO ２ R ｂ , -COR ｃ or -CF ３ . R ａ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. R ｂ and R ｃ are each independently a monovalent organic group having 1 to 20 carbon atoms. When there are a plurality of R １ａ and R ２ａ , the plurality of R １ａ and R ２ａ are each the same or different. However, at least one selected from the group consisting of R １ａ and R ２ａ is a group other than a hydrogen atom. n １ is an integer of 1 to 4. n ２ is 0 or 1. However, when R １ａ and R ２ａ are each independently a hydrogen atom or the above monovalent organic group (a) having 1 to 20 carbon atoms, n ２ is 1. Z ＋ is a monovalent organic cation.) 17. R bonded to the α-carbon of the sulfur atom in formula (1a) above １ and R ２ At least one selected from the group consisting of -CN, -CF ２ H, or -SO ２ R ａ The compound according to claim 16.

18. A compound represented by the following formula (1b). (In formula (1b), the number of carbon atoms in the organic acid anion is 7 or more, and A is a monovalent organic group having 2 to 40 carbon atoms that contains a polymerizable group. R １ｂ and R ２ｂ These are, independently, a hydrogen atom, -CN, and -NO. ２ -F, -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ , or -CF ２ R ａ , -SO ２ R ｂ ,-COR ｃ Or -CF ３ (a) is a monovalent organic group with 1 to 20 carbon atoms other than R. ａ R is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ｂ and R ｃ Each of these is independently a monovalent organic group having 1 to 20 carbon atoms. １ｂ and R ２ｂ If multiple R １ｂ and R ２ｂ Each of them may be the same or different. However, one or more R １ｂ One of them is -F, and R is -F. １ｂ R bonded to the carbon atom to which it is attached. ２ｂ R is a group other than -F. １ｂ and R ２ｂ At least one of the groups selected from the group consisting of is a group other than a hydrogen atom. １ n is an integer between 1 and 4. ２ Z is either 0 or 1. ＋ (This is a monovalent organic cation.) 19. R bonded to the α-carbon of the sulfur atom in formula (1b) above １ and R ２ The compound according to claim 18, wherein one of them is -F.

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