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

Abstract

The purpose of the present invention is to provide: a radiation-sensitive composition having excellent sensitivity, CDU, and development defect suppression properties during pattern formation; a pattern formation method; a compound; and a polymer. This radiation-sensitive composition contains a polymer (A) and a solvent (E), wherein at least the radiation-sensitive composition contains an onium salt (B) including a partial structure represented by formula (a), or the polymer (A) includes a structural unit (VI) having a partial structure represented by formula (a).

Description

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

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

[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] Various structures have also been investigated for radiation-sensitive acid generators, which are also major components of resist compositions (see, for example, Japanese Patent Publication No. 2021-170101).

[0005] Japanese Patent Publication No. 2021-170101

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance equivalent to or better than conventional resists in terms of sensitivity, CDU, and development defect suppression during pattern formation.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, a compound, and a polymer that exhibit excellent sensitivity, CDU, and suppression of development defects during pattern formation.

[0008] The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising a polymer (A) and a solvent (E), wherein at least the radiation-sensitive composition contains an onium salt (B) including a partial structure represented by the following formula (a) (hereinafter also referred to as "partial structure (a)"), or the polymer (A) comprises a structural unit (VI) having the partial structure represented by the following formula (a). (In formula (a), W ａ , W ｂ , W ｃ each independently represent an aromatic ring. R ａ , R ｂ , R ｃ each independently represent a polar group or an electron-withdrawing group. When a plurality of R ａ , R ｂ , R ｃ are present, the plurality of R ａ , R ｂ , R ｃ are each identical or different, provided that at least one of R ａ , R ｂ , R ｃ is the aforementioned polar group or an iodine atom. The aforementioned polar group is -CN, -SO ２ R １ , -(C=O)R ２ , -NR ３ R ４ , or -OR ５ . The aforementioned electron-withdrawing group is a fluorine atom, a fluorinated alkyl group, -NO ２ , -CN, -SO ２ R １ , -(C=O)R ２ , or an iodine atom. The aforementioned R １ is a monovalent organic group or -NH ２ . The aforementioned R ２ is -OH, -O-CH(R ２１ )(R ２２ ), -O-C(R ２１ )(R ２２ )(R ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ )(R ２２ )(R ２３), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is, -R ３１ -SO ３ - And, SO ３ -The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ This is a divalent organic group. "*" indicates a bond with another atom in the onium salt (B) or structural unit (VI).

[0010] The radiation-sensitive composition exhibits excellent sensitivity, CDU (Chemical Development Unit), and suppression of development defects during pattern formation. Although the reason for this is not entirely clear, it is presumed to be as follows.

[0011] The sulfonium cation in the substructure (a) of the onium salt (B) or structural unit (VI) has multiple substituents, such as polar groups and electron-withdrawing groups. The presence of electron-withdrawing groups improves the decomposition efficiency of the sulfonium cation, resulting in superior sensitivity. The presence of polar groups improves developer solubility, resulting in excellent suppression of development defects. Furthermore, the presence of iodine atoms improves radiation absorption, resulting in superior sensitivity and CDU. By introducing these groups in a balanced manner, the sulfonium cation in substructure (a) can improve sensitivity, CDU, and suppression of development defects. Additionally, because the three groups of the sulfonium cation are different, the sulfonium cation has an asymmetric structure. As a result, crystallinity decreases, developer solubility improves, and development defect suppression improves. It is presumed that these combined effects enable the exhibiting of the above-mentioned unique properties.

[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] This pattern formation method uses the aforementioned radiation-sensitive composition that can exhibit excellent sensitivity, CDU, and development defect suppression performance during pattern formation, and therefore can efficiently form a high-quality resist pattern.

[0014] In another embodiment, the present invention relates to a compound represented by the following formula (1) (hereinafter also referred to as "compound (1)"). (In formula (1), W ａ , W ｂ , W ｃ are each independently an aromatic ring. R ａ , R ｂ , R ｃ are each independently a polar group or an electron-withdrawing group. When a plurality of R ａ , R ｂ , R ｃ are present, the plurality of R ａ , R ｂ , R ｃ are each identical or different. However, at least one of R ａ , R ｂ , R ｃ is at least one of the aforementioned polar groups or an iodine atom. The aforementioned polar group is -CN, -SO ２ R １ , -(C=O)R ２ , -NR ３ R ４ , or -OR ５ . The aforementioned electron-withdrawing group is a fluorine atom, a fluorinated alkyl group, -NO ２ , -CN, -SO ２ R １ , -(C=O)R ２ , or an iodine atom. The aforementioned R １ is a monovalent organic group or -NH ２ . The aforementioned R ２ is -OH, -O-CH(R ２１ )(R ２２ ), -O-C(R ２１ )(R ２２ )(R ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ )(R ２２ )(R ２３), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. １ - R ３２ -SO ３ - And, SO ３- The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３２ (This is a monovalent organic group.)

[0015] Since compound (1) has the above-described specific substructure (a), when used in a radiation-sensitive composition, it can contribute to improving sensitivity, CDU, and development defect suppression.

[0016] In another embodiment, the present invention relates to a compound represented by the following formula (2-1) (hereinafter also referred to as "compound (2-1)"). (In the above formula (2-1), W １ W is a polymerizable group. ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO ２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２ That is the case. ２ is -OH, -O-CH(R２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is *-R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ is a divalent organic group. The above "*" represents W １ (This is a combination of the two.)

[0017] Since the compound (2-1) has the above-described specific substructure (a), when used in a radiation-sensitive composition, it can contribute to improving sensitivity, CDU, and development defect suppression.

[0018] In another embodiment, the present invention relates to a polymer comprising a structural unit derived from the above compound (2-1).

[0019] Since the polymer contains structural units having the specific substructure (a) described above, it can contribute to improving sensitivity, CDU, and development defect suppression when used in a radiation-sensitive composition.

[0020] In this specification, "organic group" means a group containing at least one carbon atom. However, cyano groups, carboxyl groups, formyl groups, carbonyl groups, etc., which can function or be characterized groups on their own as organic groups are excluded. In this specification, "hydrocarbon group" means a group consisting only of carbon and hydrogen atoms, such as a chain hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group, but "substituted hydrocarbon group" means a group in which one or more hydrogen atoms of the hydrocarbon group are substituted with a heteroatom-containing group.

[0021] 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.

[0022] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") contains a polymer (A) and a solvent (E), and further contains an onium salt (B) containing a partial structure (a), or the polymer (A) contains a structural unit (VI) having a partial structure (a). The composition may contain both the onium salt (B) and the polymer (A) containing the structural unit (VI). The composition may contain other optional components as long as they do not impair the effects of the present invention. The components will be described below.

[0023] <Onium Salt (B)> The above onium salt (B) includes a substructure represented by the following formula (a). The onium salt (B) has a salt structure formed by an organic acid anion and a sulfonium cation, and the substructure (a) is incorporated into the salt structure. (In formula (a), W ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO ２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２ That is the case.２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃAt least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is, -R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ This is a divalent organic group. "*" indicates a bond with another atom in the onium salt (B) or structural unit (VI).

[0024] The onium salt (B) described above has the above-mentioned organic acid anion and sulfonium cation, and is a compound that generates an acid that dissociates the acid-dissociable group upon exposure. The acid generated from the onium salt (B) can be said to be a relatively stronger acid (an acid with a lower pKa) than the acid generated from the acid diffusion control agent (D) described later. The onium salt (B) exists as a compound on its own and is a form liberated from the polymer.

[0025] The overall structure of the onium salt (B) is not particularly limited as long as it has substructure (a).

[0026] W ａ , W ｂ , W ｃ The aromatic ring represented by 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. ａ , Wｂ , W ｃ It is more preferable that all of them are benzene rings.

[0027] R ａ , R ｂ , R ｃ It is a polar group or an electron-withdrawing group.

[0028] Examples of the polar groups mentioned above include -CN and -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ These are -CN, -SO ２ R １ ,-(C=O)R ２ It also functions as an electron-withdrawing group.

[0029] The above R １ , R ３ , R ４ , R ５ The monovalent organic group represented by is preferably a monovalent organic group having 1 to 20 carbon atoms. Examples of monovalent organic groups having 1 to 20 carbon atoms include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (a) having a divalent heteroatom-containing linking group between carbon atoms (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with a monovalent heteroatom-containing substituent, or combinations thereof.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Examples of heteroatoms constituting a divalent heteroatom-containing linking group or a monovalent heteroatom-containing substituent include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0035] Examples of divalent heteroatom-containing linking groups include -CO-, -CS-, -NR'-, -O-, -S-, and -SO ２ - and combinations thereof are examples. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0036] Examples of monovalent heteroatom-containing substituents include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0037] The above R ２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is the case.

[0038] The above R２１ , R ２２ , R ２３ , R ２４ As for the monovalent organic group in, the above R １ A monovalent organic group represented by can be suitably adopted.

[0039] R ２１ and R ２２ The cyclic structure having 3 to 20 carbon atoms, formed by combining these elements with the carbon atoms to which they are bonded, may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be an alicyclic structure, an aromatic ring structure (excluding benzene rings), or a combination thereof. In the case of a combination, the ring structures may be linked in a chain-like structure, and two or more ring structures may have a fused ring structure, a spirocyclic structure, a ring aggregate structure, or a combination thereof. The hydrogen atoms on the carbon atoms of these cyclic structures may be substituted with other substituents.

[0040] The above alicyclic structure is R １ A structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0041] The above aromatic ring structure is W ａ , W ｂ , W ｃ Aromatic rings represented by can be suitably used, excluding benzene rings.

[0042] The above chain-like structure is R １ A structure corresponding to a monovalent chain hydrocarbon group having 1 to 20 carbon atoms can be suitably adopted.

[0043] As the alicyclic structure described above, an aliphatic heterocyclic structure can also be used.

[0044] Examples of the aforementioned aliphatic heterocyclic structure include oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; and aliphatic heterocyclic structures containing a plurality of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0045] The aliphatic heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, a cyclic imide structure, a lactam structure, or a combination thereof.

[0046] Examples of the substituent that replaces a hydrogen atom on a carbon atom of the aforementioned cyclic structure or chain structure include halogen atoms such as a fluorine atom, chlorine atom, bromine atom, and iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group, alkoxy group, alkoxycarbonyl group, alkoxycarbonyloxy group, acyl group, acyloxy group, or groups obtained by replacing a hydrogen atom of these groups with a halogen atom; and substituents (T) such as an oxo group (=O).

[0047] The above R ２ The hydrocarbon group represented by can suitably employ the C1-20 monovalent hydrocarbon group in the above R １ As the substituent that replaces a hydrogen atom on a carbon atom of the hydrocarbon group, the aforementioned substituent (T) can be suitably employed.

[0048] Among the aforementioned polar groups, -CN, -SO are preferable from the viewpoint of the balance of sensitivity, CDU, and development defect suppression performance ２ R １ is preferable.

[0049] Examples of the aforementioned electron-withdrawing group include a fluorine atom, a fluorinated alkyl group, -NO ２ , -CN, -SO ２ R １ , -(C=O)R ２ , or an iodine atom.

[0050] Examples of the aforementioned fluorinated alkyl group include the aforementioned R１ A group in which at least one hydrogen atom of the alkyl group is substituted with a fluorine atom can be suitably adopted. Among fluorinated alkyl groups, the trifluoromethyl group is preferred.

[0051] The above -SO ２ R １ ,-(C=O)R ２ For this, those described above in the section on polar groups can be suitably adopted.

[0052] Among the electron-withdrawing groups mentioned above, fluorine atoms, fluorinated alkyl groups, -CN, and -SO4 are selected from the viewpoint of balancing sensitivity, CDU, and development defect suppression. ２ R １ ,-(C=O)R ２ Iodine atoms are preferred.

[0053] R ａ , R ｂ , R ｃ At least one of these is the polar group or an iodine atom, and it is preferable that both the polar group and the iodine atom are included.

[0054] The number of polar groups on the sulfonium cation is not particularly limited, but is preferably 0 to 3, and more preferably 1 or 2. Having polar groups within this range is preferable from the viewpoint of suppressing development defects. Note that -CN, -SO ２ R １ ,-(C=O)R ２ These groups possess both polar and electron-withdrawing properties, but they are counted as polar groups.

[0055] The number of iodine atoms in the sulfonium cation is not particularly limited, but it is preferably 0 to 3, and more preferably 1 or 2. Having iodine atoms within the above range is preferable from the viewpoint of sensitivity and CDU.

[0056] Furthermore, from the standpoint of sensitivity, the above R ａ , R ｂ , R ｃ At least one of them is a fluorine atom, -CF ３ , -NO ２ Preferably, it is an iodine atom.

[0057] n1, n2, and n3 are integers between 0 and 7, preferably between 0 and 3, more preferably between 0 and 2, and even more preferably 1 or 2. However, n1 + n2 + n3 ≥ 2.

[0058] The above X ａ , X ｂ , X ｃ The hydrocarbon group having 2 to 10 carbon atoms represented by the above R is １ Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted.

[0059] Examples of substituents that substitute a hydrogen atom on a carbon atom of the hydrocarbon group include the substituent (T) mentioned above.

[0060] The above X ａ , X ｂ , X ｃ Preferably, the hydrocarbon group is an unsubstituted group having 1 to 20 carbon atoms, and more preferably, an unsubstituted hydrocarbon group having 1 to 10 carbon atoms.

[0061] m1, m2, and m3 are integers between 0 and 3, preferably between 0 and 2, and more preferably 0 or 1.

[0062] The above -W ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented are all different. These differences result in an asymmetrical structure for the sulfonium cation, which improves the suppression of development defects.

[0063] The above W ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR５ A benzene ring having the above has at least one electron-withdrawing group. Preferably, the electron-withdrawing group is located at the meta position relative to the sulfur atom of the benzene ring (i.e., -OR ５ It is preferable that the carbon atom having the electron-withdrawing group is adjacent to the carbon atom having the electron-withdrawing group.

[0064] M - is, -R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group.

[0065] The above R ３１ The divalent organic group represented by the above R is １ A group obtained by removing one hydrogen atom from a monovalent organic group represented by [the formula shown] can be suitably adopted.

[0066] R ３１ It is preferable that it includes -O-, -CO-, a cyclic structure, or a combination thereof. As for the cyclic structure, the above R ２１ , R ２２ The cyclic structures with 3 to 20 carbon atoms and benzene rings listed above can be suitably employed. Among these, R ３１ It is preferable that it contains a benzene ring.

[0067] The alkyl portion of the alkyloxycarbonyl group or alkylsulfonyl group is the above R １ A suitable alkyl group can be used in this.

[0068] The above-mentioned fluorinated alkyl groups can be suitably adopted.

[0069] The onium salt (B) is preferably a compound represented by the following formula (1). (In formula (1), M １ - R ３２ -SO ３ - And, SO３ - The carbon atom at the α-position or β-position relative to the sulfur atom of has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. R ３２ is a monovalent organic group. W ａ , W ｂ , W ｃ , R ａ , R ｂ , R ｃ , n1, n2, n3, X ａ , X ｂ , X ｃ , m1, m2, and m3 have the same definitions as in the above formula (a).)

[0070] As the monovalent organic group represented by the above R ３２ , the monovalent organic group represented by R of the above formula (a) can be suitably adopted. １

[0071] R ３２ preferably contains -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure having 3 to 20 carbon atoms and the benzene ring exemplified for the above R ２１ , R ２２ can be suitably adopted. Among these, R ３２ preferably contains a benzene ring.

[0072] As the above alkyloxycarbonyl group, alkylsulfonyl group, alkyl group, and fluorinated alkyl group, those exemplified in the above formula (a) can be suitably adopted.

[0073] Specific examples of the sulfonium cation of the onium salt (B) are not particularly limited as long as they satisfy the above formula, and include, for example, structures represented by the following formulas and the like.

[0074]

[0075]

[0076]

[0077]

[0078] ​

[0079] Specific examples of organic acid anions of onium salt (B) include, but are not limited to, structures represented by the following formula.

[0080]

[0081]

[0082]

[0083]

[0084] Onium salt (B) can be obtained by combining the above organic acid anion and the above sulfonium cation (however, neither is limited to the above-executed structures). Specific examples, though not limited to them, include structures represented by the following formula.

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] These onium salts (B) may be used individually or in combination of two or more types.

[0094] If the above radiation-sensitive composition contains the above onium salt (B), the lower limit of the content of the above onium salt (B) (total amount if multiple types exist) is preferably 1 part by mass, more preferably 3 parts by mass, and still more preferably 5 parts by mass, per 100 parts by mass of the base polymer (A) described later. The upper limit of the above content is preferably 100 parts by mass, more preferably 90 parts by mass, and still more preferably 80 parts by mass. As a result, the composition can exhibit excellent sensitivity, CDU, and development defect suppression during pattern formation.

[0095] (Method for synthesizing onium salt (B)) Onium salt (B) can be synthesized by the method described in the examples.

[0096] <Polymer (A)> Polymer (A) (i.e., base polymer (A)) is preferably an aggregate of polymerization chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). In addition to structural unit (I), base polymer (A) may also contain structural units having a phenolic hydroxyl group (II), structural units having at least one selected from the group consisting of lactone structures, cyclic carbonate structures and sultone structures (III), structural units having a polar group (IV), and the like.

[0097] If the above radiation-sensitive composition does not contain the onium salt (B), the base polymer (A) contains a structural unit (VI) that includes the substructure represented by formula (a). If the above radiation-sensitive composition contains the onium salt (B), the base polymer (A) may or may not contain the structural unit (VI). Each structural unit will be described below.

[0098] [Structural Unit (I)] Structural unit (I) is a structural unit containing 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, which dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because polymer (A) contains structural unit (I).

[0099] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, and a structural unit having an acetal bond. 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 (I-1)") is preferred.

[0100]

[0101] 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 ２０ Each 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.

[0102] The above R １７ From the viewpoint of copolymerization of the monomer that gives the structural unit (I-1), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0103] 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 components.

[0104] L１１ａ Examples of the arenediyl group 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 component.

[0105] 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.

[0106] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (a), R １ Monovalent hydrocarbon groups having 1 to 20 carbon atoms can be suitably used in this material.

[0107] The above R １９ and R ２０ As a monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the above formula (a), R １ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, those with the corresponding number of carbon atoms can be suitably adopted.

[0108] The above R １９ and R ２０ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (a), R １ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used in this material.

[0109] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed when these are combined with the carbon atoms to which they are bonded, is R in formula (a) above. １ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0110] The substituents that substitute hydrogen atoms on carbon atoms of the above-mentioned monovalent hydrocarbon groups having 1 to 20 carbon atoms, monovalent linear hydrocarbon groups having 1 to 10 carbon atoms, and monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms are the above-mentioned L １１ａThe substituents that the arenediyl group represented by can have can be suitably adopted.

[0111] Examples of structural units (I-1) include those represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (I-1-1) to (I-1-15)").

[0112]

[0113]

[0114] In the above formulas (3-1) to (3-15), R １７ ~R ２０ This is equivalent to equation (3) above. R Ｌ１１ R 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. a3 are each independently integers from 0 to 3. If a3 is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0115] i and j are preferably 1 or 2. １８ Preferred groups include methyl group, ethyl group, isopropyl group, t-butyl group, cyclopentyl group, ethenyl group, butenyl group, phenyl group, and iodophenyl group. １９ and R ２０ As such, methyl groups, ethyl groups, and isopropyl groups are preferred. Ｌ１１ By employing an iodine atom, an iodine group can be suitably introduced into the structural unit (I).

[0116] Furthermore, polymer (A) may contain structural units (I) represented by the following formulas (1f) to (2f).

[0117]

[0118] 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.

[0119] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0120] The base polymer (A) may contain one or more structural units (I) in combination.

[0121] When the base polymer (A) contains structural units (I), the lower limit of the content of structural units (I) (or the total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer (A). 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 (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0122] [Structural Unit (II)] Structural unit (II) is a structural unit having a phenolic hydroxyl group. Structural unit (II) contributes to improved etching resistance and improved difference in developer solubility between exposed and unexposed areas (dissolution contrast). It can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as KrF excimer lasers, electron beams, and EUV.

[0123] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0124] (In the above formula (4), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ Or -O-. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２If multiple R １０２ They are either identical or different from each other. １３ m is an integer between 0 and 2. １３ m is an integer from 1 to 8. １４ Each of these is an independent integer between 0 and 8, where 1 ≤ m. １３ +m １４ ≤ 2n １３ (Saves +5.)

[0125] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (II), it is preferable that it be a hydrogen atom or a methyl group.

[0126] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0127] R １０２ In this mixture, fluorine or iodine atoms are preferred as halogen atoms.

[0128] The above n １３ 0 or 1 is more preferable, and 0 is even more preferable.

[0129] The above m １３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0130] The above m １４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0131] The base polymer (A) may contain one or more structural units (II) in combination.

[0132] When the base polymer (A) contains structural unit (II), the lower limit of the content of structural unit (II) to the total structural units constituting the base polymer (A) (the total content if multiple types are included) is preferably 10 mol%, and more preferably 20 mol%. Furthermore, the upper limit of the above content is preferably 70 mol%, and more preferably 60 mol%.

[0133] [Structural Unit (III)] Structural unit (III) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. The base polymer (A) can have its solubility in the developer adjusted by further comprising structural unit (III), and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer (A) and the substrate can be improved.

[0134] Examples of structural units (III) include those represented by the following formulas (T-1) to (T-11).

[0135]

[0136] In the above formula, R Ｌ１ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ These are, independently, a hydrogen atom, a C1-C4 alkyl group, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxyl group, a hydroxymethyl group, and a dimethylamino group. Ｌ４ and R Ｌ５ These may be divalent alicyclic groups having 3 to 8 carbon atoms, which can be combined with each other and bonded together with the carbon atoms. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer from 0 to 3. m is an integer from 1 to 3.

[0137] The above R Ｌ４ and R Ｌ５ When 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.

[0138] The above L ２Examples 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-.

[0139] Among these, structural units (III) are preferably those containing a lactone structure, more preferably those containing a γ-butyrolactone structure or a norbornane lactone structure, and even more preferably those derived from γ-butyrolactone-yl-(meth)acrylate or norbornane lactone-yl(meth)acrylate.

[0140] The base polymer (A) may contain one or more structural units (III) in combination.

[0141] When the base polymer (A) has structural unit (III), the lower limit of the content of structural unit (III) in the total structural units constituting the base polymer (A) (total content if multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of structural unit (III) 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.

[0142] [Structural Unit (IV)] Structural unit (IV) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (III)). The base polymer (A) can have its solubility in the developer adjusted by further containing structural unit (IV), and as a result, the lithographic performance such as resolution of the radiation-sensitive composition can be improved. Examples of the above polar group include a hydroxyl group, a carboxyl group, a cyano group, a nitro group, a sulfonamide group, etc. Among these, a hydroxyl group and a carboxyl group are preferred, and a hydroxyl group is more preferred.

[0143] [Structural Unit (V)] The base polymer (A) may have a structural unit (V) that includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and generates an acid that dissociates the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure. By containing the radiation-sensitive acid-generating structure in the base polymer (A), the polarity of the base polymer (A) in the exposed area increases, making it soluble in the developer in the case of alkaline aqueous solution development, while it becomes sparingly soluble in the developer in the case of organic solvent development.

[0144] Although the form in which the first organic acid anion and the first onium cation are contained in the structural unit (V) of the base polymer (A) is not particularly limited, it is preferable that the base polymer (A) has the first organic acid anion as a side chain portion from the viewpoint of controlling the acid diffusion length. Having it as a side chain portion means that the first organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer (A).

[0145] The structural unit (V) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (V-1)").

[0146]

[0147] In the formula, R Ｖ This is a hydrogen atom or a methyl group. V １ This is a single bond or an ester group. V ２ This is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, or an amide bond, and a portion of the methylene groups constituting the alkylene group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３This is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in R may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. ｆ１ ~R ｆ２ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer from 1 to 4. X １ ＋ This is the first onium cation.

[0148] V ２ and V ３ The C1-C20 monovalent hydrocarbon group in this is preferably a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C6-C20 aryl group. Some or all of the hydrogen atoms in these groups may be substituted with heteroatom-containing groups such as hydroxyl groups, carboxyl groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, alkoxy groups, or alkoxycarbonyl groups. Some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonic acid ester groups.

[0149] Preferably, the structural unit (V-1) is a structural unit represented by the following formula (a1-1).

[0150]

[0151] In the formula, R Ｖ , R ｆ１ ~R ｆ２ , V １ , kk and X １ ＋ This is equivalent to the above formula (a1). R ４８m is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxyl group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer from 0 to 4. n is an integer from 0 to 3.

[0152] Examples of the first organic acid anion of the monomer that gives structural unit (V) (including structural unit (V-1)) include, but are not limited to, the structure shown in the following formula. In the following, the iodine group of the iodine group-containing aromatic ring structure may be substituted with substituents other than the iodine group, hydrogen atoms, etc. In the following formula, R Ｖ This is synonymous with the above.

[0153]

[0154]

[0155]

[0156]

[0157] X in the above formula (a1) １ ＋ Examples of the first onium cation represented by include radiodegradable onium cations. Examples of radiodegradable 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.

[0158] The first onium cation described above preferably has at least one selected from the group consisting of an iodine group and a fluoro group. The first onium cation preferably contains an iodine group-containing aromatic ring structure as the form of the iodine group. An iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced by iodine groups. In the first onium cation, it is preferable that the fluoro group is contained in the form of a fluoro group-containing aromatic ring structure. A 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 fluoro groups. The aromatic ring in the iodine group-containing aromatic ring structure and the fluoro group-containing aromatic ring structure is W of formula (a) above. ａ , W ｂ , W ｃ Aromatic rings represented by can be suitably employed. By introducing an iodine group or a fluoro group, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0159] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-5).

[0160]

[0161] 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.

[0162] 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, 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.

[0163] 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.

[0164] 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 having 6 to 8 carbon atoms, or a hydroxyl group. 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.

[0165] 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.

[0166] Specific examples of the above-mentioned sulfonium cation and iodonium cation include, but are not limited to, the following structures.

[0167]

[0168]

[0169]

[0170]

[0171] The sulfonium cations mentioned above do not include the sulfonium cations described in the onium salt (B) above.

[0172] The base polymer (A) may contain one or more structural units (V) in combination.

[0173] When the base polymer (A) has structural units (V), the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of structural units (V) within the above range, the function as an acid-generating structure can be fully exhibited, and the above resist properties can be achieved.

[0174] [Structural Unit (VI)] The structural unit (VI) has a substructure represented by the above formula (a). The substructure (a) described for onium salt (B) can be suitably adopted.

[0175] The structural unit (VI) described above is preferably the structural unit represented by the following formula (2). (In the above formula (2), R Ａ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ａ , W ｂ , W ｃ , R ａ , R ｂ , R ｃ , n1, n2, n3, X ａ , X ｂ , X ｃ , m1, m2, m3, M - This is equivalent to equation (a) above.

[0176] For the organic acid anion in the above structural unit (VI), the first organic acid anion described in the above structural unit (V) can be suitably adopted.

[0177] As the sulfonium cation described above, the sulfonium cation described in the onium salt (B) can be suitably used.

[0178] The above structural unit (VI) is obtained by combining the above organic acid anion and the above sulfonium cation. Specific examples of monomers that give the above structural unit (VI) include, but are not limited to, the structure represented by the following formula. In the following formula, R Ａ This is the same as above.

[0179]

[0180] The base polymer (A) may contain one or more structural units (VI) in combination.

[0181] When the base polymer (A) has structural units (VI), the lower limit of the content of structural units (VI) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of structural units (VI) within the above range, excellent sensitivity, CDU, and development defect suppression can be achieved during pattern formation.

[0182] [Structural Unit (VII)] The base polymer (A) may include a structural unit (VII) which has a second organic acid anion and a second onium cation, and which generates an acid that does not dissociate the acid-dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid-generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid-generating structure substantially prevents the dissociation of the acid-dissociable group of structural unit (I), and in the unexposed areas, it has the function of suppressing the diffusion of acid generated from the onium salt (B) or structural unit (VI), or from structural unit (V) or the radiation-sensitive acid generator (b) described later, by salt exchange.

[0183] (Method for synthesizing base polymer (A)) Base polymer (A) 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.

[0184] The molecular weight of the base polymer (A) 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 20,000, more preferably 14,000, and even more preferably 10,000. By keeping the Mw of the base polymer (A) within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0185] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) (Mw / Mn) of the base polymer (A) by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0186] In this specification, the Mw and Mn values ​​of polymer (A) are those measured by the method described in the examples.

[0187] The content of the base polymer (A) 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.

[0188] <Other Polymers> The radiation-sensitive composition of this embodiment may also contain, as other polymers, a polymer with a higher mass content of fluorine atoms than the base polymer (A) (hereinafter also referred to as "high-fluorine content polymer (F)"). When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer (A), and as a result, the water repellency of the surface of the resist film during immersion exposure can be enhanced, and the surface modification of the resist film and the distribution of the composition within the film can be controlled during EUV exposure.

[0189] If the radiation-sensitive composition contains a high-fluorine-content polymer (F), the lower limit of the content of the high-fluorine-content polymer (F) 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 (A). The upper limit of the content is preferably 30 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass.

[0190] By setting the content of the high-fluorine polymer (F) within the above range, the high-fluorine polymer (F) can be more effectively distributed to the surface layer of the resist film. As a result, it is possible to improve 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 composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more types of high-fluorine polymers (F).

[0191] (Method for synthesizing high-fluorine-content polymer (F)) High-fluorine-content polymer (F) can be synthesized by the same method as the synthesis method for base polymer (A) described above.

[0192] <Radiation-sensitive acid generator (b)> The above radiation-sensitive composition may contain a radiation-sensitive acid generator (b) other than the above onium salt (B). The radiation-sensitive acid generator (b) is a compound having an organic acid anion and an onium cation, which generates an acid that dissociates the above acid-dissociable group upon exposure. The acid generated from the radiation-sensitive acid generator (b) can be said to be a relatively stronger acid (an acid with a small pKa) than the acid generated from the acid diffusion control agent (D) described later. The radiation-sensitive acid generator (b) exists as a compound on its own and is in a form liberated from the polymer.

[0193] Examples of organic acid anions include sulfonic acid anions, sulfonimide anions, and sulfonmethide anions.

[0194] Examples of such acids include: (1) compounds in which one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups are substituted on the α or β carbon atoms of a sulfo group, or in which an ester bond is interposed between carbon atoms; (2) compounds having a sulfonimide structure containing a fluorine atom; and (3) compounds having a sulfonemethide structure containing a fluorine atom.

[0195] The radiation-sensitive acid generator (b) is preferably a compound represented by the following formula (z-a). (In formula (z-a), R ４ｚ It is a monovalent organic group having 2 to 40 carbon atoms. However, -SO ３ - A fluorine atom, a cyano group, or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α or β position relative to the sulfur atom in the molecule. ＋ This is an onium cation.

[0196] R ４ｚ As a monovalent organic group having 2 to 40 carbon atoms represented by the above formula (a), R １A monovalent organic group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably adopted as a group with an extended number of carbon atoms, ranging from 2 to 40.

[0197] R ４ｚ It is preferable that R is a monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a ring structure, a carbonyl group, and an ether bond. As such an organic group, R in formula (a) above ２１ , R ２２ A monovalent organic group having 4 to 40 carbon atoms can be suitably adopted, which includes at least one structure selected from the group consisting of a cyclic structure having 3 to 20 carbon atoms, a benzene ring, a carbonyl group, and an ether bond, as exemplified above.

[0198] The above monovalent fluorinated hydrocarbon group is R of formula (a) above. １ A group in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms, as shown above, are replaced with fluorine atoms can be suitably adopted.

[0199] As the organic acid anion in the radiation-sensitive acid generator (b), those listed in the above-mentioned onium salt (B) can be suitably adopted.

[0200] Za ＋ Examples of onium cations represented by this formula include sulfonium cations and iodonium cations. The first onium cation shown in the above structural unit (V) can be preferably used as the sulfonium cation or iodonium cation. The above sulfonium cation does not include the sulfonium cation described in the above onium salt (B).

[0201] As the radiation-sensitive acid generator (b), a suitable combination of the above-mentioned organic acid anion and onium cation can be used.

[0202] The above-mentioned radiation-sensitive composition may contain one or more radiation-sensitive acid generators (b).

[0203] When the above-mentioned radiation-sensitive composition contains a radiation-sensitive acid generator (b), the lower limit of the content of the radiation-sensitive acid generator (b) (total if multiple types are included) is preferably 1 part by mass, more preferably 3 parts by mass, and still more preferably 5 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 90 parts by mass, more preferably 80 parts by mass, and still more preferably 70 parts by mass. As a result, the composition can exhibit the above-mentioned resist properties.

[0204] <Acid Diffusion Control Agent (D)> The radiation-sensitive composition may optionally contain an acid diffusion control agent (D). The acid diffusion control agent (D) controls the diffusion phenomenon of acids generated from the onium salt (B) or structural unit (VI) upon exposure, or from structural unit (V) or radiation-sensitive acid generator (b) added as needed, within the resist film, thereby suppressing undesirable chemical reactions in unexposed areas. Furthermore, the storage stability of the resulting radiation-sensitive composition is improved. In addition, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the holding time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0205] Examples of acid diffusion control agents (D) include compounds represented by the following formula (7) (hereinafter also referred to as "nitrogen-containing compounds (I)"), compounds having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compounds (II)"), compounds having three nitrogen atoms (hereinafter also referred to as "nitrogen-containing compounds (III)"), amide group-containing compounds, urea compounds, nitrogen-containing heterocyclic compounds, and the like.

[0206]

[0207] In the above formula (7), R ２２ , R ２３ and R ２４ Each of these is independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0208] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as the acid diffusion control agent (D). The acid generated from the above-mentioned radiation-sensitive weak acid generator is a weak acid that does not induce the dissociation of the acid-dissociable groups in the polymer under conditions that would normally cause the dissociation of those groups.

[0209] Examples of radiation-sensitive weak acid generators include onium salt compounds that decompose upon exposure and lose their ability to control acid diffusion. Examples of onium salt compounds include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Also, examples include compounds containing a sulfonium cation and anion in the same molecule, represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule, represented by the following formula (8-4).

[0210]

[0211] In the above formulas (8-1) to (8-4), J ＋ It is a sulfonium cation, U ＋ This is an iodonium cation. ＋ Examples of sulfonium cations represented by the above formulas (X-1) to (X-4) include U ＋ An example of an iodonium cation represented by the above formula (X-5) is the iodonium cation represented by E. - and Q - Each of them is independent of OH - , R α -COO - , R α -SO ３ - This is an anion represented by R. α This refers to a single bond or a monovalent organic group having 1 to 30 carbon atoms. Examples of such organic groups include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing linking group between carbon atoms or at the end of the carbon chain of this hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with a monovalent heteroatom-containing group, or a combination thereof.

[0212] As a monovalent hydrocarbon group having 1 to 20 carbon atoms, R in formula (a) above is an example. １ Monovalent hydrocarbon groups having 1 to 20 carbon atoms, as shown in the above, can be suitably used.

[0213] Examples of heteroatoms constituting a divalent heteroatom-containing linking group or a monovalent heteroatom-containing group include oxygen, nitrogen, sulfur, phosphorus, silicon, and halogen atoms. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.

[0214] As a divalent heteroatom-containing linking group, R in formula (a) above is used. １ The divalent heteroatom-containing linking group shown can be suitably adopted.

[0215] Examples of monovalent heteroatom-containing groups include hydroxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0216] Examples of anions for the acid diffusion control agent (D) described above 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 given as examples. The iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0217]

[0218]

[0219] Examples of onium cations in the acid diffusion control agent (D) above include sulfonium cations and iodonium cations. The first onium cation shown in the structural unit (V) above can be suitably used as the sulfonium cation or iodonium cation. Furthermore, the sulfonium cations listed in the onium salt (B) above can also be suitably used.

[0220] The above-mentioned acid diffusion control agent (D) can also be synthesized by known methods, particularly by salt exchange reactions.

[0221] These acid diffusion control agents (D) may be used individually or in combination of two or more.

[0222] When the above-mentioned radiation-sensitive composition contains an acid diffusion control agent (D), the lower limit of the content of the acid diffusion control agent (D) (total in the case of multiple types) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 10 mol%, relative to the total number of moles of anions of the onium salt (B), the radiation-sensitive acid generator (b), the monomer that gives structural unit (V) of the base polymer (A), and the monomer that gives structural unit (VI) (collectively referred to as "acid generator"). The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%.

[0223] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains solvent (E). Solvent (E) is not particularly limited as long as it is a solvent capable of dissolving or dispersing the base polymer (A), onium salt (B), and any optional components that may be contained therein.

[0224] Examples of solvents (E) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, hydrocarbon-based solvents, and the like.

[0225] 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), which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents. 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.

[0226] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents in which the hydroxyl groups of the above-mentioned polyhydric alcohol solvents, such as propylene glycol monomethyl ether, have been etherified.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferred, alcoholic acid ester-based solvents, C1-C18 monoalcohol-based solvents, 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.

[0232] <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.

[0233] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a polymer (A), an onium salt (B), and optionally a high-fluorine-content polymer (F), an acid diffusion control agent (D), and a solvent (E) in predetermined proportions. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.40 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.

[0234] ≪Pattern Forming Method≫ A pattern forming method according to one embodiment of the present invention includes the steps of: (1) applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as the "resist film forming step"); (2) exposing the resist film (hereinafter also referred to as the "exposure step"); and (3) developing the exposed resist film with a developer (hereinafter also referred to as the "development step").

[0235] According to the pattern formation method described above, since the above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, CDU, and development defect suppression, is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0236] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the 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, pre-baking (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 170°C, with 80°C to 150°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0237] The lower limit of the thickness of the formed resist film is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 350 nm, and even more preferably 200 nm.

[0238] When performing immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer (F) in the above-mentioned radiation-sensitive composition, an immersion-insoluble protective film may be provided on the formed resist film to avoid direct contact between the immersion liquid and the resist film. As the immersion-protective film, either a solvent-peelable protective film that is peeled off with a solvent before the development process (see, for example, Japanese Patent Application Publication No. 2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development process (see, for example, International Publication No. 2005 / 069076 and International Publication No. 2006 / 035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable immersion-protective film.

[0239] [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 (and, in some cases, through an immersion liquid such as water). 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 light (wavelength 193 nm), electron beams, and EUV are even more preferred.

[0240] When exposure is performed by immersion lithography, the immersion liquid used can be, for example, water or a fluorine-based inert liquid. The immersion liquid is preferably transparent to the exposure wavelength and has the smallest possible temperature coefficient of refractive index to minimize distortion of the optical image projected onto the film. In particular, when the exposure light source is ArF excimer laser light (wavelength 193 nm), in addition to the above considerations, water is preferred due to its availability and ease of handling. When water is used, a small amount of an additive that reduces the surface tension of the water and increases its surfactant properties may be added. This additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0241] 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 acid generated from structural unit (V), structural unit (VI), onium salt (B), or radiation-sensitive acid generator (b) due to exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0242] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed. 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.

[0243] 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.

[0244] Furthermore, 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, ether solvents, ester solvents, and ketone solvents are preferred. As for ether solvents, glycol ether solvents are preferred, and ethylene glycol monomethyl ether and propylene glycol monomethyl ether are more preferred. As for ester solvents, acetate 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 solvents 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.

[0245] As mentioned above, either an alkaline developer or an organic solvent developer may be used as the developer. The appropriate developer can be selected depending on whether a positive or negative pattern is desired.

[0246] 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).

[0247] Compound (1) Compound (1) according to one embodiment of the present invention is represented by the following formula (1). (In formula (1), W ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO ２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２That is the case. ２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃAt least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. １ - R ３２ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３２ (This is a monovalent organic group.)

[0248] As such a compound, the onium salt (B) in the above-mentioned radiation-sensitive composition can be suitably used.

[0249] Compound (2-1) Compound (2-1) according to one embodiment of the present invention is represented by the following formula (2-1). (In the above formula (2-1), W １ W is a polymerizable group. ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２ That is the case. ２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ )ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is *-R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ is a divalent organic group. The above "*" represents W １ (This is a combination of the two.)

[0250] The above W １ Examples of polymerizable groups represented by include groups containing carbon-carbon double bonds. Typical structures include ethylenically unsaturated double bonds, or structures containing ethylenically unsaturated double bonds as a substructure constituting a ring. Polymerizable groups may have substituents.

[0251] The polymerizable group is preferably a (meth)acrylic group or a vinyl group.

[0252] Such compounds can preferably be monomers that provide structural unit (VI) in the above-mentioned radiation-sensitive composition.

[0253] <<Polymer>> A polymer according to one embodiment of the present invention includes a structural unit derived from the above compound (2-1).

[0254] As such a polymer, polymer (A) containing structural unit (VI) in the above-mentioned radiation-sensitive composition can be suitably adopted.

[0255] The present invention will be specifically described below with reference to synthesis examples, examples, and comparative examples, but the present invention is not limited to the following examples. The methods for measuring various physical properties are shown below.

[0256] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "G2000HXL" columns, one "G3000HXL" column, and one "G4000HXL" column) under the following conditions: Eluent: Tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Column temperature: 40°C Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0257] <Synthesis of Polymers (A) and (F)> [Synthesis Examples 1-41] Synthesis of base polymers (A-1) to (A-39) and high-fluorine content polymers (F-1) and (F-2) Each monomer was combined and copolymerized under tetrahydrofuran (THF) solvent. Crystallization was performed in methanol, and further washing with hexane was repeated. After isolation and drying, base polymers (A-1) to (A-39) and high-fluorine content polymers (F-1) and (F-2) with the compositions shown below were obtained. The compositions of the obtained base polymer (A) and high-fluorine content polymer (F) are １ Mw and dispersion (Mw / Mn) were confirmed by 1H-NMR under the GPC conditions described above. The types and amounts of each monomer are shown in Table 1. Note that "-" in Table 1 indicates that the corresponding monomer was not used (the same applies to subsequent tables).

[0258]

[0259]

[0260]

[0261] <Manufacturing of Radiation-Sensitive Compositions> The manufacturing procedures for each component used in the examples or comparative examples are shown below.

[0262] <Radiation-sensitive acid generator (specific compound (onium salt (B)) and comparative compound)> (Synthesis of specific compound (B-1)) Specific compound (B-1) was synthesized based on the following scheme.

[0263]

[0264] 50 mL of methylene chloride was mixed with B-1-A (5.0 g) and iodobenzene (9.0 g). The resulting mixed solution was cooled to -40°C, then trifluoromethanesulfonic acid (2.7 mL) and trifluoroacetic anhydride (5.8 mL) were added, and the mixture was stirred at room temperature for 2 hours. Methylene chloride was added to the resulting mixture, and the organic layer was washed with water, after which the solvent was removed by distillation. After drying with sodium sulfate, the solvent was removed by distillation, and B-1-B was obtained in good yield by purification by column chromatography.

[0265] B-1-B (6.0 g) was dissolved in methylene chloride, passed through an ion exchange resin, and the solvent was removed by distillation to obtain B-1-C in good yield.

[0266] 3.0 g of B-1-C was mixed with 50 mL of methylene chloride, 50 mL of water, and 3.9 g of B-1-1, and the mixture was stirred at room temperature for 2 hours. After dilution with water, methylene chloride was added for extraction, and the organic layer was separated. The obtained organic layer was washed with water, dried over sodium sulfate, the solvent was removed by distillation, and B-1 was purified by column chromatography to obtain B-1 in good yield.

[0267] Based on the synthesis method described above, the radiation-sensitive acid generators (B-2) to (B-36) of the examples were synthesized. The structures of the radiation-sensitive acid generators (B-1) to (B-36) are shown below.

[0268]

[0269]

[0270]

[0271]

[0272] The comparative compounds (BC-1) to (BC-9) are shown below.

[0273]

[0274] <Acid diffusion control agent (D)> Compounds represented by (D-1) to (D-10) were used as acid diffusion control agents.

[0275]

[0276] <Organic Solvent (E)> (E-1): PGMEA (Propylene Glycol Monomethyl Ether Acetate) (E-2): PGME (Propylene Glycol Monomethyl Ether)

[0277] [Example 1] 100 parts by mass of (A-1) as polymer (A), 45 parts by mass of (B-1) as radiation-sensitive acid generator (B), 35 mol% of (D-1) as acid diffusion control agent (D) relative to the anion of (B-1), 5,500 parts by mass of (E-1) and 1,500 parts by mass of (E-2) as organic solvents (E) were blended. This was filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0278] [Examples 2-89 and Comparative Examples 1-9] Radiation-sensitive compositions (R-2) to (R-89) and (CR-1) to (CR-9) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2-1 and 2-2 below were used.

[0279]

[0280]

[0281] <Formation of Resist Pattern> On the surface of a 12-inch silicon wafer with a 20 nm thick underlayer (AL412 (manufactured by Brewer Science)) formed on it, the radiation-sensitive compositions prepared above were applied using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Limited). After performing a soft bake (SB) at 100°C for 60 seconds, it was cooled at 23°C for 30 seconds to form a resist film with a thickness of 45 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was subjected to a post-exposure bake (PEB) at 110°C for 60 seconds. Next, the image was developed at 23°C for 30 seconds using a 2.38 mass% TMAH aqueous solution to form a positive-type 48 nm pitch, 24 nm contact hole pattern.

[0282] <Evaluation> The sensitivity, CDU, and number of development defects of each radiation-sensitive composition were evaluated for each resist pattern formed as described above by measuring according to the method below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The evaluation results are shown in Tables 3-1 and 3-2 below.

[0283] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 24 nm contact hole pattern is set as the optimal exposure amount, and this optimal exposure amount is set as the sensitivity (mJ / cm²). ２ The sensitivity was set to 35 mJ / cm². A smaller value indicates better sensitivity. ２ If the value is less than 35 mJ / cm², it is classified as "A" (very good). ２ More than 40mJ / cm ２ The following cases are classified as "B" (good), 40 mJ / cm². ２ Exceeding 45 mJ / cm² ２ The following cases were rated as "C" (fairly good).

[0284] [CDU] The mask size was adjusted to form a 24 nm contact hole pattern by irradiating with the optimal exposure amount determined 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 1 sigma value was calculated from the distribution of the measured values, which was defined as CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and is therefore better. CDU values ​​were evaluated as "A" (excellent) if less than 3.3 nm, "B" (good) if between 3.3 nm and 3.6 nm, and "C" (fairly good) if 3.6 nm or more.

[0285] [Development Defect Count] A resist film was exposed at the optimal exposure level to form a 24 nm contact hole pattern, and this was used as a wafer for defect inspection. The number of defects on this wafer was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Of the measured defects, those with a diameter of 50 μm or less were determined to be originating from the resist film, and their number was calculated. The number of defects after development was evaluated as follows: if the number of defects determined to be originating from the resist film was less than 15, it was rated as "A" (excellent); if it was 15 or more but less than 30, it was rated as "B" (good); and if it was 30 or more but 45, it was rated as "C" (fairly good).

[0286] [Overall Evaluation] In each of the above evaluations, "A" was assigned 3 points, "B" 2 points, and "C" 1 point, and the total score for each evaluation was calculated. A higher total score indicates a better balance of sensitivity, CDU, and number of development defects.

[0287]

[0288]

[0289] As is clear from the results in Tables 3-1 and 3-2, the radiation-sensitive compositions of the examples showed good sensitivity, CDU, and number of defects after development, whereas the comparative examples were inferior to the examples in each characteristic, or their overall score was inferior to the examples.

[0290] The radiation-sensitive composition, pattern-forming method, compound, and polymer described above can form resist patterns that exhibit good sensitivity to exposure light and excellent suppression of CDU and development defects. 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 comprising a polymer (A) and a solvent (E), wherein at least the radiation-sensitive composition contains an onium salt (B) including a partial structure represented by the following formula (a), or the polymer (A) comprises a structural unit (VI) having a partial structure represented by the following formula (a). (In formula (a), W ａ , W ｂ , W ｃ each independently represent an aromatic ring. R ａ , R ｂ , R ｃ each independently represent a polar group or an electron-withdrawing group. In the case where a plurality of R ａ , R ｂ , R ｃ are present, the plurality of R ａ , R ｂ , R ｃ are each identical or different. Provided that at least one of R ａ , R ｂ , R ｃ is the polar group or an iodine atom. The polar group is -CN, -SO ２ R １ , -(C=O)R ２ , -NR ３ R ４ , or -OR ５ . The electron-withdrawing group is a fluorine atom, a fluorinated alkyl group, -NO ２ , -CN, -SO ２ R １ , -(C=O)R ２ , or an iodine atom. The R １ is a monovalent organic group or -NH ２ . The R ２ is -OH, -O-CH(R ２１ )(R ２２ ), -O-C(R ２１ )(R ２２ )(R ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ )(R ２２ )(R ２３ ), a substituted or unsubstituted hydrocarbon group, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is, -R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ This is a divalent organic group. "*" indicates a bond with another atom in the onium salt (B) or structural unit (VI).

2. The above W ａ , W ｂ , W ｃ The radiation-sensitive composition according to claim 1, wherein the ring is a benzene ring.

3. The radiation-sensitive composition according to claim 1, wherein the onium salt (B) is a compound represented by the following formula (1). (In formula (1), M １ - is R ３２ -SO ３ - , and the carbon atom at the α-position or β-position relative to the sulfur atom of SO ３ - has a cyano group, nitro group, alkyloxycarbonyl group, alkylsulfonyl group, fluorine atom, or fluorinated alkyl group. R ３２ is a monovalent organic group. W ａ , W ｂ , W ｃ , R ａ , R ｂ , R ｃ , n1, n2, n3, X ａ , X ｂ , X ｃ , m1, m2, and m3 have the same definitions as in the above formula (a).) 4. The radiation-sensitive composition according to claim 1, wherein the above structural unit (VI) is represented by the following formula (2). (In the above formula (2), R Ａ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ａ , W ｂ , W ｃ , R ａ , R ｂ , R ｃ , n1, n2, n3, X ａ , X ｂ , X ｃ , m1, m2, m3, M - This is equivalent to equation (a) above.

5. The above R ａ , R ｂ , R ｃ At least one of them is a fluorine atom, -CF ３ , -NO ２ The radiation-sensitive composition according to claim 1, wherein the atom is either iodine or iodine.

6. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the radiation-sensitive composition contains an onium salt (B), and the amount of the onium salt (B) is 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the polymer (A).

7. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the polymer (A) contains the structural unit (VI), and the proportion of the structural unit (VI) to the total structural units constituting the polymer (A) is 1 mol% or more and 30 mol% or less.

8. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the polymer (A) comprises a structural unit (I) having an acid-dissociable group.

9. The radiation-sensitive composition according to any one of claims 1 to 5, wherein the polymer (A) comprises a structural unit (II) having a phenolic hydroxyl group.

10. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 5 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.

11. The pattern forming method according to claim 10, wherein the exposure is performed using extreme ultraviolet light or an electron beam.

12. A compound represented by the following formula (1). (In formula (1), W ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO ２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２ That is the case. ２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. １ - R ３２ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３２ (This is a monovalent organic group.) 13. A compound represented by the following formula (2-1). (In the above formula (2-1), W １ W is a polymerizable group. ａ , W ｂ , W ｃ Each of these is an independent aromatic ring. ａ , R ｂ , R ｃ Each of these is independently a polar group or an electron-withdrawing group. ａ , R ｂ , R ｃ If multiple R ａ , R ｂ , R ｃ They are either the same or different. However, R ａ , R ｂ , R ｃ At least one of these is the polar group or iodine atom. The polar groups are -CN, -SO ２ R １ ,-(C=O)R ２ ,-NR ３ R ４ , or -OR ５ The above electron-withdrawing groups are fluorine atoms, fluorinated alkyl groups, and -NO ２ -CN, -SO ２ R １ ,-(C=O)R ２ , or an iodine atom. The above R １ is a monovalent organic group or -NH ２ That is the case. ２ is -OH, -O-CH(R ２１ ) (Caution ２２ ), -O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), -O-CH ２ -(C=O)-O-C(R ２１ ) (Caution ２２ ) (Caution ２３ ), substituted or unsubstituted hydrocarbon groups, or -NHR ２４ That is. R ２１ , R ２２ Each of these is independently a monovalent organic group, or R ２１ and R ２２ These are cyclic structures with 3 to 20 carbon atoms (excluding benzene rings) formed by combining them with the carbon atoms to which they are bonded. ２３ R is a monovalent organic group. ２４ R is a hydrogen atom or a monovalent organic group. ３ , R ４ Each of these is independently a hydrogen atom or a monovalent organic group. ５ n1 is a hydrogen atom or a monovalent organic group. n1, n2, and n3 are each independent integers from 0 to 7, where n1 + n2 + n3 ≥ 2. ａ , X ｂ , X ｃ Each of these is independently a substituted or unsubstituted hydrocarbon group having 2 to 10 carbon atoms. m1, m2, and m3 are each independently integers from 0 to 3. (See above -W) ａ - (R ａ ) ｎ１ (X ａ ) ｍ１ , -W ｂ - (R ｂ ) ｎ２ (X ｂ ) ｍ２ , -W ｃ - (R ｃ ) ｎ３ (X ｃ ) ｍ３ The groups represented by the above W are all different. ａ , W ｂ , W ｃ At least one of them is a benzene ring, and at the para position relative to the sulfur atom of the benzene ring is -OR ５ If it has, then -OR ５ A benzene ring having the above electron-withdrawing group has at least one of the above electron-withdrawing groups. - is *-R ３１ -SO ３ - And, SO ３ - The carbon atom at the α or β position relative to the sulfur atom has a cyano group, a nitro group, an alkyloxycarbonyl group, an alkylsulfonyl group, a fluorine atom, or a fluorinated alkyl group. ３１ is a divalent organic group. The above "*" represents W １ (This is a combination of the two.) 14. A polymer comprising a structural unit derived from the compound described in claim 13.

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