Radiation-sensitive composition, pattern formation method, radiation-sensitive acid generator, and compound

Abstract

Provided are a radiation-sensitive composition, a pattern formation method, a radiation-sensitive acid generator, and a compound that are exceptional in sensitivity, LWR, and CDU during pattern formation. This radiation-sensitive composition contains an onium salt having a partial structure represented by formula (i), a polymer having a structural unit (I) that contains an acid-dissociable group, and a solvent. (In formula (i), X1 − is S− or O−. Each of X2 and X3 independently is S or O. However, S is included in at least one selected from the group consisting of X1 −, X2, and X3. Z+ is an organic cation. Each * is a bond to another atom in the onium salt.)

Description

Radiation-sensitive compositions, pattern-forming methods, radiation-sensitive acid generators, and compounds

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

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

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

[0004] As pattern miniaturization progresses, various technologies have been proposed for radiation-sensitive acid generators, which are components of resist compositions, with the aim of improving roughness and other aspects (for example, Japanese Patent Publication No. 7015295).

[0005] Patent No. 7015295

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

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, a radiation-sensitive acid generator, and a compound that exhibit excellent sensitivity, LWR, and CDU 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 containing an onium salt having a partial structure represented by the following formula (i) (hereinafter also referred to as "partial structure (i)"), a polymer having a structural unit (I) containing an acid dissociable group, and a solvent. (In formula (i), １ - X - is S - or O ２ . X ３ and X １ - are each independently S or O. However, at least one selected from the group consisting of X ２ , X ３ contains S. Z ＋ is an organic cation. * is a bond with other atoms in the above onium salt, respectively.)

[0010] According to the radiation-sensitive composition, excellent sensitivity, LWR, and CDU can be exhibited during pattern formation. Although the reason for this is not clear, it is speculated as follows.

[0011] The partial structure (i) possessed by the onium salt (i) is an acid-generating structure that generates an acid for dissociating an acid dissociable group by exposure. In the partial structure (i), a structure in which at least one of the three oxygen atoms constituting the sulfonic acid anion (-SO ３ - ) is substituted with a sulfur atom (hereinafter, regardless of the number and substitution position of the sulfur atoms, also referred to as "thiosulfonic acid anion" or "thiosulfonic acid anion structure", and the corresponding acid structure is also referred to as "thiosulfonic acid" or "thiosulfonic acid structure") is introduced. As a result, the acidity of the generated acid is improved compared to the sulfonic acid anion, and the dissociation of the acid dissociable group in the exposed area is sufficiently promoted, improving the sensitivity. In addition, by promoting the dissociation of the acid dissociable group, a region with high hydrophobicity in the polymer can be reduced. As a result, the dissolution contrast between the exposed area and the unexposed area is increased, and the roughness can be improved. It is speculated that these combined actions can exhibit the above-mentioned unique performance.

[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 above-mentioned radiation-sensitive composition, which exhibits excellent sensitivity, LWR, and CDU during pattern formation, thus enabling the efficient formation of high-quality resist patterns.

[0014] In another embodiment, the present invention relates to a radiation-sensitive acid generator having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ ( is an organic cation. * represents the bonding site with other atoms in the above-mentioned radiation-sensitive acid generator.)

[0015] Since the radiation-sensitive acid generator has the above-described specific substructure (i), it can contribute to improving sensitivity, LWR, and CDU when used in a radiation-sensitive composition.

[0016] In one embodiment, the present invention relates to a compound represented by the following formula (A1-1) (hereinafter also referred to as "compound (A1-1)"). (In formula (A1-1), n １ n is an integer between 1 and 3. １ If there are two or more X １ - , X ２ , X ３ and Z １ ＋ These are either identical or different from one another.ｆ n, which has 1 to 40 carbon atoms. １ It is a valence organic group. However, n １ If R is 1, ｆ This is a fluorinated alkyl group other than a perfluoroalkyl group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. １ ＋ is an organic cation. However, n １ If Z is 1, １ ＋ (This is a radiation-sensitive onium cation.)

[0017] In a further embodiment, the present invention relates to a compound represented by the following formula (A2) (hereinafter also referred to as "compound (A2)"). (In formula (A2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of the following.

[0018] Since compound (A1-1) and compound (A2) have the above-described specific structural structure (i), when applied as radiation-sensitive acid generators in radiation-sensitive compositions, they can contribute to improving sensitivity, LWR, and CDU.

[0019] 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.

[0020] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") contains an onium salt (i) having a partial structure (i), a polymer (hereinafter also referred to as "base polymer") having a structural unit (II) containing an acid-dissociable group, and a solvent. The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0021] (Onium salts) Onium salts (i.e., onium salt(i)) are compounds having a substructure represented by the following formula (i). Onium salt(i) has a salt structure formed by an organic acid anion (thiosulfonic acid anion) and an organic cation, and the substructure(i) is incorporated into this salt structure. (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ is an organic cation. * represents the bonding site with other atoms in the onium salt described above.

[0022] The overall structure of the onium salt is not particularly limited as long as it has the partial structure (i). The overall structure of the onium salt is roughly classified into two types according to the bonding mode between the organic acid anion (thiosulfonic acid anion) and the organic cation. The first is a mode in which the organic acid anion and the organic cation form a salt structure by ionic bonding in the onium salt molecule (hereinafter, the onium salt according to this mode is also referred to as "onium salt (A1)"). The second is a mode in which the organic acid anion and the organic cation connected to each other by a covalent bond locally form a salt structure in the onium salt molecule (hereinafter, the onium salt according to this mode is also referred to as "onium salt (A2)").

[0023] The structures of the organic acid anion and the organic cation will be described later together with specific structural formulas.

[0024] In the above formula (i), X １ - is S - and it is preferable that both X ２ and X ３ are O.

[0025] The onium salt (i) is preferably a compound represented by the following formula (A1) (that is, onium salt (A1)). (In formula (A1), R １ is an n-valent organic group having 1 to 40 carbon atoms. Z １ is an organic cation. n １ ＋ is an integer of 1 to 3. When n １ is 2 or more, a plurality of X １ １ - ２ ３ １ ＋ １ - ２ ３ are the same as or different from each other. X １ - ２ ３ and X ３ are synonymous with the above formula (i).)

[0026] In the above formula (A1), R １ represented by an n-valent organic group having 1 to 40 carbon atoms １As for valence organic groups, from monovalent organic groups with 1 to 40 carbon atoms, n １ - A group with one hydrogen atom removed can be suitably adopted.

[0027] Examples of the monovalent organic groups having 1 to 40 carbon atoms include monovalent hydrocarbon groups having 1 to 40 carbon atoms, groups (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, groups in which some or all of the hydrogen atoms of the hydrocarbon group or group (a) are replaced with monovalent heteroatom-containing substituents, or combinations thereof.

[0028] Examples of monovalent hydrocarbon groups having 1 to 40 carbon atoms include monovalent linear hydrocarbon groups having 1 to 40 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 40 carbon atoms, or combinations thereof.

[0029] Examples of monovalent chain hydrocarbon groups having 1 to 40 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.

[0030] Examples of monovalent alicyclic hydrocarbon groups having 3 to 40 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.

[0031] Examples of monovalent aromatic hydrocarbon groups having 6 to 40 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.

[0032] Examples of heteroatoms that constitute 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.

[0033] Examples of divalent heteroatom-containing linking groups include -CO-, -CS-, -NR'-, -O-, -S-, and combinations thereof. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0034] Examples of monovalent heteroatom-containing substituents include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0035] R １ It is preferable that the group includes at least one structure selected from the group consisting of a cyclic structure, -CO-, -O-, and -NR'-. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. The cyclic structure may be monocyclic, polycyclic, or a combination thereof. The cyclic structure may also be an alicyclic structure, an aromatic ring structure, or a combination thereof. In the case of a combination, the cyclic structures may be linked by a chain structure, and two or more cyclic structures may have a fused ring structure, a spiro-ring structure, a ring aggregate structure, or a combination thereof. It is preferable that these structures are included as the smallest basic skeleton of the cyclic structure. The number of cyclic structures as the basic skeleton in the organic group may be one or two or more. The above-mentioned divalent heteroatom-containing linking groups may be present between carbon atoms or at the ends of carbon chains forming the skeleton of the cyclic or chain structure, and hydrogen atoms on carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0036] As the above-mentioned alicyclic structure, a structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms can be suitably adopted.

[0037] The above aromatic ring structure is not particularly limited as long as it is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, perylene rings, and coronene rings; aromatic heterocycles such as furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, carbazole rings, and dibenzofuran rings; or combinations thereof. Among these, benzene rings are preferred as aromatic rings.

[0038] As the above-mentioned chain-like structure, a structure corresponding to a monovalent chain-like hydrocarbon group having 1 to 40 carbon atoms can be suitably adopted.

[0039] Aliphatic heterocyclic structures can also be used as the alicyclic structures described above. Examples of such aliphatic heterocyclic structures include oxygen-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur-containing aliphatic heterocyclic structures such as thiethane, thiolane, and thian; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0040] Aliphatic heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetal structures, cyclic imide structures, lactam structures, or combinations thereof.

[0041] Examples of substituents that substitute hydrogen atoms on carbon atoms in the above-mentioned cyclic or chain structures include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and oxo groups (=O).

[0042] The above cyclic structure preferably includes an iodine group-containing aromatic ring structure. As the iodine group-containing aromatic ring structure, a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by iodine groups can be suitably adopted.

[0043] In the above formula (A1), R １ In this formula, it is preferable that a fluorine atom, a monovalent fluorinated hydrocarbon group, or a cyano group is bonded to the carbon atom at the α or β position relative to S. This makes it possible to further improve the acidity of the thiosulfonic acid generated by exposure.

[0044] Examples of the above-mentioned monovalent fluorinated hydrocarbon groups include monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms and monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms.

[0045] Examples of the above-mentioned monovalent fluorinated chain hydrocarbon groups having 1 to 20 carbon atoms include fluorinated alkyl groups such as trifluoromethyl group, difluoromethyl group, 2,2,2-trifluoroethyl group, pentafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 1,1,1,3,3,3-hexafluoropropyl group, heptafluoron-propyl group, heptafluoroisopropyl group, nonafluoron-butyl group, nonafluoroisobutyl group, nonafluorot-butyl group, 2,2,3,3,4,4,5,5-octafluoron-pentyl group, tridecafluoron-hexyl group, and 5,5,5-trifluoro-1,1-diethylpentyl group; fluorinated alkenyl groups such as trifluoroethenyl group and pentafluoropropenyl group; and fluorinated alkynyl groups such as fluoroethynyl group and trifluoropropynyl group.

[0046] Examples of the above-mentioned monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as fluorocyclopentyl group, difluorocyclopentyl group, nonafluorocyclopentyl group, fluorocyclohexyl group, difluorocyclohexyl group, undecafluorocyclohexylmethyl group, fluoronorbornyl group, fluoroadamantyl group, fluorobornyl group, fluoroisobornyl group, and fluorotricyclodecyl group; and fluorinated cycloalkenyl groups such as fluorocyclopentenyl group and nonafluorocyclohexenyl group.

[0047] The above-mentioned fluorinated hydrocarbon group is preferably a monovalent fluorinated linear hydrocarbon group having 1 to 8 carbon atoms, and more preferably a monovalent fluorinated linear hydrocarbon group having 1 to 5 carbon atoms.

[0048] In the above formula (A1), n １ It is preferable that this value is 1.

[0049] The organic acid anion of the onium salt (A1) preferably has a structure represented by the following formula (Aa). (In formula (Aa), X １ - , X ２ and X ３ This is equivalent to the above formula (A). Cy １１ and Cy １２ These are, independently, substituted or unsubstituted cyclic structures. １２ If there are multiple Cy １２ They are either identical or different from each other. １２ and L １３ Each of these is independently a single bond, a substituted or unsubstituted divalent hydrocarbon group having 1 to 10 carbon atoms, a divalent heteroatom-containing linking group, or a combination thereof. １２ If there are multiple L １２ They are either identical or different from each other. ｆ１ and R ｆ２ Each of these is independently a hydrogen atom, a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. However, R ｆ１ and R ｆ２At least one selected from the group consisting of the following is a cyano group, a fluorine atom, or a fluorinated hydrocarbon group. (z12 is an integer from 0 to 3. z13 is an integer from 1 to 4.)

[0050] L １１ ~L １３ The divalent heteroatom-containing linking group represented by is R in the above formula (A1). １ The divalent heteroatom-containing linking group shown can be suitably adopted.

[0051] Cy １１ and Cy １２ The cyclic structure represented by the above formula (A1) is R １ The cyclic structure shown in can be suitably adopted. The substituents that the cyclic structure may have include R in formula (A) above. １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0052] L １２ and L １３ In this, the divalent hydrocarbon group having 1 to 10 carbon atoms is R in the above formula (A1). １ Among the monovalent hydrocarbon groups having 1 to 40 carbon atoms shown above, groups corresponding to 1 to 10 carbon atoms with one hydrogen atom removed can be suitably adopted. Substituents that the hydrocarbon group may have include, R in the above formula (A1) １ The substituents that the cyclic structure shown can have can be suitably adopted.

[0053] R ｆ１ and R ｆ２ As the fluorinated hydrocarbon group represented by the above formula (A1), the fluorinated hydrocarbon group shown can be suitably adopted.

[0054] z11 is preferably 1. z12 is preferably an integer between 0 and 2, and more preferably 0 or 1. z13 is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0055] Specific examples of organic acid anions of the onium salt (A1) (including the structure represented by formula (Aa) above) include, but are not limited to, the structures represented by the following formulas (A-1-1) to (A-1-31).

[0056]

[0057]

[0058]

[0059]

[0060] Z １ ＋ The monovalent organic cation represented by is not particularly limited, and examples include onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of onium cations include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, pyridinium cations, and ammonium cations.

[0061] Z １ ＋ It is preferable that the onium cation is a monovalent radiation-sensitive onium cation. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0062] The above organic cation preferably has at least one selected from the group consisting of an iodine group and a fluoro group. The above organic cation preferably contains an iodine group-containing aromatic ring structure as the form of iodine group content. An iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are substituted with iodine groups. In the organic 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 substituted with fluoro groups. The aromatic ring in the iodine group-containing aromatic ring structure and the fluoro group-containing aromatic ring structure is R of formula (A1) above. １ The aromatic rings shown can be suitably adopted. By introducing an iodine group or a fluoro group, the radiation absorption efficiency can be increased, thereby improving sensitivity.

[0063] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0064]

[0065] 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.

[0066] In the above equation (X-2), R ｂ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyloxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a halogen atom, or a hydroxyl group. ｋ n is either 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When k4 is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ They may be the same or different, and there may be multiple R's. ｂ１ R may represent a ring structure formed by combining with other elements. ｂ２ This is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ k5 is a single bond or a divalent linking group. k5 is an integer from 0 to 4. ｂ２ If there are multiple R ｂ２ They may be the same or different, and there may be multiple R's. ｂ２ may represent a ring structure formed by combining with each other. q is an integer from 0 to 3. In the formula, S ＋ The ring structure containing may include heteroatoms such as O and S between the carbon-carbon bonds that form the skeleton.

[0067] 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.

[0068] In the above equation (X-4), R ｇ１ This is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group, halogen atom, or hydroxyl group having 6 to 8 carbon atoms. ｋ２ n is either 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ They may be the same or different, and there may be multiple R's. ｇ１ R may represent a ring structure formed by combining with other elements. ｇ２ and R ｇ３ Each of these independently represents a substituted or unsubstituted linear or branched alkyl group, alkoxy group or alkoxycarbonyloxy group having 1 to 12 carbon atoms, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group, hydroxyl group, halogen atom having 6 to 12 carbon atoms, or a ring structure formed by combining these groups. k11 and k12 are each independently integers from 0 to 4. R ｇ２ and R ｇ３ If each of them is multiple, then multiple R ｇ２ and R ｇ３ These may be the same or different.

[0069] 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.

[0070] In the above formula (X-6), R ｅ１ and R ｅ２ k8 and k9 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0071] Specific examples of organic cations as the above-mentioned radiation-sensitive onium cations include, but are not limited to, the structures shown in formulas (1-2-1) to (1-2-59) and (1-3-1) to (1-3-21) below.

[0072]

[0073]

[0074]

[0075]

[0076] Onium salt (A1) 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 formulas (A1-1) to (A1-31).

[0077]

[0078]

[0079]

[0080]

[0081] The onium salt (i) may be a compound represented by the following formula (A2) (i.e., onium salt (A2)). (In formula (A2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - , X ２ and X ３ This is equivalent to equation (i) above.

[0082] Z ２ ＋ As a monovalent organic cation represented by the above formula (A1), Z １ ＋ A structure obtained by removing one hydrogen atom from the organic cation represented by Z can be suitably adopted. ２ ＋ It is preferable that this is a monovalent triarylsulfonium cation or diaryliodonium cation.

[0083] L Ａ２ The divalent linking group represented by is R in the above formula (A1). １ A group obtained by removing one hydrogen atom from a monovalent organic group having 1 to 40 carbon atoms, as shown in [reference], can be suitably adopted. Ａ２ The linking group is preferably a single bond or a divalent linking group containing an ester bond.

[0084] In the above formula (A2), L Ａ２ and Z ２ ＋ Preferably, at least one selected from the group consisting of the above contains an iodine group. Preferably, the iodine group is incorporated in the form of the above iodine group-containing aromatic ring structure.

[0085] Specific examples of onium salts (A2) include, but are not limited to, structures represented by the following formulas (A2-1) to (A2-4).

[0086]

[0087] The lower limit of the onium salt content (total amount if multiple types exist) is preferably 1 part by mass, more preferably 5 parts by mass, and still more preferably 8 parts by mass, per 100 parts by mass of the base polymer described later. The upper limit of the above content ratio is preferably 40 parts by mass, more preferably 30 parts by mass, and still more preferably 25 parts by mass. As a result, the composition can exhibit excellent sensitivity, LWR, and CDU during pattern formation.

[0088] (Synthesis method for onium salts) Onium salts can typically be synthesized according to the following scheme. In the above formula (A1), X １ - S - X ２ and X ３ All of them are O, n １ The case where the answer is 1 will be explained. However, this is not limited to this case, and known methods may be adopted.

[0089]

[0090] In the scheme, R １ and Z １ ＋ This is equivalent to the above formula (A1). Y Ｅ M is a halogen atom. M is an alkali metal. Y Ｇ - It is a halide ion.

[0091] A thiosulfonate is produced by reacting a halide (preferably a bromide) of an organic acid anion structure with an alkali metal salt of dithionic acid, followed by a reaction with sulfur. The desired onium salt can then be synthesized by salt exchange with a halide salt having a predetermined organic cation. Other structures can also be synthesized by appropriately changing the starting materials and intermediate components.

[0092] (Polymers) A polymer (i.e., a base polymer) is an aggregate of polymerization chains having structural units (I) containing acid-dissociable groups. In addition to structural unit (I), the base polymer may also contain structural units (II) having phenolic hydroxyl groups, structural units (III) containing at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures, structural units (IV) containing polar groups, and so on. Each structural unit will be described below.

[0093] [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 that dissociates upon the action of an acid. The radiation-sensitive composition exhibits excellent pattern-forming properties because the polymer contains structural unit (I).

[0094] 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.

[0095]

[0096] 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. ３１ teeth, ＊ -COO-, ＊ -L ３１ａ COO- or＊ -COOL ３１ａ Represents COO-. ３１ａ * 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.

[0097] 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.

[0098] L ３１ａ 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. ３１ａ Methylene groups and ethanediyl groups are preferred as the base group.

[0099] L ３１ａ Examples of allenediyl groups represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. ３１ａ A benzenediyl group is preferred as the group.

[0100] L ３１ａ 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.

[0101] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (A1), R １ Among the monovalent hydrocarbon groups having 1 to 40 carbon atoms shown above, groups corresponding to 1 to 20 carbon atoms can be suitably adopted.

[0102] The above R １８ Preferably, the hydrocarbon group is a straight-chain or branched-chain saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0103] The above R １９ and R ２０The 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 (A1) above. １ Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms shown above, groups corresponding to those with 1 to 20 carbon atoms can be suitably adopted by removing one hydrogen atom.

[0104] Among these, R １８ R is an alkyl group, alkenyl group, or phenyl group having 1 to 4 carbon atoms. １９ and R ２０ It is preferable that the alicyclic structure formed by combining these elements with the carbon atoms to which they are bonded is a polycyclic or monocyclic cycloalkane structure.

[0105] The above R １８ ~R ２０ The substituents that can be present are L ３１ａ The substituents that the arenediyl group represented by can have can be suitably adopted.

[0106] 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)").

[0107]

[0108]

[0109] In the above equations (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. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from each other. a4 is an integer between 1 and 3.

[0110] i and j are preferably 1 or 2. １８Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. 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).

[0111] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f).

[0112]

[0113] 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-like alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0114] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0115] The lower limit of the content of structural unit (I) (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. 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 unit (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved.

[0116] [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.

[0117] The structural unit having a phenolic hydroxyl group is preferably represented by the following formula (4).

[0118] (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. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ Each of these is an independent integer between 0 and 8, where 1 ≤ m. ３ +m ４ ≤ 2n ３ (Saves +5.)

[0119] 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.

[0120] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0121] R １０２ In this mixture, fluorine or iodine atoms are preferred as halogen atoms.

[0122] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0123] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0124] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0125] When the base polymer contains structural unit (II), the lower limit of the content of structural unit (II) in relation to the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 10 mol%, and more preferably 20 mol%. The upper limit of the above content is preferably 70 mol%, and more preferably 60 mol%.

[0126] [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. By further comprising structural unit (III), the solubility of the base polymer in the developer can be adjusted, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. Furthermore, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0127] Examples of structural units (III) include those represented by the following formulas (T-1) to (T-11).

[0128]

[0129] 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.

[0130] 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 ２０Examples 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.

[0131] The above L ２ Examples of divalent linking groups represented by include divalent linear or branched hydrocarbon groups having 1 to 10 carbon atoms, divalent alicyclic hydrocarbon groups having 4 to 12 carbon atoms, or groups composed of one or more of these hydrocarbon groups and at least one of the groups -CO-, -O-, -NH-, and -S-.

[0132] 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.

[0133] When the base polymer contains structural unit (III), the lower limit of the content of structural unit (III) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 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.

[0134] [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 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.

[0135] Examples of structural units (IV) include structural units represented by the following formula.

[0136]

[0137]

[0138] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0139] When the base polymer has a structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) in the total structural units constituting the base polymer (the total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of structural unit (IV) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0140] [Structural Unit (V)] The base polymer 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 above radiation-sensitive acid-generating structure in the base polymer, the polarity of the base polymer 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.

[0141] 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 is not particularly limited, it is preferable that the base polymer 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.

[0142] The above-mentioned first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions as the acid anion portion. As for the acid generated by exposure, sulfonic acid, carboxylic acid, and sulfonimide can be cited, corresponding to the above-mentioned acid anion portion.

[0143] The above-mentioned first organic acid anion has a structure other than the acid anion portion, which is R in formula (A1). １ The structure of the above formula (Aa) and structures other than the thiosulfonic acid anion structure of the organic acid anion can be suitably adopted.

[0144] In the above-described first acid generation structure, the first organic acid anion preferably has a sulfonic acid anion as the acid anion portion, and an electron-withdrawing group is preferably bonded to the carbon atom at the α or β position of the sulfur atom in the sulfonic acid anion. This allows the first acid generation structure to efficiently exhibit the above-described function. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, and cyano groups. As the fluorinated hydrocarbon group, a perfluoroalkyl group having 1 to 5 carbon atoms is preferred.

[0145] The first organic acid anion described above preferably has an iodine group. The first organic acid anion preferably contains the iodine group-containing aromatic ring structure described above as the form in which the iodine group is contained.

[0146] Examples of the first onium cation mentioned above include radiation-sensitive onium cations. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0147] The first onium cation described above preferably has an iodine group or a fluoro group. The first onium cation preferably contains an iodine group-containing aromatic ring structure as an iodine group-containing configuration. The first onium cation preferably contains a fluoro group-containing aromatic ring structure as an fluoro group-containing configuration. These configurations increase radiation absorption efficiency, thereby improving sensitivity. The first onium cation is Z of formula (A1) described above. １ ＋ Organic cations represented by can be suitably used.

[0148] The structural unit (V) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0149] The structural unit (V) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (V-1)").

[0150]

[0151] 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. ３ This 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 the compound may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. Rf １ ~Rf ２ 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 a sulfonium cation or an iodonium cation.

[0152] 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.

[0153] Preferably, the structural unit (V-1) is a structural unit represented by the following formula (a1-1).

[0154]

[0155] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ ,kk and X １ ＋ This is equivalent to the above formula (a1). R ４８ m 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.

[0156] 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 is a hydrogen atom or R in the above formula (A1). １ Substitutions may be made with the substituents shown in [reference].

[0157]

[0158]

[0159]

[0160]

[0161]

[0162] In the above formula, R Ｖ This is equivalent to equation (a1) above.

[0163] X in the above formula (a1) １ ＋ As for Z in the above formula (A1) １ ＋ A sulfonium cation or iodonium cation can be suitably used in the monovalent organic cation represented by [formula].

[0164] When the base polymer has structural units (V), the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 10 mol%, relative to the total structural units constituting the base polymer. 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.

[0165] [Structural Unit (VI)] The base polymer may include structural unit (VI), which has a second organic acid anion and a second onium cation, and contains a second acid generating structure that generates an acid by exposure without dissociating the acid-dissociable group. 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 radiation-sensitive composition, the second acid generating structure substantially prevents the dissociation of the acid-dissociable group of structural unit (I), and has the function of suppressing the diffusion of the acid generated from the onium salt or structural unit (V) (if included) in the unexposed area by salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the onium salt or structural unit (V). Whether an onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable groups of the base polymer, and the acidity of the onium salt structure or the generated acid.

[0166] Regarding the inclusion of the second organic acid anion and the second onium cation in the structural unit (VI) of the base polymer, from the viewpoint of development contrast, it is preferable that the base polymer has the second organic acid anion as a side chain portion. Having it as a side chain portion means that the corresponding second organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer.

[0167] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion, and more preferably a carboxylic acid anion. However, when the above-mentioned second organic acid anion has the above-mentioned sulfonic acid anion, no electron-withdrawing group is bonded to either the α-position or the β-position carbon atom of the sulfur atom in the sulfonic acid anion. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, cyano groups, etc. The acid generated by exposure corresponds to the above-mentioned acid anion portion and is a carboxylic acid or sulfonic acid.

[0168] The above-mentioned second organic acid anion preferably includes -O-, -CO-, a cyclic structure, or a combination thereof, as a structure other than the acid anion portion. Suitable examples of such structures include the organic acid anion of the onium salt (A1) (excluding the thiosulfonic acid anion structure).

[0169] The above-mentioned second organic acid anion preferably has an iodine group or a hydroxyl group. The above-mentioned second organic acid anion preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0170] As the second onium cation mentioned above, an organic cation of the onium salt (A1) can be suitably used.

[0171] The above-mentioned second onium cation preferably has an iodine group. The above-mentioned second onium cation preferably contains the above-mentioned iodine group-containing aromatic ring structure as the form in which the iodine group is contained.

[0172] The secondary onium cation in structural unit (VI) preferably has the above-mentioned fluorogroup-containing aromatic ring structure. This can improve sensitivity by increasing the radiation absorption efficiency.

[0173] The structural unit (VI) can efficiently perform the above-mentioned functions by combining the above-mentioned structures.

[0174] The structural unit (VI) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (VI-1)").

[0175]

[0176] In formula (p1), R A This is either a hydrogen atom or a methyl group.

[0177] In formula (p1), X 1 These are single bonds, ester bonds, ether bonds, phenylene groups, naphthylene groups, or combinations thereof.

[0178] In formula (p1), X ２ This is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may include an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by can be linear, branched, or cyclic, and specific examples include methylene group, ethane-1,1-diyl group, ethane-1,2-diyl group, propane-1,2-diyl group, propane-1,3-diyl group, propane-2,2-diyl group, butane-1,2-diyl group, butane-1,3-diyl group, butane-1,4-diyl group, butane-2,2-diyl group, butane-2,3-diyl group, 2-methylpropane-1,3- Examples include C1-C12 alkanediyl groups such as diyl groups, pentane-1,5-diyl groups, hexane-1,6-diyl groups, heptane-1,7-diyl groups, octane-1,8-diyl groups, nonane-1,9-diyl groups, and decane-1,10-diyl groups; C3-C12 cyclic saturated hydrocarbylene groups such as cyclopentanediyl groups, cyclohexanediyl groups, norbornanediyl groups, and adamantanediyl groups; and groups obtained by combining these.

[0179] In formula (p1), X 3 These are single bonds, ester bonds, or ether bonds.

[0180] In formula (p1), X 1 ~X ２ Some or all of the hydrogen atoms in may be substituted with substituents. Examples of substituents include R in formula (A1) above. １ The substituents shown in can be suitably adopted. 1 ~X２ When it has a phenylene group, it is preferable that some or all of the hydrogen atoms of the phenylene group are substituted with fluorine atoms or iodine atoms.

[0181] In formula (p1), R ｘ is a halogen atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group or a group in which a hydrogen atom of these groups is substituted with a halogen atom.

[0182] In formula (p1), Z ２ ＋ is a second onium cation. As the second onium cation, the organic cations shown in the onium salt (A1) can be preferably employed.

[0183] Examples of the second organic acid anion of the monomer that gives the structural unit (VI) (including the structural unit (VI-1)) include, but are not limited to, those shown below. In the following formulas, the iodine group or the hydroxy group may be substituted with a hydrogen atom or a substituent shown in R of the above formula (A). In the following formulas, R １ is the same as described above. The second organic acid anion preferably has a carboxylic acid anion and a hydroxy group. In this case, it is preferable that the carboxylic acid anion and the hydroxy group are bonded to the same aromatic ring of the second organic acid anion, and in the same aromatic ring, the carbon atom to which the carboxylic acid anion is bonded and the carbon atom to which the hydroxy group is bonded are more preferably directly bonded to each other. Ａ is the same as above.

[0184]

[0185]

[0186]

[0187]

[0188] When the base polymer contains structural unit (VI), the lower limit of the content of structural unit (VI) (or the 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. The upper limit of the above content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of structural unit (VI) within the above range, the structure can fully exhibit its function as an acid diffusion control structure.

[0189] [Other structural units] The base polymer may also contain structural units other than those listed above, such as structural units having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)"). (In the above formula (6), R １α R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α (It is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.)

[0190] In the above formula (6), R ２α As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (A1), R １ The monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown in the above can be suitably used.

[0191] When the base polymer contains structural unit (VII), the lower limit of the content of structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0192] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0193] Examples of the radical polymerization initiators mentioned above include azo-based radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(isobutyrate)dimethyl (MAIB), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide-based radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used individually or in combination of two or more.

[0194] Solvents used in the above polymerization include, for example, alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; and ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone. Examples include linear ethers such as dimethoxyethanes and diethoxyethanes; cyclic ethers such as tetrahydrofurans and 1,4-dioxanes; polyhydric alcohol partial ethers such as 1-methoxy-2-propanol (propylene glycol monomethyl ether); alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol; and lactones such as γ-butyrolactone. The solvents used in these polymerizations may be used alone or in combination of two or more.

[0195] The reaction temperature in the polymerization described above is usually 40°C to 150°C, with 50°C to 120°C being preferred. The reaction time is usually 1 hour to 48 hours, with 1 hour to 24 hours being preferred.

[0196] The molecular weight of the base polymer is not particularly limited, but the lower limit of the polystyrene-equivalent weight-average molecular weight (Mw) determined by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 14,000, and even more preferably 10,000. By keeping the Mw of the base polymer within the above range, good heat resistance and developability can be obtained in the resulting resist film.

[0197] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0198] In this specification, the Mw and Mn values ​​of polymers are measured using gel permeation chromatography (GPC) under the following conditions.

[0199] GPC columns: 2 x G2000HXL, 1 x G3000HXL, 1 x G4000HXL (all manufactured by Tosoh) Column temperature: 40°C Elution solvent: Tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0200] The base polymer content is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0201] (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 (hereinafter also referred to as a "high-fluorine content polymer"). 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, and as a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, or to modify the surface of the resist film and control the distribution of the composition within the film during EUV exposure.

[0202] High-fluorine-content polymers may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VIII)").

[0203]

[0204] In the above formula (5), R １３ This is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ It consists of a single bond, an alkanediyl group with 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, and -SO ２ ONH-, -CONH-, -OCONH-, or a combination thereof. １４ This is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0205] The above R １３ From the viewpoint of copolymerization of monomers that give structural unit (VIII), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0206] The above G Ｌ From the viewpoint of copolymerization of monomers that give structural unit (VIII), single bonds and -COO- are preferred, and -COO- is more preferred.

[0207] The above R １４ Examples of monovalent fluorinated linear hydrocarbon groups having 1 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a linear or branched alkyl group having 1 to 20 carbon atoms are substituted with fluorine atoms.

[0208] The above R １４ Examples of monovalent fluorinated alicyclic hydrocarbon groups having 3 to 20 carbon atoms, represented by , include those in which some or all of the hydrogen atoms in a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms are substituted with fluorine atoms.

[0209] The above R １４Preferably, the group is a fluorinated chain hydrocarbon group, more preferably a fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0210] When a high-fluorine-content polymer has structural unit (VIII), the lower limit of the content of structural unit (VIII) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of structural unit (VIII) within the above range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting the uneven distribution on the surface of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0211] High-fluorine polymers may have a fluorine atom-containing structural unit (hereinafter also referred to as structural unit (IX)) represented by the following formula (f-2), either together with or in place of structural unit (VIII). The presence of structural unit (f-2) in high-fluorine polymers improves solubility in alkaline developers and suppresses the occurrence of development defects.

[0212]

[0213] Structural units (IX) can be broadly classified into two types: (x) those having an alkali-soluble group, and (y) those having a group that dissociates under the action of alkali, increasing its solubility in an alkaline developer (hereinafter also simply referred to as an "alkali-dissociable group"). In common to both (x) and (y), in the above formula (f-2), R Ｃ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ R is a single bond, a (s+1) valent hydrocarbon group with 1 to 20 carbon atoms, and this hydrocarbon group Ｅ At the end of the side are an oxygen atom, a sulfur atom, and -NR ｄｄ- A structure in which a carbonyl group, -COO-, -OCO- or -CONH- is bonded, or a structure in which a part of the hydrogen atoms of this hydrocarbon group is substituted by an organic group having a hetero atom. R ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0214] When the structural unit (IX) has a (x) alkali-soluble group, R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-*, or -SO ２ O-*. * indicates the bonding site to R Ｆ . W １ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms or a divalent fluorinated hydrocarbon group. When A １ is an oxygen atom, W １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group at the carbon atom to which A １ is bonded. R Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different from each other. By having the (x) alkali-soluble group in the structural unit (IX), the affinity for the alkali developer can be increased and development defects can be suppressed. As the structural unit (IX) having the (x) alkali-soluble group, it is particularly preferable when A １ is an oxygen atom and W １ is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0215] When the structural unit (IX) has a (y) alkali-dissociable group, R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-*, or -SO ２ O-*. R ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * indicates the bonding site to R Ｆ . W １R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ A is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ -COO-*, -OCO-*, or -SO ２ If it is O-*, then W １ or R Ｆ is A １ It has a fluorine atom on the carbon atom bonded to it or on an adjacent carbon atom. １ If is an oxygen atom, W １ , R Ｅ It is a single bond, R Ｄ R is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ It is a structure in which a carbonyl group is bonded to the terminal end, R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, multiple R Ｅ , W １ A １ and R Ｆ These may be the same or different. The presence of a (y) alkali-dissociable group in the structural unit (IX) causes the resist film surface to change from hydrophobic to hydrophilic during the alkali development process. As a result, the affinity for the developer is significantly increased, and development defects can be suppressed more efficiently. Examples of structural units (IX) having a (y) alkali-dissociable group include A １ is -COO-*, R Ｆ Or W １ Alternatively, it is particularly preferable that both of these contain fluorine atoms.

[0216] R Ｃ From the viewpoint of copolymerizability of monomers that provide structural units (IX), hydrogen atoms and methyl groups are preferred, and methyl groups are more preferred.

[0217] When a high-fluorine-content polymer has structural units (IX), the content of structural units (IX) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of structural units (IX) within the above range, it is possible to improve the water repellency of the resist film during immersion exposure and improve solubility in alkaline developers, thereby suppressing the occurrence of development defects.

[0218] [Other structural units] High-fluorine polymers may, if necessary, include structural units other than those listed above, such as structural unit (I), structural unit (IV), and structural unit (VII) in the base polymer.

[0219] When a high-fluorine-content polymer contains structural unit (I), the content of structural unit (I) is preferably 4 mol%, and more preferably 8 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 40 mol%, and more preferably 30 mol%.

[0220] When a high-fluorine-content polymer contains structural units (IV), the content of structural units (IV) is preferably 8 mol%, and more preferably 15 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 50 mol%, and more preferably 40 mol%.

[0221] When a high-fluorine-content polymer contains structural unit (VII), the content of structural unit (VII) is preferably 20 mol%, and more preferably 30 mol%, relative to the total structural units constituting the high-fluorine-content polymer. Furthermore, the upper limit of the above content is preferably 60 mol%, and more preferably 50 mol%.

[0222] The lower limit of Mw for the high-fluorine-content polymer is preferably 4,000, more preferably 5,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 10,000, and even more preferably 8,000.

[0223] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred.

[0224] If the radiation-sensitive composition contains a high-fluorine content polymer, the lower limit of the high-fluorine content polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass.

[0225] By setting the content of the high-fluorine polymer within the above range, the high-fluorine polymer 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 internal composition during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine polymers.

[0226] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the base polymer synthesis method described above.

[0227] (Acid Diffusion Control Agent) The radiation-sensitive composition may optionally contain an acid diffusion control agent. The acid diffusion control agent controls the diffusion phenomenon of the acid generated from the onium salt or structural unit (V) in the resist film upon exposure, and has the effect of suppressing undesirable chemical reactions in the unexposed areas. In addition, the storage stability of the resulting radiation-sensitive composition is improved. Furthermore, 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.

[0228] Examples of acid diffusion control agents 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.

[0229]

[0230] 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.

[0231] Examples of nitrogen-containing compounds (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline and 2,6-di-i-propylaniline.

[0232] Examples of nitrogen-containing compounds (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0233] Examples of nitrogen-containing compounds (III) include polyamine compounds such as polyethyleneimine and polyallylamine; and polymers such as dimethylaminoethylacrylamide.

[0234] Examples of amide group-containing compounds include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone.

[0235] Examples of urea compounds include urea, methyl urea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0236] Examples of nitrogen-containing heterocyclic compounds include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; and pyrazines and pyrazoles.

[0237] Furthermore, compounds having an acid-dissociable group can also be used as the nitrogen-containing organic compound. Examples of nitrogen-containing organic compounds having an acid-dissociable group include N-t-butoxycarbonylpiperidine, N-t-butoxycarbonylimidazole, N-t-butoxycarbonylbenzimidazole, N-t-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, N-t-butoxycarbonyl-4-hydroxypiperidine, N-t-butoxycarbonyl-4-acetoxypiperidine, and N-t-amyloxycarbonyl-4-hydroxypiperidine.

[0238] Furthermore, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as an acid diffusion control agent. 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.

[0239] 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).

[0240]

[0241] 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 ＋ Examples of iodonium cations represented by the above formulas (X-5) to (X-6) include iodonium cations 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 monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups having a divalent heteroatom-containing linking group between carbon atoms or at the end of the carbon chain of the hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with a monovalent heteroatom-containing group, or combinations thereof. α -SO ３ - In the case of an anion represented by R, α SO in ３ - The electron-withdrawing group is not bonded to either the α- or β-position carbon atom of the sulfur atom.

[0242] As a monovalent hydrocarbon group having 1 to 20 carbon atoms, R in the above formula (A1) is １ Among the monovalent hydrocarbon groups having 1 to 40 carbon atoms shown above, groups corresponding to 1 to 20 carbon atoms can be suitably adopted.

[0243] Examples of heteroatoms that constitute 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.

[0244] As a divalent heteroatom-containing linking group, R in formula (A1) above １The divalent heteroatom-containing linking group shown can be suitably adopted.

[0245] Examples of monovalent heteroatom-containing groups include hydroxyl groups, sulfanyl groups, cyano groups, nitro groups, and halogen atoms.

[0246] Examples of anions for the above-mentioned acid diffusion control agent include, but are not limited to, those listed below. Compounds containing both an iodonium cation and anion within the same molecule, and compounds containing both a sulfonium cation and anion within the same molecule are also given as examples. The iodine group in the following formulas may be substituted with a hydrogen atom or other substituents.

[0247]

[0248]

[0249] As the onium cation in the above acid diffusion control agent, the structure of the organic cation of the above onium salt (A1) can be suitably adopted.

[0250] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0251] These acid diffusion control agents may be used individually or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion control agent, the lower limit of the acid diffusion control agent content (total in the case of multiple types) is preferably 1 part by mass, more preferably 2 parts by mass, and still more preferably 3 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 20 parts by mass, more preferably 16 parts by mass, and still more preferably 12 parts by mass.

[0252] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it is capable of dissolving or dispersing the base polymer and any optional components that may be included.

[0253] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0254] 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.

[0255] 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.

[0256] 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.

[0257] 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.

[0258] 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.

[0259] 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.

[0260] 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.

[0261] (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 promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0262] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared by mixing, for example, a polymer, and optionally a high-fluorine-content polymer, and a solvent in a predetermined ratio. After mixing, the above radiation-sensitive composition is preferably filtered using, for example, a filter with a pore size of about 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.

[0263] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention includes a step (1) of 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"), a step (2) of exposing the resist film (hereinafter also referred to as the "exposure step"), and a step (3) of developing the exposed resist film with a developer solution (hereinafter also referred to as the "development step").

[0264] According to the pattern formation method described above, since the radiation-sensitive composition that exhibits excellent sensitivity, CDU, and LWR is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0265] [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, such as those disclosed in 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.

[0266] 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.

[0267] When performing immersion exposure, regardless of the presence or absence of water-repellent polymer additives such as the high-fluorine-content polymer 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, Japanese Patent Application Publication Nos. WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable immersion-protective film.

[0268] [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; for example, electron beams and charged particle beams such as alpha rays. 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.

[0269] 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.

[0270] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the structural unit (I-1) or the radiation-sensitive acid generator due to the 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.

[0271] [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.

[0272] 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.

[0273] Furthermore, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, etc., 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.

[0274] 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.

[0275] 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 leaving it 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).

[0276] <Radiation-sensitive acid generator> The radiation-sensitive acid generator is a compound having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ ( is an organic cation. * represents the bonding site with other atoms in the above-mentioned radiation-sensitive acid generator.)

[0277] As such a radiation-sensitive acid generator, the onium salt (i) in the above-mentioned radiation-sensitive composition can be suitably used.

[0278] <Compound> The compound in question is represented by the following formula (A1-1). (In formula (A1-1), n １ n is an integer between 1 and 3. １ If there are two or more X １ - , X ２ , X ３ and Z １ ＋These are either identical or different from one another. ｆ n, which has 1 to 40 carbon atoms. １ It is a valence organic group. However, n １ If R is 1, ｆ This is a fluorinated alkyl group other than a perfluoroalkyl group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. １ ＋ is an organic cation. However, n １ If Z is 1, １ ＋ (This is a radiation-sensitive onium cation.)

[0279] As such a compound, the onium salt (A1) in the above-mentioned radiation-sensitive composition can be suitably used. However, n １ If R is 1, ｆ This is a fluorinated alkyl group other than a perfluoroalkyl group, and n １ If Z is 1, １ ＋ It is a radiation-sensitive onium cation.

[0280] <Compound> The compound in question is represented by the following formula (A2). (In formula (A2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X３ S is included in at least one of the groups selected from the group consisting of the following.

[0281] As such a compound, the onium salt (A2) in the above-mentioned radiation-sensitive composition can be suitably used.

[0282] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are shown below.

[0283] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The degree of dispersion (Mw / Mn) was calculated from the measured results of Mw and Mn.

[0284] [ １３ [C-NMR analysis] Polymer １３ C-NMR analysis was performed using a nuclear magnetic resonance spectrometer (JEOL Ltd.'s "JNM-Delta400").

[0285] <Synthesis of Polymers> The monomers used in the synthesis of each polymer in each example and comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refers to the value when the total mass of the monomers used is 100 parts by mass, and mol% refers to the value when the total number of moles of the monomers used is 100 mol%.

[0286]

[0287] [Synthesis Example 1] (Synthesis of Polymer (A-1)) Monomers (M-1), (M-2), (M-5), (M-10), and (M-14) were dissolved in 200 parts by mass of 2-butanone in a molar ratio of 40 / 10 / 20 / 20 / 10 (mol%). AIBN (azobisisobutyronitrile) (5 mol% relative to the total 100 mol% of the monomers used) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered again, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 85%). The Mw of polymer (A-1) was 7,100, and the Mw / Mn ratio was 1.61. Furthermore, １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from (M-1), (M-2), (M-5), (M-10), and (M-14) was 40.3 mol%, 9.2 mol%, 20.5 mol%, 19.8 mol%, and 10.2 mol%, respectively.

[0288] [Synthesis Examples 2-11] (Synthesis of Polymers (A-2) to (A-11)) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that monomers of the types and proportions shown in Table 1 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymers are also shown in Table 1 below. Note that "-" in Table 1 below indicates that the corresponding monomer was not used (the same applies to subsequent tables).

[0289]

[0290] (Synthesis of Polymer (A-12)) Monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to a molar ratio of 50 / 50 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 100 parts by mass of 1-methoxy-2-propanol was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The cooled polymerization solution was added to hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered again, and dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and the hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After the reaction was complete, the residual solvent was removed by distillation, and the obtained solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to solidify the polymer. The obtained solid was filtered off and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 81%). The Mw of polymer (A-12) was 5,500, and the Mw / Mn was 1.62. １３ C-NMR analysis revealed that the content of each structural unit derived from (M-1) and (M-18) was 50.2 mol% and 49.8 mol%, respectively.

[0291] [Synthesis Examples 13-15] (Synthesis of Polymers (A-13) to (A-15)) Polymers (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that monomers of the types and proportions shown in Table 2 below were used. Note that the monomers that give structural unit (II) in the polymer are, １３ 13C-NMR measurements confirmed the disappearance of the carbonyl group peak of the acetyl group, indicating that virtually all alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content (mol%), yield (%), and physical properties (Mw and Mw / Mn) of each structural unit of the obtained polymer are shown in Table 2 below.

[0292]

[0293] [Synthesis Example 16] (Synthesis of High Fluorine-Content Polymer (F-1)) Monomer (M-1) and monomer (M-20) were dissolved in 200 parts by mass of 2-butanone to a molar ratio of 20 / 80 (mol%), and AIBN (4 mol%) was added as an initiator to prepare a monomer solution. 100 parts by mass of 2-butanone was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the temperature inside the reaction vessel was set to 80°C, and the monomer solution was added dropwise over 3 hours while stirring. The start of the dropwise addition was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C by water cooling. The solvent was replaced with acetonitrile (400 parts by mass), and hexane (100 parts by mass) was added and stirred, and the acetonitrile layer was recovered. This process was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of high fluorine-content polymer (F-1) was obtained (yield: 75%). The Mw of the high-fluorine-content polymer (F-1) was 6,200, and the Mw / Mn ratio was 1.77. １３ ¹³C-NMR analysis revealed that the content of each structural unit derived from (M-1) and (M-20) was 19.5 mol% and 80.5 mol%, respectively.

[0294] [Synthesis Examples 17-20] (Synthesis of high-fluorine content polymers (F-2) to (F-5)) High-fluorine content polymers (F-2) to (F-5) were synthesized in the same manner as in Synthesis Example 16, except that monomers of the types and proportions shown in Table 3 below were used. The content percentage (mol%) and physical properties (Mw and Mw / Mn) of each structural unit of the obtained high-fluorine content polymers are shown in accordance with Table 3 below.

[0295]

[0296] <Synthesis of Onium Salt as Radiation-Sensitive Acid Generator B> [Example B1] (Synthesis of Compound (B-1)) Compound (B-1) as an onium salt was synthesized according to the following synthesis scheme.

[0297]

[0298] 20.0 mmol of compound (B-1-a), 20.0 mmol of cyclopentadiene, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (B-1-b) was obtained in good yield by purification by column chromatography.

[0299] To the above compound (B-1-b), 40.0 mmol of potassium permanganate and 50 g of acetonitrile were added and the mixture was stirred at 60°C for 6 hours. Then, saturated sodium thiosulfate aqueous solution was added to stop the reaction, and ethyl acetate was added for extraction, separating the organic layer. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (B-1-c) was obtained in good yield by purification by column chromatography.

[0300] To the above compound (B-1-c), 20.0 mmol of 2-adamantanone, 2.00 mmol of sulfuric acid, and 50 g of dichloromethane were added and the mixture was stirred at room temperature for 6 hours. After dilution with water, the mixture was extracted with ethyl acetate, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the compound (B-1-d) was obtained in good yield by purification by column chromatography.

[0301] Compound (B-1-d) was mixed with acetonitrile and water (1:1 by mass) to make a 1 M solution. Then, 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added, and the mixture was reacted at 60°C for 3 hours. After extraction with acetonitrile and removal of the solvent by distillation, methanol was added to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (B-1-e) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0302] To the above compound (B-1-e), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-1) was obtained in good yield by purification by column chromatography.

[0303] [Examples B2 to B6] (Synthesis of compounds (B-2) to (B-6)) Radiation-sensitive acid generators represented by the following formulas (B-2) to (B-6) were synthesized in the same manner as in Example B1, except that the raw materials and precursors were appropriately changed.

[0304]

[0305] [Example B7] (Synthesis of compound (B-7)) Compound (B-7) was synthesized according to the following synthesis scheme.

[0306]

[0307] 20.0 mmol of compound (B-7-a), 30.0 mmol of 1-adamantane methanol, 30.0 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDCI), and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (B-7-b) was obtained in good yield by purification by column chromatography.

[0308] Compound (B-7-b) was mixed with acetonitrile and water (1:1 by mass) to make a 1 M solution. Then, 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added, and the mixture was reacted at 60°C for 3 hours. After extraction with acetonitrile and removal of the solvent by distillation, methanol was added to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (B-7-c) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0309] To the above compound (B-7-c), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-7) was obtained in good yield by purification by column chromatography.

[0310] [Examples B8 to B11] (Synthesis of compounds (B-8) to (B-11)) Radiation-sensitive acid generators represented by the following formulas (B-8) to (B-11) were synthesized in the same manner as in Example B7, except that the raw materials and precursors were appropriately changed.

[0311]

[0312] [Example B12] (Synthesis of compound (B-12)) Compound (B-12) was synthesized according to the following synthesis scheme.

[0313]

[0314] 20.0 mmol of compound (B-12-a), 30.0 mmol of 1-adamantane carbonyl chloride, 30.0 mmol of pyridine, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with dichloromethane, and the organic layer was separated. The obtained organic layer was washed with saturated sodium chloride aqueous solution, and then with water. After drying over sodium sulfate, the solvent was removed by distillation, and the compound (B-12-b) was obtained in good yield by column chromatography.

[0315] To the above compound (B-12-b), a mixture of acetonitrile and water (1:1 by mass ratio) was added to make a 1 M solution. Then, 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added, and the mixture was reacted at 60°C for 3 hours. After extraction with acetonitrile and removal of the solvent by distillation, methanol was added to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (B-12-c) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0316] To the above compound (B-12-c), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-12) was obtained in good yield by purification by column chromatography.

[0317] [Examples B13 to B16] (Synthesis of compounds (B-13) to (B-16)) Radiation-sensitive acid generators represented by the following formulas (B-13) to (B-16) were synthesized in the same manner as in Example B12, except that the raw materials and precursors were appropriately changed.

[0318]

[0319] [Example B17] (Synthesis of compound (B-17)) Compound (B-17) was synthesized according to the following synthesis scheme.

[0320]

[0321] Compound (B-17-a) and a mixture of acetonitrile and water (1:1 by mass) were added to a reaction vessel to make a 1 M solution. Then, 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added, and the mixture was reacted at 60°C for 3 hours. After extraction with acetonitrile and removal of the solvent by distillation, methanol was added to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (B-17-b) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0322] To the above compound (B-17-b), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass ratio) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-17) was obtained in good yield by purification by column chromatography.

[0323] [Example B18] (Synthesis of compound (B-18)) A radiation-sensitive acid generator represented by the following formula (B-18) was synthesized in the same manner as in Example B17, except that the raw materials and precursors were appropriately changed.

[0324]

[0325] [Example B19] (Synthesis of compound (B-19)) Compound (B-19) was synthesized according to the following synthesis scheme.

[0326]

[0327] Compound (B-19-a) and methanol were added to a reaction vessel to make a 0.5 M solution. 20.0 mmol of sulfur was added, and the mixture was heated and stirred at 60°C for 3 hours. Compound (B-19-b) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0328] To the above compound (B-19-b), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-19) was purified by column chromatography in good yield.

[0329] [Example B20] (Synthesis of compound (B-20)) Compound (B-20) was synthesized according to the following synthesis scheme.

[0330]

[0331] 20.0 mmol of compound (B-20-a) and 200 g of methanol were added to a reaction vessel to make a 0.1 M solution. Then, 20.0 mmol of sodium hydrogen sulfide was added, and the mixture was stirred at room temperature for 4 hours. Compound (B-20-b) was obtained by extraction with acetonitrile and removal of the solvent by distillation.

[0332] To the above compound (B-20-b), 20.0 mmol of triphenylsulfonium bromide was added, and a mixture of water and dichloromethane (1:3 by mass) was added to prepare a 0.5 M solution. After vigorous stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the compound (B-20) was obtained in good yield by purification by column chromatography.

[0333] [Examples B21 to B26] (Synthesis of compounds (B-21) to (B-26)) Radiation-sensitive acid generators represented by the following formulas (B-21) to (B-26) were synthesized in the same manner as in Example B20, except that the raw materials and precursors were appropriately changed.

[0334] [Radiation-sensitive acid generators other than (B-1) to (B-26)] Compounds (b-1) to (b-7): Compounds represented by the following formulas (b-1) to (b-7)

[0335]

[0336] [[D] Acid Diffusion Control Agents] Compounds (D-1) to (D-8): Compounds represented by the following formulas (D-1) to (D-9).

[0337]

[0338] [Solvents] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: Methyl 2-hydroxyisobutyrate E-4: Diacetone alcohol E-5: γ-Butyrolactone

[0339] [Preparation of positive-type radiation-sensitive polymer composition for ArF immersion exposure] [Example 1] A radiation-sensitive composition (J-1) was prepared by mixing 100 parts by mass of (A-1) as a polymer, 5.0 parts by mass (solids) of (F-1) as a high-fluorine-content polymer, 10.0 parts by mass of (B-1) as a radiation-sensitive acid generator, 4.0 parts by mass of (D-1) as an acid diffusion control agent, and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0340] [Examples 2-50 and Comparative Examples 1-5] Radiation-sensitive compositions (J-2) to (J-50) and (CJ-1) to (CJ-5) were prepared in the same manner as in Example 1, except that the components of the types and amounts shown in Tables 4-1 and 4-2 below were used.

[0341]

[0342]

[0343] <Formation of a resist pattern using a positive-type radiation-sensitive composition for ArF immersion lithography> An anti-reflective underlayer film formation composition (ARC66 from Brewer Sciences) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 100 nm. The positive-type radiation-sensitive composition for ArF lithography prepared above was applied to this anti-reflective underlayer film using the spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 90 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed to a 60 nm line-and-space mask pattern using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Dipole (σ = 0.9 / 0.7). After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (60 nm line-and-space pattern).

[0344] <Evaluation> The sensitivity and LWR of the resist patterns formed using the above ArF immersion exposure positive-type radiation-sensitive composition were evaluated according to the following method. The results are shown in Table 5 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The results are shown in Table 5 below.

[0345] [Sensitivity] In forming a resist pattern using the above ArF immersion lithography positive-type radiation-sensitive composition, the exposure amount used to form a 60 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２ The sensitivity was set to 30 mJ / cm². ２ The following conditions are considered "good": 30 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0346] [LWR] A 60 nm line-and-space resist pattern was formed by irradiating with the optimal exposure amount determined in the sensitivity evaluation above. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less line roughness and better performance. LWR performance was evaluated as "good" if it was 3.0 nm or less, and "poor" if it was greater than 3.0 nm.

[0347]

[0348] As is clear from the results in Table 5, the radiation-sensitive composition of the example showed good sensitivity and LWR when used in ArF immersion lithography, whereas the comparative example exhibited inferior characteristics compared to the example. Therefore, when the radiation-sensitive composition of the example is used in ArF immersion lithography, a resist pattern with optimal sensitivity and good LWR can be formed.

[0349] [Preparation of positive-type radiation-sensitive composition for extreme ultraviolet (EUV) exposure] [Example 51] A radiation-sensitive composition (J-51) was prepared by mixing 100 parts by mass of (A-12) as a polymer, 3.0 parts by mass (solids) of (F-5) as a high-fluorine-content polymer, 20.0 parts by mass of (B-3) as a radiation-sensitive acid generator, 10.0 parts by mass of (D-1) as an acid diffusion control agent, and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0350] [Examples 52-64 and Comparative Examples 6-7] Radiation-sensitive compositions (J-52) to (J-64) and (CJ-6) to (CJ-7) were prepared in the same manner as in Example 51, except that the components of the types and amounts shown in Table 6 below were used.

[0351]

[0352] <Formation of a resist pattern using a positive-type radiation-sensitive composition for EUV exposure> An anti-reflective underlayer film (ARC66 from Brewer Sciences) was applied to a 12-inch silicon wafer using a spin coater (CLEAN TRACK ACT12 from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form an anti-reflective underlayer film with an average thickness of 105 nm. The positive-type radiation-sensitive composition for EUV exposure prepared above was applied to this anti-reflective underlayer film using the spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 55 nm was formed by cooling at 23°C for 30 seconds. Next, the resist film was exposed using an EUV lithography system (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was alkaline developed using a 2.38 mass% TMAH aqueous solution as the alkaline developer, washed with water after development, and then dried to form a positive-type resist pattern (25 nm line and space pattern).

[0353] <Evaluation> The sensitivity and LWR of the resist patterns formed using the above-mentioned positive-type radiation-sensitive composition for EUV exposure were evaluated according to the following method. The results are shown in Table 7 below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns.

[0354] [Sensitivity] In forming a resist pattern using the above-mentioned positive-type radiation-sensitive composition for EUV exposure, the exposure amount used to form a 25 nm line-and-space pattern is defined as the optimal exposure amount, and this optimal exposure amount is defined as the sensitivity (mJ / cm²). ２The sensitivity was set to 40 mJ / cm². ２ The following conditions are considered "good": 40 mJ / cm² ２ If it exceeded this value, it was rated as "poor."

[0355] [LWR] The mask size was adjusted to form a 25 nm line-and-space pattern by irradiating with the optimal exposure amount determined in the sensitivity evaluation above, and a resist pattern was formed. The formed resist pattern was observed from the top of the pattern using the scanning electron microscope described above. The variation in line width was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements, and this 3-sigma value was defined as LWR (nm). A smaller LWR value indicates less jaggedness in the lines and a better result. An LWR of 4.0 nm or less was evaluated as "good," and an LWR greater than 4.0 nm was evaluated as "poor."

[0356]

[0357] [Preparation of a negative-type radiation-sensitive composition for ArF exposure, formation and evaluation of a resist pattern using this composition] [Example 65] A radiation-sensitive composition (J-65) was prepared by mixing 100 parts by mass of (A-1) as a polymer, 2.0 parts by mass (solids) of (F-3) as a high-fluorine-content polymer, 12.0 parts by mass of (B-1) as a radiation-sensitive acid generator, 10.0 parts by mass of (D-1) as an acid diffusion control agent, and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0358] On a 12-inch silicon wafer, a base layer anti-reflective coating composition ("ARC66" from Brewer Science) was applied using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a base layer anti-reflective coating with an average thickness of 100 nm. On this base layer anti-reflective coating, the ArF exposure negative-type radiation-sensitive composition (J-65) prepared above was applied using the same spin coater, and pre-bake (PB) was performed at 100°C for 60 seconds. Subsequently, a resist film with an average thickness of 90 nm was formed by cooling at 23°C for 30 seconds. Next, this resist film was exposed using an ArF excimer laser immersion lithography system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and Annular (σ = 0.8 / 0.6) through a mask pattern with 50 nm holes and a 100 nm pitch. After exposure, post-exposure baking (PEB) was performed at 100°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as the organic solvent developer and dried to form a negative-type resist pattern (a contact hole pattern with 50 nm holes and a 100 nm pitch).

[0359] The sensitivity of the resist pattern using the above-mentioned ArF exposure negative-type radiation-sensitive composition was evaluated in the same manner as the evaluation of the resist pattern using the above-mentioned ArF exposure positive-type radiation-sensitive composition. Furthermore, the CDU was evaluated according to the following method.

[0360] [CDU Performance] The optimal exposure dose determined in the sensitivity evaluation above was used to form 50 nm holes and 100 nm pitch contact holes. The formed resist pattern was observed from the top using the scanning electron microscope described above. The variation of the contact holes was measured at a total of 500 points, and the 3-sigma value was determined from the distribution of these measurements. This 3-sigma value was defined as the CDU (nm). A smaller CDU value indicates less roughness of the holes and better performance. A CDU of less than 3.5 nm was evaluated as "good," and a CDU of 3.5 nm or more was evaluated as "poor."

[0361] As a result, the radiation-sensitive composition of Example 65 showed good sensitivity and CDU even when a negative-type resist pattern was formed by ArF exposure.

[0362] [Preparation of a negative-type radiation-sensitive composition for EUV exposure, formation and evaluation of a resist pattern using this composition] [Example 66] A radiation-sensitive composition (J-66) was prepared by mixing 100 parts by mass of (A-15) as a polymer, 5.0 parts by mass (solids) of (F-5) as a high-fluorine-content polymer, 30.0 parts by mass of (B-3) as a radiation-sensitive acid generator, 10.0 parts by mass of (D-1) as an acid diffusion control agent, and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as a solvent, and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0363] On a 12-inch silicon wafer, a base layer anti-reflective coating composition ("ARC66" from Brewer Science) was applied using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a base layer anti-reflective coating with an average thickness of 105 nm. On this base layer anti-reflective coating, the prepared negative-type radiation-sensitive composition for EUV exposure (J-66) was applied using the same spin coater, and PB (plate blot) was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 55 nm was formed by cooling at 23°C for 30 seconds. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" from ASML) with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR15. After exposure, PEB was performed at 120°C for 60 seconds. Subsequently, the resist film was developed using n-butyl acetate as the organic solvent developer and dried to form a negative-type resist pattern (a contact hole pattern with 20 nm holes and a 40 nm pitch).

[0364] The resist pattern using the above-mentioned negative-type radiation-sensitive composition for EUV exposure was evaluated in the same manner as the resist pattern using the above-mentioned negative-type radiation-sensitive composition for ArF exposure. As a result, the radiation-sensitive composition of Example 66 showed good sensitivity and CDU even when a negative-type resist pattern was formed by EUV exposure.

[0365] The radiation-sensitive composition, pattern formation method, radiation-sensitive acid generator, and compound described above can form resist patterns with good sensitivity to exposure light and excellent LWR and CDU. Therefore, these can be suitably used in semiconductor device processing processes and the like, where further miniaturization is expected in the future.

Claims

1. A radiation-sensitive composition containing an onium salt having a partial structure represented by the following formula (i), a polymer having a structural unit (I) containing an acid dissociable group, and a solvent. (In formula (i), １ - X - is S - or O ２ X ３ and X １ - are each independently S or O. However, at least one selected from the group consisting of X ２ , X ３ contains S. ＋ Z is an organic cation. * is a bond with other atoms in the above onium salt, respectively.) 2. The radiation-sensitive composition according to claim 1, wherein the onium salt is a compound represented by the following formula (A1) or (A2). (In formula (A1), R １ n, which has 1 to 40 carbon atoms. １ It is a valence organic group. Z １ ＋ n is an organic cation. １ n is an integer between 1 and 3. １ If there are two or more X １ - , X ２ , X ３ and Z １ ＋ These are either identical or different from one another. １ - , X ２ and X ３ This is equivalent to equation (i) above. (In formula (A2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - , X ２ and X ３ This is equivalent to equation (i) above.

3. In the above formula (A1), n １ The radiation-sensitive composition according to claim 2, wherein is 1.

4. In the above formula (A1), R １ The radiation-sensitive composition according to claim 2, wherein is comprised of at least one structure selected from the group consisting of a cyclic structure, -CO-, -O-, and -NR'-, and R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

5. In the above formula (A1), Z １ ＋ The radiation-sensitive composition according to claim 2, wherein is a sulfonium cation or an iodonium cation.

6. In the above formula (A2), Z ２ ＋ The radiation-sensitive composition according to claim 2, wherein is a monovalent sulfonium cation or iodonium cation.

7. In the above formula (A2), Z ２ ＋ L is a monovalent triarylsulfonium cation or diaryliodonium cation. Ａ２ The radiation-sensitive composition according to claim 2, wherein is a divalent linking group containing a single bond or an ester bond.

8. X １ - is, S - X ２ and X ３ The radiation-sensitive composition according to any one of claims 1 to 7, wherein all of the elements are O.

9. The radiation-sensitive composition according to any one of claims 1 to 7, wherein the content of the onium salt is 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the polymer.

10. The radioactive composition according to any one of claims 1 to 7, wherein the above-mentioned structural unit (I) having an acid-dissociable group is represented by the following formula (3). (In formula (3), R １７ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these is independently either a monovalent substituted or unsubstituted linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ These elements combine with each other to form a divalent alicyclic group with 3 to 20 carbon atoms, which is then bonded to the carbon atoms. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ Represents COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

11. The radiation-sensitive composition according to any one of claims 1 to 7, further comprising an acid diffusion control agent.

12. A pattern forming method comprising the steps of: applying a radiation-sensitive composition according to any one of claims 1 to 7 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

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

14. A radiation-sensitive acid generator having a substructure represented by the following formula (i). (In formula (i), X １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from Z. ＋ ( is an organic cation. * represents the bonding site with other atoms in the above-mentioned radiation-sensitive acid generator.) 15. A compound represented by the following formula (A1-1). (In formula (A1-1), １ n １ is an integer of 1 to 3. When n １ - is 2 or more, a plurality of X ２ X ３ and Z １ ＋ are each the same as or different from each other. R ｆ is an n-valent organic group having 1 to 40 carbon atoms. However, when n １ is 1, R １ is a fluorinated alkyl group other than a perfluoroalkyl group. X ｆ １ - is S - or O - X ２ and X ３ are each independently S or O. However, X １ - ２ X ３ and at least one selected from the group consisting of X １ ＋ contains S. Z １ is an organic cation. However, when n １ is 1, Z ＋ is a radiation-sensitive onium cation. )​ 16. A compound represented by the following formula (A2). (In formula (A2), Z ２ ＋ L is a monovalent organic cation. Ａ２ X is a single bond or a divalent linking group. １ - is, S - or O - That is. X ２ and X ３ Each is independently either S or O. However, X １ - , X ２ , and X ３ S is included in at least one of the groups selected from the group consisting of the following.

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