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

Abstract

Provided are a radiation-sensitive composition and the like that make it possible to achieve excellent sensitivity, excellent CDU, and an excellent minimum CD during pattern formation. A radiation-sensitive composition according to the present invention contains: a polymer that includes a structural unit (I) that has an acid-dissociable group; and a solvent. At least: the radiation-sensitive composition contains an onium salt compound (1) that includes a partial structure (a) represented by formula (a) and produces an acid when exposed to light; or the polymer includes a partial structure (a) represented by formula (a). (In the formula, R1 is an acid dissociable group, L1 is a divalent linear organic group, Ar is a C3–20 aromatic ring, L2 is a single bond or a (y+2)-valent organic group, W- is -SO3 - or -COO-, Z+ is a monovalent onium cation, n1+n2≥1, x and y are 0 or 1, and when L2 is a single bond, y is 0, and, in the partial structure (a) of the polymer, x+y is 1 or 2.)

Description

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

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

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

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

[0004] As pattern miniaturization progresses, development is also underway on acid generators, which are components of resist materials, from the perspective of improving resist performance (Japanese Patent Publication No. 2023-135555).

[0005] Japanese Patent Publication No. 2023-135555

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance equivalent to or better than conventional resists in terms of sensitivity during pattern formation, critical dimension uniformity (CDU), which is an indicator of the uniformity of line width and hole diameter, and Min CD, which is an indicator of resolution in low exposure areas.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, an onium salt compound, and a polymer that exhibit excellent sensitivity, CDU, and MinCD during pattern formation.

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

[0009] In one embodiment, the present invention provides a radiation-sensitive composition containing a polymer containing a structural unit (I) having an acid-dissociable group and a solvent, wherein at least the radiation-sensitive composition has a partial structure (a) represented by the following formula (a) and contains an onium salt compound (1) that generates an acid upon exposure, or the polymer has a partial structure (a) represented by the following formula (a). The present invention relates to a radiation-sensitive composition. (In formula (a), ＋ R is an acid-dissociable group. When a plurality of R １ are present, the plurality of R １ are the same as or different from each other. L １ is a divalent chain organic group. When a plurality of L １ are present, the plurality of L １ are the same as or different from each other. Ar is an (m1 + n1 + x + 1)-valent aromatic ring having 3 to 20 carbon atoms. L ２ is a single bond or a (y + 2)-valent organic group. W - is -SO ３ - or -COO - Z is a monovalent onium cation. m1 is an integer of 1 to 3. n1 and n2 are each independently an integer of 0 to 4. When a plurality of n2 are present, the plurality of n2 are the same as or different from each other. However, n1 + n2 ≥ 1. x and y are each independently 0 or 1. However, when L ２ is a single bond, y is 0, and in the partial structure (a) in the polymer, x + y is 1 or 2. * is a bond with another structure in the corresponding component.)

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

[0011] ​​The radiation-sensitive composition contains at least one polymer or onium salt compound into which a substructure (a) having an iodine group is introduced. Since the iodine group has high absorption of radiation such as EUV at a wavelength of 13.5 nm, this increases the efficiency of secondary electron generation, resulting in a highly sensitive resist film, as well as improved acid generation efficiency and good CDU. Furthermore, since the main skeleton of substructure (a) has an acid-dissociable group via a chain structure, development defects are suppressed along with hydrophobicity, particularly in onium salt compounds, and excellent development contrast can be achieved. It is presumed that the above-mentioned unique performance can be achieved through the combined effects of these factors.

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

[0013] In this pattern formation method, since the above-mentioned radiation-sensitive composition, which has excellent sensitivity, CDU, and Min CD, is used during pattern formation, high-quality resist patterns can be efficiently formed.

[0014] In another embodiment, the present invention relates to an onium salt compound represented by the following formula (ac) and which generates acid upon exposure. (In formula (ac), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + 1) valency. L ２ This is a single bond or a divalent organic group. - is, -SO ３ - or -COO - That is. Z ＋m1 is a monovalent onium cation. n1 is an integer between 1 and 3. n1 and n2 are independent integers between 0 and 4. If there are multiple n2s, they are either identical or distinct from one another. (However, n1 + n2 ≥ 1.)

[0015] Because the onium salt compound has a specific substructure (a), it is suitable as a component of radiation-sensitive compositions where sensitivity, CDU, and Min CD are required.

[0016] In another embodiment, the present invention relates to a polymer comprising a structural unit (I) having an acid-dissociable group and having a substructure (a) represented by the following formula (a). (In formula (a), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + x + 1) valency. L ２ This is a single bond or an organic group with (y+2) valency. - is, -SO ３ - or -COO - That is. Z ＋ m1 is a monovalent onium cation. m1 is an integer from 1 to 3. n1 and n2 are each independent integers from 0 to 4. If there are multiple n2s, they are either identical or distinct from one another. However, n1 + n2 ≥ 1. x and y are each independent 0 or 1. However, x + y is 1. L ２ If it is a single bond, y is 0. (* represents a bond with other structures in the polymer described above.)

[0017] Because the polymer has a specific substructure (a), it is suitable as a component of radiation-sensitive compositions where sensitivity, CDU, and Min CD are required.

[0018] 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.

[0019] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer (hereinafter also referred to as "base polymer") having an acid-dissociable structural unit (I) and a solvent. Furthermore, the radiation-sensitive composition satisfies at least one of condition (1) or condition (2). The radiation-sensitive composition may satisfy both condition (1) and condition (2). Condition (1): The radiation-sensitive composition contains an onium salt compound (1) containing the above-mentioned substructure (a). Condition (2): The polymer has the above-mentioned substructure (a).

[0020] The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0021] The substructure (a) will be described by explaining how it is applied to each component of the radiation-sensitive composition.

[0022] <Onium Salt Compound (1)> Onium salt compound (1) is a compound having the above substructure (a) and generating acid upon exposure. Depending on the structure of the organic acid anion in the above substructure (a), onium salt compound (1) functions as a radiation-sensitive acid generator or an acid diffusion controller. A radiation-sensitive acid generator is a compound that generates an acid that dissociates the above acid-dissociable group upon exposure. An acid diffusion controller is a compound that generates an acid that does not dissociate the above acid-dissociable group upon exposure, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in the unexposed area. The acid generated from the acid diffusion controller can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the radiation-sensitive acid generator. Whether onium salt compound (1) functions as a radiation-sensitive acid generator or an acid diffusion controller depends on the energy required for the dissociation of the acid-dissociable group of the base polymer, and the acidity of the acid generated upon exposure, etc. First, we will explain the structure common to each function. Then, regarding the functions, we will refer to the case where onium salt compound (1) functions as a radiation-sensitive acid generator as onium salt compound (1a) and the case where onium salt compound (1) functions as an acid diffusion control agent as onium salt compound (1b), and will describe them later.

[0023] The onium salt compound (1) is preferably a compound represented by the following formula (ac). The onium salt compound (1) corresponds to the case where both x and y are 0 in the above formula (a). The structure in the following formula (ac) that is common with the above formula (a) can also be applied to the explanation of the above formula (a). (In formula (ac), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (n1 + n2 + 1) valency. L ２ This is a single bond or a divalent organic group. - is, -SO ３ - or -COO- That is. Z ＋ m1 is a monovalent onium cation. n1 is an integer between 1 and 3. n1 and n2 are independent integers between 0 and 4. If there are multiple n2s, they are either identical or distinct from one another. (However, n1 + n2 ≥ 1.)

[0024] R １ The acid-dissociable group represented by refers to a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, sulfo group, etc., which dissociates upon the action of an acid. The acid generated by exposure from the onium salt compound (1) as a radiation-sensitive acid generator or from the partial structure (a) as a radiation-sensitive acid-generating structure in the polymer is R １ The acid-dissociable group represented by is dissociated, generating carboxyl groups and the like. This creates a dissolution contrast of the onium salt compound (1) between the exposed and unexposed areas of the resist film, allowing the desired resist performance to be achieved.

[0025] The structure of the acid-dissociable group is not particularly limited, and examples include a tertiary carboxylic acid ester structure, a structure in which an aromatic group and an aliphatic hydrocarbon group are bonded to a secondary carbon atom in a secondary carboxylic acid ester structure, a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary carbon atom, a structure having an acetal bond, and a structure in which an unsaturated bond is present between the β-carbon and γ-carbon of the oxygen atom in one of the two aliphatic groups (including alicyclic groups containing a secondary carbon atom) bonded to the secondary carbon atom of a secondary carboxylic acid ester.

[0026] In the above formula (ac), R １ It is preferable that the acid-dissociable group is represented by the following formula (β1). (In formula (β1), R １８ R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０Each of these independently represents a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a substituted or unsubstituted divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. * represents L in formula (a) above. １ This is a combination of the above. However, if n2 in equation (a) is 1 or greater, R １ The iodine atom bonded to it is R １８ , R １９ and R ２０ (Combines with at least one selected from the group consisting of the following.)

[0027] R １８ Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, or combinations thereof.

[0028] R １８ ~R ２０ Examples of monovalent chain hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups; alkenyl groups such as ethenyl, propenyl, and butenyl groups; and alkynyl groups such as ethynyl, propynyl, and butynyl groups.

[0029] R １８ ~R ２０ Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopentyl and cyclohexyl groups; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl groups; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, and tricyclodecyl groups; and bridged ring unsaturated hydrocarbon groups such as norbornyl and tricyclodecenyl groups.

[0030] R １８Examples of monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0031] R １９ and R ２０ When these are combined with each other, the divalent alicyclic group having 3 to 20 carbon atoms, which is formed together with the carbon atoms to which they are bonded, is R １８ A group obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, as shown above, can be suitably adopted.

[0032] R １８ ~R ２０ Examples of substituents that may be present include halogen atoms such as fluorine, chlorine, bromine, and iodine; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino 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; oxo groups (=O), etc.

[0033] Examples of alkoxy groups as substituents include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy groups. Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl groups. Examples of alkoxycarbonyloxy groups include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy groups. Examples of acyl groups include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl groups. Examples of acyloxy groups include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy, propionyloxy, benzoyloxy, and acryloyloxy groups.

[0034] In the above formula (ac), if n2 is 1 or greater, the iodine atom is R １ It is preferable that it is bonded to the aromatic hydrocarbon group.

[0035] R １ Examples of acid-dissociable groups represented by the following formulas (β1-1) to (β1-8) include structures represented by the following formulas.

[0036] In the above formulas (β1-1) to (β1-8), R １８ ~R ２０ This is equivalent to the above formula (β1). 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 one another.

[0037] i and j are preferably 1. １８ Preferred groups include methyl, ethyl, isopropyl, t-butyl, cyclopentyl, ethenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. In the above formula (ac), if n2 is 1 or more, R １ is one of the above formulas (β1-1) to (β1-3) and R １８ For example, an iodophenyl group is used, or R １ The above formula (β1-4) is given and R Ｌ１１ It is preferable to use iodine atoms as such.

[0038] In the above formula (ac), m1 is preferably 1 or 2.

[0039] In the above formula (ac), n2 is preferably an integer between 0 and 3, more preferably an integer between 0 and 2, and even more preferably 0 or 1.

[0040] In the above formula (ac), L１ The divalent chain organic group represented by [the formula] is not particularly limited as long as it is a divalent chain group having at least one carbon atom. L １ is preferably a substituted or unsubstituted divalent chain hydrocarbon group having 1 to 10 carbon atoms, or a divalent group combined with at least one selected from the group consisting of -CO-, -CS-, -NR'-, -O-, -S- and -SO ２ -. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0041] L １ As the divalent chain hydrocarbon group having 1 to 10 carbon atoms in L, a group obtained by removing one hydrogen atom from the group corresponding to 1 to 10 carbon atoms among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms shown in R of the above formula (β1) can be preferably employed. Among them, a group obtained by removing one hydrogen atom from a monovalent chain hydrocarbon group having 1 to 4 carbon atoms is preferable. Therefore, L １８ is preferably a C1-C4 alkanediyl group, or a divalent group combined with at least one selected from the group consisting of -CO-, -CS-, -NR'-, -O-, -S- and -SO １ -. ２ When L has a substituent, as the substituent, a substituent that R of the above formula (β1) can have can be preferably employed.

[0042] L １ is preferably a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, or a divalent group combined with at least one selected from the group consisting of -CO-, -NR'- and -O- of the alkylene group, more preferably a divalent group combined with C1-C5 alkylene and -COO-, -CONR'- or -O-, and even more preferably a divalent group combined with a methylene group or an ethylene group and -CONR'- or -O-. １８

[0043] Among them, L １ is preferably a substituted or unsubstituted alkylene group having 1 to 5 carbon atoms, or a divalent group combined with at least one selected from the group consisting of -CO-, -NR'- and -O- of the alkylene group, more preferably a divalent group combined with C1-C5 alkylene and -COO-, -CONR'- or -O-, and even more preferably a divalent group combined with a methylene group or an ethylene group and -CONR'- or -O-.

[0044] ​The (m1 + n1 + x + 1)-valent aromatic ring represented by Ar, having 3 to 20 carbon atoms, can preferably adopt a structure obtained by removing (m1 + n1 + x + 1) hydrogen atoms from an aromatic ring having 3 to 20 carbon atoms. The aromatic ring having 3 to 20 carbon atoms is not particularly limited as long as it has an aromatic ring structure. Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and aromatic heterocyclic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, dibenzofuran ring, or combinations thereof. Among them, the benzene ring is preferable as the aromatic ring.

[0045] The aromatic ring of Ar may have a substituent. As the substituent, a substituent other than an iodine atom among the substituents that R １８ in the above formula (β1) can have can be preferably adopted.

[0046] n1 is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 1 or 2.

[0047] L ２ Examples of the divalent organic group represented by include a group obtained by removing one hydrogen atom from a monovalent organic group having 1 to 40 carbon atoms. Examples of the monovalent organic group having 1 to 40 carbon atoms include a monovalent hydrocarbon group having 1 to 40 carbon atoms, a group (α) having a divalent heteroatom-containing group between carbon-carbon bonds of the hydrocarbon group or at the terminal of the hydrocarbon group, a group (β) obtained by substituting part or all of the hydrogen atoms of the hydrocarbon group or the group (α) with a monovalent heteroatom-containing group, or combinations thereof.

[0048] As the monovalent hydrocarbon group having 1 to 40 carbon atoms, a group obtained by expanding the monovalent hydrocarbon group having 1 to 20 carbon atoms shown in R １８ in the above formula (β1) to 1 to 40 carbon atoms can be preferably adopted.

[0049] Examples of heteroatoms that constitute the monovalent heteroatom-containing groups and divalent heteroatom-containing groups mentioned above include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0050] Examples of the monovalent heteroatom-containing groups mentioned above include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, halogen atoms, and the like.

[0051] Examples of the above-mentioned divalent heteroatom-containing groups include -CO-, -C(=O)O-, -CS-, -NR'-, -O-, -S-, -SO-, and -SO ２ - or combinations thereof are examples. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0052] L ２ The divalent organic group represented by is preferably a divalent hydrocarbon group which is an alkanediyl group, a cycloalkanediyl group or an arenediyl group, the above-mentioned divalent heteroatom-containing group, a group in which the methylene group or methine group of the above-mentioned divalent hydrocarbon group is substituted with the above-mentioned divalent heteroatom-containing group, or a group which is a combination thereof. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups are R of the above formula (β1). １８ It may be substituted with substituents that it may have.

[0053] The alkanediyl group described above is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0054] Examples of the above-mentioned cycloalkanediyl groups include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups; and polycyclic cycloalkanediyl groups such as norbornanediyl, adamantanediyl, and tricyclododecanediyl groups. A cycloalkanediyl group having 5 to 12 carbon atoms is preferred.

[0055] Groups having an aliphatic heterocyclic structure in which the methylene group of the above-mentioned cycloalkanediyl group is replaced with the above-mentioned divalent heteroatom-containing group are also preferred. Examples of aliphatic heterocyclic structures include cyclic acetal structures, lactone structures, sultone structures, cyclic carbonate structures, cyclic ether structures, and lactam structures.

[0056] Examples of the above-mentioned arenediyl group include a benzenediyl group, a naphthalenediyl group, and anthracenediyl group. A preferred arenediyl group is one having 6 to 10 carbon atoms.

[0057] Z ＋ Examples of monovalent onium cations represented by include radiodegradable onium cations. Examples of radiodegradable onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0058] Z in the above formula (ac) ＋ Preferably, it is a sulfonium cation represented by the following formula (Q-1).

[0059]

[0060] In the above formula (Q-1), Ra1 and Ra2 each independently represent substituents. n1 represents an integer from 0 to 5, and if n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer from 0 to 5, and if n2 is 2 or greater, multiple Ra2s may be the same or different. Ra3 represents a substituent. n3 represents an integer from 0 to 5, and if n3 is 2 or greater, multiple Ra3s may be the same or different. Ra1 and Ra2 may be linked to each other to form a ring. If n1 is 2 or greater, multiple Ra1s may be linked to each other to form a ring. If n2 is 2 or greater, multiple Ra2s may be linked to each other to form a ring.

[0061] Preferred substituents represented by Ra1, Ra2, and Ra3 are alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, alkylsulfonyl groups, hydroxyl groups, halogen atoms, and halogenated hydrocarbon groups.

[0062] The alkyl groups Ra1 and Ra2 may be linear or branched alkyl groups. Preferably, these alkyl groups have 1 to 10 carbon atoms, and examples include methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl groups. Of these, methyl, ethyl, n-butyl, and t-butyl groups are particularly preferred.

[0063] Examples of cycloalkyl groups for Ra1 and Ra2 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0064] Examples of the alkyl groups of the alkoxy groups of Ra1 and Ra2 include those previously listed as alkyl groups of Ra1 and Ra2. Methoxy, ethoxy, n-propoxy, and n-butoxy groups are particularly preferred as alkoxy groups.

[0065] Examples of the cycloalkyl group portions of Ra1 and Ra2 include those previously listed as cycloalkyl groups of Ra1 and Ra2. Cyclopentyloxy and cyclohexyloxy groups are particularly preferred as these cycloalkyl groups.

[0066] Examples of the alkoxy carbonyl groups of Ra1 and Ra2 include those previously listed as alkoxy groups of Ra1 and Ra2. Methoxycarbonyl groups, ethoxycarbonyl groups, and n-butoxycarbonyl groups are particularly preferred as alkoxycarbonyl groups.

[0067] Examples of the alkyl group portion of the alkylsulfonyl groups of Ra1 and Ra2 include those previously listed as alkyl groups of Ra1 and Ra2. Similarly, examples of the cycloalkyl group portion of the cycloalkylsulfonyl groups of Ra1 and Ra2 include those previously listed as cycloalkyl groups of Ra1 and Ra2. Among these alkylsulfonyl groups or cycloalkylsulfonyl groups, methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups are particularly preferred.

[0068] Each of the Ra1 and Ra2 groups may have further substituents. Examples of such substituents include halogen atoms such as fluorine atoms (preferably fluorine atoms), hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkoxy groups, cycloalkyloxy groups, alkoxyalkyl groups, cycloalkyloxyalkyl groups, alkoxycarbonyl groups, cycloalkyloxycarbonyl groups, alkoxycarbonyloxy groups, and cycloalkyloxycarbonyloxy groups.

[0069] Examples of halogen atoms for Ra1 and Ra2 include fluorine, chlorine, bromine, and iodine atoms, with fluorine and iodine atoms being preferred.

[0070] As the halogenated hydrocarbon groups of Ra1 and Ra2, halogenated alkyl groups are preferred. The alkyl groups and halogen atoms constituting the halogenated alkyl groups are the same as those described above. Among these, fluorinated alkyl groups are preferred, and CF ３ This is preferable.

[0071] As described above, Ra1 and Ra2 may be linked to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are linked to each other to form a single bond or a divalent linking group. Examples of divalent linking groups include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, alkylene group, cycloalkylene group, alkenylene group, or combination of two or more of these, preferably with a total carbon number of 20 or less. When Ra1 and Ra2 are linked to each other to form a ring, Ra1 and Ra2 are linked to each other as -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ - or single bond formation is preferable. Among these, -O-, -S-, or single bond formation is more preferable, and single bond formation is particularly preferable. Furthermore, when n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring. An example of such a configuration is one in which two Ra1s are linked to each other and form a naphthalene ring together with the benzene ring to which they are linked.

[0072] Ra3 is preferably a fluorine atom, a group having one or more fluorine atoms, or an iodine atom. Examples of groups having fluorine atoms include alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, and alkylsulfonyl groups, which are substituted with fluorine atoms as Ra1 and Ra2. Among these, fluorinated alkyl groups are particularly preferred, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ ,CH ２ CF ３ ,CH ２ CH ２CF ３ ,CH ２ C ２ F ５ ,CH ２ CH ２ C ２ F ５ ,CH ２ C ３ F ７ ,CH ２ CH ２ C ３ F ７ ,CH ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ The following can be more preferably listed: CF ３ The following can be particularly preferred.

[0073] Ra3 is a fluorine atom, an iodine atom, or CF ３ It is preferable that it be a fluorine atom or an iodine atom.

[0074] n1 and n2 are each independently preferably integers between 0 and 3, and preferably integers between 0 and 2.

[0075] n3 is preferably an integer between 1 and 3, and more preferably 1 or 2.

[0076] (n1 + n2 + n3) is preferably an integer from 1 to 15, more preferably an integer from 1 to 9, even more preferably an integer from 2 to 6, and particularly preferably an integer from 3 to 6. When (n1 + n2 + n3) is 1, n3 = 1 and Ra3 is a fluorine atom, an iodine atom, or CF ３ It is preferable that (n1 + n2 + n3) is 2, then n1 = n3 = 1 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combinations are as follows, and n3=2 and Ra3 is a fluorine atom, an iodine atom or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 3, n1 = n2 = n3 = 1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３The following combinations are preferred. When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 5, n1 = n2 = 1 and n3 = 3, and Ra1 to Ra3 each independently contain a fluorine atom, an iodine atom, or CF ３ The combination is such that n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combinations are such that n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ The following combinations are preferred. When (n1 + n2 + n3) is 6, n1 = n2 = n3 = 2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ The combination is preferable.

[0077] Specific examples of sulfonium cations represented by the above formula (Q-1) include the following. The fluorine and iodine atoms in the following sulfonium cations are hydrogen atoms and R in the above formula (β1). １８ It may be substituted with substituents that it may have.

[0078]

[0079]

[0080]

[0081]

[0082] The above monovalent onium cation may be a substituted or unsubstituted diaryliodonium cation. As the aryl group, the aromatic ring in Ar of formula (ac) above can be suitably used. A phenyl group is preferred as the aryl group. If the aryl group has a substituent, the substituent in formula (β1) above is R. １８ The substituents that can be present can be suitably adopted. The aryl group preferably has one or more fluorine or iodine atoms.

[0083] Specific examples of such iodonium cations include the following:

[0084]

[0085] (Onium salt compound (1a)) Onium salt compound (1a) is a compound that functions as a radiation-sensitive acid generator. In this case, in the above formula (ac), W - ha-SO ３ - And, -SO ３ - It is preferable that an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom. Examples of electron-withdrawing groups include fluorine atoms, fluorinated hydrocarbon groups, nitro groups, and cyano groups. As for fluorinated hydrocarbon groups, perfluoroalkyl groups having 1 to 5 carbon atoms are preferred, and trifluoromethyl groups are more preferred. The above formula (ac) L ２ in -SO ３ - It is preferable that an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom.

[0086] Examples of organic acid anions for the onium salt compound (1a) include structures represented by the following formulas (1a-1-1) to (1a-1-20).

[0087]

[0088]

[0089]

[0090] The above onium salt compound (1a) can be obtained by arbitrarily combining the organic acid anion and the onium cation (neither of which are limited to specific examples) described above. Examples of the above onium salt compound (1a) include compounds represented by the following formulas (1a-1) to (1a-20).

[0091]

[0092]

[0093]

[0094] If the composition contains an onium salt compound (1a), the lower limit of the onium salt compound (1a) content (total in the case of multiple types) is preferably 1 part by mass, more preferably 10 parts by mass, and still more preferably 25 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the above content is preferably 80 parts by mass, more preferably 60 parts by mass, and still more preferably 40 parts by mass. This makes it possible to exhibit the excellent resist performance described above.

[0095] These onium salt compounds (1a) may be used alone or in combination of two or more. The composition may also contain other known radiation-sensitive acid generators, as long as they do not impair the effects of the present invention.

[0096] (Synthesis method for onium salt compound (1a)) The synthesis method for onium salt compound (1a) is not particularly limited, and known methods can be employed. Typically, as shown in the scheme below, L in the main skeleton of onium salt compound (1a) １ Ya L ２ It can be synthesized by reactions that give ether bonds, acetal bonds, ester bonds, amide bonds, etc. in the above formula (ac). In the scheme below, W in formula (ac) above - is SO ３ - Let's explain using the example where m1 is 1, n1 is 1, and n2 is 0.

[0097] (In the scheme, R １ , L １ Ar, L ２ and Z ＋ This is equivalent to the above formula (ac). L １１ , L ２２ and L ２３ Each of these is an independent divalent linking group. １１ (Cy is a halogen atom.)

[0098] In the scheme shown in formula (aa1) above, an onium salt compound (1a) is obtained by forming an ether bond through a nucleophilic reaction between a halide having an acid-dissociable group and an onium salt having a phenolic hydroxyl group and an iodine group. In the scheme shown in formula (aa2) above, an onium salt compound (1a) is obtained by forming a cyclic acetal bond through a nucleophilic reaction between an aldehyde having an acid-dissociable group and an iodine group and an onium salt having a dihydroxy structure. In the scheme shown in formula (aa3) above, an onium salt compound (1a) is obtained by forming an ester bond through a dehydration condensation reaction between a phenol derivative having an acid-dissociable group and an iodine group and an onium salt having a carboxyl group. Other structures can also be synthesized by appropriately changing the starting materials and reaction substrates.

[0099] (Onium salt compound (1b)) Onium salt compound (1b) is a compound that functions as an acid diffusion control agent. In this case, in formula (ac) above, W - is, -SO ３ - or -COO - (However, W - ga-SO ３ - If so, -SO ３ - It is preferable that no electron-withdrawing groups are bonded to either the α- or β- carbon atoms of the sulfur atom, and -COO - It is even more preferable that W in formula (ac) above - The other structures are common to the onium salt compound (1a), however, in the above formula (ac), L ２ It is either a single bond or W - It is preferable that the group is a divalent organic group having an aromatic ring on its side. The aromatic ring in Ar of the above formula (ac) can be suitably adopted.

[0100] Examples of organic acid anions for the onium salt compound (1b) include structures represented by the following formulas (1b-1-1) to (1b-1-16).

[0101]

[0102]

[0103]

[0104] The above onium salt compound (1b) can be obtained by arbitrarily combining the organic acid anion and the onium cation described above (neither of which is limited to specific examples). Examples of the above onium salt compound (1b) include compounds represented by the following formulas (1b-1) to (1b-16).

[0105]

[0106]

[0107]

[0108] If the composition contains an onium salt compound (1b), the lower limit of the onium salt compound (1b) content (total if there are multiple types) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total amount of the onium salt compound (1a) as a radiation-sensitive acid generator and the monomers that give structural units having a radiation-sensitive acid-generating structure in the base polymer (if both are included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. This allows the composition to exhibit the excellent resist performance described above.

[0109] These onium salt compounds (1b) may be used alone or in combination of two or more. The composition may also contain other known acid diffusion control agents, as long as they do not impair the effects of the present invention.

[0110] (Synthesis Method for Onium Salt Compound (1b)) The synthesis method for onium salt compound (1b) is not particularly limited, and known salt exchange methods can be employed. Typically, it can be synthesized by salt exchange between the target carboxylic acid anion precursor and a compound having an onium cation structure, as shown in the scheme below. In the scheme below, W in formula (ac) above is used. - COO - Let's explain using the example where m1 is 1, n1 is 1, and n2 is 0.

[0111] (In the scheme, R １ , L １ Ar, L ２ and Z ＋ This is equivalent to the above formula (ac). X ２２ - (This is a halide ion.)

[0112] In the scheme shown above, an onium salt compound (1b) is obtained by a salt exchange reaction between a carboxylic acid having an acid-dissociable group and an iodine group and a halide of an onium cation. Other structures can also be synthesized by appropriately changing the starting materials and reaction substrates.

[0113] <Polymer> The polymer (i.e., the base polymer) is an aggregate of polymerization chains containing structural unit (I) having an acid-dissociable group. The radiation-sensitive composition exhibits excellent pattern-forming properties because the base polymer contains structural unit (I). Furthermore, the base polymer may have the above-mentioned substructure (a). When the base polymer has the above-mentioned substructure (a), it is preferable that the base polymer has the substructure (a) incorporated into the structural unit. The structural unit having substructure (a) may be structural unit (II) or (III) depending on the function of substructure (a). The base polymer may also contain structural units other than structural units (I) to (III).

[0114] (Structural Unit (I)) Structural unit (I) is a structural unit having an acid-dissociable group. The acid-dissociable group is R of the above formula (ac). １ An acid-dissociable group represented by can be suitably adopted.

[0115] The above acid-dissociable group preferably contains an iodine group, and more preferably contains an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms of the aromatic ring are replaced by iodine groups. As the aromatic ring in the iodine group-containing aromatic ring structure, the aromatic ring in Ar of the above formula (ac) can be suitably adopted. The number of iodine atoms in the above iodine group-containing aromatic ring structure is not particularly limited, but it is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2. This allows for good sensitivity and suppression of development defects.

[0116] As structural unit (I), from the viewpoint of improving the pattern-forming properties of the above-mentioned radiation-sensitive composition, a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0117] (In formula (1), R α L is a hydrogen atom, a fluorine atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. α R is a divalent linking group. １Ａ and R １Ｂ Each of these independently represents a hydrogen atom, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, or a monovalent 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. However, R １Ａ and R １Ｂ It is not possible for both to be hydrogen atoms. １ａ This is an aromatic ring with 5 to 20 members and a (p+q+1) valency. １０１ R is a nitro group, cyano group, hydroxyl group, alkoxy group, or amino group. １０１ If multiple R １０１ ma and mb are either identical or different. ma and mb are independently either 0 or 1. However, when ma is 1, mb is also 1. p is an integer between 0 and 3. q is an integer between 0 and 3. However, p + q is less than or equal to 5.

[0118] R αExamples of C1-C6 alkyl groups represented by this formula include linear or branched alkyl groups having C1-C6, such as methyl, ethyl, and propyl groups.

[0119] R α When an alkyl group having 1 to 6 carbon atoms represented by has substituents, the substituent is R of the above formula (β1). １８ The substituents that it may have can be suitably adopted.

[0120] L α Examples of divalent linking groups represented by include divalent hydrocarbon groups such as alkanediyl groups, cycloalkanediyl groups, alkenediyl groups, or arenediyl groups; divalent heteroatom-containing groups; groups in which the divalent heteroatom-containing group is incorporated between the carbon-carbon bonds of the divalent hydrocarbon group; or groups combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of divalent heteroatom-containing groups include -CO-, -CS-, -O-, -S-, and -SO ２ -, -NR'-, or a combination of two or more of these groups. Some or all of the hydrogen atoms in these groups are Ar of formula (A1) above. １ The aromatic ring in may be substituted with substituents that it may have.

[0121] The above alkanediyl group, cycloalkanediyl group, arenediyl group and divalent heteroatom-containing group are L of the above formula (ac). ２ In the divalent organic group represented by [the formula], the corresponding groups shown can be suitably adopted.

[0122] Examples of the alkenediyl group mentioned above include ethendiyl group, propenediyl group, and butenediyl group. A preferred alkenediyl group is one having 2 to 6 carbon atoms.

[0123] L α The divalent linking group represented by is preferably an alkanediyl group or an arenediyl group, more preferably an alkanediyl group having 1 to 4 carbon atoms or an arenediyl group having 6 to 10 carbon atoms, and even more preferably a methanediyl group or a benzenediyl group.

[0124] R１Ａ and R １Ｂ As a monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the above formula (β1), R １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, groups corresponding to 1 to 10 carbon atoms can be suitably adopted.

[0125] R １Ａ and R １Ｂ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (β1), R １８ The above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0126] R １Ａ and R １Ｂ As a divalent alicyclic group having 3 to 20 carbon atoms that is formed when these are combined with each other and bonded together with the carbon atoms, a group obtained by removing one hydrogen atom from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0127] R １Ａ and R １Ｂ Examples include monovalent chain hydrocarbon groups having 1 to 10 carbon atoms, or R １Ａ and R １Ｂ Divalent alicyclic groups having 3 to 20 carbon atoms are preferred, formed by combining these groups with the carbon atoms to which they are bonded; monovalent linear hydrocarbon groups having 1 to 10 carbon atoms or divalent alicyclic groups having 5 to 10 carbon atoms are more preferred; and methyl groups, ethyl groups, cyclopentanediyl groups, and cyclohexanediyl groups are even more preferred.

[0128] Ar １ａ As the aromatic ring in the above formula (ac), the aromatic ring in Ar can be suitably adopted. In particular, Ar １ａ The aromatic ring in is preferably a benzene ring, a thiophene ring, or a furan ring, with a benzene ring being more preferred. １ａ As an aromatic ring with 5 to 20 members and a (p+q+1) value, represented by the above Ar １ａ A group obtained by removing (p + q + 1) hydrogen atoms from the aromatic ring can be suitably adopted.

[0129] R １０１Examples of alkoxy groups represented by this symbol include alkoxy groups having 1 to 10 carbon atoms, such as methoxy groups and ethoxy groups.

[0130] p is preferably an integer between 1 and 3, and preferably 1 or 2. q is preferably 0 or 1.

[0131] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f) (hereinafter also referred to as "structural unit (I-2)").

[0132]

[0133] In the above equations (1f) to (2f), R α This is equivalent to equation (1) above. R βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0134] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0135] Specific examples of structural unit (I) (including structural unit (I-1) and structural unit (I-2)) are not particularly limited, but examples include structures represented by the following formulas (1-1) to (1-54). In the following formulas, R α This is equivalent to equation (1) above.

[0136]

[0137]

[0138]

[0139]

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

[0141] The lower limit of the content of the above structural unit (I) (total 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.

[0142] (Structural Unit (II)) Structural unit (II) has a first acid-generating structure formed from a first organic acid anion and a first onium cation. This first acid-generating structure generates an acid that dissociates the acid-dissociable group upon exposure. Structural unit (II) may include the above substructure (a) as the first acid-generating structure. In this case, substructure (a) functions as a radiation-sensitive acid-generating structure.

[0143] In the structural unit (II) of the base polymer, the substructure (a) is contained in such a form that the first organic acid anion is bonded to the main chain in the * of formula (a) above. In this case, the first onium cation is ionically bonded to the first organic acid anion as its counterion.

[0144] The structural unit (II) is preferably a structural unit represented by the following formula (2-a) or formula (2-b) (hereinafter referred to as "structural unit (II-a)", etc.). In structural unit (II-a), the substructure (a) is such that in formula (a) above, x is 1, y is 0, and W - ga-SO ３ - This corresponds to the form in which the substructure (a) in the structural unit (II-a) is such that in the above formula (a), x is 0, y is 1, and W - ga-SO ３ - This corresponds to the state of being.

[0145] (In equations (2-a) and (2-b), R ２ａ Each of these is independently a hydrogen atom, a fluorine atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. ２ａEach of these is independently a single bond or a divalent linking group. １ , L １ Ar, L ２ , m1, n1, n2 and Z ＋ This is equivalent to the above formula (ac).

[0146] R ２ａ The substituted or unsubstituted C1-C6 alkyl group represented by is R in formula (1) above. α A substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, represented by [the formula shown], can be preferably used.

[0147] L ２ａ The divalent linking group represented by is L in formula (1) above. α A divalent linking group represented by can be suitably adopted. Among them, L ２ａ Examples include single bonds, or alkanediyl groups, arenediyl groups, -O-, -COO- ＊ Alternatively, a combination of these is preferable. * indicates Ar or L ２ It is a side joint.

[0148] Ar ２ As a substituted or unsubstituted divalent aromatic ring group represented by the above formula (A1), Ar ２ A group obtained by removing one hydrogen atom from a substituted or unsubstituted monovalent aromatic ring group represented by [the formula shown] can be suitably adopted.

[0149] Similar to the onium salt compound (1a), L of formulas (2-a) and (2-b) above. ２ in -SO ３ - It is preferable that an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom. The electron-withdrawing group shown in onium salt compound (1a) can be suitably adopted as the electron-withdrawing group.

[0150] Specific examples of the first organic acid anion (sulfonic acid anion) of the monomer that gives structural units (II-a) and (II-b) include, for example, the structures represented by the following formulas (2-1) to (2-6). In the following formulas, R ２ａ This is equivalent to equations (2-a) and (2-b) above.

[0151]

[0152] As the first onium cation of structural unit (II), the onium cation in the onium salt compound (1a) can be suitably adopted.

[0153] When the base polymer contains structural unit (II), the lower limit of the content of structural unit (II) (total 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 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (II) within the above range, the function as an acid-generating structure can be fully exhibited, and the above resist properties can be achieved.

[0154] The monomers that give structural unit (II) are typically Ar or L in the above formula (ac). ２ It can be synthesized in the same manner as the onium salt compound (1a), except that a polymerizable group (e.g., a vinyl group) is introduced.

[0155] (Structural Unit (III)) Structural unit (II) has a second acid generation structure formed by a second organic acid anion and a second onium cation. This second acid generation structure generates an acid that does not dissociate the acid-dissociable group upon exposure. Structural unit (III) may include the above substructure (a) as the second acid generation structure. In this case, substructure (a) functions as an acid diffusion control structure. The acid generated from the second acid generation structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the onium salt compound (1a) or structural unit (II).

[0156] In the structural unit (III) of the base polymer, the substructure (a) is contained in such a form that the second organic acid anion is bonded to the main chain in the * of formula (a) above. In this case, the second onium cation is ionically bonded to the second organic acid anion as its counterion.

[0157] The structural unit (III) is preferably a structural unit represented by the following formula (3-a) or formula (3-b) (hereinafter referred to as "structural unit (III-a)", etc.). In structural unit (III-a), the substructure (a) is such that in formula (a) x is 1, y is 0, and W - ga-COO - This corresponds to the form in which the substructure (a) in the structural unit (II-a) is such that in the above formula (a), x is 0, y is 1, and W - ga-COO - This corresponds to the state of being.

[0158] (In equations (3-a) and (3-b), R ２ａ , L ２ａ , R １ , L １ Ar, L ２ , m1, n1, n2 and Z ＋ This is equivalent to equations (2-a) and (2-b) above.

[0159] W in the above formula (a) - As such, the -COO in the above formulas (3-a) and (3-b) - Instead - SO ３ - This can be adopted. In this case, L ２ in -SO ３ - It is preferable that no electron-withdrawing group is bonded to either the α- or β-position carbon atom of the sulfur atom.

[0160] Specific examples of the second organic acid anion (carboxylic acid anion) monomer that gives structural units (III-a) and (III-b) include, for example, the structures represented by the following formulas (3-1) to (3-6). In the following formulas, R ２ａ This is equivalent to equations (3-a) and (3-b) above.

[0161]

[0162] As the second onium cation of structural unit (III), the onium cation in the onium salt compound (1a) can be suitably adopted.

[0163] When the base polymer contains structural unit (III), the lower limit of the content of structural unit (III) (total if multiple types are included) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, relative to the total amount of the onium salt compound (1a) and the monomer that gives structural unit (II) (if both are included). The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. When the onium salt compound (1b) is included, the total amount of the monomer that gives structural unit (III) and the onium salt compound (1b) should be within the above range. By setting the content of structural unit (III) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0164] The monomers that give structural unit (III) are typically Ar or L in the above formula (ac). ２ It can be synthesized in the same manner as the onium salt compound (1b), except that a polymerizable group (e.g., a vinyl group) is introduced.

[0165] (Structural Unit (IV)) Structural unit (IV) is a structural unit having a phenolic hydroxyl group (except in cases where it corresponds to structural unit (I)). By including structural unit (IV) in the base polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the above-mentioned radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, etc. are used as the radiation irradiated in the exposure step in the resist pattern formation method, structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as electron beams and EUV. Structural unit (IV) is preferably represented by the following formula (4).

[0166] (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. R１０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxy 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.)

[0167] The above R β From the viewpoint of copolymerization of the monomer that gives the structural unit (IV), it is preferable that it be a hydrogen atom or a methyl group.

[0168] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0169] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group, or acyloxy group in the above formula (β1) is R １８ The groups listed below can be suitably adopted as substituents that R may have. １０２ In this case, an iodine atom is preferred as the halogen atom.

[0170] The above n ３ 0 or 1 is more preferable, and 0 is even more preferable.

[0171] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0172] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0173] The above structural unit (IV) is preferably a structural unit represented by the following formulas (4-1) to (4-22) (hereinafter also referred to as "structural unit (IV-1) to structural unit (IV-22)"). In the following formulas, R β This is the same as equation (4) above.

[0174]

[0175]

[0176] When the base polymer contains structural unit (IV), the lower limit of the content of structural unit (IV) (total if multiple types exist) 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 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of structural unit (IV) within the above range, the radiation-sensitive composition can further improve sensitivity and development contrast. (Structural unit (V)) Structural unit (V) is a structural unit comprising at least one selected from the group consisting of lactone structure, cyclic carbonate structure, sultone structure, and cyclic sulfone structure. By further containing structural unit (V), the solubility in the developer can be adjusted in the base polymer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer and the substrate can be improved.

[0177] Among these, structural units (V) that include a lactone structure are preferred, and structural units that include a γ-butyrolactone structure, norbornane lactone structure, or adamantane lactone structure are more preferred.

[0178] The base polymer may contain one or more structural units (V).

[0179] When the above base polymer contains the above structural unit (V), the lower limit of the content of the above structural unit (V) (total if multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, relative to the total structural units constituting the base polymer. The upper limit of the above content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of structural unit (V) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0180] (Structural Unit (VI)) Structural unit (VI) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (V)). The base polymer can have its solubility in the developer adjusted by further containing structural unit (VI), 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.

[0181] Examples of structural units (VI) include structural units represented by the following formula.

[0182]

[0183]

[0184] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0185] When the base polymer has a structural unit (VI) having the polar group, the lower limit of the content of the structural unit (VI) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 25 mol%, and even more preferably 20 mol%. By setting the content of structural unit (VI) within the above range, the lithographic performance, such as resolution, of the radiation-sensitive composition can be further improved.

[0186] (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.

[0187] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight-average molecular weight (Mw) in polystyrene terms, as 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 16,000, and even more preferably 12,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0188] 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.

[0189] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0190] The lower limit of the base polymer content is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, relative to the total solid content of the radiation-sensitive composition. The upper limit of the above content is preferably 95% by mass, and more preferably 90% by mass.

[0191] (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, surface modification of the resist film and control of the distribution of the film composition during EUV exposure can be achieved.

[0192] As a high-fluorine-content polymer, it is preferable to have a structural unit (hereinafter also referred to as "structural unit (i)") having a structure in which a fluorine atom is bonded to at least one carbon atom at the α, β, or γ position of the ester bond, and may optionally have structural unit (I), structural units (V) to (VI), and other structural units in the base polymer. Examples of structural unit (i) include the structure represented by the following formula.

[0193]

[0194]

[0195] When a high-fluorine-content polymer contains structural unit (i), the lower limit of the content of structural unit (i) (total if multiple types are included) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 40 mol% relative to the total structural units constituting the high-fluorine-content polymer. The upper limit of the above content may be 100 mol%, 90 mol%, or 85 mol%. By setting the content of structural unit (i) within the above range, the surface segregation of the high-fluorine-content polymer and the solubility of the resist film surface can be improved.

[0196] The lower limit of Mw for the high-fluorine-content polymer is preferably 2,000, more preferably 4,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 15,000, and even more preferably 10,000.

[0197] The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, with 1.1 being more preferred. The upper limit of Mw / Mn is usually 5, with 3 being preferred, and 2 being more preferred.

[0198] If the radiation-sensitive composition contains a high-fluorine content polymer, the amount of the high-fluorine content polymer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the base polymer. Furthermore, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0199] (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.

[0200] <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 optionally contained onium salt compound (1), additives, etc.

[0201] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0202] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, 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 in which some of the hydroxyl groups of the above-mentioned polyhydric alcohol solvents have been etherified.

[0203] 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.

[0204] 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 obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0205] 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.

[0206] 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.

[0207] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate ester solvents such as diethylene glycol acetate mono-n-butyl ether, propylene glycol acetate monomethyl ether, and dipropylene glycol acetate monomethyl ether; 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.

[0208] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0209] Among these, alcohol-based solvents, ester-based solvents, and ether-based solvents are preferred, with C1-C18 monoalcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, and polyhydric alcohol partial ether-based solvents being more preferred, and diacetone alcohol, propylene glycol acetate monomethyl ether, and propylene glycol monomethyl ether being even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0210] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0211] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a base polymer and a solvent with an onium salt compound (1) and other optional components in a predetermined ratio, if necessary. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.4 μm. The solid content concentration of the above radiation-sensitive composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0212] ≪Pattern Forming Method≫ The pattern forming method in this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (1) (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (2) (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with a developer (3) (hereinafter also referred to as the "development step").

[0213] According to the pattern formation method described above, since the above-mentioned radiation-sensitive composition, which has excellent sensitivity, CDU, and Min CD, is used during pattern formation, high-quality resist patterns can be formed with good yield. The following describes each step.

[0214] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the radiation-sensitive composition described above. 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, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The SB temperature is usually 80°C to 180°C, with 100°C to 150°C being preferred. The SB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0215] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask. The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; electron beams, alpha rays, and other charged particle beams. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0216] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups of polymers, etc., in the exposed portion of the resist film by the acid generated from the radiation-sensitive acid generator during exposure. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 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.

[0217] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed with a developer. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0218] 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.

[0219] In addition, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As for ester solvents, acetic acid ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0220] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0221] Onium salt compounds: These onium salt compounds are represented by the following formula (ac) and are compounds that generate acid upon exposure. (In formula (ac), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + 1) valency. L ２ This is a single bond or a divalent organic group. - is, -SO ３ - or -COO - That is. Z ＋ m1 is a monovalent onium cation. n1 is an integer between 1 and 3. n1 and n2 are independent integers between 0 and 4. If there are multiple n2s, they are either identical or distinct from one another. (However, n1 + n2 ≥ 1.)

[0222] As such an onium salt compound, the onium salt compound (1) in the above-mentioned radiation-sensitive composition can be suitably used.

[0223] 《Polymer》 The polymer in question contains a structural unit (I) having an acid-dissociable group and is a polymer having a substructure (a) represented by the following formula (a). (In formula (a), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other.１ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + x + 1) valency. L ２ This is a single bond or an organic group with (y+2) valency. - is, -SO ３ - or -COO - That is. Z ＋ m1 is a monovalent onium cation. m1 is an integer from 1 to 3. n1 and n2 are each independent integers from 0 to 4. If there are multiple n2s, they are either identical or distinct from one another. However, n1 + n2 ≥ 1. x and y are each independent 0 or 1. However, x + y is 1. L ２ If it is a single bond, y is 0. (* represents a bond with other structures in the polymer described above.)

[0224] As such a polymer, the base polymer in the above-mentioned radiation-sensitive composition can be suitably used.

[0225] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" refer to mass unless otherwise specified. The measurement methods for each physical property are shown below.

[0226] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymers] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymers were measured by gel permeation chromatography (GPC) using Tosoh Corporation's GPC columns (two "G2000HXL" columns, one "G3000HXL" column, and one "G4000HXL" column) under the following conditions: Eluent: Tetrahydrofuran (Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Column temperature: 40°C Detector: Differential refractometer Standard material: Monodisperse polystyrene

[0227] <Synthesis of Compound (M)> [Synthesis Example M-15] (Synthesis of Monomer (M-15)) Monomer (M-15) was synthesized according to the reaction scheme below.

[0228]

[0229] 30 mmol of the compound represented by formula (S-2), 39 mmol of the compound represented by formula (S-1), 39 mmol of 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC), 6 mmol of 4-dimethylaminopyridine (DMAP), and 50 mL of dichloromethane (DCM) were added to a reaction vessel and stirred for 2 hours. 50 mL of 2 M hydrochloric acid was added to separate the organic layer. The layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (pM-15).

[0230] 29.74 mmol of the compound represented by formula (pM-15), 148.7 mmol of potassium carbonate, and 100 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 59.47 mmol of the compound represented by formula (S-3) was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. The filtrate was purified by silica gel column chromatography to obtain (M-15).

[0231] [Synthesis Example M-16] (Synthesis of monomer (M-16)) Monomer (M-16) was synthesized according to the reaction scheme below.

[0232]

[0233] 30 mmol of the compound represented by formula (S-4), 150 mmol of potassium carbonate, and 100 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 60 mmol of the compound represented by formula (S-5) was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. The filtrate was purified by silica gel column chromatography to obtain (pM-16).

[0234] 20 mmol of the compound represented by formula (S-6), 21 mmol of the compound represented by formula (pM-16), 4 mmol of p-toluenesulfonic acid (pTsOH), and 100 mL of toluene were added to the reaction vessel. A Dean-Stark tube was placed in the reaction vessel, and the mixture was heated and stirred under reflux conditions for 4 hours. 50 mL of saturated sodium bicarbonate aqueous solution was added to separate the organic layer. The organic layer was dried over sodium sulfate, and the solvent was removed. The monomer (M-16) was obtained by purification by silica gel chromatography.

[0235] [Synthesis Example M-19] (Synthesis of monomer (M-19)) Monomer (M-19) was synthesized according to the reaction scheme below.

[0236]

[0237] 20 mmol of methyl 5-bromo-2,4-hydroxysalicylate, 22 mmol of vinylboronic acid, 0.2 mmol of palladium acetate, 60 mmol of sodium carbonate, and 80 mL of ultrapure water were added to a reaction vessel and stirred at room temperature for 1 hour. 320 mL of ultrapure water was added and the mixture was filtered, and the filtrate was neutralized with 2 M hydrochloric acid. After filtering and drying the precipitated solid, it was dissolved in 300 mL of acetone and filtered again. 500 mL of ultrapure water was added to the filtrate and recrystallized to obtain (ppppM-19).

[0238] 20 mmol of the compound represented by the above formula (ppppM-19), 24 mmol of potassium carbonate, 6 mmol of potassium iodide, and 200 mL of ultrapure water were added to a reaction vessel. 24 mmol of iodine was added, and the mixture was stirred at room temperature for 6 hours. 100 mL of 2N hydrochloric acid and 200 mL of dichloromethane were added, and the organic layer was separated. The organic layer was dried over sodium sulfate, and the solvent was removed. The monomer (ppppM-19) was obtained by purification by silica gel chromatography.

[0239] 10 mmol of the compound represented by the above formula (pppM-19), 50 mmol of potassium carbonate, and 30 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 30 mmol of 2-phenylpropyl-2-bromoacetate was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. The filtrate was purified by silica gel column chromatography to obtain (pppM-19).

[0240] 15 mmol of (ppM-19), 75 mmol of lithium hydroxide, 10 mL of tetrahydrofuran, and 20 mL of ultrapure water were added to a reaction vessel and stirred at room temperature. 50 mL of dichloromethane was added, and the mixture was washed once with 2 M hydrochloric acid and twice with ultrapure water to separate the organic layer. The mixture was then concentrated to obtain (pM-19).

[0241] 10 mmol of the compound represented by the above formula (pM-19), 20 mmol of sodium bicarbonate, 125 mL of dichloromethane, 125 mL of ultrapure water, and 11 mmol of tris(4-fluorophenyl)-phenylsulfonium bromide were added to a reaction vessel and stirred at room temperature for 1 hour. After separating the organic layer, it was washed with 100 mL of ultrapure water to obtain (M-19).

[0242] [Synthesis Example M-20] (Synthesis of monomer (M-20)) Monomer (M-20) was synthesized according to the reaction scheme below.

[0243]

[0244] 20 mmol of zinc, 0.1 mmol of 1,2-dibromoethane, 20 ml of tetrahydrofuran, 1.6 mmol of trimethylsilyl chloride, and 20 mmol of methyl bromodifluoroacetate were added to a reaction vessel and stirred at room temperature for 3 hours. 10 mmol of the compound represented by formula (S-7) was added and stirred at room temperature for 6 hours. 100 mL of ethyl acetate and 100 mL of saturated ammonium chloride aqueous solution were added and the organic layer was separated. The mixture was purified by silica gel column chromatography to obtain (pppM-20).

[0245] 30 mmol of the compound represented by the above formula (pppM-20), 39 mmol of methacrylic acid, 39 mmol of EDC, 6 mmol of DMAP, and 50 mL of dichloromethane were added to a reaction vessel and stirred for 2 hours. 50 mL of 2 M hydrochloric acid was added to separate the organic layer. The mixture was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (pppM-20).

[0246] 15 mmol of (ppM-20), 75 mmol of lithium hydroxide, 10 mL of tetrahydrofuran, and 20 mL of ultrapure water were added to a reaction vessel and stirred at room temperature. 50 mL of dichloromethane was added, and the mixture was washed once with 2 M hydrochloric acid and twice with ultrapure water to separate the organic layer. The mixture was then concentrated to obtain (pM-20).

[0247] 10 mmol of the compound represented by the above formula (pM-20), 20 mmol of sodium bicarbonate, 125 mL of dichloromethane, 125 mL of ultrapure water, and 11 mmol of bis(4-trifluoromethylphenyl)-phenylsulfonium chloride were added to a reaction vessel and stirred at room temperature for 1 hour. After separating the organic layer, it was washed with 100 mL of ultrapure water to obtain (M-20).

[0248] <Synthesis of Compound (B)> [Example B-1] (Synthesis of radiation-sensitive acid generator (B-1) as onium salt compound (1a)) Radiation-sensitive acid generator (B-1) was synthesized according to the reaction scheme below.

[0249]

[0250] 40 mmol of 2-bromoacetyl bromide, 20 mmol of 1-methylcyclopentanol, 40 mmol of pyridine, and 40 mL of tetrahydrofuran were added to a reaction vessel and stirred at room temperature. 100 mL of saturated ammonium chloride aqueous solution and 100 mL of ethyl acetate were added and the organic layer was separated. The layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (S-8).

[0251] 30 mmol of the compound represented by formula (S-9), 39 mmol of 5-iodosalicylic acid, 39 mmol of EDC, 6 mmol of DMAP, and 50 mL of dichloromethane were added to a reaction vessel and stirred for 2 hours. 50 mL of 2 M hydrochloric acid was added to separate the organic layer. The mixture was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (pB-1).

[0252] 10 mmol of the compound represented by the above formula (pB-1), 50 mmol of potassium carbonate, and 30 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 30 mmol of the compound represented by the above formula (S-8) was added, and the mixture was heated with stirring at 55 °C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. It was purified by silica gel column chromatography to obtain (B-1).

[0253] [Examples B-2 to B-4, B-8] (Synthesis of radiation-sensitive acid generators (B-2) to (B-4), (B-8)) Radiation-sensitive acid generators (B-2) to (B-4), (B-8) were synthesized in the same manner as in Example B-1, except that the substrates used were appropriately selected.

[0254]

[0255] [Example B-5] (Synthesis of radiation-sensitive acid generator (B-5)) The radiation-sensitive acid generator (B-5) was synthesized according to the following reaction scheme.

[0256]

[0257] 10 mmol of 4-hydroxy-3,5-diiodobenzaldehyde, 50 mmol of potassium carbonate, and 30 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 30 mmol of tert-butyl bromoacetate was added, and the mixture was heated with stirring at 55 °C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. It was purified by silica gel column chromatography to obtain (pB-5).

[0258] 20 mmol of the compound represented by the above formula (S-10), 21 mmol of the compound represented by the above formula (pB-5), 4 mmol of pTsOH, and 100 mL of toluene were added to a reaction vessel. A Dean-Stark tube was installed in the reaction vessel, and the mixture was heated with stirring under reflux conditions for 4 hours. 50 mL of a saturated aqueous sodium hydrogen carbonate solution was added to separate the organic layer. The organic layer was dried over sodium sulfate, and the solvent was removed. It was purified by silica gel chromatography to obtain (B-5).

[0259] [Examples B-6, B-9 to B-11, B-13 to B-14] (Synthesis of radiation-sensitive acid generators (B-6), (B-9) to (B-11), (B-13) to (B-14)) Radiation-sensitive acid generators (B-6), (B-9) to (B-11), (B-13) to (B-14) were synthesized in the same manner as in Example B-4, except that the substrate used was appropriately selected in Example B-5.

[0260]

[0261] [Example B-7] (Synthesis of radiation-sensitive acid generator (B-7)) A radiation-sensitive acid generator (B-7) was synthesized according to the reaction scheme below.

[0262]

[0263] 10 mmol of 1-thienylethanol, 50 mmol of potassium carbonate, and 30 mL of acetone were added to the reaction vessel. After stirring for 1 hour, 30 mmol of succinic anhydride was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. The solution was purified by silica gel column chromatography to obtain (ppB-7).

[0264] 30 mmol of the compound represented by the above formula (ppB-7), 39 mmol of 2,6-diiodo-4-aminophenol, 39 mmol of EDC, 6 mmol of DMAP, and 50 mL of dichloromethane were added to a reaction vessel and stirred for 2 hours. 50 mL of 2 M hydrochloric acid was added to separate the organic layer. The mixture was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (pB-7).

[0265] 30 mmol of the compound represented by formula (S-11), 39 mmol of the compound represented by formula (pB-7), 39 mmol of EDC, 6 mmol of DMAP, and 50 mL of dichloromethane were added to a reaction vessel and stirred for 2 hours. 50 mL of 2 M hydrochloric acid was added to separate the organic layer. After washing twice with 50 mL of saturated sodium bicarbonate aqueous solution, the layer was washed once with 50 mL of ultrapure water to obtain (B-7).

[0266] [Example B-12] (Synthesis of radiation-sensitive acid generator (B-12)) A radiation-sensitive acid generator (B-12) was synthesized in the same manner as in Example B-7, except that the substrate used was appropriately selected.

[0267]

[0268] <Synthesis of Compound (Z)> [Example Z-1] (Synthesis of Acid Diffusion Control Agent (Z-1) as Onium Salt Compound (1b)) Acid diffusion control agent (Z-1) was synthesized according to the reaction scheme below.

[0269]

[0270] 10 mmol of methyl 2,4-dihydroxy-3,5-diiodobenzoate, 50 mmol of potassium carbonate, and 30 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 30 mmol of 1-methylcyclopentyl bromoacetate was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. The solution was purified by silica gel column chromatography to obtain (ppZ-1).

[0271] 15 mmol of (ppZ-1), 75 mmol of lithium hydroxide, 10 ml of tetrahydrofuran, and 20 ml of ultrapure water were added to a reaction vessel and stirred at room temperature. 50 ml of dichloromethane was added, and the mixture was washed once with 2 M hydrochloric acid and twice with ultrapure water to separate the organic layer. The mixture was then concentrated to obtain (pZ-1).

[0272] 10 mmol of (pZ-1), 20 mmol of sodium bicarbonate, and 50 mL of ultrapure water were added to a reaction vessel and stirred for 30 minutes. Next, 10 mmol of triphenylsulfonium bromide and 50 mL of dichloromethane were added and the mixture was stirred vigorously for 3 hours. The organic layer was separated and washed twice with 50 mL of ultrapure water. The organic layer was concentrated to obtain (Z-1).

[0273] [Examples Z-2 to Z-5, Z-7 to Z-13] (Synthesis of acid diffusion control agents (Z-2) to (Z-5), (Z-7) to (Z-13)) Acid diffusion control agents (Z-2) to (Z-5), (Z-7) to (Z-13) were synthesized in the same manner as in Example Z-1, except that the substrates used were appropriately selected.

[0274]

[0275] [Example Z-6] (Synthesis of Acid Diffusion Control Agent (Z-6)) The acid diffusion control agent (Z-6) was synthesized according to the reaction scheme below.

[0276]

[0277] 40 mmol of ethyl chloroglyoxylate, 20 mmol of 2,6-diiodo-4-aminophenol, 40 mmol of pyridine, and 40 mL of tetrahydrofuran were added to a reaction vessel and stirred at room temperature. 100 mL of saturated ammonium chloride aqueous solution and 100 mL of ethyl acetate were added, and the organic layer was separated. The layer was washed twice with 50 mL of saturated sodium bicarbonate aqueous solution, and then once with 50 mL of ultrapure water to obtain (pppZ-6).

[0278] 10 mmol of (pppZ-6), 50 mmol of potassium carbonate, and 30 mL of acetone were added to a reaction vessel. After stirring for 1 hour, 30 mmol of the compound represented by the above formula (S-12) was added, and the mixture was heated and stirred at 55°C for 5 hours. After cooling to room temperature, the precipitated solid was filtered, and the filtrate was concentrated. (ppZ-6) was obtained by purification by silica gel column chromatography.

[0279] 15 mmol of (ppZ-6), 75 mmol of lithium hydroxide, 10 mL of tetrahydrofuran, and 20 mL of ultrapure water were added to a reaction vessel and stirred at room temperature. 50 mL of dichloromethane was added, and the mixture was washed once with 2 M hydrochloric acid and twice with ultrapure water to separate the organic layer. The mixture was then concentrated to obtain (pZ-6).

[0280] 10 mmol of (pZ-6), 20 mmol of sodium bicarbonate, and 50 mL of ultrapure water were added to a reaction vessel and stirred for 30 minutes. Next, 10 mmol of bis(4-trifluoromethylphenyl)-phenylsulfonium chloride and 50 mL of dichloromethane were added and the mixture was vigorously stirred for 3 hours. The organic layer was separated and washed twice with 50 mL of ultrapure water. The organic layer was concentrated to obtain (Z-6).

[0281] <Synthesis of Base Polymer> [Synthesis Examples A-1 to A-21 and Examples 1 to 5] Synthesis of Base Polymer Monomers were combined with the compositions shown in Table 1 below, and a copolymerization reaction was carried out in a tetrahydrofuran (THF) solvent. The product was crystallized in methanol and further washed repeatedly with hexane, and then isolated and dried to obtain A-1 to A-26 as base polymers. In the table, "-" indicates that the corresponding component was not used. The same applies to the following tables.

[0282]

[0283] The monomers used for the synthesis of the base polymer are shown below.

[0284]

[0285]

[0286] <Preparation and Evaluation of Radiation-Sensitive Composition> The compounds used for the preparation of the radiation-sensitive composition are shown below.

[0287] <[B] Radiation-Sensitive Acid Generator> B-1 to B-19: Compounds represented by the following formulas (B-1) to (B-19) (Compounds (B-1) to (B-14) are the above-mentioned synthetic components)

[0288]

[0289]

[0290]

[0291] <[Z] Acid Diffusion Controller> Z-1 to Z-17: Compounds represented by the following formulas (Z-1) to (Z-17) (Compounds (Z-1) to (Z-13) are the above-mentioned synthetic components)

[0292]

[0293]

[0294]

[0295] [D] Solvent D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether D-3: Diacetone alcohol

[0296] <Preparation of Radiation-Sensitive Composition> [Example 1] A radiation-sensitive composition (R-1) was prepared by blending [A] 100 parts by mass of polymer (A-1), [B] 30 parts by mass of (B-1) as a radiation-sensitive acid generator, [Z] 50 mol% of (Z-14) as an acid diffusion control agent relative to the radiation-sensitive acid generator (B-1), [D] 2,000 parts by mass of (D-1) and 4,800 parts by mass of (D-2) as solvents.

[0297] [Examples 2-48 and Comparative Examples 1-13] Radiation-sensitive compositions (R-2) to (R-48) and (CR-1) to (CR-13) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2-1 to 2-2 below were used. In Examples 43, 44, and Comparative Examples 9 and 10, the amount of the [Z] acid diffusion control agent was blended so that it was 50 mol% of the amount of monomers that give structural units (II) contained in 100 parts by mass of the [A] base polymer.

[0298]

[0299]

[0300] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 40 nm thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After soft baking at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 60 nm thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89, mask: imecDEFECT32FFR02). Subsequently, PEB was performed on the resist film at 110°C for 60 seconds. Next, a 2.38 mass% TMAH aqueous solution was used to develop the film at 23°C for 30 seconds, forming a positive-type 48 nm contact hole pattern.

[0301] <Evaluation> The sensitivity, CDU, and process margin (Min CD) of each radiation-sensitive composition were evaluated by measuring each resist pattern formed as described above according to the method below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-4100") was used to measure the length of the resist patterns. The evaluation results are shown in Tables 3-1 to 3-2 below.

[0302] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 48 nm contact hole pattern is set as the optimal exposure amount, and this optimal exposure amount is set as the sensitivity (mJ / cm²). ２ The smaller the sensitivity value, the better, as it allows for the formation of the desired resist pattern with less exposure.

[0303] [CDU] The formed resist pattern was observed from above using the scanning electron microscope described above. The hole width was measured at 50 arbitrary points, and the 3-sigma value was determined from the distribution of these measurements, which was defined as the CDU (unit: nm). A smaller CDU value indicates less hole play and a better result.

[0304] [Min CD] In forming the resist pattern described above, the hole width was measured while decreasing the exposure amount, and the minimum hole width at which holes could be formed was defined as Min CD (unit: nm). A smaller Min CD value indicates a wider and better process margin for forming contact holes.

[0305]

[0306]

[0307] As is clear from the results in Tables 3-1 to 3-2, the radiation-sensitive compositions of the examples exhibited a good balance of sensitivity, CDU, and Min CD compared to the radiation-sensitive compositions of the comparative examples.

[0308] The radiation-sensitive composition, pattern-forming method, onium salt compound, and polymer of the present invention can improve sensitivity, CDU, and Min CD compared to conventional methods. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition containing a polymer comprising a structural unit (I) having an acid-dissociable group and a solvent, wherein at least the radiation-sensitive composition has a partial structure (a) represented by the following formula (a) and contains an onium salt compound (1) that generates an acid upon exposure, or the polymer has a partial structure (a) represented by the following formula (a). Radiation-sensitive composition. (In formula (a), １ R is an acid-dissociable group. When there are a plurality of R １ , the plurality of R １ are the same as or different from each other. L １ is a divalent chain organic group. When there are a plurality of L １ , the plurality of L １ are the same as or different from each other. Ar is an (m1 + n1 + x + 1)-valent aromatic ring having 3 to 20 carbon atoms. L ２ is a single bond or a (y + 2)-valent organic group. W - is -SO ３ - or -COO - . Z ＋ is a monovalent onium cation. m1 is an integer of 1 to 3. n1 and n2 are each independently an integer of 0 to 4. When there are a plurality of n2, the plurality of n2 are the same as or different from each other. However, n1 + n2 ≧ 1. x and y are each independently 0 or 1. However, when L ２ is a single bond, y is 0, and in the partial structure (a) in the polymer, x + y is 1 or 2. * is a bond to another structure in the corresponding component.) 2. In the above formula (a), R １ The radiation-sensitive composition according to claim 1, wherein is an acid-dissociable group represented by the following formula (β1). (In formula (β1), R １８ R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ Each of these independently represents a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a substituted or unsubstituted divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. * represents L in formula (a) above. １ This is a combination of the above. However, if n2 in equation (a) is 1 or greater, R １ The iodine atom bonded to it is R １８ , R １９ and R ２０ (Combines with at least one selected from the group consisting of the following.) 3. In the above formula (a), L １ This includes a substituted or unsubstituted divalent chain hydrocarbon group having 1 to 10 carbon atoms, or a divalent chain hydrocarbon group with -CO-, -CS-, -NR'-, -O-, -S-, and -SO ２ The radiation-sensitive composition according to claim 1, wherein R' is a divalent group combined with at least one selected from the group consisting of -, and R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

4. The radiation-sensitive composition according to claim 1, wherein Ar is a benzene ring in formula (a) above.

5. The radiation-sensitive composition according to claim 1, wherein in formula (a) above, m1 is 1, n1 is an integer from 1 to 3, and n2 is 0 or 1.

6. The above radiation-sensitive composition contains the above onium salt compound (1), and in the above formula (a), W - ha-SO ３ - And, -SO ３ - The radiation-sensitive composition according to claim 1, wherein an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom.

7. The radiation-sensitive composition according to claim 6, wherein the content of the onium salt compound (1) is 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the polymer.

8. The above radiation-sensitive composition contains the above onium salt compound (1), and in the above formula (a), W - is, -SO ３ - or -COO - (However, W - ga-SO ３ - If so, -SO ３ - The radiation-sensitive composition according to claim 1, wherein neither the α-position nor the β-position carbon atom of the sulfur atom is bonded to an electron-withdrawing group.

9. The radiation-sensitive composition according to claim 1, wherein the onium cation is a sulfonium cation or an iodonium cation.

10. The radiation-sensitive composition according to claim 1, wherein the polymer comprises at least one selected from the group consisting of: a structural unit (II) having a first organic acid anion and a first onium cation, which generates an acid that dissociates the acid-dissociable group upon exposure; and a structural unit (III) having a second organic acid anion and a second onium cation, which generates an acid that does not dissociate the acid-dissociable group upon exposure; and at least one selected from the group consisting of the first acid-dissociable structure and the second acid-dissociable structure comprises the substructure (a).

11. The radiation-sensitive composition according to any one of claims 1 to 10, wherein the polymer further comprises a structural unit (IV) having a phenolic hydroxyl group.

12. The radiation-sensitive composition according to any one of claims 1 to 10, further comprising a high-fluorine-content polymer having a higher mass content of fluorine atoms than the polymer.

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

14. The pattern forming method according to claim 13, wherein the exposure is performed using extreme ultraviolet light or an electron beam.

15. An onium salt compound represented by the following formula (ac) and which generates acid upon exposure. (In formula (ac), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + 1) valency. L ２ This is a single bond or a divalent organic group. - is, -SO ３ - or -COO - That is. Z ＋ m1 is a monovalent onium cation. n1 is an integer between 1 and 3. n1 and n2 are independent integers between 0 and 4. If there are multiple n2s, they are either identical or distinct from one another. (However, n1 + n2 ≥ 1.) 16. A polymer comprising a structural unit (I) having an acid-dissociable group, and having a substructure (a) represented by the following formula (a). (In formula (a), R １ R is an acid-dissociable group. １ If multiple R １ They are either identical or different from each other. １ L is a divalent chain-like organic group. １ If there are multiple L １ They are either identical or different from each other. Ar is an aromatic ring with 3 to 20 carbon atoms and a (m1 + n1 + x + 1) valency. L ２ This is a single bond or an organic group with (y+2) valency. - is, -SO ３ - or -COO - That is. Z ＋ m1 is a monovalent onium cation. m1 is an integer from 1 to 3. n1 and n2 are each independent integers from 0 to 4. If there are multiple n2s, they are either identical or distinct from one another. However, n1 + n2 ≥ 1. x and y are each independent 0 or 1. However, x + y is 1. L ２ If it is a single bond, y is 0. (* represents a bond with other structures in the polymer described above.)

Images