Radiation-sensitive composition and pattern formation method

Abstract

The purpose of the present invention is to provide: a radiation-sensitive composition which has excellent storage stability and is capable of exhibiting sensitivity, CDU, and bridge margin at levels that are comparable or superior those of conventional compositions during pattern formation; and a pattern formation method. This radiation-sensitive composition contains a polymer, one or more onium salts including an organic acid anion and a radiation-sensitive onium cation, a compound represented by formula (2), and a solvent, at least a portion of the organic acid anion in the onium salt being an organic acid anion (1) represented by formula (1).　

Description

Radiation-sensitive composition and pattern-forming method 【0001】 The present invention relates to a radiation-sensitive composition and a pattern-forming method. 【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 efforts toward further technological advancements progress, a technique has been proposed to improve lithography performance by incorporating a quencher (acid diffusion control agent) into the resist composition and capturing the acid that has diffused to the unexposed areas through a salt exchange reaction (International Publication No. 2021 / 065450). 【0005】 International Publication No. 2021 / 065450 【0006】 In deploying the above-mentioned next-generation technologies, the resist composition is required to have storage stability, sensitivity, CDU (Critical Dimension Uniformity), an indicator of hole diameter uniformity, and bridge margins that are equivalent to or better than those of conventional resists. 【0007】 The present invention aims to provide a radiation-sensitive composition and a pattern-forming method that have good storage stability and can exhibit sensitivity, CDU, and bridge margin at levels equivalent to or better than conventional methods during pattern formation. 【0008】The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention. 【0009】 In one embodiment, the present invention relates to a radiation-sensitive composition (hereinafter also referred to as the "first radiation-sensitive composition") that contains a polymer, one or more onium salts comprising an organic acid anion and a radiation-sensitive onium cation, a compound represented by the following formula (2), and a solvent, wherein at least a portion of the organic acid anions in the onium salt is an organic acid anion (1) represented by the following formula (1). (In formula (1), Ar is an aromatic ring having 5 to 20 carbon atoms. １ R is a fluorine atom or a fluorinated hydrocarbon group. １ If multiple R １ These are either the same or different. ２ is an aprotic substituent (however, R １ (Excluding those that fall under the above category). ２ If multiple R ２ They are either the same or different. n1 is an integer between 0 and 5. n2 is an integer between 0 and 5. (In formula (2), R ３ (where X is a monovalent organic group; X is a hydrogen atom or an acid-dissociable group.) 【0010】In the radiation-sensitive composition, by introducing the specific organic acid anion and containing the specific acid, it is possible to exhibit good storage stability and sensitivity, CDU, and bridge margin equivalent to or better than those of the prior art. Although the reason for this is not clear, it is speculated as follows. Since the specific organic acid anion does not have a protic substituent, the acid diffusion control agent having the organic acid anion has strong basicity. The presence of a strongly basic acid diffusion control agent in the pattern can highly suppress the diffusion of the acid generated from the radiation-sensitive acid generator, and as a result, excellent CDU and bridge margin can be exhibited. In addition, although problems with storage stability have been conventionally known for strongly basic acid diffusion control agents, by adding the specific acid, it is possible to suppress the activation of nucleophiles considered to be the cause of the decrease in storage stability, and it is speculated that the storage stability is improved. It is also speculated that these combined actions can exhibit the above resist performance and the like. 【0011】 In another embodiment, the present invention relates to a radiation-sensitive composition (hereinafter, also referred to as "second radiation-sensitive composition") containing one or more onium salts containing an organic acid anion and a radiation-sensitive onium cation, a compound represented by the following formula (2), and a solvent, wherein at least a part of the organic acid anions in the onium salt is an organic acid anion (1) represented by the following formula (1). (In formula (1), Ar is an aromatic ring having 5 to 20 carbon atoms. R １ is a fluorine atom or a fluorinated hydrocarbon group. When a plurality of R １ are present, the plurality of R １ are the same or different from each other. R ２ is an aprotic substituent (excluding those corresponding to R １ ). When a plurality of R ２ are present, the plurality of R ２ are the same or different from each other. n1 is an integer of 0 to 5. n2 is an integer of 0 to 5.) (In formula (2), R ３ is a monovalent organic group. X is a hydrogen atom or an acid dissociable group.) 【0012】The second radioactive composition, like the first radioactive composition, incorporates the specific organic acid anion and contains the specific acid, thereby exhibiting good storage stability, sensitivity, CDU, and bridge margin equivalent to or better than conventional compositions. The reason for this is presumed to be the same as that for the first radioactive composition. 【0013】 In another embodiment, the present invention relates to a pattern forming method comprising the steps of: directly or indirectly applying a composition obtained by compounding a polymer with the first radiation-sensitive composition or the second radiation-sensitive composition to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer. 【0014】 This pattern formation method uses the above-mentioned radiation-sensitive composition, which has good storage stability and can exhibit sensitivity, CDU, and bridge margin during pattern formation, thus enabling the efficient formation of high-quality resist patterns. 【0015】 In this specification, "organic group" means a group having at least one carbon atom (excluding groups that constitute a functional group or characteristic group on their own, such as -CN, -COOH, -CO-, -COO-, -O-CO-O-, etc.). 【0016】 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. 【0017】 ≪First Radiation-Sensitive Composition≫ The first radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the first composition") contains a polymer (A), one or more onium salts (B) containing an organic acid anion and a radiation-sensitive onium cation, a compound (C) represented by the above formula (2), and a solvent (D), wherein at least a portion of the organic acid anion in the onium salt (B) is the organic acid anion (1) represented by the above formula (1). The above composition may contain other optional components as long as they do not impair the effects of the present invention. The components contained in the first radiation-sensitive composition will be described below. 【0018】<Polymer (A)> Polymer (A) is preferably an aggregate of polymerization chains containing a structural unit (I) having an acid-dissociable group (hereinafter also referred to as "base polymer (A)"). In addition to structural unit (I), base polymer (A) may also contain structural units (II) having a phenolic hydroxyl group, structural units (III) containing a lactone structure, etc., structural units (IV) containing an acid-generating structure, structural units (V) containing a polar group, etc. 【0019】 (Structural Unit (I)) Structural unit (I) is a structural unit having an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group, which dissociates upon the action of an acid. When the base polymer contains structural unit (IV) due to exposure, the acid generated from the acid-generating structure, the onium salt compound (B2) described later, etc., dissociates the acid-dissociable group in structural unit (I), generating a carboxyl group, etc. This creates a difference in solubility in the developer between the exposed and unexposed areas of the resist film, enabling pattern formation. In this specification, "dissociation" of an acid-dissociable group refers to dissociation when post-exposure baking is performed at 110°C for 60 seconds. 【0020】 The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (i) (hereinafter also referred to as "structural unit (I-1)") is preferred. 【0021】 (In formula (i), R １７ R is a hydrogen atom, a fluorine atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. １８ R is a monovalent substituted or unsubstituted 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 divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO- ＊ -L １１ａ -COO-, or ＊ -COOL- １１ａ Represents -COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded. 【0022】 R １７ Examples of C1-C6 alkyl groups represented by include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, and the like. 【0023】 R １７ When an alkyl group having 1 to 6 carbon atoms represented by has substituents, examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; 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; and substituents (T) such as oxo groups (=O). 【0024】 R １７Examples 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. 【0025】 The above R １７ From the viewpoint of copolymerization of the monomer that gives structural unit (I-1), hydrogen atoms and methyl groups are preferred. 【0026】 L １１ａ Examples of alkanediyl groups represented by include divalent alkanediyl groups having 1 to 10 carbon atoms, such as methylene groups, ethanediyl groups, and propanediyl groups. １１ａ The alkanediyl group represented is preferably a methylene group or an ethanediyl group. 【0027】 L １１ａ Examples of the arenediyl group represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the allenediyl group represented by . 【0028】 L １１ａ When an alkanediyl group or arenediyl group represented by is substituted, the substituent is R １７ The substituent (T) shown above can be suitably adopted. 【0029】 L １１ teeth,＊ -COO- ＊ -L １１ａ -COO- is preferred, ＊ -COO- is preferable. 【0030】 The above R １８ Examples of monovalent hydrocarbon groups having 1 to 20 carbon atoms, represented by , include chain hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, and monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms. 【0031】 Examples of the above-mentioned monovalent linear hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms, or monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms. Examples of the above-mentioned monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, isopentyl group, and neopentyl group. Examples of the above-mentioned monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms include alkenyl groups such as ethenyl group, propenyl group, and butenyl group; and alkynyl groups such as ethynyl group, propynyl group, and butynyl group. 【0032】Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norborneyl, tricyclodecenyl, and tetracyclododecenyl groups. A bridged alicyclic hydrocarbon group is a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are bonded together by a linking group containing one or more carbon atoms. 【0033】 Examples of the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthyl groups; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl groups. 【0034】 R １９ and R ２０ As a monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the above R １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, groups with the corresponding number of carbon atoms can be suitably adopted. 【0035】 R １９ and R ２０ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above R １８ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used in this material. 【0036】 The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining these with the carbon atoms to which they are bonded, is the above R １８Examples include groups obtained by removing one hydrogen atom from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. 【0037】 The above R １８ ~R ２０ The substituent (T) described above can be suitably adopted as a substituent that can be possessed. 【0038】 Among these, R １８ The C1-C5 alkyl group, alkenyl group, or aromatic hydrocarbon group is preferred. １９ and R ２０ Preferably, each of these groups is either an independent methyl group or an ethyl group, or they can be combined to form a cycloalkane structure with the carbon atoms to which they are bonded. 【0039】 Examples of structural units (I-1) include the structural units represented by the following formulas (i-1) to (i-11) (hereinafter also referred to as "structural units (I-1-1) to (I-1-11)"). 【0040】 【0041】 In the above equations (i-1) to (i-11), R １７ ~R ２０ This is equivalent to equation (i) above. R Ｌ１１ R is a halogen atom; hydroxyl group; carboxyl group; cyano group; nitro group; amino group; alkoxy group; alkoxycarbonyl group; alkoxycarbonyloxy group; acyl group; acyloxy group, or a group in which a hydrogen atom of any of these groups is substituted with a halogen atom. h, i, and j are each independently integers from 1 to 4. k1, k2, and k3 are each independently 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. 【0042】 h, i, and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, ethenyl (vinyl), butenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group.Ｌ１１ Preferred elements include hydroxyl groups, iodine atoms, alkyl groups, and alkoxy groups. 【0043】 Furthermore, the polymer may also contain structural units (I) represented by the following formulas (1f) to (2f) (hereinafter also referred to as "structural unit (I-2)"). 【0044】 【0045】 In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4. 【0046】 The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred. 【0047】 While there are no particular limitations on specific examples of structural unit (I) (including structural unit (I-1) and structural unit (I-2)), examples include structures represented by the following formula. In the following formula, R １７ This is equivalent to equation (i) above. 【0048】 【0049】 【0050】 【0051】 The base polymer (A) may contain one or more structural units (I) in combination. 【0052】The lower limit of the content of structural unit (I) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer (A). 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 (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved. 【0053】 (Structural Unit (II)) Structural unit (II) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to structural unit (I)). By including structural unit (II) in the polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the first 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 (II) 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 (II) is preferably represented by the following formula (ii). 【0054】 (In the above equation (ii), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ , -O- or -CONH- ＊ * indicates a bond on the aromatic ring side. １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. １１ n is an integer between 0 and 2, and n １２ n is an integer between 1 and 8. １３ Each of these is an independent integer between 0 and 8, where 1 ≤ n. １２+n １３ ≤2n １１ satisfies +5.) 【0055】 Regarding the above R β From the viewpoint of the copolymerizability of the monomer that gives the structural unit (II), it is preferably a hydrogen atom or a methyl group. 【0056】 Regarding L ＣＡ is preferably a single bond or -COO- ＊ is preferred. 【0057】 Regarding R １０２ As the halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in R, the groups respectively listed as the above substituent (T) can be preferably adopted. As the halogen atom in R １０２ iodine atom or fluorine atom is preferred, and iodine atom is more preferred. 【0058】 Regarding the above n １１ 0 or 1 is more preferred, and 0 is even more preferred. When n １１ is 1 or more, -OH and -R in the above formula (2) １０２ may be bonded to any of the plurality of benzene rings to be condensed, respectively. 【0059】 Regarding the above n １２ is preferably an integer of 1 to 3, and 1 or 2 is more preferred. 【0060】 Regarding the above n １３ is preferably an integer of 0 to 3, and an integer of 0 to 2 is more preferred. 【0061】 Regarding the above structural unit (II), it is preferably a structural unit represented by the following formula (ii-1) to (ii-24) (hereinafter, also referred to as "structural unit (ii-1) to structural unit (ii-24)"). In the following formula, R β is the same as the above formula (ii). 【0062】 【0063】 【0064】When the base polymer has structural unit (II), the lower limit of the content of structural unit (II) (total if there are multiple types of structural unit (II)) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 85 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content of structural unit (II) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast. 【0065】 (Structural Unit (III)) Structural Unit (III) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. The base polymer (A) can have its solubility in the developer adjusted by further comprising structural unit (III), and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer (A) and the substrate can be improved. 【0066】 Among these, structural units (III) that include a lactone structure are preferred, and structural units that include a γ-butyrolactone structure are more preferred. 【0067】 When the base polymer has structural unit (III), the lower limit of the content of structural unit (III) (total content 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 (A). The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 55 mol%. By setting the content of structural unit (III) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate. 【0068】(Structural Unit (IV)) Structural unit (IV) has an organic acid anion (b1) and an onium cation (c1), and generates an acid that induces the dissociation of the above-mentioned acid-dissociable group upon exposure. The onium salt structure (i.e., the acid-generating structure) formed by the organic acid anion (b1) and the onium cation (c1) functions as a radiation-sensitive acid-generating structure. Polymer (A) having a radiation-sensitive acid-generating structure (acid-generating structure) is distinguished from low-molecular-weight forms (radiation-sensitive acid generators) in which the onium salt structure exists as a compound on its own (released from the polymer). 【0069】 The form in which the organic acid anion (b1) and onium cation (c1) are contained in the structural unit (IV) of the base polymer (A) is not particularly limited, and the base polymer (A) may have the organic acid anion (b1) as a side chain portion, or it may have the onium cation (c1) as a side chain portion. Having as a side chain portion means that the corresponding organic acid anion (b1) or onium cation (c1) is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer. When the organic acid anion (b1) is bonded to the main chain as a side chain structure of the base polymer, the onium cation (c1) is ionically bonded to the organic acid anion (b1) as its counterion. On the other hand, when the onium cation (c1) is bonded to the main chain as a side chain structure of the base polymer, the organic acid anion (b1) is ionically bonded to the onium cation (c1) as its counterion. From the viewpoint of development contrast, it is preferable that the base polymer has the above-mentioned organic acid anion (b1) as a side chain portion. 【0070】 The above organic acid anion (b1) preferably has at least one selected from the group consisting of sulfonic acid anions, carboxylic acid anions, and sulfonimide anions as the acid anion portion. As for the acid generated by exposure, corresponding to the above acid anion portion, examples include sulfonic acid, carboxylic acid, and sulfonimide. Among these, it is more preferable to have a sulfonic acid anion, and it is even more preferable that an electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonic acid anion. 【0071】Examples of the electron-withdrawing groups mentioned above include acyl groups such as acetyl, propionyl, benzoyl, and acryloyl groups; alkylsulfonyl groups such as methylsulfonyl groups; cyano groups; nitro groups; halogen groups such as fluorine and iodine atoms; and monovalent hydrocarbon groups having 1 to 5 carbon atoms in which some or all of the hydrogen atoms are substituted by at least one of these groups. 【0072】 The above organic acid anion (b1) preferably contains -O-, -CO-, a cyclic structure, or a combination thereof. This combination also includes structures (heterocyclic structures) in which -O- or -CO- are incorporated as ring-forming parts within the cyclic structure. Furthermore, the organic acid anion (b1) preferably has an iodine group, and more preferably contains an iodine group-containing aromatic ring structure. 【0073】 The aromatic ring in the iodine group-containing aromatic ring structure is not particularly limited as long as it is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, perylene rings, and coronene rings; heteroaromatic rings such as furan rings, pyrrole rings, thiophene rings, phosphole rings, pyrazole rings, oxazole rings, isoxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, triazine rings, carbazole rings, and dibenzofuran rings; or combinations thereof. Among these, the benzene ring is preferred as the aromatic ring. 【0074】 The number of iodine atoms in the above-described iodine group-containing aromatic ring structure is not particularly limited, but it is preferably 1 to 4, more preferably 1, 2, or 3, and even more preferably 1 or 2. 【0075】As the above-mentioned cyclic structure, any of a monocyclic, polycyclic or a combination thereof may be used. Further, the cyclic structure may be any of an alicyclic structure, an aromatic ring structure, a heterocyclic structure or a combination thereof. In the case of a combination, the ring structure may be a structure in which ring structures are connected by a chain structure, or two or more ring structures may form a condensed ring structure, a bridged ring structure or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon-carbon atoms forming the skeleton of the cyclic structure or the chain structure, and part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or the chain structure may be substituted with other substituents. 【0076】 As the above-mentioned alicyclic structure, a structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in R in the above formula (i) １８ can preferably be adopted. 【0077】 As the above-mentioned aromatic ring structure, a structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in R in the above formula (i) １８ can preferably be adopted. 【0078】 Examples of the above-mentioned heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, dioxane, etc.; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, piperazine, etc.; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, thiane, etc.; aliphatic heterocyclic structures containing a plurality of types of heteroatoms such as morpholine, 1,2-oxathiolane, 1,3-oxathiolane, etc.; oxygen atom-containing aromatic heterocyclic structures such as furan, benzofuran, etc.; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, triazine, etc.; sulfur atom-containing aromatic heterocyclic structures such as thiophene, etc.; aromatic heterocyclic structures containing a plurality of types of heteroatoms such as oxazole, isothiazole, thiazine, etc. 【0079】 The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11). 【0080】 (In the above formula, g is an integer between 1 and 3.) 【0081】 The above chain structure is R in formula (i) above. １８ A monovalent chain hydrocarbon group having 1 to 20 carbon atoms can be suitably used in this material. 【0082】 Examples of divalent heteroatom-containing groups include -CO-, -CS-, -NR'-, -O-, -S-, and -SO ２ - Or, divalent groups combining these. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. 【0083】 The substituent (T) described above can be suitably used as a substituent to replace some or all of the hydrogen atoms on the carbon atoms of the above-mentioned cyclic or chain-like structure. 【0084】 Examples of the above onium cation (c1) include radiation-sensitive onium cations. Examples of radiation-sensitive onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations. Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred. 【0085】 The onium cation (c1) in structural unit (IV) may have an iodine group and may contain the iodine group-containing aromatic ring structure. Furthermore, the onium cation (c1) in structural unit (IV) may be a fluorogroup-containing onium cation having a fluorogroup. The fluorogroup-containing onium cation preferably has a fluorogroup-containing aromatic ring structure. The fluorogroup-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are replaced by fluorogroups. This increases the radiation absorption efficiency, thereby improving sensitivity. 【0086】 In the above fluorogroup-containing aromatic ring structure, the aromatic ring in the above iodine group-containing aromatic ring structure can be suitably adopted. 【0087】The number of fluorine atoms in the above fluorogroup-containing aromatic ring structure is not particularly limited, but it is preferably 1 to 4, and more preferably 1, 2, or 3. 【0088】 The base polymer (A) preferably contains a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (IV-1)") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit (IV-2)"). 【0089】 【0090】 In the formula, R Ａ X is a hydrogen atom or a methyl group. １ X is a single bond or an ester group. ２ This is a linear, branched, or cyclic alkanediyl group having 1 to 12 carbon atoms, a cycloalkanediyl group having 3 to 12 carbon atoms, or an arenediyl group having 6 to 10 carbon atoms, or a combination thereof, and a portion of the methylene group constituting the alkanediyl group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ This is a single bond, an ether group, an ester group, or a linear or branched alkanediyl group having 1 to 12 carbon atoms, or a cyclic cycloalkanediyl group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkanediyl group may be substituted with an ether group or an ester group. ２ and X ３ Some or all of the hydrogen atoms in X may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. ２ However, it is preferable that the above-mentioned iodine group-containing aromatic ring structure is included. 【0091】 The above alkanediyl group and arenediyl group are L of formula (i) above. １１ａ The alkanediyl group and arenediyl group represented by can be suitably adopted. The above cycloalkanediyl group is R of formula (i) above. １８ A group obtained by removing one hydrogen atom from a cycloalkyl group can be suitably adopted. 【0092】 The above Rｆ１ ~R ｆ４ Each of these is independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a trifluoromethyl group. The above s1 is 0 or 1. R ４３ ~R ４７ Each of these is independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, which may contain heteroatoms, and R ４３ and R ４４ These may bond with each other, forming a ring together with the sulfur atom to which they are bonded. ４３ ~R ４５ At least one of the following, and R ４６ ~R ４７ Preferably, at least one of these structures contains the above-mentioned iodine group-containing aromatic ring structure or fluoro group-containing aromatic ring structure. 【0093】 R ４３ ~R ４７ In this, the monovalent hydrocarbon group having 1 to 20 carbon atoms is R in formula (i) above. １８ A monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula can be suitably used, and some or all of the hydrogen atoms of these groups may be substituted with the substituent (T) mentioned above. 【0094】 The structural units (IV-1) and (IV-2) are preferably represented by the following formulas (a1-1) to (a1-4) and (a2-1) to (a2-3), respectively. 【0095】 【0096】 【0097】 In the formula, R Ａ , R ４３ ~R ４７ , R ｆ１ ~R ｆ４ , X １ , and s1 are equivalent to the above formulas (a1) and (a2). R ４８m is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxyl group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer from 0 to 4. n is an integer from 0 to 3, where 0 ≤ m + n ≤ 4. s and s² are integers from 1 to 5. 【0098】 Examples of monomeric organic acid anions (b1) that give structural unit (IV) (including structural unit (IV-1) and structural unit (IV-2)) are, but are not limited to, those listed below. Furthermore, among those listed below, for structures having the above-mentioned iodine group-containing aromatic ring structure, structures in which the iodine atom in the following formula is replaced with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably adopted. In the following formula, R A This is equivalent to the above equations (a1) and (a2). 【0099】 【0100】 【0101】 【0102】 【0103】 【0104】 【0105】 【0106】 The onium cation (c1) of structural unit (IV-1) is preferably represented by the following formula (Q-1). 【0107】 【0108】 In the above formula (Q-1), R ａ１ ~R ａ３ Each of these independently represents a substituent. m1 represents an integer from 0 to 5, and if m1 is 2 or greater, there are multiple R ａ１ They may be the same or different. m2 represents an integer from 0 to 5, and if m2 is 2 or greater, there may be multiple R ａ２They may be the same or different. m3 represents an integer from 0 to 5, and if m3 is 2 or greater, there may be multiple R ａ３ They may be the same or different. ａ１ and R ａ２ They may be connected to each other to form a ring. If m1 is 2 or more, multiple R ａ１ They may be connected to each other to form a ring. If m2 is 2 or more, multiple R ａ２ They may be connected to each other to form a ring. 【0109】 R ａ１ , R ａ２ , and R ａ３ Preferred substituents represented by are alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, alkylsulfonyl groups, hydroxyl groups, halogen atoms, and halogenated hydrocarbon groups. 【0110】 R ａ１ , R ａ２ , and R ａ３ The alkyl group may be a linear alkyl group or a branched alkyl group. The alkyl group may be R in formula (i) above. １８ Monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms can be suitably used. Among these, methyl, ethyl, n-butyl, and t-butyl groups are particularly preferred. 【0111】 R ａ１ , R ａ２ , and R ａ３ Examples of cycloalkyl groups 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. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred. 【0112】 R ａ１ , R ａ２ , and R ａ３For example, the alkyl group portion of the alkoxy group is R ａ１ , R ａ２ and R ａ３ The alkyl groups listed are examples. Methoxy, ethoxy, n-propoxy, and n-butoxy groups are particularly preferred as alkoxy groups. 【0113】 R ａ１ , R ａ２ , and R ａ３ For example, the cycloalkyl group portion of the cycloalkyloxy group is R ａ１ , R ａ２ and R ａ３ The cycloalkyl groups listed are examples of the cycloalkyl groups listed above. Cyclopentyloxy and cyclohexyloxy groups are particularly preferred among these cycloalkyloxy groups. 【0114】 R ａ１ , R ａ２ , and R ａ３ For example, the alkoxy group portion of the alkoxycarbonyl group is R ａ１ , R ａ２ and R ａ３ The alkoxy groups listed above are examples of such groups. Methoxycarbonyl groups, ethoxycarbonyl groups, and n-butoxycarbonyl groups are particularly preferred among these alkoxycarbonyl groups. 【0115】 R ａ１ , R ａ２ , and R ａ３ For example, the alkyl group portion of the alkylsulfonyl group is R ａ１ , R ａ２ , and R ａ３ The alkyl groups listed are listed below. Also, R ａ１ , R ａ２ , and R ａ３ For example, the cycloalkyl group of the cycloalkylsulfonyl group is R ａ１ , R ａ２ , and R ａ３The cycloalkyl groups listed above are examples of the alkylsulfonyl groups or cycloalkylsulfonyl groups in particular: methanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group, n-butanesulfonyl group, cyclopentanesulfonyl group, and cyclohexanesulfonyl group. 【0116】 R ａ１ , R ａ２ , and R ａ３ Each of these groups may have further substituents. Examples of these substituents include halogen 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. 【0117】 R ａ１ , R ａ２ , and R ａ３ Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms, with fluorine and iodine atoms being preferred. 【0118】 R ａ１ , R ａ２ , and R ａ３ As the halogenated hydrocarbon group, halogenated alkyl groups are preferred. The alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among these, fluorinated alkyl groups are preferred, and CF ３ This is preferable. 【0119】 As mentioned above, R ａ１ and R ａ２ They may be linked together to form a ring (i.e., a heterocycle containing sulfur atoms). In this case, R ａ１ and R ａ２ It is preferable that these groups bond to each other to form single bonds or divalent linking groups. Examples of divalent linking groups include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２- Examples include alkylene groups, cycloalkylene groups, alkenylene groups, or combinations of two or more thereof, preferably with a total carbon number of 20 or less. ａ１ and R ａ２ When they are connected to each other to form a ring, R ａ１ and R ａ２ These combine with each other to form -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. Also, if m1 is 2 or more, multiple R ａ１ They may be connected to each other to form a ring, and if m2 is 2 or more, multiple R ａ２ They may be connected to each other to form a ring. For example, two R ａ１ One embodiment is one in which these elements are linked to one another, and together with the benzene ring to which they are linked, they form a naphthalene ring. 【0120】 R ａ３ It is preferable that it is a fluorine atom or a group having one or more fluorine atoms. As for groups having fluorine atoms, R ａ１ and R ａ２ Examples of groups in which alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, and alkylsulfonyl groups are substituted with a fluorine atom can be cited. 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 ２ CF ３ ,CH ２ C ２ F５ ,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. 【0121】 R ａ３ is a fluorine atom, an iodine atom, or CF ３ It is preferable that it be a fluorine atom or an iodine atom. 【0122】 m1 and m2 are each independently preferably integers between 0 and 3, and preferably integers between 0 and 2. 【0123】 m3 is preferably an integer from 1 to 3, and more preferably 1 or 2. 【0124】 (m1 + m2 + m3) is preferably an integer between 1 and 15, more preferably an integer between 1 and 9, even more preferably an integer between 2 and 6, and particularly preferably an integer between 3 and 6. 【0125】 Specific examples of onium cations (c1) represented by the above formula (Q-1) include the following: 【0126】 【0127】 【0128】 【0129】 【0130】Specific examples of iodonium cations of structural unit (IV-2) include the following. The hydrogen atoms on the aromatic ring in the iodonium cations below may be substituted with iodine atoms, fluorine atoms, groups containing these atoms, or other substituents. 【0131】 【0132】 The monomers that give structural unit (IV-1) and structural unit (IV-2) can be synthesized, for example, by the same method as the sulfonium salt having polymerizable anion described in Japanese Patent No. 5201363. 【0133】 The lower limit of the content of structural unit (IV) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, relative to the total structural units constituting the base polymer (A). 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 (IV) within the above range, the acid-generating agent can be fully exhibited. 【0134】 (Structural Unit (V)) Structural unit (V) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (IV)). The solubility of the base polymer (A) in the developer can be adjusted by further containing structural unit (V). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred. 【0135】 Examples of structural units (V) include structural units represented by the following formula. 【0136】 【0137】 【0138】 In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 【0139】When the base polymer (A) has structural units (V) having the polar group described above, the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%. By setting the content of structural units (V) within the above range, the solubility of the base polymer (A) in the developer can be efficiently adjusted. 【0140】 (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. 【0141】 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 15,000, and even more preferably 10,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability. 【0142】 The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) (Mw / Mn) of the base polymer (A) by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less. 【0143】 The methods for measuring Mw and Mn of polymers in this specification are as described in the examples. 【0144】 The lower limit of the content of the base polymer (A) 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. 【0145】(Other Polymers) The first radiation-sensitive composition of this embodiment may also contain, as other polymers, polymers with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as "high-fluorine content polymers"). When the radiation-sensitive composition contains a high-fluorine content polymer, it can be unevenly distributed on the surface of the resist film relative to the base polymer (A), and as a result, it is possible to improve the water repellency of the surface of the resist film during immersion exposure, or to control the surface modification of the resist film and the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine content polymers. 【0146】 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. 【0147】 The lower limit of Mw / Mn for high-fluorine-content polymers is usually 1, and 1.1 is more preferred. The upper limit of Mw / Mn is usually 5, 3 is preferred, and 2 is more preferred. 【0148】 If the radiation-sensitive composition contains a high-fluorine-content polymer, the amount of the high-fluorine-content polymer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the base polymer (A). Furthermore, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 5 parts by mass or less. 【0149】 (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the synthesis method for the base polymer (A) described above. 【0150】 <Onium salt compound (B)> The above first radiation-sensitive composition contains one or more onium salts (B) comprising an organic acid anion and a radiation-sensitive onium cation. 【0151】The onium salt compound (B) described above has a form in which the onium salt structure exists as a low molecular weight compound on its own (liberated from the polymer), and is different from the acid-generating structure in polymer (A), where an organic acid anion (b1) or onium cation (c1) is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer, as in structural unit (IV). 【0152】 In the present invention, at least a portion of the organic acid anion of the onium salt compound (B) is the organic acid anion (1) represented by the above formula (1), thereby enabling excellent sensitivity, CDU, and bridge margin. 【0153】 Furthermore, from the viewpoint of sensitivity, it is preferable that at least a portion of the above-mentioned radiation-sensitive onium cation is a fluorine-containing radiation-sensitive onium cation containing at least one selected from the group consisting of a fluorine atom and a fluorinated hydrocarbon group. 【0154】 The above onium salt compound (B) is a compound that generates acid upon exposure, and specifically includes an acid diffusion control agent containing an organic acid anion (1) and a radiation-sensitive onium cation (1) (hereinafter also referred to as "onium salt compound (B1)"), and a radiation-sensitive acid generator containing an organic acid anion (2) different from the organic acid anion (1) and a radiation-sensitive onium cation (2) (hereinafter also referred to as "onium salt compound (B2)"). The radiation-sensitive acid generator is a compound that generates an acid that dissociates the above-mentioned acid-dissociating group upon exposure. The acid diffusion control agent is a compound that generates an acid that does not dissociate the above-mentioned acid-dissociating group upon exposure, and has the function of suppressing the diffusion of acid generated from the radiation-sensitive acid generator, etc., in the unexposed area. The acid generated from the acid diffusion control agent can be said to be a relatively weaker acid (an acid with a large pKa) than the acid generated from the radiation-sensitive acid generator, etc. Whether the onium salt compound (B) functions as a radiation-sensitive acid generator or acid diffusion controller depends on the energy required for the acid-dissociable groups of the polymer (A) to dissociate, and the acidity of the acid generated by exposure. 【0155】Furthermore, from the viewpoint of sensitivity, it is preferable that at least one of the above-mentioned radiation-sensitive onium cation (1) and the above-mentioned radiation-sensitive onium cation (2) is the above-mentioned fluorine-containing radiation-sensitive onium cation. 【0156】 (Onium salt compound (B1)) Onium salt compound (B1) is an acid diffusion control agent containing an organic acid anion (1) and a radiation-sensitive onium cation (1). The above organic acid anion (1) is an organic acid anion represented by the following formula (1). (In formula (1), Ar is an aromatic ring having 5 to 20 carbon atoms. １ R is a fluorine atom or a fluorinated hydrocarbon group. １ If multiple R １ These are either the same or different. ２ is an aprotic substituent (however, R １ (Excluding those that fall under the above category). ２ If multiple R ２ They are either the same or different. n1 is an integer between 0 and 5. n2 is an integer between 0 and 5. 【0157】 The aromatic ring in Ar described above is not particularly limited as long as it has 5 to 20 carbon atoms and is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, and perylene rings; aromatic heterocycles such as 1,3-benzodioxole rings, pyridine rings, carbazole rings, benzofuran rings, and dibenzofuran rings; or combinations thereof. Among these, benzene rings and naphthalene rings are preferred as aromatic rings in Ar, with benzene rings being more preferred. 【0158】 R １ The fluorinated hydrocarbon group in is R in formula (i) above. １８ Examples include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are substituted with fluorine atoms, and fluorinated alkyl groups are preferred. 【0159】 The above R １Preferably, the fluorine atom and a fluorinated alkyl group having 1 to 3 carbon atoms are used, and the fluorine atom and -CF ３ ,-CHF ２ More preferably, a fluorine atom, -CF ３ That is even more preferable. 【0160】 The above R ２ A is an aprotic substituent. An aprotic substituent is a group that does not contain a hydrogen atom bonded to a heteroatom such as an oxygen atom or a nitrogen atom, and is therefore unable to donate a hydrogen atom. For example, hydroxyl groups and carboxyl groups are protic substituents because they contain a hydrogen atom bonded to a hydrogen atom. 【0161】 Examples of aprotic substituents include halogen atoms other than fluorine atoms, monovalent organic groups having 1 to 20 carbon atoms that do not have aprotic substituents, cyano groups, nitro groups, etc. Examples of monovalent organic groups having 1 to 20 carbon atoms that do not have aprotic substituents include alkoxy groups, alkylthio groups, alkylcarbonyloxy groups, alkyloxycarbonyl groups, alkylcarbonyl groups, etc. 【0162】 Other halogen atoms besides the fluorine atom mentioned above include chlorine, bromine, and iodine atoms, but among these, iodine is preferred. 【0163】 As for the monovalent organic group having 1 to 20 carbon atoms mentioned above, R in formula (B2) described later is ６０ From among the monovalent organic groups having 1 to 40 carbon atoms represented by , those with the corresponding number of carbon atoms can be suitably adopted. However, those having protic substituents such as hydroxyl groups are not included. 【0164】 Among the above organic groups having 1 to 20 carbon atoms, substituted or unsubstituted hydrocarbon groups having 1 to 20 carbon atoms, -OR ２１ , -C (=O) OR ２１ The following are preferred. ２１ This is a substituted or unsubstituted hydrocarbon group having 1 to 10 carbon atoms. 【0165】 The above hydrocarbon group having 1 to 20 carbon atoms is R of formula (i) above. １８Suitablely, monovalent substituted or unsubstituted hydrocarbon groups having 1 to 20 carbon atoms can be used. When the hydrocarbon group has substituents, examples of substituents include halogen atoms other than fluorine, cyano groups, nitro groups, alkoxy groups, and the like. 【0166】 The above R ２ Examples include iodine group, -OR ２１ It is preferable. 【0167】 n1 is an integer from 0 to 5, preferably an integer from 1 to 5, more preferably an integer from 1 to 3, and even more preferably 1 or 2. When n1 is 1 or greater, the organic acid anions can be unevenly distributed on the surface of the pattern, and the diffusion of acid generated from the radiation-sensitive acid generator on the pattern surface can be highly suppressed, resulting in excellent CDU and bridge margin, which is therefore preferable. In particular, when n1 is 1 or greater and at least one R １ It is more preferable that the alkyl group is a fluorinated alkyl group. 【0168】 n2 is an integer between 0 and 5, preferably between 1 and 3, and more preferably 1 or 2. 【0169】 It is preferable that the above organic acid anion (1) is an organic acid anion represented by the following formula (1-1). (In formula (1-1), R １ , R ２ n1 and n2 are equivalent to those in equation (1) above. 【0170】 In the above equation (1-1), n1 is an integer from 1 to 5, and R １ One of them is -COO － It is preferable from the viewpoint of surface eccentricity that the group is located at the para position. 【0171】 A specific example of the organic acid anion (1) represented by the above formula (1) is the structure represented by the following formula. 【0172】 (In the formula, Me represents a methyl group.) 【0173】 【0174】Examples of the above-mentioned radioactive onium cation (2) 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. 【0175】 The above-mentioned radiation-sensitive onium cation (2) is preferably a sulfonium cation represented by the above formula (Q-1). Among these, from the viewpoint of sensitivity, a sulfonium cation containing an iodine group is preferred. 【0176】 The above-mentioned radiation-sensitive onium cation (1) may be a diaryliodonium cation. The diaryliodonium cation exemplified in the above-mentioned structural unit (IV) can be suitably adopted. 【0177】 Among the above, the radiation-sensitive onium cation (1) is preferably a fluorine-containing radiation-sensitive onium cation containing at least one selected from the group consisting of a fluorine atom and a fluorinated hydrocarbon group, and more preferably a fluorine-containing sulfonium cation. As the fluorinated hydrocarbon, R of formula (i) above is preferred. １８ Examples include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are replaced by fluorine atoms. 【0178】 As specific examples of the onium salt compound (B1) described above, any combination of the radiation-sensitive onium cation (1) and the organic acid anion (1) can be suitably adopted, and is not limited to such combinations, but the following structures can be given as specific examples of the onium salt compound (B1). 【0179】 【0180】 【0181】 In the present invention, the above onium salt compound (B1) can be used alone or in combination of two or more types. 【0182】If the above-mentioned first radiation-sensitive composition contains an onium salt compound (B1) as an acid diffusion control agent, the lower limit of the content of the onium salt compound (B1) (total in the case of multiple types) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total amount of monomers that give structural units (IV) of the base polymer (A) and the onium salt compound (B2) (total amount if multiple types are included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. 【0183】 (Onium salt compound (B2)) The above radiation-sensitive composition preferably contains an onium salt compound (B2) as a radiation-sensitive acid generator. The onium salt compound (B2) contains an organic acid anion (2) different from the above organic acid anion (1) and a radiation-sensitive onium cation (2). 【0184】 The organic acid anion (2) of the above onium salt compound (B2) is preferably selected from the group consisting of sulfonic acid anions, sulfonimide anions, and methide anions, with sulfonic acid anions being more preferred. Furthermore, it is preferable that an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom of the above sulfonic acid anion or sulfonimide anion. 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. 【0185】 As the onium salt compound (B2), a compound represented by the following formula (B2) can be suitably used. (In formula (B2), R ６０ R is a monovalent organic group having 1 to 40 carbon atoms. ｆ１ and R ｆ２ Each of these is independently a hydrogen atom, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ If multiple R ｆ１ and R ｆ２ These are either the same or different. t is an integer between 0 and 4. Z ＋(This is a radiation-sensitive onium cation.) 【0186】 R ６０ Examples of monovalent organic groups having 1 to 40 carbon atoms represented by this formula include monovalent hydrocarbon groups having 1 to 40 carbon atoms, groups having a divalent heteroatom-containing group between carbon atoms or at the end of the carbon chain of this hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with a monovalent heteroatom-containing group, or combinations thereof. 【0187】 As the above monovalent hydrocarbon group having 1 to 40 carbon atoms, R in formula (i) above is １８ A monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by [the formula shown], can be suitably adopted by extending the number of carbon atoms from 1 to 40. 【0188】 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. 【0189】 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. 【0190】 Examples of the above-mentioned divalent heteroatom-containing groups include -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ - or combinations thereof are examples. 【0191】 The above R ６０ From the viewpoint of being able to appropriately control the diffusion length of the generated acid, it is preferable that the structure includes a cyclic structure. 【0192】 As the above-mentioned cyclic structure, the cyclic structure described in structural unit (IV) above can be suitably adopted. Among these, alicyclic structures, aromatic ring structures, and cyclic acetals are preferred as cyclic structures. 【0193】 R ｆ１ and R ｆ２As a monovalent fluorinated hydrocarbon group represented by the above formula (i), R １８ Examples include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are replaced by fluorine atoms. 【0194】 From the viewpoint of sensitivity, the above organic acid anion (2) preferably has an iodine group, and more preferably contains the above iodine group-containing aromatic ring structure. 【0195】 Specific examples of the above-mentioned sulfonate anions include, but are not limited to, the structure shown in the following formula. 【0196】 【0197】 【0198】 【0199】 【0200】 【0201】 Z ＋ As the radiation-sensitive onium cation represented by , the radiation-sensitive onium cation (1) listed in the above onium salt compound (B1) can be suitably adopted. 【0202】 Among the above, the radiation-sensitive onium cation (2) is preferably a fluorine-containing radiation-sensitive onium cation containing at least one selected from the group consisting of a fluorine atom and a fluorinated hydrocarbon group, and more preferably a fluorine-containing sulfonium cation. 【0203】 As specific examples of the onium salt compound (B2) described above, any combination of the radiation-sensitive onium cation (2) and the organic acid anion (2) described above can be suitably adopted, and is not limited to such combinations, but the following structures can be given as specific examples of the onium salt compound (B2). 【0204】 【0205】 【0206】 【0207】 【0208】 The above onium salt compound (B2) may be used alone or in combination of two or more types. 【0209】 When the above-mentioned first radiation-sensitive composition contains an onium salt compound (B2), the lower limit of the onium salt compound (B2) content (total in the case of multiple types) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass, per 100 parts by mass of the base polymer (A). The upper limit of the above content is preferably 80 parts by mass, more preferably 70 parts by mass, and even more preferably 60 parts by mass. This allows for excellent sensitivity during resist pattern formation. 【0210】 <Compound (C)> The above radiation-sensitive composition contains a compound represented by the following formula (2). (In formula (2), R ３ (where X is a monovalent organic group; X is a hydrogen atom or an acid-dissociable group.) 【0211】 The above R ３ As a monovalent organic group represented by the above formula (B2), R ６０ A monovalent organic group having 1 to 40 carbon atoms, represented by , can be suitably used. Among these, R ３ From the viewpoint of CDU, bridge margin, and storage stability, it is preferable that the structure includes a cyclic structure and a carbonyl group. 【0212】 As the above-mentioned cyclic structure, the cyclic structure described in structural unit (IV) above can be suitably adopted. Among these, an aromatic ring structure is preferred as the cyclic structure, and a benzene ring is more preferred. 【0213】 Furthermore, the above aromatic ring structure is preferably substituted from the viewpoint of storage stability, and examples of substituents include the substituent (T) mentioned above. Among substituents (T), hydroxyl groups and fluorinated hydrocarbon groups are preferred, and hydroxyl groups and trifluoromethyl groups are more preferred. 【0214】 Examples of the acid-dissociable group represented by X above include the group represented by the following formula (iii). (In formula (iii), R ３１ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. ３２ and R ３３ Each of these independently represents a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 10 carbon atoms, a substituted or unsubstituted 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. * represents a bond with an oxygen atom. 【0215】 The above R ３１ In the above formula (i), the R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １８ Monovalent substituted or unsubstituted hydrocarbon groups having 1 to 20 carbon atoms can be suitably used in this material. 【0216】 The above R ３２ and R ３３ As for the substituted or unsubstituted monovalent chain hydrocarbon group having 1 to 10 carbon atoms and the substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, R in formula (i) above is １９ and R ２０ Substituted or unsubstituted monovalent chain hydrocarbon groups having 1 to 10 carbon atoms, or substituted or unsubstituted monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms can be suitably employed. 【0217】 The above R ３２ and R ３３ 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 in formula (i) above. １９ and R ２０ Divalent alicyclic groups having 3 to 20 carbon atoms can be suitably used, as these groups can be combined with each other and formed together with the carbon atoms to which they are bonded. 【0218】 It is preferable that the compound represented by formula (2) above is the compound represented by formula (2-1) below. (In formula (2-1), R ４ R is a halogen atom, a nitro group, a hydroxyl group, or a monovalent organic group having 1 to 20 carbon atoms. ４If multiple R ４ These are either identical or different. n3 is an integer between 0 and 4. X is equivalent to equation (2). 【0219】 The above R ４ In this, the monovalent organic group having 1 to 20 carbon atoms is R in formula (B2) above. ６０ From among the monovalent organic groups having 1 to 40 carbon atoms represented by , those with the corresponding number of carbon atoms can be suitably adopted. 【0220】 The above n3 is an integer from 0 to 4, and is preferably an integer from 0 to 2. 【0221】 Examples of compounds represented by formula (2) or formula (2-1) above include acetic acid, butyric acid, salicylic acid, benzoic acid, 4-(trifluoromethyl)salicylic acid, lactic acid, oxalic acid, pyruvic acid, 2-naphthoic acid, 4-(trifluoromethyl)benzoic acid, trifluoroacetic acid, poly(4-vinylbenzoic acid), 4-fluorosalicylic acid, 5-fluorosalicylic acid, 6-fluorosalicylic acid, 5-(trifluoromethyl)salicylic acid, 6-(trifluoromethyl)salicylic acid, 6-(trifluoromethyl)-5-methylsalicylic acid, 5-nitrosalicylic acid, 4-methylsalicylic acid, 2,6-dihydroxybenzoic acid, 2,3,5-triiodobenzoic acid, 3,5-diiodosalicylic acid, 2-thiophenecarboxylic acid, and the like. Among these, salicylic acid, 4-(trifluoromethyl)benzoic acid, oxalic acid, pyruvic acid, 4-(trifluoromethyl)salicylic acid, acetic acid, butyric acid, lactic acid, and benzoic acid are preferred from the viewpoint of storage stability, and salicylic acid, 4-(trifluoromethyl)benzoic acid, oxalic acid, pyruvic acid, and 4-(trifluoromethyl)salicylic acid are more preferred. 【0222】 In the present invention, the above compound (C) can be used alone or in combination of two or more types. 【0223】The lower limit of the content of compound (C) above (total in the case of multiple types) is preferably 0.1 parts by mass, more preferably 0.6 parts by mass, even more preferably 1 part by mass, and particularly preferably 2 parts by mass, per 100 parts by mass of base polymer (A). The upper limit of the above content is preferably 20 parts by mass, more preferably 15 parts by mass, and even more preferably 10 parts by mass. By setting it within the above range, better storage stability can be achieved. 【0224】 <Solvent (D)> The above-mentioned first radiation-sensitive composition contains solvent (D). Solvent (D) is not particularly limited as long as it is a solvent capable of dissolving or dispersing the base polymer (A), onium salt (B), compound (C), and optionally contained additives. 【0225】 Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents. 【0226】 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, such as propylene glycol 1-monomethyl ether, which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents. 【0227】 In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents. 【0228】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. 【0229】 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. 【0230】 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. 【0231】 Examples of ester solvents include polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate. 【0232】 Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene. 【0233】 Among these, alcohol-based solvents, ester-based solvents, and ether-based solvents are preferred, alcohol-based solvents, polyhydric alcohol partial ether acetate-based solvents, and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol 1-monomethyl ether, and diacetone alcohol are even more preferred. The radiation-sensitive composition may contain one or more solvents. 【0234】 <Acid diffusion control agent (Y) other than onium salt compound (B1)> The above radiation-sensitive composition may also use an acid diffusion control agent (Y) other than the onium salt compound (B1) as the acid diffusion control agent. The acid diffusion control agent (Y) represented by the following formula (Y1) can be suitably adopted. R ７０ - COO － Z ＋ (Y1) (In formula (Y1), R ７０ Z is a monovalent organic group having 1 to 40 carbon atoms. ＋ (This is a radiation-sensitive onium cation.) 【0235】 The above R ７０ As a monovalent organic group having 1 to 40 carbon atoms, R in the above formula (B2) is ６０ A monovalent organic group having 1 to 40 carbon atoms, represented by the formula shown below, can be suitably used. However, the group represented by formula (1') below is not included. (In formula (1'), Ar, R １ , R ２ n1 and n2 are equivalent to equation (1) above. * is -COO － (This represents a combination of two elements.) 【0236】 The following are examples of organic acid anions for the above-mentioned acid diffusion control agent (Y), but are not limited to these. 【0237】 【0238】 As the onium cation in the above-mentioned acid diffusion control agent (Y), the radiation-sensitive onium cation (1) listed in the above-mentioned onium salt compound (B1) can be suitably used. 【0239】If the above-mentioned first radiation-sensitive composition contains an acid diffusion control agent (Y), the lower limit of the content of the acid diffusion control agent (Y) (total if there are multiple types) is preferably 0.1 mol%, more preferably 1 mol%, and even more preferably 3 mol%, relative to the total amount of monomers that give structural units (IV) of the base polymer (A) and onium salt compounds (B2) (total amount if multiple types are included). The upper limit of the above content is preferably 20 mol%, more preferably 10 mol%, and even more preferably 5 mol%. 【0240】 <Other Optional Components> The above-mentioned first radioactive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization promoters, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types. 【0241】 <Method for preparing the first radiation-sensitive composition> The first radiation-sensitive composition can be prepared, for example, by mixing a base polymer (A), an onium salt compound (B), a compound (C), and a solvent (D) with other optional components in predetermined proportions. The mixing order is not particularly limited; for example, the base polymer (A), onium salt compound (B), compound (C), and solvent (D) may all be mixed at once, or a solution consisting of the base polymer (A), onium salt compound (B), and solvent (D) may be prepared first, and then compound (C) may be added later, or a solution consisting of the onium salt compound (B), compound (C), and solvent (D) may be prepared first, and then polymer (A) may be added later. Alternatively, a solution consisting of polymer (A) and solvent (D), a solution consisting of onium salt compound (B) and solvent (D), and a solution consisting of compound (C) and solvent (D) may be prepared separately, and then these three solutions may be mixed. After mixing, the above radiation-sensitive composition is preferably filtered using, for example, a filter with a pore size of about 0.05 μm to 0.4 μm. The solid content concentration of the above-mentioned radiation-sensitive composition is typically 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass. 【0242】≪Second Radiation-Sensitive Composition≫ The second radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the second composition") contains one or more onium salts containing an organic acid anion and a radiation-sensitive onium cation, a compound represented by the following formula (2), and a solvent, wherein at least a portion of the organic acid anion in the onium salt is an organic acid anion (1) represented by the following formula (1). (In formula (1), Ar is an aromatic ring having 5 to 20 carbon atoms. １ R is a fluorine atom or a fluorinated hydrocarbon group. １ If multiple R １ These are either the same or different. ２ is an aprotic substituent (however, R １ (Excluding those that fall under the above category). ２ If multiple R ２ They are either the same or different. n1 is an integer between 0 and 5. n2 is an integer between 0 and 5. (In formula (2), R ３ (where X is a monovalent organic group; X is a hydrogen atom or an acid-dissociable group.) 【0243】 In the second radiation-sensitive composition according to this embodiment, the onium salt, the compound represented by formula (2), and the solvent can preferably be the onium salt (B), compound (C), and solvent (D) of the first radiation-sensitive composition. 【0244】 Furthermore, the organic acid anion (1) represented by formula (1) above can also be the same as that of the first radiation-sensitive composition described above. 【0245】 The above-mentioned second radiation-sensitive composition may further contain a polymer. The polymer (A) of the above-mentioned first radiation-sensitive composition can be suitably used as the polymer. That is, the second radiation-sensitive composition can be suitably used in the preparation of the first radiation-sensitive composition. 【0246】≪Pattern Forming Method≫ The pattern forming method in this embodiment includes the steps of: (1) forming a resist film by directly or indirectly applying a composition obtained by blending a polymer with the first radiation-sensitive composition or the second radiation-sensitive composition to a substrate (hereinafter also referred to as the "resist film forming step"), (2) exposing the resist film (hereinafter also referred to as the "exposure step"), and (3) developing the exposed resist film with a developer (hereinafter also referred to as the "development step"). 【0247】 According to the pattern formation method described above, high-quality resist patterns can be efficiently formed because the radiation-sensitive composition used exhibits good storage stability and provides sensitivity, CDU, and bridge margin during pattern formation. Each step will be described below. 【0248】 [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, pre-baking (PB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm. 【0249】 Furthermore, when the subsequent exposure process is carried out with radiation of a wavelength of 50 nm or less, it is preferable to use a polymer having the above structural unit (II) as the base polymer in the above composition. 【0250】[Exposure Process] In this process (the above process (2)), the resist film formed in the resist film forming process which is the above process (1) is irradiated with radiation through a photomask for exposure. Examples of the radiation used for exposure include electromagnetic waves such as visible light, ultraviolet rays, far ultraviolet rays, EUV (extreme ultraviolet rays), X-rays, and γ-rays; charged particle beams such as electron beams and α-rays. Among these, far ultraviolet rays, 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 a wavelength of 50 nm or less positioned as the next-generation exposure technology are even more preferred. 【0251】 After the above exposure, post-exposure bake (PEB) is performed. In the exposed portion of the resist film, it is preferable to promote the dissociation of the acid-dissociable groups of polymers and the like generated by the acid generated from the acid generation structure of the structural unit (IV) and the onium salt compound (B2) by exposure. By this PEB, a difference in solubility in the developer occurs between the exposed portion and the unexposed portion. The PEB temperature is usually 50°C to 180°C, and 80°C to 150°C is preferable. The PEB time is usually 5 seconds to 600 seconds, and 10 seconds to 300 seconds is preferable. 【0252】 [Development Process] In this process (the above process (3)), the resist film exposed in the above exposure process which is the above process (2) is developed with a developer. Thereby, a predetermined resist pattern can be formed. After development, it is common to wash with a rinse solution such as water or alcohol and then dry. 【0253】Examples of developers used in the above-mentioned development 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. 【0254】 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. 【0255】 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). 【0256】Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. The physical property values in the examples were measured as follows. 【0257】 [Weight average molecular weight (Mw) and number average molecular weight (Mn)] Using GPC columns manufactured by Tosoh Corporation (G2000HXL: 2 pieces, G3000HXL: 1 piece, G4000HXL: 1 piece), flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40 °C, detector: differential refractometer, it was measured by gel permeation chromatography (GPC) with monodisperse polystyrene as a standard. Also, the dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn. 【0258】 <Synthesis of polymer (A)> The monomers used in the synthesis of each polymer in each example and comparative example are shown below. 【0259】 【0260】 [Synthesis Examples A1 to A18] Synthesis of polymers (A-1) to (A-18) After copolymerization reaction was carried out in a tetrahydrofuran (THF) solvent by combining each monomer, isolation and drying were performed to obtain base polymers (A-1) to (A-18) having the following compositions. The content of each structural unit, the values of Mw and Mw / Mn in the obtained polymers are shown in Table 1. 【0261】 【0262】 <Radiation-sensitive acid generator (B1)> Compounds represented by the following (B1-1) to (B1-10) were used as the radiation-sensitive acid generator. 【0263】 【0264】 <Acid diffusion control agent (B2)> Compounds represented by the following (B2-1) to (B2-13), (B2X-1) to (B2X-2) were used as the acid diffusion control agent. 【0265】 【0266】<Solvent (D)> D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether D-3: Diacetone alcohol 【0267】 <Compound (C)> C-1: Acetic acid C-2: Butyric acid C-3: Salicylic acid C-4: Benzoic acid C-5: 4-(trifluoromethyl)salicylic acid C-6: Lactic acid C-7: Oxalic acid C-8: Pyruvate C-9: 2-Naphthoic acid C-10: 4-(trifluoromethyl)benzoic acid C-11: Trifluoroacetic acid C-12: Poly(4-vinylbenzoic acid) 【0268】 [Example 1] Preparation of radiation-sensitive composition (R-1) 100 parts by mass of (A-1) as polymer (A), 50 parts by mass of (B1-1) as radiation-sensitive acid generator (B1), 40 mol% of (B2-1) as acid diffusion control agent (B2) relative to (B1-1), 1,500 parts by mass of (D-1) and 5,500 parts by mass of (D-2) as solvents (D), and 3 parts by mass of (C-3) as compound (C) were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare the radiation-sensitive composition (R-1). 【0269】 [Examples 2-54 and Comparative Examples 1-5] Preparation of radiation-sensitive compositions (R-2)-(R-54) and (RX-1)-(RX-5) The radiation-sensitive compositions (R-2)-(R-54) and (RX-1)-(RX-5) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2-1 and 2-2 were used. In (R-17)-(R-18), (B2-1) as the acid diffusion control agent (B2) was prepared by blending 40 mol% of the total amount of (M-18) component in (A-17) and (A-18), respectively. 【0270】 【0271】 <Evaluation> The sensitivity, CDU, bridge margin, and storage stability of the radiation-sensitive compositions prepared above were evaluated according to the following method. The evaluation results are shown in Tables 3-1 and 3-2 below. 【0272】[Sensitivity] A 12-inch silicon wafer surface with a 20 nm thick underlayer (AL412 (manufactured by Brewer Science)) was coated with each of the radiation-sensitive compositions shown in Tables 2-1 and 2-2 using a spin coater, and PB was performed at 130°C for 60 seconds. Subsequently, a resist film with an average thickness of 50 nm was formed by cooling at 23°C for 30 seconds. This resist film was exposed using an EUV scanner (ASML's "NXE3300" (NA 0.33, σ 0.9 / 0.6, quadruple pole illumination, wafer dimensions with a pitch of 50 nm, +20% bias hole pattern mask)). PEB was performed on a hot plate at 100°C for 60 seconds, and development was performed with a 2.38 mass% tetramethylammonium hydroxide (TMAH) aqueous solution for 30 seconds to form a grid-like resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as the "25 nm contact hole pattern"). The exposure amount used to form the 25 nm contact hole pattern described above is defined as the optimal exposure amount, and this optimal exposure amount is set to the sensitivity (mJ / cm²). ２ The sensitivity is set to 47 mJ / cm². A smaller value indicates better sensitivity. ２ If the value is less than 47 mJ / cm², it is classified as "A" (very good) and 47 mJ / cm². ２ More than 50mJ / cm ２ In the following cases, the rating is "B" (good), and the temperature is 50 mJ / cm². ２ If the value exceeded this, it was rated as "C" (poor). 【0273】 [CDU] The optimal exposure dose determined in the [Sensitivity] section above was used to form a 25 nm contact hole pattern in the same manner as described above. The formed resist pattern was observed from above using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), and the hole diameter was measured at a total of 800 arbitrary points. The dimensional variation (3σ) was determined and defined as the CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and is therefore of better quality. The CDU was evaluated as "A" (excellent) if it was less than 2.1 nm, "B" (good) if it was between 2.1 nm and 2.4 nm, and "C" (poor) if it was 2.4 nm or greater. 【0274】[Bridge Margin] The bridge margin refers to the resist dimension where bridge defects (connections between holes) do not occur. Generally, bridge defects are observed at high exposure levels. From the optimal exposure level that can form the aforementioned 25 nm contact hole pattern, it is 0.5 mJ / cm². ２ The exposure dose was gradually increased, and the hole diameter of the resist pattern formed at the maximum exposure dose in which no bridge defects occurred was defined as the bridge margin (unit: nm). A larger bridge margin indicates a lower likelihood of bridge defects occurring, which is considered good as it allows for a wider process window. Bridge margins were evaluated as follows: "A" (excellent) if 35 nm or more, "B" (good) if 33 nm or more but less than 35 nm, and "C" (poor) if less than 33 nm. 【0275】 [Storage Stability] After preparing the radiation-sensitive composition, it was stored at -15°C for two weeks or at 35°C for two weeks. Then, the above radiation-sensitive composition was applied to the surface of a 12-inch silicon wafer on which a 20 nm thick underlayer film (DUV42 (manufactured by Nissan Chemical Corporation)) had been formed, using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Limited). After performing PB at 130°C for 60 seconds, it was cooled at 23°C for 30 seconds to form a 50 nm thick resist film. Next, this resist film was irradiated with KrF light using a KrF exposure machine (model "S210D", manufactured by Nikon, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). PEB was performed at 110°C for 60 seconds. Next, the material was developed at 23°C for 30 seconds using a 2.38 mass% TMAH aqueous solution to form a positive-type 150 nm line and space pattern. The optimal exposure dose Eop1 for forming the 150 nm line and space pattern was determined. Using Eop1 as a reference, if the optimal exposure dose Eop2 of the radiation-sensitive composition stored at 35°C for two weeks was 1.5% or more more sensitive, or 1.5% or more less sensitive, it was judged as "C". If it was less than 1.5% but 1.0% or more sensitive, or less than 1.5% but 1.0% or more less sensitive, it was judged as "B". In all other cases, it was judged as "A". 【0276】 【0277】 As is clear from the results in Tables 3-1 and 3-2, all of the radiation-sensitive compositions in the examples were able to maintain storage stability while forming good patterns in sensitivity, CDU, and bridge margin compared to the radiation-sensitive compositions of the comparative examples. 【0278】 [Example 55] [Preparation of Acid Diffusion Control Agent Solution (S-1)] 100 parts by mass of (B2-1) as the acid diffusion control agent (B2), 1,000 parts by mass of (D-2) as the solvent (D), and 10 parts by mass of (C-3) as the compound (C) were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare the acid diffusion control agent solution (S-1). 【0279】 [Preparation of Radiation-Sensitive Composition] The prepared acid diffusion control agent solution (S-1) was stored at -15°C for 3 days or at 60°C for 3 days to obtain acid diffusion control agent solution (S-1α) and acid diffusion control agent solution (S-1β), respectively. Next, (A-1), (B1-1), (S-1α) stored at -15°C for 3 days, (C-1), (D-1), and (D-2) were used to mix the components to the amounts shown in Table 5. The resulting mixture was filtered through a 0.2 μm pore size filter to prepare the radiation-sensitive composition (SR-1α). However, the amount of (S-1α) added was such that the ratio of the acid diffusion control agent (B2) to the radiation-sensitive acid generator (B1) in the final radiation-sensitive composition (SR-1α) was as shown in Table 5. 【0280】[Evaluation of Storage Stability of Radiation-Sensitive Composition] A radiation-sensitive composition (SR-1α) was applied to the surface of a 12-inch silicon wafer with a 20 nm thick underlayer (DUV42 (manufactured by Nissan Chemical Corporation)) using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron Limited). After performing PB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 50 nm thick resist film. This resist film was irradiated with KrF light using a KrF exposure machine (model "S210D", manufactured by Nikon, NA = 0.55, illumination conditions: Annular s = 0.8, mask 150 nm LS). PEB was performed at 110°C for 60 seconds. Subsequently, development was performed using a 2.38 mass% TMAH aqueous solution at 23°C for 30 seconds to form a positive-type 150 nm line and space pattern. The optimal exposure amount for forming a 150 nm line-and-space pattern is defined as Eopα. A radiation-sensitive composition (SR-1β) was prepared in the same manner as the preparation of the radiation-sensitive composition (SR-1α) using the acid diffusion control agent solution (S-1α), except that the acid diffusion control agent solution (S-1β), obtained by storing at 60°C for 3 days, was used instead of (S-1α). Next, a positive-type 150 nm line-and-space pattern was formed in the same manner as above, except that the radiation-sensitive composition (SR-1β) was used instead of the radiation-sensitive composition (SR-1α). The optimal exposure amount for forming the 150 nm line-and-space pattern is defined as Eopβ. Based on Eopα, if Eopβ increased sensitivity by 1.5% or more, or decreased sensitivity by 1.5% or more, it was judged as "C". If the sensitivity increased by 1.0% or more but less than 1.5%, or decreased sensitivity by 1.0% or more but less than 1.5%, it was judged as "B". In all other cases, it was judged as "A". 【0281】[Examples 56 to 57 and Comparative Examples 6 to 8] Acid diffusion control agent solutions (S-2) to (S-3), (SX-1) to (SX-3) were prepared in the same manner as in Example 55, except that the components of the types and contents shown in Table 4 were used. Next, radiation-sensitive compositions (SR-1α) to (SR-3α), (SR-1β) to (SR-3β), (SRX-1α) to (SRX-3α) and (SRX-1β) to (SRX-3β) were prepared in the same manner as in Example 55, except that the components of the types and contents shown in Table 5 were used. However, the addition amount of the acid diffusion control agent solution was adjusted so that the acid diffusion control agent (B2) was in the ratio described in Table 5 with respect to the radiation-sensitive acid generator (B1) in the finally obtained radiation-sensitive composition. 【0282】 【0283】 【0284】 As is clear from the results in Table 5, all of the radiation-sensitive compositions of the examples are excellent in storage stability as compared with the radiation-sensitive compositions of the comparative examples. From this, it was found that even when the acid diffusion control agent solution was prepared first, stored for a certain period, and then the polymer and the radiation-sensitive acid generator were added later, excellent storage stability could be obtained by adding an onium salt containing the organic acid anion (1) represented by the formula (1) to the acid diffusion control agent solution. 【0285】 According to the radiation-sensitive composition of the present invention, the storage stability can be improved, and at the time of pattern formation, the sensitivity, CDU, and bridge margin can be exhibited at a level equal to or higher than the conventional level. Further, regardless of the method for preparing the radiation-sensitive composition (that is, any blending method), the storage stability can be improved. 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

Polymers and, One or more onium salts containing an organic acid anion and a radiation-sensitive onium cation, The compound represented by the following formula (2), Solvent and It contains, A radiation-sensitive composition wherein at least some of the organic acid anions in the above onium salt are organic acid anions (1) represented by the following formula (1). (In formula (1), Ar is an aromatic ring with 5 to 20 carbon atoms. R １ R is a fluorine atom or a fluorinated hydrocarbon group. １ If multiple R １ They are either the same or different. R ２ is an aprotic substituent (however, R １ (Excluding those that fall under the above category). ２ If multiple R ２ They are either the same or different. 　 n1 is an integer between 0 and 5. n² is an integer between 0 and 5. (In formula (2), R ３ It is a monovalent organic group. X is a hydrogen atom or an acid-dissociable group. 　 The radiation-sensitive composition according to claim 1, wherein at least a portion of the radiation-sensitive onium cations in the onium salt are fluorine-containing radiation-sensitive onium cations comprising at least one selected from the group consisting of a fluorine atom and a fluorinated hydrocarbon group. 　 As the above onium salt, An acid diffusion control agent comprising the above-mentioned organic acid anion (1) and a radiation-sensitive onium cation (1), and A radiation-sensitive acid generator comprising an organic acid anion (2) different from the above organic acid anion (1) and a radiation-sensitive onium cation (2). It contains, The radiation-sensitive composition according to claim 2, wherein at least one of the above-mentioned radiation-sensitive onium cation (1) and the above-mentioned radiation-sensitive onium cation (2) is the above-mentioned fluorine-containing radiation-sensitive onium cation. 　 The radiation-sensitive composition according to claim 1, wherein n1 is an integer from 1 to 5. 　 In the above formula (1), R １ is a fluorinated alkyl group having 1 to 3 carbon atoms, the radiation-sensitive composition according to any one of claims 1 to 4. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the above-mentioned organic acid anion (1) is an organic acid anion represented by the following formula (1-1). (In formula (1-1), R １ , R ２ n1 and n2 are equivalent to those in equation (1) above. 　 In the above equation (1-1), n1 is an integer from 1 to 5, and R １ One of them is -COO － The radiation-sensitive composition according to claim 6, which is present at the para position of the base. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the compound represented by formula (2) above is the compound represented by formula (2-1) below. (In formula (2-1), R ４ R is a halogen atom, a nitro group, a hydroxyl group, or a monovalent organic group having 1 to 20 carbon atoms. ４ If multiple R ４ They are either the same or different. 　 n3 is an integer between 0 and 4. X is equivalent to equation (2) above. 　 The radiation-sensitive composition according to claim 3, wherein the content of the acid diffusion control agent is 10 mol% or more and 80 mol% or less relative to the radiation-sensitive acid generator. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the content of the compound represented by formula (2) is 2 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the polymer. 　 The radiation-sensitive composition according to claim 2 or 3, wherein the fluorine-containing radiation-sensitive onium cation is a fluorine-containing sulfonium cation. 　 The radiation-sensitive composition according to any one of claims 1 to 4, wherein the polymer comprises a structural unit (I) having an acid-dissociable group. 　 The radiation-sensitive composition according to claim 12, wherein the polymer further comprises a structural unit (II) having a phenolic hydroxyl group. 　 A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 4 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following. 　 The pattern forming method according to claim 14, wherein the exposure is performed using extreme ultraviolet light or an electron beam. 　 One or more onium salts containing an organic acid anion and a radiation-sensitive onium cation, The compound represented by the following formula (2), Solvent and It contains, A radiation-sensitive composition wherein at least some of the organic acid anions in the above onium salt are organic acid anions (1) represented by the following formula (1). (In formula (1), Ar is an aromatic ring with 5 to 20 carbon atoms. R １ R is a fluorine atom or a fluorinated hydrocarbon group. １ If multiple R １ They are either the same or different. R ２ is an aprotic substituent (however, R １ (Excluding those that fall under the above category). ２ If multiple R ２ They are either the same or different. 　 n1 is an integer between 0 and 5. n² is an integer between 0 and 5. (In formula (2), R ３ It is a monovalent organic group. X is a hydrogen atom or an acid-dissociable group. 　 The radiation-sensitive composition according to claim 16, further containing a polymer. 　 A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to claim 17 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following.

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