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

Abstract

One purpose of the present invention is to provide: a radiation-sensitive composition which is capable of exhibiting sensitivity, CDU, and development defects at sufficient levels during the formation of a resist pattern using a next-generation technology; and a pattern forming method. Another purpose of the present invention is to provide a compound and a polymer, each of which is suitable for use in the radiation-sensitive composition. This radiation-sensitive composition contains: a polymer (A) that comprises a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by formula (1); and a solvent (E). (In formula (1), R1 and R2 each independently represent a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. L1 and L2 each independently represent a single bond or a divalent linking group. W represents an aromatic ring. R3 represents a divalent organic group having 1 to 20 carbon atoms. M+ represents a monovalent onium cation.)

Description

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

[0001] The present invention relates to a radiation-sensitive composition, a pattern forming method, a compound, and a polymer.

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the polymer in an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above uses short-wavelength radiation such as ArF excimer lasers, or combines this radiation with liquid immersion lithography to promote 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] In the formation of circuits on semiconductor elements by photolithography, various studies have been conducted on photoacid generators, which are one of the main components of resist compositions, in order to form finer resist patterns (for example, JP 2013-195844 A).

[0005] JP 2013-195844 A

[0006] The above-mentioned next-generation technology also requires resist performances that are equal to or better than conventional ones in terms of sensitivity, critical dimension uniformity (CDU) which is an index of uniformity of hole diameter, and development defects.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that can exhibit sufficient levels of sensitivity, CDU, and development defects when forming a resist pattern using next-generation technology, and also to provide a compound and a polymer that can be suitably used in the radiation-sensitive composition.

[0008] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0009] That is, in one embodiment, the present invention relates to a radiation-sensitive composition containing: a polymer (A) including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1); and a solvent (E): (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋ is a monovalent onium cation.

[0010] The radiation-sensitive composition contains a polymer (A) including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from the compound represented by formula (1), and therefore can form a resist film that exhibits sufficient levels of sensitivity, CDU, and development defects. Without being bound by any theory, the reason for this is presumed to be as follows.

[0011] Because the polymer (A) in the radiation-sensitive composition has a structural unit (II) containing a rigid polycyclic structure, the glass transition temperature of the radiation-sensitive acid-generating polymer containing the structural unit (II) can be increased. As a result, it is presumed that the diffusion length of the generated acid can be controlled, resulting in an improved CDU. Furthermore, although the polycyclic structure has low solubility in an alkaline developer, because the polymer (A) contains the structural unit (I), the acid-dissociable group of the structural unit (I) is dissociated by acid to generate a carboxyl group or the like, thereby improving the solubility in an alkaline developer despite the polycyclic structure. As a result, it is presumed that the occurrence of development defects can be suppressed. It is presumed that these combined effects enable the resist performance to be exhibited.

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

[0013] The pattern formation method uses the radiation-sensitive composition described above, which is capable of forming a resist film with excellent sensitivity and CDU and reduced development defects, and therefore can efficiently form a high-quality resist pattern.

[0014] In another embodiment, the present invention relates to a compound represented by the following formula (1'): (In formula (1'), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. X １ is an ester bond, an amide bond, or a sulfonamide bond. ５ is a divalent organic group having 1 to 15 carbon atoms. ＋ is a monovalent onium cation.

[0015] By preparing a radiation-sensitive composition containing the compound, it is possible to form a resist film that is excellent in sensitivity and CDU and has reduced development defects.

[0016] In another embodiment, the present invention relates to a polymer including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1): (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋is a monovalent onium cation.

[0017] By preparing a radiation-sensitive composition containing the polymer, it is possible to form a resist film that is excellent in sensitivity and CDU and has reduced development defects.

[0018] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0019] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer (A) including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from the compound represented by formula (1), and a solvent (E). The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0020] <Polymer (A)> The polymer (A) is an aggregate of polymer chains including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from the compound represented by the above formula (1) (hereinafter, this polymer will also be referred to as a "base polymer (A)"). The radiation-sensitive composition has excellent CDU because the polymer (A) includes the structural unit (II). Furthermore, the polymer (A) includes the structural unit (I), which allows the radiation-sensitive composition to have excellent pattern formability and suppress the occurrence of development defects.

[0021] The structural unit (I) and the structural unit (II) may be contained in the same polymer chain, or the structural unit (I) may be contained in one polymer chain and the structural unit (II) may be contained in another polymer chain. The entire polymer chain constituting the base polymer (A) may contain the structural unit (I) and the structural unit (II). The base polymer (A) may contain structural units other than the structural unit (I) and the structural unit (II). Each structural unit will be described below.

[0022] [Structural Unit (I)] The structural unit (I) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The acid generated from a radiation-sensitive acid generator or a radiation-sensitive acid-generating polymer upon exposure dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern. The radiation-sensitive composition has excellent pattern formability and can suppress the occurrence of development defects because the polymer (A) has the structural unit (I).

[0023] The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof 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 substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (2) (hereinafter, also referred to as "structural unit (I-1)") is preferred. (In the above formula (2), R Ａ is a hydrogen atom, a fluorine atom, an organic group having 1 to 3 carbon atoms, or a trifluoromethyl group. Ａ１ is a divalent linking group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are bonded to form a divalent cyclic group having 3 to 20 carbon atoms. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1.

[0024] R Ａ２ and R Ａ３Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, and a combination thereof.

[0025] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0026] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 40 carbon atoms include alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0027] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms that constitute the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0028] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0029] Examples of heteroatoms constituting the monovalent heteroatom-containing group and divalent heteroatom-containing group 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.

[0030] Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0031] Examples of the divalent heteroatom-containing group include -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ -, or a combination thereof.

[0032] R Ａ２ and RＡ３ Examples of divalent cyclic groups having 3 to 20 carbon atoms formed by combining together with the carbon atoms to which they are bonded include groups in which two hydrogen atoms have been removed from a cyclic structure having 3 to 20 carbon atoms.

[0033] The cyclic structure having 3 to 20 carbon atoms may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the backbone of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0034] The alicyclic structure may be any of the above R Ａ２ and R Ａ３ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0035] The aromatic ring structure may be any of the above R Ａ２ and R Ａ３ A structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be suitably employed.

[0036] Examples of the heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan, benzofuran, and dibenzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0037] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof.

[0038] The chain structure may be any of the above R Ａ２ and R Ａ３ and divalent chain hydrocarbon groups obtained by removing one hydrogen atom from the monovalent chain hydrocarbon groups.

[0039] The divalent heteroatom-containing group includes the above-mentioned R Ａ２ and R Ａ３ The divalent heteroatom-containing groups shown in the monovalent organic group having 1 to 20 carbon atoms represented by the following formula can be suitably used.

[0040] Examples of the substituent that substitutes some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include substituents (T) such as halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; hydroxy groups; carboxy groups; cyano groups; nitro groups; alkyl groups; alkoxy groups; alkoxycarbonyl groups; alkoxycarbonyloxy groups; acyl groups; and groups in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0041] Examples of the alkyl group as the substituent (T) include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy. Examples of the alkoxycarbonyl group include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group.

[0042] The above R Ａ２ and R Ａ３ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R Ａ２ and R Ａ３ are combined together together with the carbon atoms to which they are bonded, a divalent alicyclic group having 3 to 20 carbon atoms is preferred, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms is more preferred, and a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a cyclopentanediyl group, or a cyclohexanediyl group is even more preferred.

[0043] The above R Ａ The organic group having 1 to 3 carbon atoms represented by the above R Ａ２ and R Ａ３ Among these, monovalent organic groups having 1 to 20 carbon atoms and represented by the formula: Ａ is preferably a hydrogen atom, a methyl group, or a methoxymethyl group.

[0044] The above L Ａ１Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, an arenediyl group, and groups having —CO—, —CS—, —O—, —S—, —SO— between the carbon-carbon bonds of these groups. ２ Examples of the substituent include -, -NR'-, or a group containing a combination of two or more of these, or a group combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted, for example, with a substituent. As the substituent, those exemplified above as the substituents substituting some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure can be suitably used. In addition, L Ａ１ As the divalent linking group represented by the following formula, a divalent group obtained by removing two hydrogen atoms from the heterocyclic structure can also be suitably used.

[0045] Examples of the alkanediyl group include alkanediyl groups having 1 to 8 carbon atoms, such as methanediyl, ethanediyl, 1,3-propanediyl, and 2,2-propanediyl.

[0046] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as a cyclopentanediyl group and a cyclohexanediyl group; and polycyclic cycloalkanediyl groups such as a norbornanediyl group and an adamantanediyl group.

[0047] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0048] Examples of the arenediyl group include a benzenediyl group, a toluenediyl group, a naphthalenediyl group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms, and more preferably a benzenediyl group.

[0049] The above L Ａ１ As the group, an arenediyl group having 6 to 15 carbon atoms and a divalent group obtained by removing two hydrogen atoms from a heterocyclic structure are preferred, and a benzenediyl group and a furandiyl group are more preferred.

[0050] The above R Ａ１ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above R Ａ２ and R Ａ３ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the above R Ａ１ is preferably a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and more preferably a methyl group, an ethyl group, or a substituted or unsubstituted phenyl group.

[0051] The above m1 is preferably 0.

[0052] From the viewpoint of sensitivity, the structural unit (I) preferably has an iodine group, and more preferably contains an iodine group-containing aromatic ring structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups.

[0053] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity. Examples of the aromatic ring include an aromatic hydrocarbon ring, a heteroaromatic ring, or a combination thereof. The aromatic hydrocarbon ring includes the above-mentioned R Ａ２ and R Ａ３ A structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be preferably used. As the heteroaromatic ring, an aromatic heterocyclic structure in the above heterocyclic structure can be preferably used. Among these, a benzene ring is preferred as the aromatic ring.

[0054] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

[0055] Examples of the structural unit (I) include structural units represented by the following formulas (1-1) to (1-14) (hereinafter also referred to as "structural units (I-1) to (I-14)").

[0056]

[0057]

[0058] In the above formulas (1-1) to (1-14), R Ａ , R Ａ１ ~R Ａ３ has the same meaning as in formula (2) above. X is a substituent, and the above-mentioned substituent (T) can be suitably employed. i and j are each independently an integer of 1 to 4. k and l are 0 or 1. a1 is an integer of 0 to 3. When a1 is 2 or more, multiple Xs are the same or different. a4 is an integer of 1 to 3.

[0059] i and j are preferably 1 or 2. k and l are preferably 1. R Ａ１ R is preferably a methyl group, an ethyl group, a phenyl group, or an iodophenyl group. Ａ２ and R Ａ３ As X, a methyl group, an ethyl group, or an isopropyl group is preferable. As X, a hydroxy group, an iodine atom, or an alkyl group is preferable.

[0060] Furthermore, the polymer (A) may contain, as the structural unit (I), structural units represented by the following formulae (1f) to (2f).

[0061]

[0062] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer of 1 to 4.

[0063] The above R βｆ is preferably a hydrogen atom, a methyl group or an ethyl group. h1 is preferably 1 or 2.

[0064] Specific examples of the structural unit (I) include, but are not limited to, those shown below.

[0065] (In the formula, R Ａ is the same as the above formula (2).

[0066] (In the formula, R Ａ is the same as the above formula (2).

[0067] The base polymer (A) may contain one type of structural unit (I) or a combination of two or more types.

[0068] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer (A) is preferably 10 mol%, more preferably 15 mol%, and even more preferably 20 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved and the occurrence of development defects can be suppressed.

[0069] [Structural Unit (II)] The structural unit (II) is a structural unit derived from a compound represented by the following formula (1), and is a structural unit containing an acid-generating structure that generates an acid that induces dissociation of the acid-dissociable group upon exposure. Since the polymer (A) contains the structural unit (II), it functions as a radiation-sensitive acid-generating polymer. (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋ is a monovalent onium cation.

[0070] The above R １ , R ２ The monovalent organic group having 1 to 5 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ Among the monovalent organic groups having 1 to 20 carbon atoms represented by the following formula, those having the corresponding number of carbon atoms can be suitably used.

[0071] The above L １ , L ２ The divalent linking group represented by the formula (2) is L Ａ１ The divalent linking group represented by the following formula can be preferably used.１ , L ２ is a single bond, an alkylene group having 1 to 5 carbon atoms, —O—, —S—, or —NR １１ - (R １１ is a hydrogen atom or a monovalent hydrocarbon group.) is preferable, a single bond, —O—, or —S— is more preferable, and a single bond is even more preferable. １１ The monovalent hydrocarbon group represented by the formula (2) is R Ａ２ and R Ａ３ A monovalent hydrocarbon group having 1 to 20 carbon atoms in the above formula can be suitably used.

[0072] The aromatic ring in the iodo group-containing aromatic ring structure can be suitably used as the aromatic ring represented by W. Among these, a benzene ring, a naphthalene ring, an anthracene ring, or a furan ring is preferred, a benzene ring or a naphthalene ring is more preferred, and a naphthalene ring is even more preferred.

[0073] The above R ３ The divalent organic group having 1 to 20 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ A group in which one hydrogen atom has been removed from a monovalent organic group having 1 to 20 carbon atoms, represented by the following formula:

[0074] The above M ＋ Examples of the monovalent onium cation represented by the formula (I) include a radiation-sensitive onium cation. Examples of the radiation-sensitive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0075] From the viewpoint of sensitivity, the onium cation preferably has an iodo group, and more preferably contains the iodo group-containing aromatic ring structure.

[0076] The onium cation preferably has a fluoro group, and more preferably has a fluoro group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity. The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro group-containing aromatic ring structure can be suitably the same as the aromatic ring in the iodo group-containing aromatic ring structure. Among these, a benzene ring is preferred as the aromatic ring.

[0077] The number of fluorine atoms in the fluoro group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 3.

[0078] The sulfonium cation is preferably represented by the following formula (Q-1).

[0079]

[0080] In the above formula (Q-1), Ra １ ~Ra ３ Each of n11 independently represents a substituent. n11 represents an integer of 0 to 5, and when n11 is 2 or more, a plurality of Ra １ may be the same or different. n12 represents an integer of 0 to 5, and when n12 is 2 or more, a plurality of Ra ２ n13 represents an integer of 0 to 5, and when n13 is 2 or more, a plurality of Ra ３ may be the same or different. １ and Ra ２ may be linked to each other to form a ring. １ may be linked to each other to form a ring. ２ may be linked to each other to form a ring.

[0081] Ra １ , Ra ２ , and Ra ３The substituent represented by the formula (I) is preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a cyano group, a halogen atom, or a halogenated hydrocarbon group.

[0082] Ra １ , Ra ２ , and Ra ３ The alkyl group in the formula (2) may be a linear alkyl group or a branched alkyl group. Ａ２ and R Ａ３ Preferably, a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms in the following formula can be used. Among these, a methyl group, an ethyl group, an n-butyl group, and a t-butyl group are particularly preferred.

[0083] Ra １ , Ra ２ , and Ra ３ Examples of the cycloalkyl group include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), and R Ａ２ and R Ａ３ Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0084] Ra １ , Ra ２ , and Ra ３ The alkyl group moiety of the alkoxy group of Ra may be, for example, １ , Ra ２ and Ra ３ As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group and an n-butoxy group are particularly preferred.

[0085] Ra １ , Ra ２ , and Ra ３ The cycloalkyl group moiety of the cycloalkyloxy group of the formula Ra may be, for example, １ , Ra ２ and Ra ３As the cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0086] Ra １ , Ra ２ , and Ra ３ The alkoxy group moiety of the alkoxycarbonyl group of Ra may be, for example, １ , Ra ２ and Ra ３ As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group and an n-butoxycarbonyl group are particularly preferred.

[0087] Ra １ , Ra ２ , and Ra ３ The alkyl group moiety of the alkylsulfonyl group of the formula Ra １ , Ra ２ , and Ra ３ Examples of the alkyl group include those listed above. １ , Ra ２ , and Ra ３ The cycloalkyl group moiety of the cycloalkylsulfonyl group of the formula Ra may be, for example, １ , Ra ２ , and Ra ３ As these alkylsulfonyl groups or cycloalkylsulfonyl groups, a methanesulfonyl group, an ethanesulfonyl group, an n-propanesulfonyl group, an n-butanesulfonyl group, a cyclopentanesulfonyl group, and a cyclohexanesulfonyl group are particularly preferred.

[0088] Ra １ , Ra ２ , and Ra ３Each of the groups may further have a substituent, such as a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0089] Ra １ , Ra ２ , and Ra ３ Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0090] Ra １ , Ra ２ , and Ra ３ The halogenated hydrocarbon group is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those mentioned above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0091] As mentioned above, Ra １ and Ra ２ may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, Ra １ and Ra ２ are preferably bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. １ and Ra ２ When they are linked to each other to form a ring, Ra １ and Ra ２ are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２It is preferable to form -O-, -S- or a single bond. Among these, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. １ may be linked to each other to form a ring, and when n12 is 2 or more, a plurality of Ra ２ may be linked to each other to form a ring. １ may be linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0092] Ra ３ is preferably a fluorine atom or a group having one or more fluorine atoms. １ and Ra ２ Examples of the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group substituted with a fluorine atom include fluorinated alkyl groups, 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 , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ Particularly preferred examples include: ３ is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0093] n11, n12 and n13 each independently represent preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

[0094] Specific examples of such onium cations represented by the above formula (Q-1) include the following:

[0095] (In the formula, tBu represents a t-butyl group, and Me represents a methyl group.)

[0096]

[0097] (In the formula, Me represents a methyl group.)

[0098]

[0099]

[0100] (In the formula, Me represents a methyl group.)

[0101]

[0102] (In the formula, Me represents a methyl group.)

[0103]

[0104] Specific examples of the iodonium cation include the following:

[0105] From the viewpoint of sensitivity, the structural unit (II) preferably has an iodine group, and more preferably contains an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups. As the iodine group-containing aromatic ring structure, those shown in the structural unit (I) can be suitably used.

[0106] The structural unit (II) is preferably a structural unit represented by the following formula (1-1). (In formula (1-1), X is an ester bond, an ether bond, an amide bond, or a sulfonamide bond. R ４ is a divalent organic group having 1 to 10 carbon atoms. n is 0 or 1. R ｆ１ and R ｆ２ are each independently a hydrogen atom, a halogen atom, a hydroxy group, a nitro group, a thiol group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different from each other, provided that -SO ３ － R on the carbon atom at the α- or β-position of the sulfur atom ｆ１ or R ｆ２ is a fluorine atom or a fluorinated hydrocarbon group. m is an integer of 0 to 5, provided that 1≦m+n. R １ , R ２ , L １ , L ２ , W., M. ＋ has the same meaning as the above formula (1).

[0107] The above X is preferably an ester bond or an ether bond, and more preferably an ester bond.

[0108] The above R ４ The divalent organic group having 1 to 10 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ Among monovalent organic groups having 1 to 20 carbon atoms, represented by the following formula, groups in which one hydrogen atom has been removed from the group having the corresponding carbon number can be suitably used.

[0109] The above R ｆ１ and R ｆ２ The monovalent organic group having 1 to 20 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0110] Examples of the anion structure of the compound represented by the above formula (1) include the following structures.

[0111]

[0112]

[0113] The compound represented by the formula (1) can be obtained by appropriately combining the anion and the onium cation. Specific examples include, but are not limited to, structures of the following formulas:

[0114]

[0115]

[0116]

[0117]

[0118] The base polymer (A) may contain one type of structural unit (II) or a combination of two or more types.

[0119] The lower limit of the content of the structural unit (II) (the total content when multiple types are contained) relative to all structural units constituting the base polymer (A) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. By keeping the content of the structural unit (II) within the above range, the CDU can be improved.

[0120] (Structural Unit (III)) The polymer (A) preferably further contains a structural unit (III) having a phenolic hydroxyl group. When the polymer (A) contains the structural unit (III), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (III) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the present invention is suitable for pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (III) is preferably represented by the following formula (4):

[0121] (In the above formula (4), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ５ is an integer from 0 to 8, provided that 1≦m ３ +m ５ ≦2n ３ Meets +5.)

[0122] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (III), it is preferable that the alkyl group is a hydrogen atom or a methyl group.

[0123] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0124] R １０２As the halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in R, the groups exemplified above as the substituent (T) can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0125] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0126] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0127] The above m ５ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0128] The structural unit (III) is preferably a structural unit represented by the following formula:

[0129] (In the formula, R β is the same as the above formula (4).

[0130] In order to obtain the structural unit (III), it is preferable to carry out polymerization in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group) during polymerization, and then to obtain the structural unit (III) by deprotecting the phenolic hydroxyl group by hydrolysis. Alternatively, a monomer that gives the structural unit (III) may be polymerized without protecting the phenolic hydroxyl group.

[0131] The base polymer (A) may contain one type of structural unit (III) or a combination of two or more types.

[0132] When the base polymer contains the structural unit (III), the lower limit of the content of the structural unit (III) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 15 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of this content is preferably 50 mol%, more preferably 45 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (III) within the above range, the sensitivity and CDU of the radiation-sensitive composition can be further improved.

[0133] [Structural Unit (IV)] The structural unit (IV) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, a sultone structure, and a cyclic sulfone structure. By further including the structural unit (IV), the base polymer (A) can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Furthermore, the adhesion between a resist pattern formed from the base polymer (A) and a substrate can be improved.

[0134] Examples of the structural unit (IV) include structural units represented by the following formulae (T-1) to (T-11).

[0135]

[0136] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, a dimethylamino group, or —COOR Ｌ６ It is. Ｌ６ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ｌ４ and R Ｌ５ may be combined with each other to form a divalent alicyclic hydrocarbon group having 3 to 8 carbon atoms together with the carbon atoms to which they are attached. ２is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0137] The above R Ｌ４ and R Ｌ５ Examples of the divalent alicyclic hydrocarbon group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded include R Ａ２ and R Ａ３ Examples of such groups include groups in which one hydrogen atom has been removed from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms corresponding to the number of carbon atoms in the formula (I). One or more hydrogen atoms on this alicyclic hydrocarbon group may be substituted with a hydroxy group.

[0138] The above R Ｌ６ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ A monovalent hydrocarbon group having 1 to 20 carbon atoms in the above formula can be suitably used.

[0139] The above L ２ Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH-, and -S-.

[0140] The above L ２ As the divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms in the formula (2), R Ａ２ and R Ａ３ A group in which one hydrogen atom has been removed from a monovalent chain hydrocarbon group having 1 to 20 carbon atoms can be suitably used.

[0141] The above L ２ As the divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, R Ａ２ and R Ａ３ Among the monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms in the above, groups in which one hydrogen atom has been removed from those having the corresponding number of carbon atoms can be suitably used.

[0142] Of these, the structural unit (IV) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0143] The base polymer (A) may contain one type of structural unit (IV) or a combination of two or more types.

[0144] When the base polymer (A) contains the structural unit (IV), the lower limit of the content of the structural unit (IV) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on all structural units constituting the base polymer (A). The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (IV) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0145] [Structural Unit (V)] In addition to the above structural units, the base polymer (A) optionally contains other structural units. Examples of the other structural units include structural units (V) containing polar groups (excluding those corresponding to the structural unit (III)). The base polymer (A) preferably further contains the structural unit (V), which can adjust the solubility in a developer and thereby improve the lithography performance, such as the resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0146] Examples of the structural unit (V) include structural units represented by the following formula:

[0147]

[0148]

[0149] In the above formula, R Ｋis a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0150] When the base polymer (A) contains the structural unit (V), the lower limit of the content of the structural unit (V) (the total content when multiple structural units are contained) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on all structural units constituting the base polymer (A). The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By keeping the content of the structural unit (V) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved, which is preferable.

[0151] (Method for Synthesizing Base Polymer (A)) The base polymer (A) can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0152] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0153] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; lactones such as γ-butyrolactone and δ-valerolactone; ketones such as acetone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-methoxy-2-propanol, 4-methyl-2-pentanol, etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0154] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0155] The molecular weight of the base polymer (A) is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 12,000, and particularly preferably 10,000. By setting the Mw of the base polymer within the above range, good developability can be imparted to the resulting resist film.

[0156] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer (A) determined 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.

[0157] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the conditions described in the examples.

[0158] The content of the base polymer (A) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0159] The radiation-sensitive composition preferably contains, in addition to the polymer (A), the radiation-sensitive acid generator (C) and the acid diffusion controller (D) described below.

[0160] <Radiation-Sensitive Acid Generator (C)> Examples of the radiation-sensitive acid generator (C) include onium salt compounds (C) represented by the following formula (C-1): The radiation-sensitive acid generator (C) has an onium salt structure that exists alone as a low-molecular-weight compound (i.e., free from a polymer), and is different from the polymer (A) having the radiation-sensitive acid-generating structure (radiation-sensitive acid-generating polymer). (In formula (C-1), R ４０ R is a monovalent organic group having 1 to 40 carbon atoms. ｆ２１ and R ｆ２２ are each independently a hydrogen atom, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ２１ and R ｆ２２ If there are multiple R ｆ２１ and R ｆ２２ are the same or different, and n is an integer of 0 to 4. Z ２ ＋ is a radiation-sensitive onium cation.

[0161] R ４０ The monovalent organic group having 1 to 40 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the following formula (I) are groups having 1 to 40 carbon atoms.

[0162] R ｆ２１ and R ｆ２２Examples of the monovalent fluorinated hydrocarbon group represented by the formula (2) include a group in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 40 carbon atoms have been substituted with fluorine atoms. Ａ２ and R Ａ３ Examples of such groups include monovalent hydrocarbon groups having 1 to 20 carbon atoms, which are extended to groups having 1 to 40 carbon atoms.

[0163] Specific examples of the anion of the onium salt compound (C) include, but are not limited to, structures of the following formulae:

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170] Specific examples of the radiation-sensitive onium cation of the onium salt compound (C) include, but are not limited to, M ＋ A monovalent onium cation represented by the following formula can be suitably used.

[0171] The onium salt compound (C) may have a structure in which the above anion and the above radiation-sensitive onium cation are combined in any order.

[0172] When the radiation-sensitive composition contains a radiation-sensitive acid generator (C), the lower limit of the content of the radiation-sensitive acid generator (C) (the total content when multiple types are contained) is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 3 parts by mass, relative to 100 parts by mass of the polymer (A). The upper limit of the content is preferably 100 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass.

[0173] <Acid Diffusion Controller (D)> The acid diffusion controller (D) is not particularly limited, but an onium salt compound (D1) that generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator or the like upon irradiation with radiation can be suitably used. The acid generated from the onium salt compound (D1) is a weak acid that does not induce dissociation of the acid-dissociable group in the polymer under conditions that dissociate the acid-dissociable group. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

[0174] The onium salt compound (D1) is preferably represented by the following formulas (8-1) to (8-4).

[0175] In the above formula (8-1) and formula (8-2), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. E in the above formula (8-1) and formula (8-2) － and Q － are each independently R ８ SO ３ － , R ８ COO － , and (R ８ SO ２ ) N － Preferably, R is at least one selected from the group consisting of ８ COO － Further, examples of the compound include a compound represented by the above formula (8-3) containing a sulfonium cation and an anion in the same molecule, and a compound represented by the above formula (8-4) containing an iodonium cation and an anion in the same molecule. In the above formulas (8-3) and (8-4), J' ＋ is a monovalent group having a sulfonium cation structure, and U' ＋ is a monovalent group having an iodonium cation structure. － and Q' － are each independently -R ８１ SO ３ － , -R ８１ COO－ , and -R ８１ SO ２ N － SO ２ R ８ Preferably, the group is at least one selected from the group consisting of -R ８１ COO － It is more preferable that the above R ８ is a monovalent organic group, and the R ８１ is a single bond or a divalent organic group.

[0176] The monovalent organic group is R ４０ A monovalent organic group having 1 to 40 carbon atoms and represented by the following formula can be suitably used.

[0177] The divalent organic group is R ４０ A group in which one hydrogen atom has been removed from a monovalent organic group having 1 to 40 carbon atoms, represented by the following formula:

[0178] Examples of the onium salt compound (D1) include compounds represented by the following formula:

[0179]

[0180]

[0181]

[0182] The onium salt compound (D1) can also be synthesized by a known method, particularly by a salt exchange reaction.

[0183] These acid diffusion controllers (D) may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (D) (the total content when multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on the total amount (100 mol%) of the radiation-sensitive acid generator and the radiation-sensitive acid-generating polymer contained in the composition. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%.

[0184] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer. As a result, it is possible to increase the water repellency of the surface of the resist film during immersion exposure, and to modify the surface of the resist film during EUV exposure and control the distribution of composition within the film.

[0185] The high-fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VII)"), and may optionally have the structural unit (I) of the base polymer.

[0186]

[0187] In the above formula (5), R ７３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, —OCO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. ７４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0188] The above R ７３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0189] Above G Ｌ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a combination of at least one of a single bond, —COO—, —COO—, and —OCO— with an alkanediyl group having 1 to 5 carbon atoms is preferred, and —COO— is more preferred.

[0190] The above R ７４Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0191] The above R ７４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0192] The above R ７４ As the alkyl group, a fluorinated chain hydrocarbon group is preferred, and a fluorinated alkyl group is more preferred.

[0193] When the high-fluorine-content polymer has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of this content is preferably 90 mol%, more preferably 85 mol%, and even more preferably 80 mol%. By setting the content of the structural unit (VII) within this range, the mass content of fluorine atoms in the high-fluorine-content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0194] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VIII)) in addition to or instead of the structural unit (VII). By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and the occurrence of development defects can be suppressed.

[0195]

[0196] The structural unit (VIII) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter, also simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄ R has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0197] When the structural unit (VIII) has (x) an alkali-soluble group, R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VIII) has (x) an alkali-soluble group, it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VIII) having (x) an alkali-soluble group, A １ is an oxygen atom and W １It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0198] When the structural unit (VIII) has (y) an alkali-dissociable group, R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VIII) has (y) an alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit (VIII) having (y) an alkali-dissociable group, A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0199] RＣ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VIII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0200] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and even more preferably a group having a norbornane lactone structure.

[0201] When the high-fluorine-content polymer has the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 30 mol %, more preferably 40 mol %, based on all structural units constituting the high-fluorine-content polymer. The upper limit of this content is preferably 100 mol %. By setting the content of the structural unit (VIII) within this range, the water repellency of the resist film during immersion exposure can be further improved, and development defects can be suppressed.

[0202] [Other Structural Units] The high fluorine content polymer may contain structural units other than the structural units listed above, such as the structural unit (I) in the base polymer.

[0203] When the high fluorine content polymer contains the structural unit (I), the content ratio of each structural unit in the high fluorine content polymer can suitably be the same as that described for the base polymer.

[0204] The lower limit of Mw of the high fluorine content polymer is preferably 2,000, more preferably 3,000, even more preferably 4,000, and particularly preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 20,000, even more preferably 10,000, and particularly preferably 8,000.

[0205] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0206] When the radiation-sensitive composition contains a high-fluorine polymer, the content of the high-fluorine polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 13 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less.

[0207] By setting the content of the high-fluorine-containing polymer within the above range, the high-fluorine-containing polymer can be more effectively localized in the surface layer of the resist film, which in turn makes it possible to improve the water repellency of the surface of the resist film during immersion lithography, and to modify the surface of the resist film and control the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine-containing polymers.

[0208] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0209] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains a solvent (E). The solvent (E) is not particularly limited as long as it is a solvent that can dissolve or disperse at least the polymer (A) and, optionally, a radiation-sensitive acid generator, an acid diffusion controller, and the like.

[0210] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0211] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based 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-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified.

[0212] In the present embodiment, alcoholic 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 alcoholic solvents.

[0213] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0214] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, and acetophenone.

[0215] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0216] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0217] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene.

[0218] Among these, ester-based solvents and ether-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, lactone-based solvents, monocarboxylic acid ester-based solvents and ketone-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, γ-butyrolactone, ethyl lactate, cyclohexanone and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0219] (Other Optional Components) The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0220] The surfactant is not particularly limited, but a non-fluorine-based surfactant or a non-silicone-based surfactant can be suitably used.

[0221] When the radiation-sensitive composition contains a surfactant, the content of the surfactant is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the base polymer (A).

[0222] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A), the solvent (E), and, if necessary, the radiation-sensitive acid generator (C), the acid diffusion controller (D), the high-fluorine-content polymer, and the like, in predetermined proportions. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.40 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0223] <<Pattern Forming Method>> A pattern forming method according to one embodiment of the present invention includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0224] According to the above-described resist pattern forming method, a high-quality resist pattern can be formed because the above-described radiation-sensitive composition is used, which is capable of forming a resist film that has excellent sensitivity and CDU and has reduced development defects. Each step is described below.

[0225] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 150°C, and preferably 80°C to 140°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0226] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure step described below, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0227] When performing immersion exposure, regardless of whether the radiation-sensitive composition contains a water-repellent polymer additive such as a high-fluorine-content polymer, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-removable protective film that is removed with a solvent before the development step (see, for example, JP-A 2006-227632), or a developer-removable protective film that is removed simultaneously with development in the development step (see, for example, WO 2005 / 069076 and WO 2006 / 035790). However, from the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion exposure.

[0228] When the subsequent exposure step is carried out with radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural units (I) and (III) as the base polymer in the composition.

[0229] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion liquid such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0230] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser beam (wavelength 193 nm), water is preferred from the above-mentioned viewpoints, as well as from the viewpoints of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0231] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0232] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0233] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, 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.

[0234] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, chain ketones are preferred, with 2-heptanone being more preferred. The content of the 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 the organic solvent in the developer include water and silicone oil.

[0235] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0236] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispense method).

[0237] <Compound> The compound according to this embodiment is represented by the following formula (1'). (In formula (1'), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. X １ is an ester bond, an amide bond, or a sulfonamide bond. ５ is a divalent organic group having 1 to 15 carbon atoms. ＋ is a monovalent onium cation.

[0238] The above R ５ The divalent organic group having 1 to 15 carbon atoms represented by the formula (2) is R Ａ２ and R Ａ３ Among monovalent organic groups having 1 to 20 carbon atoms, represented by the following formula, groups in which one hydrogen atom has been removed from the group having the corresponding carbon number can be suitably used.

[0239] R １ , R ２ , L １ , L ２ , W., M. ＋ is synonymous with the above formula (1).

[0240] Examples of the compound represented by the above formula (1') include the following structures.

[0241]

[0242]

[0243] <Polymer> The present embodiment relates to a polymer including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1). (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋ is a monovalent onium cation.

[0244] Suitable examples of the structural unit (II) include the same structural unit (II) as that contained in the polymer (A) in the radiation-sensitive composition.

[0245] The structural unit (I) is preferably a structural unit represented by the following formula (2): (In the above formula (2), R Ａ is a hydrogen atom, a fluorine atom, an organic group having 1 to 3 carbon atoms, or a trifluoromethyl group. Ａ１ is a divalent linking group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are bonded to form a divalent cyclic group having 3 to 20 carbon atoms. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1.

[0246] Suitable examples of the structural unit (I) include the same structural unit (I) as that contained in the polymer (A) in the radiation-sensitive composition.

[0247] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. Various physical properties in the examples and comparative examples were measured by the measurement methods shown below.

[0248] [Weight average molecular weight (Mw) and number average molecular weight (Mn)] Using GPC columns manufactured by Tosoh Corporation (G2000HXL: 2 columns, G3000HXL: 1 column, G4000HXL: 1 column), the following analytical conditions were used: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection amount: 100 μL, column temperature: 40 ° C., detector: differential refractometer. Measurement was performed by gel permeation chromatography (GPC) using monodisperse polystyrene as a standard. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0249] [ １ H-NMR analysis and １３ C-NMR analysis] １ H-NMR analysis and １３ C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0250] <Synthesis of Compound (A) (Radiation-Sensitive Monomer)> [Synthesis Example A-1: ​​Synthesis of Compound (A-1)] Compound (A-1) was synthesized according to the following synthesis scheme.

[0251]

[0252] Compound (Z-1) (20 mmol) and dichloromethane (100 mL) were added to a reaction vessel and cooled to 0°C. 1,1'-carbonylbis-1H-imidazole (30 mmol) and compound (Z-2) (30 mmol) were then added, and the mixture was returned to room temperature and stirred. The organic layer was washed twice with an aqueous ammonium chloride solution. The organic layer was dried over sodium sulfate and filtered. The solvent was distilled off, and compound (A-1) was obtained by isolation using column chromatography.

[0253] [Synthesis Examples A-2 to A-17, cA-18, cA-19: Synthesis of Monomers (A-2) to (A-17) and Monomers (cA-18) to (cA-19)] Compounds represented by the following formulae (A-2) to (A-17) and (cA-18) to (cA-19) were synthesized in the same manner as in Synthesis Example A-1, except that the raw materials and precursors were appropriately changed.

[0254]

[0255]

[0256]

[0257] Among the monomers used in the synthesis of the polymers in each Example and Comparative Example, the structures of the monomers other than the above-mentioned monomers are shown below.

[0258]

[0259] <Synthesis of Polymer (P)> [Examples P-1 to P-39, Comparative Examples cP-1 to cP-5: Synthesis of Polymers (P-1) to (P-39) and (cP-1) to (cP-5)] Each monomer was combined and copolymerized in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomers) as a solvent. The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, then filtered off, and dissolved in 1-methoxy-2-propanol (300 parts by mass). The polymer was coagulated by dropping the mixture into 500 parts by mass of water, and the resulting solid was filtered off. The mixture was dried at 50°C for 12 hours to obtain white powdery polymers (P-1) to (P-39) and (cP-1) to (cP-5). The resulting polymers had the following composition: １ The Mw and dispersity (Mw / Mn) were confirmed by H-NMR under the GPC conditions described above. The results are shown in Tables 1 and 2 along with the type and amount of each monomer. In Tables 1 and 2, "-" indicates that the corresponding component was not used. The same applies to the following tables.

[0260]

[0261]

[0262] [Synthesis of High Fluorine Content Polymer] [Synthesis Example 1: Synthesis of Polymer (F-1)] Each monomer was combined and copolymerized in a solvent of 2-butanone (200 parts by mass). After the polymerization reaction was completed, the polymer solution was cooled with water to 30°C or less. After replacing the solvent with acetonitrile (400 parts by mass), hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was collected. This procedure was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of polymer (F-1) was obtained in good yield. The composition of the obtained polymer was １ The Mw and dispersity (Mw / Mn) were confirmed by H-NMR under the above-mentioned GPC conditions, and are shown in Table 3 together with the type and amount of each monomer.

[0263]

[0264] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator, acid diffusion controller, and solvent that constitute the radiation-sensitive composition are described below.

[0265] [Radiation-Sensitive Acid Generator] Compounds represented by the following formulae (C-1) to (C-9).

[0266] [Acid Diffusion Controller] Compounds represented by the following formulae (D-1) to (D-6).

[0267] [Organic solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[0268] [Preparation of Radiation-Sensitive Compositions] [Examples 1 to 69 and Comparative Examples 1 to 5] Polymers (P-1) to (P-39), radiation-sensitive acid generators (C-1) to (C-9), acid diffusion controllers (D-1) to (D-6), high-fluorine content polymer (F-1), and organic solvents (E-1) and (E-2) were combined and mixed. This mixture was filtered through a membrane filter with a pore size of 0.2 μm to prepare radiation-sensitive compositions (R-1) to (R-69) and (CR-1) to (CR-5). The types and amounts of each component are shown in Tables 4 and 5.

[0269]

[0270]

[0271] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron Limited). Prebaking (PB) was performed at 100°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a 30-nm-thick resist film. This resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was then post-exposure baked (PEB) at 100°C for 60 seconds. The resist was then developed with a 2.38% by mass aqueous solution of TMAH at 23° C. for 30 seconds to form a positive 36 nm contact hole pattern.

[0272] <Evaluation> The sensitivity, CDU, and number of development defects of each radiation-sensitive composition were evaluated by measuring each of the resist patterns formed above according to the methods described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Tables 6 and 7 below.

[0273] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 36 nm contact hole pattern was set as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the value, the better the sensitivity. ２ If it is less than 40 mJ / cm, it is "A" (very good). ２ More than 44mJ / cm ２ The following cases are "B" (good): 44 mJ / cm ２ If it exceeded this, it was judged as "C" (poor).

[0274] [CDU] In forming the resist pattern, a 36 nm contact hole pattern was formed. The formed resist pattern was observed from above using the scanning electron microscope. The hole diameter variation was measured at a total of 600 points, and a 3 sigma value was calculated from the distribution of the measured values. This 3 sigma value was defined as CDU (nm). The smaller the CDU value, the smaller the long-period hole diameter variation and the better the result. CDU was evaluated as "A" (very good) when it was less than 3.0 nm, "B" (good) when it was 3.0 nm or more but 3.4 nm or less, and "C" (poor) when it exceeded 3.4 nm.

[0275] [Number of Defects Developed] A 36 nm contact hole pattern was formed on a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Of the defects measured, defects with a diameter of 50 μm or less were determined to be originating from the resist film, and the number of defects was calculated. The number of defects after development was determined as "A" (very good) if the number of defects determined to be originating from the resist film was less than 35, "B" (good) if the number was 35 to 60, and "C" (poor) if the number was more than 60.

[0276]

[0277]

[0278] The radiation-sensitive composition and method for forming a resist pattern of the present invention can improve sensitivity, CDU, and the number of development defects compared to conventional methods, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition comprising: a polymer (A) including a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1); and a solvent (E). (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋ is a monovalent onium cation.

2. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) is represented by the following formula (2): (In the above formula (2), R Ａ is a hydrogen atom, a fluorine atom, an organic group having 1 to 3 carbon atoms, or a trifluoromethyl group. Ａ１ is a divalent linking group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are bonded to form a divalent cyclic group having 3 to 20 carbon atoms. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1.

3. The radiation-sensitive composition according to claim 1, wherein the structural unit (II) is represented by the following formula (1-1): (In formula (1-1), X is an ester bond, an ether bond, an amide bond, or a sulfonamide bond. R ４ is a divalent organic group having 1 to 10 carbon atoms. n is 0 or 1. R ｆ１ and R ｆ２ are each independently a hydrogen atom, a halogen atom, a hydroxy group, a nitro group, a thiol group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different from each other, provided that -SO ３ － R on the carbon atom at the α- or β-position of the sulfur atom ｆ１ or R ｆ２ is a fluorine atom or a fluorinated hydrocarbon group. m is an integer of 0 to 5, provided that 1≦m+n. R １ , R ２ , L １ , L ２ , W., M. ＋ has the same meaning as the above formula (1).

4. The radiation-sensitive composition according to claim 1, wherein the aromatic ring in W in the formula (1) is a benzene ring or a naphthalene ring.

5. The above L １ and L ２ are each independently a single bond, an alkylene group having 1 to 5 carbon atoms, —O—, —S—, or —NR １１ - (R １１ The radiation-sensitive composition according to claim 1 , wherein:

6. The radiation-sensitive composition according to claim 1, wherein the structural unit (II) has an iodine group.

7. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) has an iodo group.

8. The radiation-sensitive composition according to any one of claims 1 to 7, wherein the content of the structural unit (II) in all structural units constituting the polymer (A) is 1 mol % or more and 50 mol % or less.

9. The radiation-sensitive composition according to any one of claims 1 to 7, wherein the content of the structural unit (I) in all structural units constituting the polymer (A) is 10 mol % or more and 80 mol % or less.

10. The radiation-sensitive composition according to any one of claims 1 to 7, wherein the polymer (A) further contains a structural unit (III) having a phenolic hydroxyl group.

11. The radiation-sensitive composition according to claim 10, wherein the content of the structural unit (III) in all structural units constituting the polymer (A) is 15 mol % or more and 50 mol % or less.

12. The radiation-sensitive composition according to any one of claims 1 to 7, further comprising a radiation-sensitive acid generator.

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

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

15. The pattern forming method according to claim 14, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

16. A compound represented by the following formula (1'): (In formula (1'), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. X １ is an ester bond, an amide bond, or a sulfonamide bond. ５ is a divalent organic group having 1 to 15 carbon atoms. ＋ is a monovalent onium cation.

17. A polymer comprising a structural unit (I) having an acid-dissociable group and a structural unit (II) derived from a compound represented by the following formula (1): (In formula (1), R １ , R ２ are each independently a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 5 carbon atoms. １ , L ２ are each independently a single bond or a divalent linking group. W is an aromatic ring. R ３ is a divalent organic group having 1 to 20 carbon atoms. ＋ is a monovalent onium cation.

18. The polymer according to claim 17, wherein the structural unit (I) is represented by the following formula (2): (In the above formula (2), R Ａ is a hydrogen atom, a fluorine atom, an organic group having 1 to 3 carbon atoms, or a trifluoromethyl group. Ａ１ is a divalent linking group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R Ａ２ and R Ａ３ are combined together with the carbon atoms to which they are bonded to form a divalent cyclic group having 3 to 20 carbon atoms. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1.

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