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

Abstract

The purpose of the present invention is to provide: a radiation-sensitive composition having excellent sensitivity and LWR when forming a pattern; a pattern formation method; and a radiation-sensitive acid generator. This radiation-sensitive composition comprises: a polymer (A) which contains a structural unit (I) having an acid-dissociable group and has an iodine group; and a solvent (D), wherein said radiation-sensitive composition contains a radiation-sensitive acid generator (B) represented by formula (1), or the polymer (A) contains a structural unit (II) represented by formula (1'). (In formula (1), R1 is a C1-C40 monovalent organic group. When a plurality of R2s are present, the plurality of R2s are each independently a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxy group, a thiol group, a halogen atom, or a monovalent organic group, or a C3-C20 divalent cyclic group composed of two R2s aligned with each other and a carbon atom to which the two R2s are bonded. n is an integer of 0-20. W represents a ring structure with 5-8 membered rings which is formed together with a carbon atom and a nitrogen atom to which W is bonded.) (In formula (1'), R1a is a C1-C40 divalent organic group. Ra is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R2, n, and W have the same meanings as those in formula (1).)

Description

Radiation-sensitive composition, pattern forming method, and radiation-sensitive acid generator

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

[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] As patterns become finer, there is a demand for highly precise control of acid diffusion, and development of acid generators, which are components of resist materials, is also progressing (Patent No. 6665031).

[0005] Patent No. 6665031

[0006] In developing the above-mentioned next-generation technology, resist performances equivalent to or better than conventional ones are required in terms of sensitivity, line width, and LWR (Line Width Roughness) which indicates the variation in line width of a resist pattern.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern forming method, and a radiation-sensitive acid generator that are excellent in sensitivity and LWR during pattern formation.

[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] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer (A) which contains a structural unit (I) having an acid-dissociable group and which has an iodine group; and a solvent (D), wherein the radiation-sensitive composition contains a radiation-sensitive acid generator (B) represented by the following formula (1), or the polymer (A) contains a structural unit (II) represented by the following formula (1'): (In formula (1), R １ is a monovalent organic group having 1 to 40 carbon atoms. ２ When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together and formed together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8 membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded. (In formula (1'), R １ａ is a divalent organic group having 1 to 40 carbon atoms. a is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ , n, and W have the same meanings as in formula (1) above.

[0010] The radiation-sensitive composition can exhibit excellent sensitivity and LWR during resist pattern formation. Although the reason for this is not clear, it is presumed to be as follows.

[0011] Nonionic acid-generating structures, such as nonionic radiation-sensitive acid generators, have inferior acid generation efficiency compared to ionic acid-generating structures. The radiation-sensitive composition contains a nonionic acid-generating structure, but also contains a polymer having an iodine group that exhibits high absorption of radiation, such as EUV, at a wavelength of 13.5 nm. This enhances the secondary electron generation efficiency, resulting in a highly sensitive resist film. Furthermore, the nonionic acid-generating structure contained in the radiation-sensitive composition is less likely to generate clusters compared to ionic acid-generating structures, which is believed to result in improved performance, such as improved LWR. It is believed 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] In this pattern formation method, the above-mentioned radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity and LWR when forming a resist pattern, and therefore a high-quality resist pattern can be formed efficiently.

[0014] In another embodiment, the present invention relates to a radiation-sensitive acid generator represented by the following formula (i): (In formula (i), R Ａ is *-R １３ -X-R １４ R is a group represented by the formula: １３ and R １４ is a fluoro- or iodine-containing hydrocarbon group, and R １３ is a fluoro group-containing hydrocarbon group, R １４ is an iodo group-containing hydrocarbon group, and R １３ is an iodo group-containing hydrocarbon group, R １４ is a fluoro-containing hydrocarbon group. X is a single bond or a divalent linking group. * represents a bond to the sulfur atom in formula (i). R ２When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8-membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded.

[0015] Because the radiation-sensitive acid generator has the above-mentioned specific structure, when used in a radiation-sensitive composition, it can impart good sensitivity and LWR to the resulting resist film.

[0016] 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.

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition (hereinafter also simply referred to as "composition") according to this embodiment contains a polymer (A) (also referred to as "base polymer (A)") that contains a structural unit (I) having an acid-dissociable group and that has an iodine group, and a solvent (D), and satisfies at least one of the following conditions (1) and (2): Condition (1): The radiation-sensitive composition contains a radiation-sensitive acid generator (B) represented by the above formula (1). Condition (2): The polymer (A) contains a structural unit (II) represented by the above formula (1').

[0018] When the radiation-sensitive composition does not contain a radiation-sensitive acid generator (B), the base polymer (A) contains the structural unit (II) represented by the formula (1'). When the radiation-sensitive composition contains a radiation-sensitive acid generator (B), the base polymer (A) may or may not contain the structural unit (II) represented by the formula (1'). The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0019] <Radiation-sensitive acid generator (B)> The radiation-sensitive acid generator (B) is represented by the following formula (1). The radiation-sensitive acid generator (B) is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer (A) to generate a carboxy group or the like. The radiation-sensitive acid generator (B) exists alone as a low-molecular-weight compound (free from the polymer), and is different from a radiation-sensitive acid-generating polymer in which the structural unit (II), which is an acid-generating structure, is bonded (covalently bonded) to the main chain of the polymer (A) as a side chain structure. (In formula (1), R １ is a monovalent organic group having 1 to 40 carbon atoms. ２ When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together and formed together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8 membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded.

[0020] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0021] The above R １ Examples of the monovalent organic group having 1 to 40 carbon atoms represented by the formula (I) include a monovalent hydrocarbon group having 1 to 40 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.

[0022] The above R １ Examples of the monovalent hydrocarbon group having 1 to 40 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 40 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 40 carbon atoms.

[0023] The above R １Examples of the monovalent linear hydrocarbon group having 1 to 40 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 40 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 40 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.

[0024] The above R １ Examples of the monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of the monocyclic saturated hydrocarbon group include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of the polycyclic saturated hydrocarbon group include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Examples of the monocyclic unsaturated hydrocarbon group include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Examples of the polycyclic unsaturated hydrocarbon group 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.

[0025] The above R １ Examples of the monovalent aromatic hydrocarbon group having 6 to 40 carbon atoms represented by the formula (I) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0026] 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.

[0027] 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.

[0028] Examples of the divalent heteroatom-containing group include -CO-, -C(=O)O-, -CS-, -NR'-, -O-, -S-, -SO-, and -SO ２ -, or a group formed by combining these groups. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0029] The above R １ From the viewpoint of sensitivity, it is preferable that the aromatic ring structure contains an iodo group-containing aromatic ring structure. The iodo group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodo groups.

[0030] 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 aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0031] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 5, more preferably 1 to 4, and even more preferably 2 or 3.

[0032] The above R １is preferably a group represented by the following formula (t): １1 -X-R １２ (t) (In formula (t), R １1 is a divalent hydrocarbon group or halogenated hydrocarbon group having 1 to 10 carbon atoms. X is a single bond or a divalent linking group. R １２ is a monovalent organic group having 1 to 30 carbon atoms. * represents a bond to the sulfur atom in formula (1).

[0033] The above R １１ The divalent hydrocarbon group having 1 to 10 carbon atoms is R １ A group obtained by removing one hydrogen atom from a monovalent hydrocarbon group having 1 to 40 carbon atoms represented by the following formula (I) and having the corresponding number of carbon atoms can be suitably used.

[0034] The above R １１ The divalent halogenated hydrocarbon group having 1 to 10 carbon atoms may be one in which some or all of the hydrogen atoms of the divalent hydrocarbon group having 1 to 10 carbon atoms have been substituted with halogen atoms. Preferred halogen atoms are iodine atoms and fluorine atoms.

[0035] The above R １１ is preferably a group selected from the group consisting of a group represented by the following formula (a) and a group represented by the following formula (b): (In formula (a), R ｆ１ and R ｆ２ are each independently a hydrogen atom, a halogen atom, or a halogenated alkyl group. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different. t is an integer of 1 to 4. * represents a bond bonding to the sulfur atom in formula (1), and ** represents a bond bonding to X in formula (t). (In formula (b), Y represents a hydroxy group, a carboxy group, a cyano group, a nitro group, an amino group, an organic group having 1 to 10 carbon atoms, or a halogen atom. When a plurality of Ys are present, the plurality of Ys may be the same or different. s represents an integer of 0 to 4. * represents a bond bonding to the sulfur atom in formula (1), and ** represents a bond bonding to X in formula (t).)

[0036] R in the above formula (a) ｆ１ and R ｆ２ Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, and among these, a fluorine atom and an iodine atom are preferred.

[0037] The above R ｆ１ and R ｆ２ The halogenated alkyl group represented by the formula (1) is １ In the above formula, some or all of the hydrogen atoms of the monovalent linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms are substituted with halogen atoms, and a group having the corresponding number of carbon atoms can be suitably used. ｆ１ and R ｆ２ Among these, a fluorine atom and an iodine atom are preferred.

[0038] Among these, R ｆ１ and R ｆ２ is preferably a hydrogen atom, a fluorine atom or a trifluoromethyl group.

[0039] In the above formula (a), t is an integer of 1 to 4, and is preferably 1 or 2.

[0040] The organic group having 1 to 10 carbon atoms in Y in the above formula (b) is １ Among the monovalent organic groups having 1 to 40 carbon atoms represented by the following formula, groups having the corresponding number of carbon atoms can be suitably used.

[0041] Among these, Y is preferably a halogen atom or a monovalent hydrocarbon group having 6 to 12 carbon atoms, more preferably a fluorine atom or a cyclohexyl group.

[0042] In the above formula (a), s is an integer of 0 to 4, preferably 2 to 4.

[0043] X is a single bond or a linking group, and preferred examples of the linking group include an alkanediyl group having 1 to 10 carbon atoms, —O—, —CO—, and a divalent group obtained by combining these. Among these, a single bond, an ester bond (—COO—), an ether bond (—O—), or an amide bond (—NHCO—) is preferred as X.

[0044] The above R １２ The monovalent organic group having 1 to 30 carbon atoms represented by the above R １ Among the monovalent organic groups having 1 to 40 carbon atoms represented by the following formula, groups having the corresponding number of carbon atoms can be suitably used.

[0045] The above R １２ Preferably, has a cyclic structure.

[0046] The cyclic structure 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.

[0047] The alicyclic structure may be any of the above R １ A structure corresponding to a monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms represented by the following formula can be suitably employed.

[0048] As the aromatic ring structure, the aromatic rings (including aromatic hydrocarbon rings and heteroaromatic rings) shown in the iodo group-containing aromatic ring structure can be suitably used.

[0049] 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 and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, 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.

[0050] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0051] (In the above formula, g is an integer of 1 to 3.)

[0052] The chain structure may be any of the above R １ A monovalent chain hydrocarbon group having 1 to 40 carbon atoms and represented by the following formula can be suitably used.

[0053] The divalent heteroatom-containing group includes the above-mentioned R １ A divalent heteroatom-containing group which can be contained in a monovalent organic group having 1 to 40 carbon atoms and represented by the following formula can be suitably used.

[0054] A part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure can be substituted with a substituent. １ The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0055] The above R １２As the alkyl group, a monovalent halogenated aromatic hydrocarbon group having 6 to 12 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms are preferred, and a halogenated phenyl group and a substituted or unsubstituted adamantyl group are more preferred.

[0056] The above R ２ The monovalent organic group represented by the above R １ A monovalent organic group having 1 to 40 carbon atoms and represented by the following formula can be suitably used.

[0057] The above two R ２ As a divalent cyclic group having 3 to 20 carbon atoms formed by combining these together with the carbon atom to which they are bonded, the above R １２ A group in which two hydrogen atoms have been removed from a cyclic structure that may be possessed by the group represented by the formula (I) can be suitably employed.

[0058] n is an integer of 0 to 20, preferably an integer of 0 to 10, and more preferably an integer of 0 to 5.

[0059] W represents a ring structure having 5 to 8 ring members formed together with the carbon atom and nitrogen atom to which it is bonded. Examples of such ring structures include the following ring structures:

[0060] The radiation-sensitive acid generator (B) is preferably a radiation-sensitive acid generator represented by the following formula (1-1). (In formula (1-1), represents a single bond or a double bond. １ , R ２ has the same meaning as the above formula (1).

[0061] Examples of the radiation-sensitive acid generator (B) include structures represented by the following formulae (B-1) to (B-41).

[0062]

[0063]

[0064]

[0065]

[0066] These radiation-sensitive acid generators (B) may be used alone or in combination of two or more.

[0067] When the radiation-sensitive composition contains a radiation-sensitive acid generator (B), the lower limit of the content of the radiation-sensitive acid generator (B) (the total content when multiple types are used) is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, relative to 100 parts by mass of the base polymer (A) described below. The upper limit of the content is preferably 100 parts by mass, more preferably 60 parts by mass, and even more preferably 50 parts by mass. This allows excellent sensitivity to be exhibited during resist pattern formation.

[0068] <Polymer (A)> The polymer (A) contains a structural unit (I) having an acid-dissociable group and is an aggregate of polymer chains having an iodine group (hereinafter, this polymer will also be referred to as a "base polymer (A)"). The radiation-sensitive composition has excellent pattern formability due to the polymer (A) containing the structural unit (I). The structural unit (I) and the iodo group may be contained in the same polymer chain or in different polymer chains, as long as the polymer (A) as a whole contains the structural unit (I) and the iodo group. The base polymer (A) may contain a structural unit other than the structural unit (I), for example, it may contain a structural unit (II) represented by the above formula (1'). When the polymer (A) contains the above structural unit (II), the structural unit (I) and the structural unit (II) may be contained in the same polymer chain or in different polymer chains, as long as the polymer (A) as a whole contains the structural unit (I) and the structural unit (II). The base polymer (A) may contain structural units other than the structural units (I) and (II), such as the structural units (III) to (VIII) and the structural unit (II') described below.

[0069] By incorporating iodine groups into the base polymer (A), the radiation absorption efficiency increases, and the secondary electron generation efficiency increases, thereby improving sensitivity.

[0070] The form in which the iodo group is contained in the base polymer (A) is not particularly limited, but it is preferably contained in the form of the above-mentioned iodo group-containing aromatic ring structure, and one or more of the structural units constituting the base polymer (A) may contain the iodo group-containing aromatic ring structure.

[0071] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0072] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. However, in this specification, a monomer corresponding to both the structural unit (I) and the structural unit (IV) described below is included in the structural unit (I). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in 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. Upon exposure, an acid generated from the structural units (II) and (II') described below or the radiation-sensitive acid generator (B) dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This creates a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0073] The acid-dissociable group preferably contains an iodine group, and more preferably contains the iodine group-containing aromatic ring structure. Generally, the introduction of an iodine group tends to reduce removability with a developer. In contrast, the acid-dissociable group dissociates with acid upon exposure to generate an acid group, which is easily removed during development. By introducing an iodine group or an iodine group-containing aromatic ring structure into the acid-dissociable group that is easily removed during development, good development defect suppression properties can be achieved.

[0074] The aromatic ring in the iodo group-containing aromatic ring structure is R １ Among these, a benzene ring, a thiophene ring, or a furan ring is preferred, and a benzene ring is more preferred.

[0075] The number of iodo groups in the acid-dissociable group is not particularly limited, but is preferably 1, 2 or 3, and more preferably 1 or 2.

[0076] The structural unit (I) is not particularly limited as long as it has 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, a structural unit having an acetal bond, etc. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, the structural unit (I) is preferably a structural unit represented by the following formula (2) (hereinafter also referred to as "structural unit (I-1)"):

[0077] (In formula (2), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a divalent linking group. １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １Ａ and R １Ｂ represents a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atoms to which they are bonded. １Ａ and R １Ｂ There is no case where both of R are hydrogen atoms. １Ｃ represents a hydrogen atom or a monovalent organic group having 1 to 10 carbon atoms. m1 and m2 each independently represent 0 or 1.

[0078] The above L １ Examples of the divalent linking group represented by the formula (I) include a divalent hydrocarbon group such as an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, or an arenediyl group, a divalent heteroatom-containing group, a group in which the divalent heteroatom-containing group is incorporated between the carbon-carbon bond of the divalent hydrocarbon group, or a group that is a combination of these. １A divalent heteroatom-containing group that can be possessed by a monovalent organic group having 1 to 40 carbon atoms, represented by the following formula (I) can be suitably employed. Some or all of the hydrogen atoms possessed by these groups may be substituted with a substituent such as a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group, or a group in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0079] The above L １ Examples of the alkyl group as a substituent 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.

[0080] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0081] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0082] 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.

[0083] 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.

[0084] The above L １ The divalent linking group represented by the formula (I) is preferably an alkanediyl group or an arenediyl group, more preferably an alkanediyl group having 1 to 4 carbon atoms or an arenediyl group having 6 to 10 carbon atoms, and even more preferably a methanediyl group or a benzenediyl group.

[0085] The above R １Ａ and R １Ｂ The monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (1) is R １ Among the monovalent chain hydrocarbon groups having 1 to 40 carbon atoms represented by the following formula, groups having the corresponding number of carbon atoms can be suitably used.

[0086] The above R １Ａ and R １Ｂ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is １ Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms represented by the following formula, groups having the corresponding number of carbon atoms can be suitably used.

[0087] The above R １Ａ and R １ＢAs the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0088] The above R １Ａ and R １Ｂ is a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R １Ａ and R １Ｂ 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 hydrogen atom, 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 hydrogen atom, a methyl group, a cyclopentanediyl group, or a cyclohexanediyl group is even more preferred.

[0089] The above R １Ｃ The monovalent organic group having 1 to 10 carbon atoms represented by the formula (1) is R １ Among the monovalent organic groups having 1 to 40 carbon atoms represented by the following formula, those having the corresponding number of carbon atoms can be suitably used.

[0090] The above R １Ｃ As the heterocyclic group, R in the above formula (a) is preferably a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms, or a heterocyclic group having 5 to 10 carbon atoms. １２ A group in which one hydrogen atom has been removed from the heterocyclic structure of the formula (I) can be suitably used.

[0091] As the structural unit (I), from the viewpoint of sensitivity, a structural unit represented by the following formula (2') (hereinafter also referred to as "structural unit (I-2)") is preferred.

[0092] (In formula (2'), Ar １ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１are the same or different. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p+q is 5 or less. R α , L １ , R １Ａ , R １Ｂ , m1 and m2 have the same meanings as in formula (2) above.

[0093] Ar １ As the aromatic ring in the above, the aromatic ring in the iodo group-containing aromatic ring structure can be suitably used. １ The aromatic ring in Ar is preferably a benzene ring, a thiophene ring or a furan ring, more preferably a benzene ring or a thiophene ring. １ The aromatic ring having 5 to 20 ring members and a valence of (p+q+1) is represented by the above Ar １ A group in which (p+q+1) hydrogen atoms have been removed from the aromatic ring of the formula (I) can be suitably used.

[0094] R １０１ The alkoxy group represented by the formula (1) is １ Examples of the alkoxy groups include those shown as the substituents of the above.

[0095] p is preferably 1 or 2. q is preferably 0 or 1.

[0096] Furthermore, the polymer (A) may contain, as the structural unit (I), structural units represented by the following formulae (1f) to (2f).

[0097]

[0098] 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, a halogen atom, or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0099] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0100] Specific examples of the structural unit (I) (including structural units (I-1) and (I-2)) are not particularly limited, but include structures represented by the following formulas (2-1) to (2-68). In the following formulas, R α is synonymous with the above formula (2).

[0101]

[0102]

[0103]

[0104]

[0105]

[0106] The base polymer (A) may contain one type of structural unit (I) or a combination of two or more types.

[0107] 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 5 mol%, more preferably 7 mol%, and even more preferably 10 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 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.

[0108] (Structural Unit (II)) The structural unit (II) is represented by the following formula (1'): The structural unit (II) generates an acid upon exposure that induces dissociation of the acid-dissociable group. That is, the structural unit (II) functions as a radiation-sensitive acid-generating structure. (In formula (1'), R １ａ is a divalent organic group having 1 to 40 carbon atoms. a is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ , n, and W have the same meanings as in formula (1) above.

[0109] The above R １ａ The divalent organic group having 1 to 40 carbon atoms represented by the formula (1) is R １A 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:

[0110] R ２ , n, and W can be suitably selected from those listed in the above formula (1).

[0111] Specific examples of the monomer that provides the structural unit (II) include the monomers represented by the following formulae (1'-1) to (1'-17). α has the same meaning as the above formula (1').

[0112]

[0113]

[0114]

[0115] When the base polymer (A) contains the structural unit (II), the lower limit of the content of the structural unit (II) (when multiple types are contained, the total content) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol% relative to the total structural units constituting the base polymer (A). The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By setting the content of the structural unit (II) within the above range, the function as an acid generating structure can be fully exerted, and the above resist properties can be exhibited.

[0116] (Structural Unit (II')) The polymer (A) may contain a structural unit (II') that is an acid-generating structure other than the structural unit (II). The structural unit (II') has a first acid-generating structure having a first organic acid anion and a first onium cation. The first acid-generating structure generates an acid that induces dissociation of the acid-dissociable group upon exposure.

[0117] The structural unit (II') is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (II'-1)") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit (II'-2)").

[0118]

[0119] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched or cyclic alkanediyl group having 1 to 12 carbon atoms, a cycloalkanediyl group having 3 to 12 carbon atoms, or an arenediyl group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkanediyl group, cycloalkanediyl group or arenediyl group may be substituted with an ether group, an ester group or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkanediyl group having 1 to 12 carbon atoms, or a cyclic cycloalkanediyl group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkanediyl group may be substituted with an ether group or an ester group. ２ and V ３ may have some or all of the hydrogen atoms substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom.

[0120] The alkanediyl group, cycloalkanediyl group, and arenediyl group are each selected from the group consisting of L １ In the divalent linking group represented by the following formula, an alkanediyl group, a cycloalkanediyl group, or an arenediyl group can be preferably used.

[0121] The above Rf １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group.

[0122] The above R ４３ ~R ４７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R ４３ and R ４４ and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. ４３ ~R ４５ and R ４６ ~R ４７Preferably, at least one of the above contains the iodo group-containing aromatic ring structure or the fluoro group-containing aromatic ring structure.

[0123] The fluoro group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in an 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.

[0124] The above V ２ and V ３ , R ４３ ~R ４７ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (1) is R １ Among monovalent hydrocarbon groups having 1 to 40 carbon atoms and represented by the following formula, groups having the corresponding number of carbon atoms can be suitably employed. Some or all of the hydrogen atoms of the hydrocarbon group may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0125] Examples of the first organic acid anion of the monomer that gives the structural unit (II') (including the structural unit (II'-1) and the structural unit (II'-2)) include, but are not limited to, those shown below. Of the first organic acid anions shown below, all of the first organic acid anions that contain an aromatic ring structure have an iodine group-containing aromatic ring structure, but the structural unit (II') does not necessarily require an iodine group-containing aromatic ring structure. As the first organic acid anion that does not have an iodine group-containing aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with a hydrogen atom or another substituent can be suitably used. In the following formula, R Ｖ has the same meaning as the above formula (a1).

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] The first onium cation in the structural unit (II'-1) can suitably be the second onium cation in the structural unit (III) described below.

[0132] When the base polymer (A) contains the structural unit (II'), the lower limit of the content of the structural unit (II') (when multiple types are contained, the total content) 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 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By setting the content of the structural unit (II') within the above range, the function as an acid generating structure can be fully exhibited, and the above-mentioned resist properties can be exhibited.

[0133] The monomers that give the structural units (II'-1) and (II'-2) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0134] (Structural Unit (III)) The structural unit (III) is a structural unit containing a second acid generating structure. The second acid generating structure has a second organic acid anion and a second onium cation, and generates an acid that does not induce dissociation of the acid-dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the radiation-sensitive composition, the second acid generating structure does not substantially dissociate the acid-dissociable group of the structural unit (I), and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator (B) and structural units (II) and (II') in unexposed areas through salt exchange. The acid generated from the second acid generating structure can be said to be a relatively weaker acid (an acid with a higher pKa) than the acids generated from the radiation-sensitive acid generator (B) and structural units (II) and (II'). Whether the onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable group in the base polymer (A) and the acidity of the onium salt structure or the acid generated.

[0135] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (III) of the base polymer (A) is not particularly limited. The base polymer (A) may have the second organic acid anion as a side chain moiety or the second onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain of the base polymer (A) as a side chain structure. When the second organic acid anion is bonded to the main chain of the base polymer (A) as a side chain structure, the second onium cation is ionically bonded to the organic acid anion as a counter ion of the second organic acid anion. On the other hand, when the second onium cation is bonded to the main chain of the base polymer (A) as a side chain structure, the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation. From the viewpoint of development contrast, it is preferable that the base polymer (A) have the second organic acid anion as a side chain moiety.

[0136] The second organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety, and more preferably has a carboxylate anion. However, when the organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, and a cyano group. The fluorinated hydrocarbon group is preferably a perfluoroalkyl group having 1 to 5 carbon atoms. The acid generated by exposure is a carboxylic acid or sulfonic acid corresponding to the acid anion moiety.

[0137] The second organic acid anion preferably contains, as a structure other than the acid anion moiety, -O-, -CO-, a cyclic structure, or a combination thereof. Such combinations also include structures (heterocyclic structures) in which -O- or -CO- is incorporated as a ring-forming moiety in the cyclic structure. Examples of the cyclic structure include R １２ The cyclic structure that can be possessed by the formula (I) can be suitably employed.

[0138] The second organic acid anion preferably has an iodo group or a hydroxy group. The second organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0139] The second onium cation may be 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.

[0140] The second onium cation preferably has an iodo group. The second onium cation preferably contains the iodo group-containing aromatic ring structure.

[0141] The second onium cation in the structural unit (III) preferably has the above-mentioned fluoro group-containing aromatic ring structure, which increases the radiation absorption efficiency and thereby improves sensitivity.

[0142] The structural unit (III) having the above structures in combination can efficiently exhibit the above functions.

[0143] The structural unit (III) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (IIII-1)").

[0144]

[0145] In formula (p1), R A is a hydrogen atom or a methyl group.

[0146] In formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group, or a naphthylene group.

[0147] In formula (p1), X ２ represents a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may contain an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-2 ... alkanediyl groups having 1 to 12 carbon atoms, such as diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; alicyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; and groups obtained by combining these.

[0148] In formula (p1), X ３ is a single bond, an ester bond or an ether bond.

[0149] In formula (p1), R Ｘ is a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

[0150] In formula (p1), R ４３ ~R ４５ has the same meaning as the above formula (a1).

[0151] In formula (p1), x1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R Ｘ are the same or different.

[0152] Examples of the second organic acid anion of the monomer that gives the structural unit (III) include, but are not limited to, those shown below. Note that although all of the second organic acid anions shown below have an iodine group or a hydroxy group, the structural unit (III) does not necessarily require an iodine group or a hydroxy group. As the second organic acid anion that does not have an iodine group or a hydroxy group, a structure in which the iodine group or the hydroxy group in the following formula is substituted with a hydrogen atom or other substituent can be suitably used. In the following formula, R Ａ is the same as above. The second organic acid anion preferably has a carboxylate anion and a hydroxy group. In this case, it is preferable that the carboxylate anion and the hydroxy group are bonded to the same aromatic ring in the second organic acid anion, and it is more preferable that the carbon atom to which the carboxylate anion is bonded and the carbon atom to which the hydroxy group is bonded are directly bonded to each other in the same aromatic ring.

[0153]

[0154]

[0155]

[0156]

[0157]

[0158]

[0159]

[0160]

[0161] The second onium cation of the structural unit (III) is preferably represented by the following formula (Q-1).

[0162]

[0163] In the above formula (Q-1), Ra1 to Ra3 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or more, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or more, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or more, multiple Ra3s may be the same or different. Ra1 and Ra2 may be linked to each other to form a ring. When n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring. When n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring.

[0164] The substituents represented by Ra1, Ra2, and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom, or a halogenated hydrocarbon group.

[0165] The alkyl groups of Ra1, Ra2, and Ra3 may be linear or branched alkyl groups. １Ａ and R １Ｂ Of these, a methyl group, an ethyl group, an n-butyl group, and a t-butyl group are particularly preferred.

[0166] The cycloalkyl groups of Ra1, Ra2, and Ra3 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0167] Examples of the alkyl group moiety of the alkoxy group of Ra1, Ra2, and Ra3 include those previously listed as the alkyl group of Ra1, Ra2, and Ra3. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0168] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1, Ra2, and Ra3 include those previously listed as the cycloalkyl groups of Ra1, Ra2, and Ra3. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0169] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1, Ra2, and Ra3 include those previously listed as the alkoxy groups of Ra1, Ra2, and Ra3. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0170] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1, Ra2, and Ra3 include those previously listed as the alkyl groups of Ra1, Ra2, and Ra3. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1, Ra2, and Ra3 include those previously listed as the cycloalkyl groups of Ra1, Ra2, and Ra3. Particularly preferred of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl.

[0171] Each of the groups Ra1, Ra2, and Ra3 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.

[0172] Examples of the halogen atom for Ra1, Ra2, and Ra3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0173] The halogenated hydrocarbon group of Ra1, Ra2, and Ra3 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0174] As described above, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are 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. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable that n1 forms - 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. Furthermore, when n1 is 2 or more, a plurality of Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, a plurality of Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0175] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF３ , 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 C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0176] Ra3 is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0177] n1 and n2 each independently represent preferably an integer of 0 to 3, more preferably an integer of 0 to 2.

[0178] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0179] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is a fluorine atom, an iodine atom, or CF３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0180] Specific examples of such a second onium cation represented by the above formula (Q-1) include the following.

[0181] (In the formula, tBu represents a t-butyl group, and Me represents a methyl group.)

[0182]

[0183] (In the formula, Me represents a methyl group.)

[0184] (In the formula, Me represents a methyl group.)

[0185]

[0186] (In the formula, Me represents a methyl group.)

[0187] Specific examples of the iodonium cation include the following: In the onium cations shown below, the hydrogen atoms on the aromatic rings may be substituted with iodine atoms, fluorine atoms, groups containing these atoms, other substituents, etc.

[0188]

[0189] The monomer that provides the structural unit (III) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0190] When the base polymer (A) contains the structural unit (III), the lower limit of the content of the structural unit (III) (when multiple types are contained, the total content) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol% relative to all structural units constituting the base polymer (A). The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 10 mol%. By setting the content of the structural unit (III) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0191] (Structural Unit (IV)) The structural unit (IV) is a structural unit having a phenolic hydroxyl group. When the polymer (A) contains the structural unit (IV), 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 (IV) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (IV) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (IV) is preferably represented by the following formula (4):

[0192] (In the above formula (4), R βis 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 ４ are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0193] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (IV), it is preferably a hydrogen atom or a methyl group.

[0194] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0195] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the formula (1) is preferably L １ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0196] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0197] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0198] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0199] The structural unit (IV) is preferably a structural unit represented by the following formulas (4-1) to (4-20) (hereinafter also referred to as "structural unit (IV-1) to structural unit (IV-20)"). β is the same as the above formula (4).

[0200]

[0201]

[0202] When the base polymer (A) contains the structural unit (IV), the lower limit of the content of the structural unit (IV) (total content when multiple structural units (IV) are present) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 20 mol%, based on all structural units constituting the base polymer (A). The upper limit of this content is preferably 80 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content of the structural unit (IV) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0203] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer 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), and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0204] (Structural Unit (V)) The structural unit (V) is a structural unit containing at least one structure 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 (V), the base polymer (A) can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve its lithography performance, such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer (A) and a substrate can be improved.

[0205] Examples of the structural unit (V) include structural units represented by the following formulae (T-1) to (T-11).

[0206]

[0207] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or a methoxymethyl 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. ２ is 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.

[0208] 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 １Ａ and R １Ｂ Among divalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms which are formed by combining together with the carbon atoms to which they are bonded, groups having 3 to 8 carbon atoms are exemplified. One or more hydrogen atoms on this alicyclic hydrocarbon group may be substituted with a hydroxy group.

[0209] The above R Ｌ６ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (1) is １ Among monovalent hydrocarbon groups having 1 to 40 carbon atoms represented by the following formula, groups having the corresponding number of carbon atoms can be suitably used.

[0210] The above L ２Examples 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-.

[0211] The above L ２ As the divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms in the formula (1), R １ A group in which one hydrogen atom has been removed from a monovalent chain hydrocarbon group having 1 to 40 carbon atoms, represented by the following formula:

[0212] The above L ２ As the divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, R １ A group in which one hydrogen atom has been removed from a monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms, represented by the following formula, can be suitably used.

[0213] Of these, the structural unit (V) is preferably a structural unit containing a lactone structure or a cyclic carbonate structure.

[0214] The base polymer (A) may contain one type of structural unit (V) or a combination of two or more types.

[0215] 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 5 mol%, and even more preferably 8 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 (V) 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.

[0216] (Structural Unit (VI)) The structural unit (VI) is a structural unit containing a polar group (excluding those corresponding to the structural units (I) to (V)). By further including the structural unit (VI), the base polymer (A) can adjust its solubility in a developer, thereby improving the lithography performance, such as 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. Of these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0217] Examples of the structural unit (VI) include structural units represented by the following formula:

[0218]

[0219]

[0220] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0221] When the base polymer (A) has the structural unit (VI) having the polar group, the lower limit of the content of the structural unit (VI) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer (A). The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content of the structural unit (VI) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0222] (Structural Unit (VII)) The structural unit (VII) is a structural unit derived from a substituted or unsubstituted styrene. When the structural unit (VII) has a substituent, examples of the substituent include L in the above formula (1). １ The substituent is preferably a halogen atom or an alkoxy group, more preferably an iodine atom or a methoxy group.

[0223] Examples of the monomer that provides the structural unit (VII) include compounds represented by the following formula:

[0224]

[0225] When the base polymer (A) has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on the total structural units constituting the base polymer (A), and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0226] (Structural Unit (VIII)) The base polymer (A) may contain, as a structural unit other than the structural units listed above, a structural unit having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VIII)"). (In the above formula (6), R １α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0227] In the above formula (6), R ２α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is １ Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms represented by the following formula, those having the corresponding number of carbon atoms can be suitably used.

[0228] When the base polymer (A) contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer (A), and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0229] (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.

[0230] 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.

[0231] As the solvent used in the polymerization, the solvent (D) described below can be suitably used. These solvents used in the polymerization may be used alone or in combination of two or more kinds.

[0232] 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.

[0233] 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 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 18,000, and even more preferably 15,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0234] 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.

[0235] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0236] The lower limit of the content of the base polymer (A) is preferably 50% by mass, more preferably 60% by mass, and even more preferably 70% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 98% by mass, more preferably 95% by mass, and even more preferably 92% by mass.

[0237] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer (F) having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as "high-fluorine-content polymer (F)"). When the radiation-sensitive composition contains the high-fluorine-content polymer (F), the high-fluorine-content polymer (F) can be unevenly distributed in the surface layer of the resist film relative to the base polymer (A), which results in surface modification of the resist film during EUV exposure and control of the distribution of composition within the film.

[0238] The high fluorine content polymer (F) preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (IX)"), and may also have the structural unit (I) and the structural units (IV) to (VIII) of the base polymer, as necessary:

[0239]

[0240] In the above formula (5), R １３ is a hydrogen atom, a monovalent organic group having 1 to 10 carbon atoms, 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—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. １４ 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.

[0241] The above R １３ The monovalent organic group having 1 to 10 carbon atoms represented by the formula (1) is R １ Among these, monovalent organic groups having 1 to 40 carbon atoms represented by the following formula (I) can be suitably used: １３As the alkyl group, a methyl group or a methoxymethyl group is preferred.

[0242] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (IX), a single bond and —COO— are preferred, and —COO— is more preferred.

[0243] The above R １４ Examples 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.

[0244] The above R １４ 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.

[0245] The above R １４ As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, and a 1,1,1,3,3,3-hexafluoro-2-propyl group are even more preferable.

[0246] When the high-fluorine content polymer (F) has the structural unit (IX), the lower limit of the content of the structural unit (IX) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on all structural units constituting the high-fluorine content polymer (F). The upper limit of the content is preferably 90 mol%, more preferably 80 mol%. By setting the content of the structural unit (IX) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer (F) can be more appropriately adjusted, and the uneven distribution of fluorine atoms in the surface layer of the resist film can be further promoted, resulting in further improvements in the surface modification properties, component distribution controllability, and water repellency of the resist film.

[0247] The high-fluorine content polymer (F) may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (X)) in addition to or instead of the structural unit (IX). When the high-fluorine content polymer (F) has the structural unit (f-2), the solubility in an alkaline developer is improved, and the occurrence of development defects can be suppressed.

[0248]

[0249] The structural unit (X) is roughly classified into two types: (x) a structural unit having an alkali-soluble group, and (y) a structural unit having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter 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.

[0250] When the structural unit (X) has an alkali-soluble group (x), 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 RＥ , W １ , A １ and R Ｆ When the structural unit (X) has an alkali-soluble group (x), it is possible to increase the affinity for an alkaline developer and suppress development defects.

[0251] When the structural unit (X) has an alkali-dissociable group (y), 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 (VI) has an alkali-dissociable group (y), 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. Examples of the structural unit (VI) having an alkali-dissociable group (y) include A １ is -COO-*, and RＦ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0252] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (X), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0253] 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.

[0254] When the high-fluorine-content polymer has the structural unit (X), the lower limit of the content of the structural unit (X) is preferably 30 mol%, more preferably 35 mol%, and even more preferably 40 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 100 mol%, more preferably 95 mol%, and even more preferably 90 mol%. By setting the content of the structural unit (VI) within the above range, the solubility in an alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0255] (Other Structural Units) The high fluorine content polymer (F) may contain, as structural units other than the structural units listed above, the structural units (I) and (IV) to (VIII) in the base polymer (A). When the high fluorine content polymer (F) contains the structural units (V) and (VI), the structural units (V) and (VI) are preferably structures containing a fluorine atom.

[0256] When the high fluorine content polymer (F) contains the structural unit (I), the structural unit (V), and the structural unit (VI), the contents of the structural unit (I), the structural unit (V), and the structural unit (VI) in the high fluorine content polymer can suitably be the same as those described for the base polymer (A).

[0257] The lower limit of Mw of the high fluorine content polymer (F) is preferably 4,000, more preferably 5,000, and even more preferably 8,000. The upper limit of Mw is preferably 40,000, more preferably 30,000, and even more preferably 25,000.

[0258] The lower limit of Mw / Mn of the high fluorine content polymer (F) is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0259] When the radiation-sensitive composition contains the high-fluorine-containing polymer (F), the content of the high-fluorine-containing polymer (F) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less.

[0260] By setting the content of the high fluorine content polymer (F) within the above range, the high fluorine content polymer (F) can be more effectively localized in the surface layer of the resist film, which in turn makes it possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film. The radiation-sensitive composition may contain one or more high fluorine content polymers (F).

[0261] (Method for synthesizing high fluorine content polymer (F)) The high fluorine content polymer (F) can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer (A).

[0262] <Acid Diffusion Controller (Z)> The radiation-sensitive composition may contain an acid diffusion controller (Z). The acid diffusion controller (Z) preferably contains an organic acid anion and an onium cation, and upon irradiation with radiation, generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator (B) or the structural units (II) and (II'). The acid diffusion controller (Z) does not substantially dissociate the acid-dissociable group of the base polymer (A) under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator (B) or the structural units (II) and (II') in unexposed areas through salt exchange.

[0263] By including the acid diffusion controller (Z) in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern with excellent resolution and development contrast.

[0264] Examples of the acid diffusion controller (Z) include sulfonium salt compounds represented by the following formula (8-1), iodonium salt compounds represented by the following formula (8-2), etc. Further examples include compounds containing a sulfonium cation and anion in the same molecule represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule represented by the following formula (8-4).

[0265]

[0266] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. － and Q － are each independently OH － and R α -COO － , R α -SO ３ － In the above formulas (8-1) and (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. α is a single bond or a divalent organic group having 1 to 30 carbon atoms. The monovalent organic group having 1 to 30 carbon atoms is R １ Among the monovalent organic groups having 1 to 40 carbon atoms represented by the following formula, those having the corresponding carbon atoms can be suitably used. Examples of the divalent organic groups having 1 to 30 carbon atoms include groups in which one hydrogen atom has been removed from the monovalent organic groups having 1 to 30 carbon atoms.

[0267] The acid diffusion controller (Z) preferably has an iodine group. The acid diffusion controller (Z) preferably contains the iodine group in the form of an aromatic ring structure containing the iodine group.

[0268] Examples of organic acid anions of the acid diffusion controller (Z) include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As organic acid anions that do not have an iodo group-containing aromatic ring structure, structures in which the iodo group in the following formula is substituted with an atom or group other than an iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0269]

[0270]

[0271] As the onium cation in the acid diffusion controller (Z), the structure of the second onium cation in the structural unit (III) in the base polymer (A) can be suitably adopted.

[0272] The acid diffusion controller (Z) can also be synthesized by a known method, particularly by a salt exchange reaction.

[0273] The acid diffusion controller (Z) may be used alone or in combination of two or more kinds.

[0274] When the radiation-sensitive composition contains an acid diffusion controller (Z), the lower limit of the content of the acid diffusion controller (Z) (total content when multiple types are used) is preferably 5 mol %, more preferably 10 mol %, and even more preferably 20 mol %, based on the total content of the monomers corresponding to the content ratios of the structural units (II) and (II') of the base polymer and the content of the radiation-sensitive acid generator (B). The upper limit of the content is preferably 120 mol %, more preferably 110 mol %, and even more preferably 100 mol %.

[0275] <Solvent (D)> The radiation-sensitive composition according to this embodiment contains a solvent (D). The solvent (D) is not particularly limited as long as it is a solvent that can dissolve or disperse the base polymer (A) and, optionally, the radiation-sensitive acid generator (B), additives, and the like.

[0276] Examples of the solvent (D) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0277] 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.

[0278] 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.

[0279] 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.

[0280] 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; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0281] 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.

[0282] 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.

[0283] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0284] Among these, ester-based solvents and ether-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0285] <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.

[0286] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the base polymer (A), the solvent (D), and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 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.

[0287] <<Pattern Forming Method>> The pattern forming method of the present embodiment 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 to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0288] According to the pattern formation method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity and LWR during pattern formation.

[0289] [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, soft baking (SB) may be performed, if necessary, to volatilize the solvent in the coating film. The SB temperature is typically 60°C to 160°C, and preferably 80°C to 140°C. The SB time is typically 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0290] When the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (IV) as the base polymer in the composition.

[0291] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), 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, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0292] 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 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0293] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. 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.

[0294] 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.

[0295] 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, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, 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.

[0296] 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 piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (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 that is rotating at a constant speed (dynamic dispense method).

[0297] <Radiation-Sensitive Acid Generator> The radiation-sensitive acid generator of the present embodiment is represented by the following formula (i). (In formula (i), R Ａ is *-R １３ -X-R １４ R is a group represented by the formula: １３ and R １４ is a fluoro- or iodine-containing hydrocarbon group, and R １３ When R is a divalent fluoro group-containing hydrocarbon group, １４ is a monovalent iodine-containing hydrocarbon group, and R １３ When R is a divalent iodine group-containing hydrocarbon group, １４ is a monovalent fluoro group-containing hydrocarbon group. X is a single bond or a divalent linking group. * represents a bond to the sulfur atom in formula (i). R２ When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8-membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded.

[0298] The monovalent fluoro group-containing hydrocarbon group is R １ In the present invention, a monovalent hydrocarbon group having 1 to 40 carbon atoms, represented by the following formula (I), in which some or all of the hydrogen atoms have been substituted with fluorine atoms can be suitably used.

[0299] As the divalent fluoro-group-containing hydrocarbon group, a group in which one hydrogen atom has been removed from the monovalent fluoro-group-containing hydrocarbon group can be suitably used.

[0300] The monovalent iodine group-containing hydrocarbon group is R １ In the present invention, a monovalent hydrocarbon group having 1 to 40 carbon atoms, represented by the following formula (I), in which some or all of the hydrogen atoms have been substituted with iodine atoms can be suitably used.

[0301] As the divalent iodo group-containing hydrocarbon group, a group obtained by removing one hydrogen atom from the monovalent iodo group-containing hydrocarbon group can be suitably used.

[0302] The above R Ａ As the above, R １３ is a divalent fluoro group-containing hydrocarbon group, and R １４ is preferably a monovalent iodine group-containing hydrocarbon group, and １３ is a divalent fluoro group-containing hydrocarbon group, and R １４ The cyclic hydrocarbon group may be any of alicyclic, aromatic, and heterocyclic. １２Examples of the iodo group-containing cyclic hydrocarbon group include groups in which some or all of the hydrogen atoms of the cyclic hydrocarbon group have been substituted with iodine atoms.

[0303] As the divalent linking group represented by X, those exemplified as X in the formula (t) can be suitably used.

[0304] The above R ２ , n, and W may be those exemplified for the radiation-sensitive acid generator (B) represented by the above formula (1).

[0305] Examples of the radiation-sensitive acid generator represented by formula (i) include (B-1), (B-2), (B-8) to (B-22), (B-28) to (B-34), and (B-36) to (B-40) listed above as the radiation-sensitive acid generator (B).

[0306] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties in the examples were measured as follows.

[0307] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn) of polymer] The weight-average molecular weight (Mw) and dispersity (Mw / Mn) of the polymer were measured by gel permeation chromatography (GPC) using GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL") manufactured by Tosoh Corporation under the following conditions: Eluent: tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0308] <Synthesis of Base Polymers> [Synthesis Examples A-1 to A-58] Synthesis of Base Polymers The monomers were combined according to the compositions shown in Tables 1 and 2 below, and copolymerization reaction was carried out in tetrahydrofuran (THF) solvent. The polymers were crystallized in methanol, and after repeated washing with hexane, isolated and dried, base polymers (A-1) to (A-37) and (cA-1) to (cA-21) with the compositions shown below were obtained. In the tables, "-" indicates that the corresponding component was not used. The same applies to the subsequent tables.

[0309]

[0310]

[0311] The monomers used in the synthesis of the base polymer are shown below.

[0312]

[0313]

[0314] <Synthesis of high fluorine content polymer (F)> [Synthesis Examples F-1 to F-19] Synthesis of high fluorine content polymers The monomers were combined according to the compositions shown in Table 3 below, and a copolymerization reaction was carried out in tetrahydrofuran (THF) solvent. After polymerization, the solvent was replaced with acetonitrile, and the product was washed with hexane. Thereafter, the solvent was replaced with propylene glycol monomethyl ether acetate, to obtain high fluorine content polymers (FP-1) to (FP-19) having the compositions shown below.

[0315]

[0316] The monomers used in the synthesis of the high fluorine content polymer are shown below.

[0317]

[0318] <Synthesis of Radiation-Sensitive Acid Generator (B)> [Synthesis Example B-1] Synthesis of Radiation-Sensitive Acid Generator (B-1) Radiation-sensitive acid generator (B-1) was synthesized according to the following reaction scheme.

[0319] 10 mmol of (ppB-1) and 50 ml of ultrapure water were added to a reaction vessel and cooled to 0°C. Next, an exhaust trap for 50% aqueous sodium hydroxide was attached to the reaction vessel, and the mixture was vigorously stirred for 30 minutes while chlorine was bubbled into the reaction solution. The precipitated solid was filtered off and washed with aqueous sodium bicarbonate and ultrapure water to obtain (pB-1). Next, 5 mmol of 1-hydroxypyrrolidine-2,5-dione, 6 mmol of triethylamine, and 20 ml of dichloromethane were added to the reaction vessel and cooled to 0°C. 5 mmol of (pB-1) was dissolved in 10 ml of dichloromethane and added dropwise, followed by stirring at room temperature for 15 hours. The reaction was quenched by adding 20 ml of 1 M HCl solution, and the mixture was washed twice with 20 ml of saturated aqueous sodium bicarbonate and once with 20 ml of saturated aqueous sodium chloride. The organic layer was dried over sodium sulfate, filtered, concentrated, and purified by silica gel column chromatography to obtain (B-1).

[0320] [Synthesis Examples B-2 to B-20] Synthesis of Radiation-Sensitive Acid Generators (B-2) to (B-20) Radiation-sensitive acid generators (B-2) to (B-20) were obtained in the same manner as in Synthesis Example B-1, except that the substrate used was appropriately selected. Radiation-sensitive acid generators (B-1) to (B-20) are shown below.

[0321]

[0322]

[0323] <Preparation and Evaluation of Radiation-Sensitive Composition> The components used in preparing the radiation-sensitive composition are shown below.

[0324] <Base Polymer (A)> A-1 to A-37, cA-1 to cA-21: Polymers obtained in Synthesis Examples A-1 to A-58

[0325] <Radiation-sensitive acid generator (B)> B-1 to B-20: Compounds obtained in Synthesis Examples B-1 to B-20 cB-1 to cB-13: Compounds represented by the following formulas (cB-1) to (cB-13), respectively

[0326]

[0327] <High Fluorine Content Polymers (F)> FP-1 to FP-19: Compounds obtained by Synthesis Examples F-1 to F-19

[0328] <Acid diffusion controller (Z)> Z-1 to Z-9: Compounds represented by the following formulas (Z-1) to (Z-9), respectively

[0329]

[0330] <Solvent (D)> D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether

[0331] <Preparation of Radiation-Sensitive Composition> [Example 1] A radiation-sensitive composition (R-1) was prepared by blending 100 parts by mass of (A-1) as the base polymer (A), 30 parts by mass of (B-1) as the radiation-sensitive acid generator (B), (Z-1) as the acid diffusion inhibitor (Z) in an amount of 30 mol% based on the total of (B-1) and the component (M-12) in (A-1), 5 parts by mass of (FP-1) as the high fluorine-containing polymer (F), 2,000 parts by mass of (D-1) as the solvent (D), and 4,800 parts by mass of (D-2).

[0332] [Examples 2 to 82 and Comparative Examples 1 to 47] Radiation-sensitive compositions (R-2) to (R-82) and (CR-1) to (CR-47) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 4 to 6 below were used.

[0333]

[0334]

[0335]

[0336] <Formation of Resist Pattern> (EUV Exposure, Alkali Development) The radiation-sensitive composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 50-nm-thick underlayer film (AL412 (Brewer Science)) had been formed using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). The wafer was then soft-baked (SB) at 130°C for 60 seconds and then cooled at 23°C for 30 seconds to form a 50-nm-thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400," ASML, NA=0.33, illumination conditions: Conventional s=0.89, mask imecDEFECT32FFR02). The resist film was subjected to PEB at 110°C for 60 seconds. Then, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive 32 nm line and space pattern.

[0337] <Evaluation> The resist patterns formed as described above were measured according to the following methods to evaluate the LWR and process window of each radiation-sensitive composition. 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 7 to 9 below.

[0338] [Sensitivity] In forming the EUV resist pattern, the exposure dose for forming a 32 nm line and space pattern is defined as the optimum exposure dose (Eop), and this optimum exposure dose is used as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ If it is less than 40 mJ / cm, it is marked "A" ２ 45mJ / cm or more ２ If it is less than 45 mJ / cm, it is "B" ２ If it exceeded this, it was judged as "C".

[0339] [LWR] The resist pattern formed by EUV was observed from above using the scanning electron microscope. The line width was measured at a total of 50 arbitrary points, and the 3 sigma value was calculated from the distribution of the measured values, which was designated as the LWR (unit: nm). The smaller the LWR value, the smaller the line rattle, indicating better performance. The smaller the LWR, the better. An LWR value of less than 2.7 nm was designated "A," 2.7 nm or more but less than 2.9 nm was designated "B," and 2.9 nm or more was designated "C."

[0340]

[0341]

[0342]

[0343] As is clear from the results in Tables 7 to 9, the radiation-sensitive compositions of the Examples all had better sensitivity and LWR than the radiation-sensitive compositions of the Comparative Examples.

[0344] The radiation-sensitive composition and method for forming a resist pattern of the present invention can improve sensitivity, LWR, and defect performance 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) which contains a structural unit (I) having an acid-dissociable group and which also has an iodine group; and a solvent (D), wherein the radiation-sensitive composition contains a radiation-sensitive acid generator (B) represented by the following formula (1), or the polymer (A) contains a structural unit (II) represented by the following formula (1'): (In formula (1), R １ is a monovalent organic group having 1 to 40 carbon atoms. ２ When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together and formed together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8 membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded. (In formula (1'), R １ａ is a divalent organic group having 1 to 40 carbon atoms. a is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ , n, and W have the same meanings as in formula (1) above.

2. The R in the formula (1) １ The radiation-sensitive composition according to claim 1, wherein *-R is a group represented by the following formula (t): １1 -X-R １２ (t) (In formula (t), R １1 is a divalent hydrocarbon group or halogenated hydrocarbon group having 1 to 10 carbon atoms. X is a single bond or a divalent linking group. R １２ is a monovalent organic group having 1 to 30 carbon atoms. * represents a bond to the sulfur atom in formula (1).

3. The R in the formula (t) １１ The radiation-sensitive composition according to claim 2 , wherein is a group selected from the group consisting of a group represented by the following formula (a) and a group represented by the following formula (b): (In formula (a), R ｆ１ and R ｆ２ are each independently a hydrogen atom, a halogen atom, or a halogenated alkyl group. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different. t is an integer of 1 to 4. * represents a bond bonding to the sulfur atom in formula (1), and ** represents a bond bonding to X in formula (t). (In formula (b), Y represents a hydroxy group, a carboxy group, a cyano group, a nitro group, an amino group, an organic group having 1 to 10 carbon atoms, or a halogen atom. When a plurality of Ys are present, the plurality of Ys may be the same or different. s represents an integer of 0 to 4. * represents a bond bonding to the sulfur atom in formula (1), and ** represents a bond bonding to X in formula (t).) 4. The R in the formula (1) １ The radiation-sensitive composition according to claim 1 , wherein comprises an iodo group-containing aromatic ring structure.

5. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive acid generator (B) is represented by the following formula (1-1): (In formula (1-1), represents a single bond or a double bond. １ , R ２ has the same meaning as the above formula (1).

6. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive composition contains a radiation-sensitive acid generator (B) represented by formula (1) above, and the content of the radiation-sensitive acid generator (B) is 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the polymer (A).

7. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group has the iodine group.

8. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group contains an aromatic ring structure containing an iodine group.

9. The radiation-sensitive composition according to claim 8, wherein the aromatic ring in the iodo group-containing aromatic ring structure is a benzene ring, a thiophene ring, or a furan ring.

10. The radiation-sensitive composition according to claim 7, wherein the number of iodo groups in the acid-dissociable group is one, two or three.

11. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) is represented by the following formula (2'): (In formula (2'), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a divalent linking group. １Ａ and R １Ｂ are each independently a hydrogen atom, a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １Ａ and R １Ｂ represents a divalent alicyclic group having 3 to 20 carbon atoms formed by combining together with the carbon atoms to which they are bonded. １Ａ and R １Ｂ There is no case where both of Ar and Ar are hydrogen atoms. １ is a (p+q+1)-valent aromatic ring having 5 to 20 ring members. １０１ is a nitro group, a cyano group, a hydroxy group, an alkoxy group, or an amino group. １０１ If there are multiple R １０１ are the same or different. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. p is an integer of 1 to 3. q is an integer of 0 to 3. However, p+q is 5 or less.

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

13. The radiation-sensitive composition according to any one of claims 1 to 11, wherein the polymer (A) further contains a structural unit (V) containing at least one structure selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure.

14. The radiation-sensitive composition according to any one of claims 1 to 11, further comprising an acid diffusion controller (Z).

15. The radiation-sensitive composition according to claim 14, wherein the acid diffusion controller (Z) has an iodine group.

16. The radiation-sensitive composition according to any one of claims 1 to 11, further comprising a high-fluorine-content polymer (F) having a higher mass content of fluorine atoms than the polymer (A).

17. A pattern forming method comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 11 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

18. The pattern forming method according to claim 17, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

19. A radiation-sensitive acid generator represented by the following formula (i): (In formula (i), R Ａ is *-R １３ -X-R １４ R is a group represented by the formula: １３ and R １４ is a fluoro- or iodine-containing hydrocarbon group, and R １３ is a fluoro group-containing hydrocarbon group, R １４ is an iodo group-containing hydrocarbon group, and R １３ is an iodo group-containing hydrocarbon group, R １４ is a fluoro-containing hydrocarbon group. X is a single bond or a divalent linking group. * represents a bond to the sulfur atom in formula (i). R ２ When a plurality of R are present, each independently represents a hydrogen atom, a nitro group, a hydroxyl group, a cyano group, a carboxyl group, a thiol group, a halogen atom, or a monovalent organic group, or two R ２ are combined together and formed together with the carbon atoms to which they are bonded, forming a divalent cyclic group having 3 to 20 carbon atoms. n is an integer from 0 to 20. W represents a 5-8 membered ring structure formed together with the carbon atom and nitrogen atom to which it is bonded.

20. The above R １３ is a fluoro group-containing hydrocarbon group, and R １４ 20. The radiation-sensitive acid generator according to claim 19, wherein is an iodo group-containing cyclic hydrocarbon group.

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