Radiation-sensitive composition, pattern forming method, and onium salt compound

Abstract

Provided are a radiation-sensitive composition excellent in sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity at the time of pattern formation, a pattern forming method, and an onium salt compound. The radiation-sensitive composition comprises an onium salt compound represented by formula (1), a polymer containing a structural unit having an acid-dissociable group, and a solvent. (In the formula, R1 is a monovalent organic group having 4-40 carbon atoms. E is -O-, -S-, -SO- or -SO2-. R2 is a hydrogen atom or a monovalent organic group having 1-20 carbon atoms. R3 is a hydroxy group or a monovalent organic group having 1-20 carbon atoms. R4 and R5 are each a monovalent organic group having 1-20 carbon atoms, or R4 and R5 are bonded to represent a ring structure having 4-12 carbon atoms together with the sulfur atom. R6 is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group or a monovalent organic group having 1-20 carbon atoms. m is 0 or 1. n is an integer of 0-4.)

Description

Radiation-sensitive composition, pattern forming method, and onium salt compound

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

[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 alkaline or organic developers between exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above is promoting pattern miniaturization by using short-wavelength radiation such as ArF excimer lasers, and further by using liquid immersion lithography, in which exposure is performed with the space between the lens of the exposure device and the resist film filled with a liquid medium. Lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation technology.

[0004] Regarding quenchers, which are also a main component of resist compositions, various structures have been investigated from the viewpoint of cationic structure (see JP-A-2022-68394).

[0005] JP 2022-68394 A

[0006] As patterns become increasingly finer, resist compositions are required to have various resist performances that are equal to or better than conventional ones in terms of sensitivity as well as LWR (Line Width Roughness), which indicates variations in line width and the line width of a resist pattern, Mask Error Enhancement Factor (MEEF), which is the amount of change in line width or hole diameter relative to the amount of change in mask size, Exposure Latitude (EL), which indicates the tolerance for variation in the dimensions of a pattern obtained when the exposure dose varies, pattern rectangularity, which indicates the rectangularity of the cross-sectional shape of the resist pattern, Critical Dimension Uniformity (CDU), which is an index of the uniformity of line width and hole diameter, and pattern circularity, which indicates the circularity of the hole shape.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern forming method, and an onium salt compound that are excellent in sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity 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] That is, in one embodiment, the present invention relates to a radiation-sensitive composition comprising: an onium salt compound represented by the following formula (1) (hereinafter also referred to as “onium salt compound (1)”); a polymer including a structural unit having an acid-dissociable group; and a solvent: (In formula (1), R １ is a monovalent organic group having 4 to 40 carbon atoms. E is -O-, -S-, -SO- or -SO ２ - is. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ is a hydroxy group or a monovalent organic group having 1 to 20 carbon atoms. ４ and R ５ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R ４ and R ５ R represents a ring structure having 4 to 12 carbon atoms formed by combining with each other and the sulfur atom to which they are attached. ６ R is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group, or a monovalent organic group having 1 to 20 carbon atoms. ６ If there are multiple R ６ are the same or different from each other. m is 0 or 1. When m is 1, R ３ -CO- and R ２ Both -E- are bonded to the six-membered ring structure to which the sulfur atom in the above formula (1) is bonded. n is an integer of 0 to 4.

[0010] The radiation-sensitive composition contains onium salt compound (1) as a quencher (acid diffusion controller), and therefore can exhibit excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity during pattern formation. Without being bound by any theory, the reason for this is presumed to be as follows: Since a substituent having an ether bond or a sulfur-containing bond, as well as a carbonyl group, is bonded to the aromatic ring of the sulfonium cation of onium salt compound (1), the polarity of the onium salt compound (1) as a whole is increased. This makes it possible to control the solubility in a developer. Furthermore, since the aromatic ring is bonded with bonds capable of extending the conjugated system, such as an ether bond, a sulfur-containing bond, and a carbonyl group, the light absorption efficiency of the sulfonium cation is improved, thereby increasing the decomposition efficiency of onium salt compound (1) upon exposure, and thereby improving the dissolution contrast between exposed and unexposed areas. Furthermore, because the number of carbon atoms in the organic acid anion of onium salt compound (1) is within a predetermined range and the onium salt compound (1) has a sulfonium cation with a specific structure, local aggregation of onium salt compound (1) is suppressed, allowing it to be dispersed throughout the resist film, while at the same time, its diffusion as an onium salt compound can be appropriately controlled. This makes it possible to efficiently quench the acid component generated from the radiation-sensitive acid generator upon exposure. It is believed that these combined effects enable the resist to exhibit the various performance properties described above.

[0011] 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.

[0012] In the pattern formation method, the radiation-sensitive composition having excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity is used in pattern formation, and therefore a high-quality resist pattern can be efficiently formed.

[0013] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1): (In formula (1), R １ is a monovalent organic group having 4 to 40 carbon atoms. E is -O-, -S-, -SO- or -SO ２ - is. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ is a hydroxy group or a monovalent organic group having 1 to 20 carbon atoms. ４ and R ５ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R ４ and R ５ R represents a ring structure having 4 to 12 carbon atoms formed by combining with each other and the sulfur atom to which they are attached. ６ R is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group, or a monovalent organic group having 1 to 20 carbon atoms. ６ If there are multiple R ６ are the same or different from each other. m is 0 or 1. When m is 1, R ３ -CO- and R ２ Both -E- are bonded to the six-membered ring structure to which the sulfur atom in the above formula (1) is bonded. n is an integer of 0 to 4.

[0014] The onium salt compound has the developer affinity, acid generation efficiency, aggregation suppression property, and mobility as described above, and is therefore suitable as an acid diffusion controller for the radiation-sensitive composition.

[0015] In this specification, "organic group" refers to a group containing at least one carbon atom (however, groups that constitute functional groups or characteristic groups by themselves, such as a cyano group or a ketone group, are excluded). "Fused ring structure" refers to a structure in which adjacent rings share one edge (two adjacent atoms). "Bridged ring hydrocarbon group" refers to a polycyclic cyclic hydrocarbon group in which two non-adjacent carbon atoms that constitute the ring are linked by a linking group containing one or more carbon atoms.

[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 aspects are also preferred.

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also referred to simply as the "composition") contains an onium salt compound (1), a polymer containing a structural unit having an acid-dissociable group (hereinafter also referred to as the "base polymer"), and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired. By containing the onium salt compound (1) as an acid diffusion controller, the radiation-sensitive composition can exhibit excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity during pattern formation.

[0018] (Onium Salt Compound (1)) The onium salt compound (1) comprises an organic acid anion represented by the above formula (1) and a sulfonium cation, and functions as an acid diffusion controller.

[0019] In the above formula (1), R ２ Examples of the monovalent organic group having 1 to 20 carbon atoms and represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (a) having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group or the group (a) have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0020] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and combinations thereof.

[0021] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group; 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.

[0022] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include cycloalkyl groups such as a cyclopentyl group and a cyclohexyl group; cycloalkenyl groups such as a cyclopropenyl group, a cyclopentenyl group and a cyclohexenyl group; bridged ring saturated hydrocarbon groups such as a norbornyl group, an adamantyl group and a tricyclodecyl group; and bridged ring unsaturated hydrocarbon groups such as a norbornenyl group and a tricyclodecenyl group.

[0023] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0024] Examples of heteroatoms constituting the divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, etc. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0025] Examples of the divalent heteroatom-containing group include —CO—, —CS—, —NR′—, —O—, —S—, and —SO ２ -, a group formed by combining these, etc. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0026] Examples of the monovalent heteroatom-containing group include a hydroxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0027] R ２ As R, a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxyalkyl group, a cycloalkoxyalkyl group, an alkoxycarbonyl group, an alkoxycarbonylalkyl group, a cycloalkoxycarbonylalkyl group, an acyl group, a group having a cyclic ether structure (a group obtained by removing one hydrogen atom from a cyclic ether structure), a group in which the hydrogen atom of such a group has been substituted with the above-mentioned monovalent heteroatom-containing group, or a combination thereof is preferred. ２As the group, a hydrogen atom, an alkyl group, or an alkoxycarbonylalkyl group is preferable, and a methyl group, an ethyl group, a methoxyethyl group, a t-butoxycarbonylmethyl group, a methylcyclopentyloxycarbonylmethyl group, an ethylcyclopentyloxycarbonylmethyl group, a methyladamantyloxycarbonylmethyl group, an ethyladamantyloxycarbonylmethyl group, an acetyl group, or a pivaloyl group is more preferable.

[0028] E is preferably —O— from the viewpoint of cation decomposition efficiency upon exposure.

[0029] R ３ As the monovalent organic group having 1 to 20 carbon atoms represented by R ２ A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used. ３ is preferably a monovalent organic group having 1 to 20 carbon atoms and having an ether bond on the bonding side.

[0030] R ３ Preferred examples of R include a hydroxy group, an alkyl group, an alkoxy group, a cycloalkoxy group, an alkoxycarbonylalkoxy group, a cycloalkoxycarbonylalkoxy group, a group combining a lactone structure-containing group (a group obtained by removing one hydrogen atom from a lactone structure) with an ether bond, a group in which the hydrogen atom of such a group is substituted with the above-mentioned monovalent heteroatom-containing group, and a combination thereof. Examples of the lactone structure include γ-butyrolactone and norbornane lactone. Among these, R ３As R, a hydroxy group, an alkoxy group, an alkoxycarbonylalkoxy group, an alkylcycloalkoxy group, or a group combining a lactone structure-containing group (a group in which one hydrogen atom has been removed from a lactone structure) with an ether bond is preferred, and a hydroxy group, a methoxy group, a group combining γ-butyrolactone with an ether bond, a t-butoxy group, a t-butoxycarbonylmethoxy group, a t-amyloxy group, a methylcyclopentyloxy group, an ethylcyclopentyloxy group, a t-butoxycarbonylmethoxy group, a methoxycarbonylmethoxy group, a methylcyclopentyloxycarbonylmethoxy group, an ethylcyclopentyloxycarbonylmethoxy group, a methyladamantyloxycarbonylmethoxy group, or an ethyladamantyloxycarbonylmethoxy group is more preferred. ３ It is preferable that the alkyl group contains an acid-dissociable group.

[0031] R ４ and R ５ As the monovalent organic group having 1 to 20 carbon atoms represented by R ２ A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0032] R ４ and R ５ Examples of the ring structure having 4 to 12 carbon atoms that is formed by combining together with the sulfur atom to which they are bonded include a sulfur atom-containing aliphatic heterocyclic structure having 4 to 12 carbon atoms and a sulfur atom-containing aromatic heterocyclic structure having 4 to 12 carbon atoms. Examples of the sulfur atom-containing aliphatic heterocyclic structure include thietane, tetrahydrothiophene, oxathiolane, thiane, dithiane, thiomorpholine, and thioxane. Examples of the sulfur atom-containing aromatic heterocyclic structure include thiophene, thiazole, benzothiophene, dibenzothiophene, and phenoxathiin. Among these, R ４ and R ５ The ring structure formed by the formula (I) is more preferably tetrahydrothiophene, thioxane, thiane, dibenzothiophene, or phenoxathiin.

[0033] R ４ and R ５The ring structure may have a substituent. Examples of the substituent include 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, or an acyloxy group, or a group in which a hydrogen atom of any of these groups has been substituted with a halogen atom; and an oxo group (═O).

[0034] R ４ and R ５ are preferably each independently a substituted or unsubstituted phenyl group. ４ and R ５ The phenyl group in R ４ and R ５ The ring structure may have a substituent that can be possessed by the ring structure.

[0035] R ６ As the monovalent organic group having 1 to 20 carbon atoms represented by R ２ A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0036] R ６ As the alkyl group, an alkyl group, an alkoxy group, a hydroxy group, a halogenated alkyl group, or a halogen atom is preferred, and a methyl group, a t-butyl group, a methoxy group, a trifluoromethyl group, a fluorine atom, or an iodine atom is more preferred.

[0037] From the viewpoint of the efficiency of cation decomposition by exposure, m is preferably 0.

[0038] n is preferably an integer of 0 to 3, more preferably an integer of 0 to 2, and even more preferably 0 or 1.

[0039] In the above formula (1), R ２ -E- vs. R ３ -CO- is preferably in the ortho or para position. ２-E- is preferably in the ortho or para position relative to the bonding position of S. This makes it possible to appropriately control the transmittance and to exhibit the above-mentioned resist performances at a higher level.

[0040] Specific examples of the sulfonium cation of the onium salt compound (1) include, but are not limited to, structures represented by the following formulae (a-1) to (a-147).

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] R １ As the monovalent organic group having 4 to 40 carbon atoms represented by R ２ A group in which the monovalent organic group having 1 to 20 carbon atoms represented by the following formula (I) is extended to have 4 to 40 carbon atoms can be suitably used.

[0051] R １is preferably a monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond. The organic group is not particularly limited and may be either a group containing only a cyclic structure or a group combining a cyclic structure with a chain structure. The cyclic structure may be a monocyclic ring, a polycyclic ring, or a combination thereof. Furthermore, the cyclic structure may be an alicyclic structure, an aromatic ring structure, or a combination thereof. In the case of a combination, the cyclic structures may be linked in a chain structure, or two or more ring structures may form a fused ring structure. These groups may contain at least one structure selected from the group consisting of a carbonyl group and an ether bond between the carbon atoms or at the carbon chain terminal. Hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0052] The alicyclic structure may be R ２ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown in the following formula can be suitably employed.

[0053] The aromatic ring structure includes R ２ Preferably, a structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms shown in the following formula (1) can be employed. In addition, aromatic heterocycles such as a furan ring, a pyrrole ring, a thiophene ring, a phosphole ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, and a triazine ring are also preferred.

[0054] The chain structure may be R ２ A structure corresponding to the monovalent chain hydrocarbon group having 1 to 20 carbon atoms shown in the following formula can be suitably employed.

[0055] The alicyclic structure may also be an aliphatic heterocyclic structure. Examples of the aliphatic heterocyclic structure include oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyrane, 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; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0056] The aliphatic heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, a cyclic imide structure, or a combination thereof.

[0057] R １ Preferably, contains the above alicyclic structure or aromatic ring structure.

[0058] Examples of the substituents that substitute hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include R ４ and R ５ The substituent may be a hydroxy group, a carboxy group, an alkyl group, or a halogen atom, and more preferably a hydroxy group, a carboxy group, a t-butyl group, a fluorine atom, or an iodine atom.

[0059] Specific examples of the organic acid anion of the onium salt compound (1) include, but are not limited to, structures represented by the following formulae (b-1) to (b-52).

[0060]

[0061]

[0062]

[0063]

[0064] Onium salt compound (1) can be obtained by any combination of the above sulfonium cation and the above organic acid anion (not limited to the structures shown as examples). Specific examples include, but are not limited to, structures represented by the following formulae (1C-1) to (1C-46).

[0065]

[0066]

[0067]

[0068]

[0069]

[0070] The lower limit of the content of onium salt compound (1) (the total content when multiple types are contained) is preferably 0.1 parts by mass, more preferably 1 part by mass, and even more preferably 2 parts by mass, relative to 100 parts by mass of the base polymer described below. The upper limit of the content is preferably 80 parts by mass, more preferably 70 parts by mass, and even more preferably 60 parts by mass. This allows the composition to exhibit excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity during pattern formation.

[0071] The composition may contain a known acid diffusion controller other than the onium salt compound (1) as long as it does not impair the effects of the present invention.

[0072] (Method for synthesizing onium salt compound (1)) The onium salt compound (1) can be typically synthesized according to the following scheme: ４ and R ５ is an aryl group, m and n are both 0, and R ２ -E- vs. R ３ The case where —CO— is bonded to the ortho position will be described, but the present invention is not limited to this, and known methods can be used.

[0073] (In the scheme, R １ ~R ３ and E are the same as in formula (1), and Ar is an aryl group.- is a trifluorosulfonate anion. ＋ is a monovalent alkali metal. - is a monovalent halide ion. ＋ is a monovalent cation.)

[0074] A diaryl sulfoxide and a benzoic acid derivative are reacted in the presence of a strong acid to form a sulfonium cation. This is then reacted with an alkali metal halide to form a halide salt, which is then reacted with a salt containing the desired organic acid anion for salt exchange, thereby synthesizing the desired onium salt compound (1). Because the cationization in the first step is a Friedel-Crafts type reaction, standard reactants used in such reactions can also be used. Other structures can also be synthesized by appropriately changing the starting materials, intermediate components, etc.

[0075] (Polymer) The polymer (i.e., base polymer) is an aggregate of polymer chains containing a structural unit having an acid-dissociable group (hereinafter also referred to as "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 that dissociates under the action of an acid. The radiation-sensitive composition has excellent pattern formability because the polymer contains the structural unit (I).

[0076] In addition to the structural unit (I), the base polymer preferably contains a structural unit (II) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, which will be described later, and may contain structural units other than the structural units (I) and (II). Each structural unit will be described below.

[0077] [Structural Unit (I)] The structural unit (I) is a structural unit containing an acid-dissociable group. 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, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0078]

[0079] In the above formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ COO-. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0080] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0081] L １１ａ Examples of the alkanediyl group represented by the formula (I) include alkanediyl groups having 1 to 10 carbon atoms, such as a methylene group, an ethanediyl group, a 1,3-propanediyl group, and a 2,2-propanediyl group. １１ａAs the alkyl group, a methylene group or an ethanediyl group is preferred.

[0082] L １１ａ Examples of the arenediyl group represented by the formula (I) include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl and naphthalenediyl groups. １１ａ As the alkyl group, a benzenediyl group is preferred.

[0083] L １１ａ The substituents that the arenediyl group represented by the formula (1) may have include R ４ and R ５ Substituents that can be possessed by the above ring structure constituted by the following formula can be suitably employed.

[0084] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0085] The above R １８ ~R ２０ Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a monovalent linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0086] The above R １８ ~R ２０ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is ２ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably used.

[0087] The above R １８ The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) is ２ A monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms in the above formula can be suitably used.

[0088] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0089] The above R１９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded can suitably be a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0090] Among these, R １８ is an alkyl group, an alkenyl group, or a phenyl group having 1 to 4 carbon atoms, and R １９ and R ２０ The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0091] The above R １８ ~R ２０ Examples of the substituent that may be possessed by L include １１ａ Substituents that can be possessed by the arenediyl group represented by the following formula can be suitably employed.

[0092] Examples of the structural unit (I-1) include structural units represented by the following formulas (3-1) to (3-12) (hereinafter also referred to as "structural units (I-1-1) to (I-1-12)").

[0093]

[0094]

[0095] In the above formulas (3-1) to (3-12), R １７ ~R ２０ has the same meaning as in formula (3). Ｌ１１ and R Ｌ１２ are each independently a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are 0 or 1. 3a and 3b are each independently an integer of 0 to 3. When 3a and 3b are 2 or more, multiple R Ｌ１１ and R Ｌ１２ are the same or different from each other. a4 is an integer of 1 to 3.

[0096] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ and R Ｌ１２ is preferably an iodine atom, a hydroxy group, or an alkoxy group. Ｌ１１ or R Ｌ１２ By employing an iodine atom as the aryl group, an iodine group can be suitably introduced into the structural unit (I).

[0097] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0098]

[0099] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0100] 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.

[0101] 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 is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By ensuring that the content of the structural unit (I) falls within this range, the pattern formability of the radiation-sensitive composition can be further improved.

[0102] [Structural Unit (II)] The structural unit (II) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (II), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Furthermore, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0103] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-11).

[0104]

[0105] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, a dimethylamino group, or a methylcyclopentyloxycarbonyl group. Ｌ４ and R Ｌ５ may be a divalent alicyclic group having 3 to 8 carbon atoms formed by combining 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. d is an integer of 0 to 3. e is an integer of 1 to 3.

[0106] The above R Ｌ４ and R Ｌ５ The divalent alicyclic group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded includes R １９ and R ２０ Among divalent alicyclic groups having 3 to 20 carbon atoms constituted by combining these 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 group may be substituted with a hydroxy group.

[0107] 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-.

[0108] Of these, the structural unit (II) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0109] The lower limit of the content of the structural unit (II) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 75 mol%. By setting the content of the structural unit (II) 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.

[0110] [Structural Unit (III)] The base polymer optionally has other structural units in addition to the structural units (I) and (II). Examples of the other structural units include a structural unit (III) containing a polar group (excluding those corresponding to the structural units (I) and (II)). By further including the structural unit (III), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as the resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0111] Examples of the structural unit (III) include structural units represented by the following formula:

[0112]

[0113]

[0114] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0115] When the base polymer has the structural unit (III) having the polar group, the lower limit of the content of the structural unit (III) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 25 mol%. By setting the content of the structural unit (III) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0116] [Structural Unit (IV)] The base polymer optionally contains, as another structural unit, a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)") in addition to the structural unit (III) having the polar group. The structural unit (IV) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. This polymer is suitable for pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as a KrF excimer laser, electron beam, or EUV. In this case, it is preferable that the polymer contains the structural unit (I) in addition to the structural unit (IV).

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

[0118] (In the above formula (4), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ is 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 １０２are 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.)

[0119] 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.

[0120] L ＣＡ is a single bond or -COO- ＊ is preferred.

[0121] R １０２ The halogen atom in is preferably an iodine atom.

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

[0123] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0124] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0125] In order to obtain the structural unit (IV), it is preferable to polymerize the corresponding 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) during polymerization, and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis. The monomer may also be polymerized without protecting the phenolic hydroxyl group.

[0126] In the case of a polymer for exposure to a KrF excimer laser or radiation having a wavelength of 50 nm or less, the content of the structural unit (IV) (the total content when multiple types are contained) is preferably 20 mol % and more preferably 30 mol % relative to all structural units constituting the base polymer, and the upper limit of this content is preferably 60 mol %, more preferably 50 mol %.

[0127] [Other Structural Units] The base polymer may contain a structural unit having an alicyclic structure represented by the following formula (6) (hereinafter also referred to as "structural unit (VII)") as a structural unit other than the structural units listed above. (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.

[0128] In the above formula (6), R ２α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is ２ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably used.

[0129] When the base polymer contains the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer, and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0130] (Method of Synthesizing Base Polymer) The base polymer 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.

[0131] 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. Among 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.

[0132] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl propionate, and propylene glycol monomethyl ether acetate; ketones such as acetone, methyl ethyl ketone, 2-butanone, 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethane, and 1,4-dioxanes; Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol, and 1-methoxy-2-propanol (propylene glycol monomethyl ether); and lactones such as γ-butyrolactone. These solvents used in the polymerization may be used alone or in combination of two or more.

[0133] 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.

[0134] The molecular weight of the base polymer 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 30,000, more preferably 20,000, and even more preferably 12,000. By setting the Mw of the base polymer within the above range, the resulting resist film can have good heat resistance and developability.

[0135] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as 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.

[0136] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0137] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh Corporation) Column temperature: 40°C Elution solvent: tetrahydrofuran Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection volume: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0138] The content of the base polymer is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0139] (Other Polymers) The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer. As a result, it is possible to increase the water repellency of the surface of the resist film during immersion exposure, and to modify the surface of the resist film during EUV exposure and control the distribution of composition within the film.

[0140] The high fluorine content polymer may have, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)").

[0141]

[0142] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, -COO-, 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.

[0143] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0144] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and -COO- are preferred, and -COO- is more preferred.

[0145] 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.

[0146] 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.

[0147] 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, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0148] When the high-fluorine content polymer has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0149] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to or instead of the structural unit (V): By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0150]

[0151] The structural unit (VI) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter, also simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ Oxygen atom, sulfur atom, -NR at the end of 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.

[0152] When the structural unit (VI) has an alkali-soluble group (x), R Ｆis a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VI) has an alkali-soluble group (x), it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VI) having an alkali-soluble group (x), A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0153] When the structural unit (VI) 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-*. R 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. １is 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 R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0154] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0155] When the high-fluorine content polymer has the structural unit (VI), the content of the structural unit (VI) is preferably 30 mol%, more preferably 40 mol%, and even more preferably 50 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 80 mol%. By setting the content of the structural unit (VI) within the above range, it is possible to increase the water repellency of the resist film during immersion exposure and to improve its solubility in an alkaline developer, thereby suppressing the occurrence of development defects.

[0156] [Other Structural Units] The high fluorine content polymer may, if necessary, contain structural units other than the structural units listed above, such as the structural unit (I), the structural unit (III), or the structural unit (VII) in the base polymer.

[0157] When the high-fluorine content polymer contains the structural unit (I), the content of the structural unit (I) is preferably 5 mol %, more preferably 8 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 40 mol %, more preferably 30 mol %.

[0158] When the high-fluorine content polymer contains the structural unit (III), the content of the structural unit (III) is preferably 5 mol %, more preferably 8 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 50 mol %, more preferably 40 mol %.

[0159] When the high-fluorine content polymer contains the structural unit (VII), the content of the structural unit (VII) is preferably 20 mol %, more preferably 30 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 60 mol %, more preferably 50 mol %.

[0160] The lower limit of Mw of the high fluorine content polymer is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 14,000, and even more preferably 10,000.

[0161] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0162] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the lower limit of the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, relative to 100 parts by mass of the base polymer, and the upper limit of the content is preferably 15 parts by mass, more preferably 8 parts by mass, and even more preferably 5 parts by mass.

[0163] By setting the content of the high fluorine content polymer within the above range, the high fluorine content polymer can be more effectively localized in the surface layer of the resist film, which results in improving the water repellency of the surface of the resist film during immersion lithography, and enabling control of the surface modification of the resist film and the distribution of the composition within the film during EUV exposure. The radiation-sensitive composition may contain one or more high fluorine content polymers.

[0164] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0165] (Radiation-sensitive Acid Generator) The radiation-sensitive composition preferably contains a radiation-sensitive acid generator. The radiation-sensitive acid generator is a compound that has an organic acid anion and an onium cation and generates an acid that dissociates the acid-dissociable group upon exposure. The acid generated from the radiation-sensitive acid generator can be said to be a relatively stronger acid (an acid with a smaller pKa) than the acid generated from the onium salt compound (1). The radiation-sensitive acid generator may be contained in the radiation-sensitive composition in a form in which it exists as a compound alone (isolated from a polymer), in a form incorporated as part of a polymer, or in both of these forms, but a form in which it exists as a compound alone is preferred.

[0166] Examples of organic acid anions include sulfonate anions, sulfonimide anions, and sulfonmethide anions.

[0167] Examples of such acids include: (1) compounds in which one or more fluorine atoms, fluorinated hydrocarbon groups, or cyano groups are substituted on the carbon atom at the α- or β-position of a sulfo group, or in which an ester bond is present between the carbon atoms; (2) compounds having a sulfonimide structure containing a fluorine atom; and (3) compounds having a sulfonmethide structure containing a fluorine atom.

[0168] The radiation-sensitive acid generator is preferably a compound represented by the following formula (za): (In formula (z-a), R ４ｚis a monovalent organic group having 2 to 40 carbon atoms. ３ - A fluorine atom, a cyano group or a monovalent fluorinated hydrocarbon group is bonded to the carbon atom at the α- or β-position of Za. ＋ is a monovalent onium cation.

[0169] R ４ｚ The monovalent organic group having 2 to 40 carbon atoms represented by the formula (1) is R ２ A group in which the monovalent organic group having 1 to 20 carbon atoms represented by the following formula (I) is extended to have 2 to 40 carbon atoms can be suitably used.

[0170] R ４ｚ is preferably a monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond. １ A monovalent organic group having 4 to 40 carbon atoms and containing at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond, as shown in the following formula, can be suitably used.

[0171] Examples of the monovalent fluorinated hydrocarbon group include a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms and a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0172] Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include fluorinated alkyl groups such as trifluoromethyl, difluoromethyl, 2,2,2-trifluoroethyl, pentafluoroethyl, 2,2,3,3,3-pentafluoropropyl, 1,1,1,3,3,3-hexafluoropropyl, heptafluoro-n-propyl, heptafluoro-i-propyl, nonafluoro-n-butyl, nonafluoro-i-butyl, nonafluoro-t-butyl, 2,2,3,3,4,4,5,5-octafluoro-n-pentyl, tridecafluoro-n-hexyl, and 5,5,5-trifluoro-1,1-diethylpentyl; fluorinated alkenyl groups such as trifluoroethenyl and pentafluoropropenyl; and fluorinated alkynyl groups such as fluoroethynyl and trifluoropropynyl.

[0173] Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as a fluorocyclopentyl group, a difluorocyclopentyl group, a nonafluorocyclopentyl group, a fluorocyclohexyl group, a difluorocyclohexyl group, an undecafluorocyclohexylmethyl group, a fluoronorbornyl group, a fluoroadamantyl group, a fluorobornyl group, a fluoroisobornyl group, and a fluorotricyclodecyl group; and fluorinated cycloalkenyl groups such as a fluorocyclopentenyl group and a nonafluorocyclohexenyl group.

[0174] The fluorinated hydrocarbon group is preferably a monovalent fluorinated chain hydrocarbon group having 1 to 8 carbon atoms, more preferably a monovalent fluorinated straight chain hydrocarbon group having 1 to 5 carbon atoms.

[0175] Za ＋ Examples of the monovalent onium cation represented by the formula (1) include a sulfonium cation and an iodonium cation. As the sulfonium cation, a substituted or unsubstituted triarylsulfonium cation is preferred, and a substituted or unsubstituted triphenylsulfonium cation is more preferred. As the iodonium cation, a substituted or unsubstituted diaryliodonium cation is preferred, and a substituted or unsubstituted diphenyliodonium cation is more preferred. When the onium cation has a substituent, the substituent may be R in the formula (1) above. ４ and R ５ It is possible to suitably employ a substituent that can be possessed by the ring structure constituted by the following formula: As the sulfonium cation, the sulfonium cation of onium salt compound (1) may be used.

[0176] Specific examples of the radiation-sensitive acid generator include, but are not limited to, structures represented by the following formulas (1B-1) to (1B-24).

[0177]

[0178]

[0179]

[0180] In addition to the above, compounds in which an organic acid anion and an onium cation are covalently bonded can also be used as the radiation-sensitive acid generator.

[0181] The lower limit of the content of the onium salt (1) as the radiation-sensitive acid generator (the total amount when multiple types are included) is preferably 1 part by mass, more preferably 3 parts by mass, even more preferably 8 parts by mass, and particularly preferably 10 parts by mass, per 100 parts by mass of the base polymer. The upper limit of the content is preferably 90 parts by mass, more preferably 80 parts by mass, and even more preferably 70 parts by mass. This improves the storage stability of the composition, and enables it to exhibit excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity during resist pattern formation.

[0182] The composition may contain a known radiation-sensitive acid generator other than the onium salt (1) as the radiation-sensitive acid generator, as long as the effect of the present invention is not impaired.

[0183] (Solvent) The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least the onium salt compound (1), the base polymer, and optional components that may be contained as desired.

[0184] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0185] 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, such as propylene glycol monomethyl ether. In this embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, isopropyl 2-hydroxyisobutyrate, isobutyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] Among these, alcohol-based solvents, ester-based solvents, and ketone-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, alcoholic acid ester-based solvents, lactone-based solvents, and cyclic ketone-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, methyl 2-hydroxyisobutyrate, γ-butyrolactone, and cyclohexanone are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0192] (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.

[0193] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the onium salt compound (1), a polymer, and, if necessary, a high-fluorine-content polymer, and a solvent 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 0.40 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0194] <Pattern Forming Method> A pattern forming method according to one embodiment of the present invention includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0195] According to the pattern formation method, the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity during pattern formation, and therefore a high-quality resist pattern can be efficiently formed. Each step will be described below.

[0196] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 160°C, and preferably 80°C to 140°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0197] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm, and the upper limit is preferably 300 nm, more preferably 200 nm, and even more preferably 150 nm.

[0198] When performing immersion exposure, regardless of whether the radiation-sensitive composition contains a water-repellent polymer additive such as a high-fluorine-content polymer, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-peelable protective film that is peeled off with a solvent before the development step (see, for example, JP-A No. 2006-227632), or a developer-peelable protective film that is peeled off simultaneously with development in the development step (see, for example, WO 2005-069076 and WO 2006-035790). However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective film for immersion exposure.

[0199] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion liquid such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0200] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser beam (wavelength 193 nm), water is preferred from the above-mentioned viewpoints, as well as from the viewpoints of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0201] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 130°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0202] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0203] In the case of alkaline development, the developer used in the development may be, for example, 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, or 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38 mass % aqueous TMAH solution is more preferred.

[0204] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As the ether solvent, glycol ether solvents are preferred, and ethylene glycol monomethyl ether and propylene glycol monomethyl ether are more preferred. As the ester solvent, acetate ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, chain ketones are preferred, and 2-heptanone is 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.

[0205] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0206] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of developing by piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispense method).

[0207] <Onium Salt Compound> The onium salt compound is a compound represented by the following formula (1): As such an onium salt compound, the onium salt compound (1) in the radiation-sensitive composition can be suitably used.

[0208] (In formula (1), R １ is a monovalent organic group having 4 to 40 carbon atoms. E is -O-, -S-, -SO- or -SO ２ - is. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ is a hydroxy group or a monovalent organic group having 1 to 20 carbon atoms. ４ and R ５ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R ４ and R ５ R represents a ring structure having 4 to 12 carbon atoms formed by combining with each other and the sulfur atom to which they are attached. ６ R is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group, or a monovalent organic group having 1 to 20 carbon atoms. ６ If there are multiple R ６ are the same or different from each other. m is 0 or 1. When m is 1, R ３ -CO- and R ２Both -E- are bonded to the six-membered ring structure to which the sulfur atom in the above formula (1) is bonded. n is an integer of 0 to 4.

[0209] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0210] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0211] [ １３ C-NMR analysis of polymer １３ C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0212] <Synthesis of Polymer> The monomers used in the synthesis of each polymer in each Example and Comparative Example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value when the total mass of the monomers used is taken as 100 parts by mass, and mol % refers to a value when the total number of moles of the monomers used is taken as 100 mol %.

[0213]

[0214]

[0215] Synthesis Example 1 Synthesis of Polymer (A-1) Monomer (M-1), monomer (M-2), monomer (M-5), monomer (M-10), and monomer (M-14) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 40 / 10 / 20 / 25 / 5 (mol%), and AIBN (azobisisobutyronitrile) (5 mol% relative to 100 mol% of the total monomers used) was added as an initiator to prepare a monomer solution. Propylene glycol monomethyl ether (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered off, and dried at 50°C for 24 hours to obtain a white powdery polymer (A-1) (yield: 83%). The Mw of the polymer (A-1) was 5,500, and the Mw / Mn was 1.58. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-2), (M-5), (M-10) and (M-14) were 40.3 mol%, 9.2 mol%, 20.8 mol%, 25.6 mol% and 4.1 mol%, respectively.

[0216] Synthesis Examples 2 to 11 (Synthesis of Polymers (A-2) to (A-11)) Polymers (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Table 1 below were used. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the resulting polymers are also shown in Table 1 below. In Table 1 below, "-" indicates that the corresponding monomer was not used (the same applies to the following tables).

[0217]

[0218] Synthesis Example 12 Synthesis of Polymer (A-12) Monomer (M-1) and monomer (M-29) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to a molar ratio of 55 / 45 (mol %), and MAIB (dimethyl 2,2'-azobisisobutyrate) (4 mol %) was added as an initiator to prepare a monomer solution. 1-Methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered, and dissolved in 1-methoxy-2-propanol (300 parts by mass). Methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were then added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After completion of the reaction, the residual solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to coagulate the polymer. The resulting solid was filtered and dried at 50°C for 13 hours to obtain a white powdery polymer (A-12) (yield: 85%). The Mw of the polymer (A-12) was 7,000, and the Mw / Mn was 1.57. １３ As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-29) were 52.3 mol % and 47.8 mol %, respectively.

[0219] [Synthesis Examples 13 to 34] (Synthesis of Polymers (A-13) to (A-34)) Polymers (A-13) to (A-34) were synthesized in the same manner as in Synthesis Example 12, except that the types and blending ratios of monomers shown in Table 2 below were used. Note that the monomer that gives the structural unit (IV) is １３ C-NMR analysis confirmed that the peaks of the carbonyl groups of the acetyl groups had disappeared, and that substantially all of the alkali-dissociable groups had been hydrolyzed to phenolic hydroxyl groups. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained polymer are also shown in Table 2 below.

[0220]

[0221] Synthesis Example 35 Synthesis of High Fluorine Content Polymer (F-1) Monomer (M-4), monomer (M-15), and monomer (M-20) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 20 / 10 / 70 (mol %), and MAIB (5 mol %) was added as an initiator to prepare a monomer solution. 2-Butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was collected. This process was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate to obtain a solution of high fluorine content polymer (F-1) (yield: 78%). The high fluorine content polymer (F-1) had an Mw of 7,000 and an Mw / Mn ratio of 1.67. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-4), (M-15) and (M-20) were 19.5 mol %, 9.7 mol % and 70.8 mol %, respectively.

[0222] [Synthesis Examples 36 to 39] (Synthesis of high fluorine content polymer (F-2) to high fluorine content polymer (F-5)) High fluorine content polymer (F-2) to high fluorine content polymer (F-5) were synthesized in the same manner as in Synthesis Example 35, except for using monomers of the types and blending ratios shown in Table 3 below. The content (mol %) of each structural unit and physical properties (Mw and Mw / Mn) of the obtained high fluorine content polymers are also shown in Table 3 below.

[0223]

[0224] <Synthesis of Acid Diffusion Controller (C)> [Example C1] (Synthesis of Onium Salt Compound (C-1)) An onium salt compound (C-1) serving as an acid diffusion controller (C) was synthesized according to the following synthesis scheme.

[0225]

[0226] A reaction vessel was charged with 20.0 mmol of diphenyl sulfoxide, 40.0 mmol of tert-butyl-2-methoxybenzoate, and trifluorosulfonic anhydride (Tf ２ 30.0 mmol of HCl and 50 g of dichloromethane were added and stirred at −78° C. for 12 hours. Subsequently, saturated aqueous sodium bicarbonate solution was added to the reaction solution to terminate the reaction, followed by extraction with dichloromethane and separation of the organic layer. The resulting organic layer was washed with saturated aqueous sodium chloride solution and then with water. After drying with sodium sulfate, the solvent was distilled off and the mixture was purified by column chromatography to obtain compound (C-1-a) in good yield.

[0227] 50 g of a 1 M aqueous solution of sodium iodide and 50 g of dichloromethane were added to the compound (C-1-a) and stirred at 50° C. for 12 hours. The reaction solution was then extracted with dichloromethane, and the organic layer was separated. The solvent in the resulting organic layer was distilled off, yielding compound (C-1-b) in good yield.

[0228] To the compound (C-1-b), 20.0 mmol of salicylic acid, 30.0 mmol of sodium bicarbonate, 50 g of dichloromethane, and 50 g of water were added, and the mixture was stirred at room temperature for 4 hours. Dichloromethane was added to the reaction solution for extraction, and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying over sodium sulfate, the solvent was distilled off, and the compound (C-1) represented by the above formula (C-1) was obtained in good yield.

[0229] Examples C2 to C27 Synthesis of Onium Salt Compounds (C-2) to (C-27) Onium salt compounds as radiation-sensitive acid generators represented by the following formulas (C-2) to (C-27) were synthesized in the same manner as in Example C1, except that the raw materials and precursors were changed appropriately.

[0230]

[0231]

[0232]

[0233] [Acid diffusion controllers other than acid diffusion controllers (C-1) to (C-27)] cc-1 to cc-9: Compounds represented by the following formulas (cc-1) to (cc-9) (hereinafter, the compounds represented by formulas (cc-1) to (cc-9) may be referred to as "compound (cc-1)" to "compound (cc-9)," respectively).

[0234]

[0235] The following compounds were used as components other than the components synthesized above.

[0236] [Radiation-sensitive acid generators (B-1) to (B-8)] (B-1) to (B-8): Compounds represented by the following formulas (B-1) to (B-8) (hereinafter, the compounds represented by formulas (B-1) to (B-8) may be referred to as "compound (B-1)" to "compound (B-8)," respectively).

[0237]

[0238] [Solvent (E)] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-butyrolactone E-4: Cyclohexanone E-5: Diacetone alcohol E-6: Methyl 2-hydroxyisobutyrate

[0239] [Other Additive Components (W)] W-1: MEGAFACE EFS-321 (manufactured by DIC Corporation) (non-fluorine-based) W-2: BYK-399 (manufactured by BYK Japan KK) (non-silicone-based)

[0240] [Preparation of positive-tone radiation-sensitive composition for ArF immersion exposure] [Example 1] 100 parts by mass of (A-1) as the polymer (A), 12.0 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 8.0 parts by mass of (C-1) as the acid diffusion controller (C), 2.0 parts by mass (solids content) of (F-1) as the high-fluorine-content polymer (F), 0.1 part by mass of (W-1) as the other additive component (W), and 3,400 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent (E) were mixed and the mixture was filtered through a membrane filter having a pore size of 0.2 μm to prepare a radiation-sensitive composition (J-1).

[0241] [Examples 2 to 53, 101 to 102 and Comparative Examples 1 to 9] Radiation-sensitive compositions (J-2) to (J-53), (J-101) to (J-102), and (CJ-1) to (CJ-9) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 4-1 and 4-2 below were used.

[0242]

[0243]

[0244] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Immersion Exposure> A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 100 nm. The positive radiation-sensitive composition for ArF exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 105 nm. Next, this resist film was exposed through a 40 nm line and space pattern using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and dipole (σ = 0.9 / 0.7). After exposure, PEB (post-exposure bake) was performed at 100°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% TMAH aqueous solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (40 nm line and space pattern).

[0245] <Evaluation> The resist patterns formed using the above-described positive-working radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity, LWR, MEEF, EL, and pattern rectangularity according to the methods described below. The results are shown in Tables 5-1 and 5-2 below. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0246] [Sensitivity] In forming a resist pattern using the positive radiation-sensitive composition for ArF immersion exposure, the exposure dose required to form a 40 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ "Good" if below 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0247] [LWR] A 40 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. LWR was evaluated as "good" when it was 3.0 nm or less, and as "poor" when it exceeded 3.0 nm.

[0248] [MEEF] In a resist pattern resolved by irradiation with the above-mentioned optimum exposure dose, the line width of a resist pattern formed using a mask pattern with a pattern line width of 42 nm, 44 nm, 46 nm, 48 nm, or 50 nm was plotted on the vertical axis against the line width of the mask pattern on the horizontal axis, and the slope of the line was calculated and defined as MEEF. MEEF values ​​closer to 1 indicate better mask reproducibility. MEEF values ​​of 2 or less were evaluated as "good," and values ​​above 2 were evaluated as "poor."

[0249] [EL (Exposure Latitude)] In the range of exposure amounts including the above-mentioned optimum exposure amount, the exposure amount is set to 1 mJ / cm ２Resist patterns were formed at different exposure doses, and the line widths of each were measured using the scanning electron microscope. From the relationship between the resulting line width and exposure dose, the exposure dose E(44) resulting in a line width of 44 nm and the exposure dose E(36) resulting in a line width of 36 nm were determined, and the exposure latitude (%) was calculated using the formula: exposure latitude (EL) = {(E(36) - E(44)) x 100} / (optimum exposure dose). The larger the exposure latitude value, the smaller the fluctuation in the dimensions of the resulting pattern when the exposure dose fluctuates, thereby increasing the yield during device fabrication. EL performance was evaluated as "good" when it was 10% or higher, and as "poor" when it was below 10%.

[0250] [Pattern rectangularity] The 40 nm line and space formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation was observed using the scanning electron microscope, and the cross-sectional shape of the line pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the lower side to the length of the upper side in the cross-sectional shape of the line pattern was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0251]

[0252]

[0253] As is clear from the results in Tables 5-1 and 5-2, when the radiation-sensitive compositions of the Examples were used in ArF immersion exposure, the sensitivity, LWR, MEEF, EL, and pattern shape were good, whereas in the Comparative Examples, each property was inferior to that of the Examples. Therefore, when the radiation-sensitive compositions of the Examples were used in ArF immersion exposure, resist patterns with high sensitivity, good roughness performance, good yield performance, and good pattern shape could be formed.

[0254] [Preparation of Negative Radiation-Sensitive Composition for ArF Immersion Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 54] 100 parts by mass of (A-8) as the polymer (A), 8.0 parts by mass of (B-5) as the radiation-sensitive acid generator (B), 3.0 parts by mass of (C-11) as the acid diffusion controller (C), 3.0 parts by mass (solids content) of (F-3) as the high fluorine-containing polymer (F), and 2,830 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) (mass ratio 1,200 / 1,600 / 30) as the solvent (E) were mixed, and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-54).

[0255] A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 100 nm. The negative radiation-sensitive composition for ArF exposure (J-54) prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 150 nm. Next, this resist film was exposed to light using an ArF excimer laser immersion exposure system (ASML's "TWINSCAN XT-1900i") under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 60 nm holes and a 120 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. The resist film was then developed using n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 60 nm holes and a 120 nm pitch).

[0256] The resist patterns prepared using the negative-tone radiation-sensitive resin composition for ArF immersion exposure were evaluated for sensitivity, MEEF, and EL in the same manner as in the evaluation of the resist patterns prepared using the positive-tone radiation-sensitive resin composition for ArF immersion exposure. Furthermore, the CDU and pattern circularity were evaluated according to the following methods.

[0257] [CDU] Contact holes with a 60 nm hole and a 120 nm pitch were formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The variation in the diameter of the contact holes was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values, and this 3 sigma value was taken as CDU (nm). The smaller the CDU value, the smaller the hole roughness and the better the result. CDU was evaluated as "good" when it was less than 3.5 nm, and as "poor" when it was 3.5 nm or more.

[0258] [Pattern circularity] The 60 nm holes and 120 nm pitch contact holes formed by irradiating with the optimum exposure dose obtained in the sensitivity evaluation were observed in plan view using the scanning electron microscope, and their vertical and horizontal sizes were measured. A ratio of vertical size to horizontal size of 0.95 or more and less than 1.05 was evaluated as "A" (very good), a ratio of 0.90 or more and less than 0.95 or 1.05 or more and less than 1.10 was evaluated as "B" (good), and a ratio of less than 0.90 or 1.10 or more was evaluated as "C" (poor).

[0259] As a result, the radiation-sensitive resin composition of Example 54 exhibited excellent sensitivity, MEEF, EL, CDU and pattern circularity even when a negative resist pattern was formed by ArF immersion exposure.

[0260] [Preparation of Positive-Working Radiation-Sensitive Composition for Extreme Ultraviolet (EUV) Exposure] [Example 55] 100 parts by mass of (A-12) as the polymer (A), 60.0 parts by mass of (B-1) as the radiation-sensitive acid generator (B), 40.0 parts by mass of (C-20) as the acid diffusion controller (C), 2.0 parts by mass (solids content) of (F-5) as the high fluorine-content polymer (F), and 6,800 parts by mass of a mixed solvent of (E-1) / (E-2) as the solvent (E) were mixed and the mixture was filtered through a membrane filter having a pore size of 0.2 μm, thereby preparing a radiation-sensitive composition (J-55).

[0261] Examples 56 to 90 and Comparative Examples 10 to 14 Radiation-sensitive compositions (J-56) to (J-90) and (CJ-10) to (CJ-14) were prepared in the same manner as in Example 55, except that the types and amounts of each component shown in Table 6 below were used.

[0262]

[0263] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for EUV Exposure> A composition for forming a bottom antireflective coating ("ARC66" from Brewer Science) was applied to a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" from Tokyo Electron Limited), and then heated at 205°C for 60 seconds to form a bottom antireflective coating with an average thickness of 105 nm. The positive radiation-sensitive composition for EUV exposure prepared above was applied to this bottom antireflective coating using the spin coater, and then subjected to PB at 130°C for 60 seconds. Subsequently, the wafer was cooled at 23°C for 30 seconds to form a resist film with an average thickness of 60 nm. Next, this resist film was exposed using an EUV exposure apparatus (ASML's "NXE3300") with NA = 0.33, illumination conditions: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38 mass% aqueous TMAH solution as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (contact hole pattern with 25 nm holes and a 50 nm pitch).

[0264] <Evaluation> The resist patterns formed using the above-described positive-tone radiation-sensitive compositions for EUV exposure were evaluated for sensitivity, CDU, and EL according to the methods described below. The results are shown in Table 7. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0265] [Sensitivity] In forming a resist pattern using the positive radiation-sensitive composition for EUV exposure, the exposure dose required to form a contact hole pattern with 25 nm holes and a 50 nm pitch was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 40 mJ / cm ２ The following cases are considered "good" and 40 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0266] [CDU] A resist pattern was formed by irradiating the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a contact hole pattern with 25 nm holes and a 50 nm pitch. The formed resist pattern was observed from above the pattern using the scanning electron microscope described above. The hole diameter was measured at 16 points within a 500 nm range to determine the average value, and this average value was measured at a total of 500 points at any point. The 1 sigma value was calculated from the distribution of the measured values, and this was defined as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, and the better. CDU was evaluated as "good" when it was 3.0 nm or less, and as "poor" when it exceeded 3.0 nm.

[0267] [EL (Exposure Latitude)] In the range of exposure amounts including the above-mentioned optimum exposure amount, the exposure amount is set to 1 mJ / cm ２ Resist patterns were formed at different exposure doses, and the hole diameters of each were measured using the scanning electron microscope. From the relationship between the resulting hole diameter and exposure dose, the exposure dose E(27.5) at which the hole diameter was 27.5 nm and the exposure dose E(22.5) at which the hole diameter was 22.5 nm were determined. The exposure latitude (%) was calculated using the formula: exposure latitude (EL) = {(E(22.5) - E(27.5)) x 100} / (optimum exposure dose). The larger the exposure latitude, the smaller the fluctuation in the pattern dimensions obtained when the exposure dose fluctuates, which increases the yield during device fabrication. EL performance was evaluated as "good" when it was 8% or higher, and "poor" when it was below 8%.

[0268]

[0269]

[0111] As is clear from the results in Table 7, when the radiation-sensitive compositions of the Examples were used for EUV exposure, the sensitivity, CDU, and EL were good, whereas in the Comparative Examples, each property was inferior to that of the Examples. [Preparation of Negative Radiation-Sensitive Composition for EUV Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 91] A radiation-sensitive composition (J-91) was prepared by mixing 100 parts by mass of (A-15) as the polymer (A), 50.0 parts by mass of (B-6) as the radiation-sensitive acid generator (B), 45.0 parts by mass of (C-23) as the acid diffusion controller (C), 2.0 parts by mass (solids content) of (F-5) as the high fluorine-containing polymer (F), and 6,110 parts by mass of a mixed solvent of (E-1) / (E-2) (mass ratio 4,280 / 1,830) as the solvent (E), and filtering the mixture through a membrane filter having a pore size of 0.2 μm.

[0270] A composition for forming a bottom anti-reflective coating (Brewer Science's ARC66) was applied to a 12-inch silicon wafer using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), and then heated at 205°C for 60 seconds to form a bottom anti-reflective coating with an average thickness of 105 nm. The negative radiation-sensitive composition for EUV exposure (J-91) prepared above was applied to this bottom anti-reflective coating using the spin coater, and baked at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 60 nm. Next, this resist film was exposed to light using an EUV exposure system (ASML's NXE3300) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR15. After the exposure, PEB was performed for 60 seconds at 120° C. Thereafter, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (a contact hole pattern with 30 nm holes and a 60 nm pitch).

[0271] The resist pattern formed using the negative-tone radiation-sensitive composition for EUV exposure was evaluated in the same manner as the resist pattern formed using the positive-tone radiation-sensitive composition for EUV exposure. As a result, the radiation-sensitive composition of Example 91 exhibited good sensitivity, CDU, and EL, even when a negative-tone resist pattern was formed by EUV exposure.

[0272] The radiation-sensitive composition and pattern forming method described above can form a resist pattern that has good sensitivity to exposure light and is excellent in LWR, MEEF, EL, pattern rectangularity, CDU, and pattern circularity. Therefore, these compositions can be suitably used in processing processes for semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: an onium salt compound represented by the following formula (1); a polymer containing a structural unit having an acid-dissociable group; and a solvent. (In formula (1), R １ is a monovalent organic group having 4 to 40 carbon atoms. E is -O-, -S-, -SO- or -SO ２ - is. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ is a hydroxy group or a monovalent organic group having 1 to 20 carbon atoms. ４ and R ５ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R ４ and R ５ R represents a ring structure having 4 to 12 carbon atoms formed by combining with each other and the sulfur atom to which they are attached. ６ R is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group, or a monovalent organic group having 1 to 20 carbon atoms. ６ If there are multiple R ６ are the same or different from each other. m is 0 or 1. When m is 1, R ３ -CO- and R ２ Both -E- are bonded to the six-membered ring structure to which the sulfur atom in the above formula (1) is bonded. n is an integer of 0 to 4.

2. The radiation-sensitive composition according to claim 1, wherein in the formula (1), E is -O-.

3. In the above formula (1), R ３ 2. The radiation-sensitive composition according to claim 1, wherein is a monovalent organic group having 1 to 20 carbon atoms and having an ether bond on its one bond side.

4. The radiation-sensitive composition according to claim 1, wherein m is 0.

5. In the above formula (1), R ２ -E- vs. R ３ 5. The radiation-sensitive composition according to claim 1, wherein --CO-- is in an ortho-position or a para-position.

6. In the above formula (1), R ２ The radiation-sensitive composition according to any one of claims 1 to 4, wherein represents a hydrogen atom, an alkyl group, an alkoxyalkyl group, an alkoxycarbonylalkyl group, or a cycloalkoxycarbonylalkyl group.

7. In the above formula (1), R １ The radiation-sensitive composition according to any one of claims 1 to 4, wherein contains at least one structure selected from the group consisting of a cyclic structure, a carbonyl group, and an ether bond.

8. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the content of the onium salt compound is 0.1 parts by mass or more and 80 parts by mass or less per 100 parts by mass of the polymer.

9. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the structural unit having an acid-dissociable group is represented by the following formula (3): (In formula (3), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊ -COOL １１ａ COO-. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.) 10. The radiation-sensitive composition according to any one of claims 1 to 4, further comprising a radiation-sensitive acid generator that generates, upon exposure to light, an acid that dissociates the acid-dissociable group.

11. A pattern forming method comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 4 directly or indirectly to a substrate to form a resist film; exposing the resist film; and developing the exposed resist film with a developer.

12. The pattern forming method according to claim 11, wherein the exposure is carried out with an ArF excimer laser or extreme ultraviolet light.

13. An onium salt compound represented by the following formula (1): (In formula (1), R １ is a monovalent organic group having 4 to 40 carbon atoms. E is -O-, -S-, -SO- or -SO ２ - is. R ２ is a hydrogen atom or a monovalent organic group having 1 to 20 carbon atoms. ３ is a hydroxy group or a monovalent organic group having 1 to 20 carbon atoms. ４ and R ５ are each independently a monovalent organic group having 1 to 20 carbon atoms, or R ４ and R ５ R represents a ring structure having 4 to 12 carbon atoms formed by combining with each other and the sulfur atom to which they are attached. ６ R is a halogen atom, a hydroxy group, a nitro group, an amino group, a carboxy group, a cyano group, or a monovalent organic group having 1 to 20 carbon atoms. ６ If there are multiple R ６ are the same or different from each other. m is 0 or 1. When m is 1, R ３ -CO- and R ２ Both -E- are bonded to the six-membered ring structure to which the sulfur atom in the above formula (1) is bonded. n is an integer of 0 to 4.

Images