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

Abstract

Provided are a radiation-sensitive composition, a pattern formation method, and an onium salt compound that make it possible to achieve sufficient sensitivity, CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude when a pattern is formed. A radiation-sensitive composition according to the present invention includes: an onium salt compound represented by formula (1); a polymer that includes a structural unit (I) represented by formula (2); and a solvent. (In formula (1), A is a C3–40 (1+n)-valent organic group that includes a cyclic structure. When A includes a straight-chain alkanediyl group, the number of carbons in the straight-chain alkanediyl group is 1 or 2. A does not include a cyclohexylcarbonyloxy structure. Rf1 and Rf2 are each independently a hydrogen atom, a C1–20 monovalent organic group, a fluorine atom, or a monovalent fluorinated hydrocarbon group. When there are multiple Rf1 and Rf2, the Rf1 and Rf2 are each the same or different. At least one of Rf1 and Rf2 is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer from 1 to 4, inclusive. m2 is 0 or 1. n is an integer from 1 to 3, inclusive. Z+ is a monovalent radiation-sensitive onium cation. The number of fluorine atoms in Z+ is no more than 8.) (In formula (2), RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L is a single bond or a divalent linking group. W is a monocyclic lactone structure, a monocyclic carbonate structure, a monocyclic sultone structure, a monocyclic sulfone structure, or a monocyclic ether structure. R11 is a C1–10 monovalent organic group, a cyano group, a nitro group, a hydroxy group, or an amino group. When there are multiple R11, the R11 are each the same or different. p is an integer from 0 to 3, inclusive. q is 0 or 1.)

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 an alkaline or organic solvent-based developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology described above promotes pattern miniaturization by using short-wavelength radiation such as ArF excimer lasers or by combining such radiation with liquid immersion lithography. As next-generation technologies, lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered.

[0004] Regarding photoacid generators, which are a major component of resist compositions, photoacid generators in which specific functional groups have been introduced into the anion have been investigated in terms of reducing pattern roughness (WO 2021 / 199841).

[0005] International Publication No. 2021 / 199841

[0006] In these efforts toward next-generation technologies, resist compositions are required to have various resist performances that are equal to or better than conventional ones in terms of sensitivity, critical dimension uniformity (CDU) performance which is an index of uniformity of line width and hole diameter, pattern circularity which indicates the circularity of the hole shape, suppression of development defects, depth of focus, line width roughness (LWR) performance which indicates variation in line width of the resist pattern, pattern rectangularity which indicates the rectangularity of the cross-sectional shape of the resist pattern, exposure latitude (EL), etc. However, existing radiation-sensitive compositions do not achieve these properties at a sufficient level.

[0007] An object of the present invention is to provide a radiation-sensitive composition, a pattern-forming method, and an onium salt compound that can exhibit sufficient levels of sensitivity, CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude when forming a pattern.

[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); a polymer including a structural unit (I) represented by the following formula (2); and a solvent. (In formula (1), A is a (1+n)-valent organic group containing a cyclic structure and having 3 to 40 carbon atoms. However, when A contains a linear alkanediyl group, the linear alkanediyl group has 1 or 2 carbon atoms. A does not contain a cyclohexylcarbonyloxy structure. R ｆ１ and R ｆ２ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different, provided that R ｆ１ and R ｆ２ At least one of the groups is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer of 1 to 4. m2 is 0 or 1. n is an integer of 1 to 3. Z ＋ is a monovalent radiation-sensitive onium cation, provided that Z ＋ The number of fluorine atoms in is 8 or less. (In formula (2), R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L is a single bond or a divalent linking group. W is a monocyclic lactone structure, a monocyclic carbonate structure, a monocyclic sultone structure, a monocyclic sulfone structure, or a monocyclic ether structure. R １１R is a monovalent organic group having 1 to 10 carbon atoms, a cyano group, a nitro group, a hydroxy group, or an amino group. １１ If there are multiple R １１ are the same or different. p is an integer of 0 to 3. q is 0 or 1.

[0010] The radiation-sensitive composition contains both an onium salt compound as a radiation-sensitive acid generator and a polymer containing a specific structural unit (I), and therefore, when forming a pattern, it is possible to exhibit sufficient levels of sensitivity, CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude. The reason for this is presumed to be as follows, without being bound by any theory.

[0011] The anion of the onium salt compound contains a carboxy group, which results in higher solubility in alkaline developers compared to conventional onium salt compounds. Furthermore, the diffusion length of the generated acid is shortened due to enhanced interaction between the carboxy group and other components, such as polymers, in the radiation-sensitive composition, and steric hindrance caused by the inclusion of a cyclic structure in the anion. Furthermore, by controlling the number of fluorine atoms in the cation of the onium salt compound to a predetermined number, a balance between acid generation efficiency, developer solubility, and dispersibility can be achieved. These effects of the onium salt compound can suppress the occurrence of roughness, such as variations in pattern shape and unevenness, and development defects. Furthermore, the polymer contains a structural unit (I) incorporating a highly polar monocyclic structure, which results in higher solubility in alkaline developers and higher dissolution inhibition in organic solvent developers. Additionally, the polar monocyclic structure reduces bulkiness, facilitating the approach of polymers to each other and between the polymer and the onium salt compound, thereby improving the interaction between the components. These synergistic effects make it possible to specifically shorten the diffusion length of the generated acid, thereby significantly suppressing the occurrence of roughness such as variations in pattern shape and unevenness. When A has a cyclohexylcarbonyloxy structure (i.e., when the anion contains a carboxycyclohexylcarbonyloxy structure), the carboxylic acid moiety may nucleophilically attack a nearby carbonyl group to form an anhydride ring, which may reduce storage stability and worsen roughness. It is presumed that the combined use of the properties of the onium salt compound and polymer described above can achieve desired resist performance. The organic group refers to a group containing at least one carbon atom.

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

[0013] The pattern formation method uses the radiation-sensitive composition that can exhibit sufficient levels of sensitivity, CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude when forming a pattern, and therefore can efficiently form a high-quality resist pattern.

[0014] In yet another embodiment, the present invention relates to an onium salt compound represented by the following formula (1-d): (In the above formula (1-d), W １ and W ２ are each independently a substituted or unsubstituted cyclic structure. Ｑ is a single bond, ＊ -OCO- or ＊ -O-CO-O-. * indicates W １ It is a bond on the R side. ｆ１ and R ｆ２ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different, provided that R ｆ１ and R ｆ２ At least one of the groups is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer of 1 to 4. n is an integer of 1 to 3. Z １ ＋ is a monovalent radiation-sensitive onium cation.

[0015] The onium salt compound has a specific structure including a cyclic structure to which a carboxy group is bonded, and can have appropriate steric hindrance, rigidity, hydrophilicity, interactivity with other components, and the like, and is therefore suitable as a radiation-sensitive acid generator for a radiation-sensitive composition.

[0016] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Combinations of preferred embodiments are also preferred.

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also referred to simply as "composition") contains an onium salt compound, a polymer containing the structural unit (I) (hereinafter also referred to as "base polymer"), and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0018] (Onium Salt Compound) The onium salt compound is represented by the above formula (1) and is a component that generates an acid upon irradiation with radiation. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer and generating a carboxyl group or the like. The composition may contain one or more onium salt compounds.

[0019] Examples of the (1+n)-valent organic group having 3 to 40 carbon atoms and containing a cyclic structure represented by A include groups obtained by removing n hydrogen atoms from a monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure. The carboxy group in the above formula (1) is directly bonded to the cyclic structure in A. However, A does not contain a cyclohexylcarbonyloxy structure. The organic group having a cyclic structure is not particularly limited, and examples thereof include monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, heterocyclic groups having a divalent heteroatom-containing linking group between the carbon atoms of these groups, groups in which some or all of the hydrogen atoms of any of the above groups have been substituted with monovalent heteroatom-containing substituents, and combinations thereof. When multiple rings are combined, adjacent rings may form a fused ring, a spiro ring, or a ring assembly (a structure in which adjacent rings are bonded by a single bond), or may be linked by a chain structure. Examples of the chain structure include a single bond, an alkanediyl group having 1 to 2 carbon atoms, a branched alkanediyl group having 3 to 10 carbon atoms, a divalent heteroatom-containing linking group, or a group formed by combining these. Examples of the divalent heteroatom-containing linking group include -CO-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ or a group in which two or more of these groups are combined.

[0020] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl; cycloalkenyl groups such as cyclopropenyl, cyclopentenyl, and cyclohexenyl; bridged ring saturated hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and bornyl; and bridged ring unsaturated hydrocarbon groups such as norbornenyl and tricyclodecenyl.

[0021] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include a phenyl group, a tolyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, and a fluorenyl group.

[0022] Examples of heteroatoms constituting the divalent heteroatom-containing linking group or monovalent heteroatom-containing substituent 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.

[0023] As the divalent heteroatom-containing linking group, the above-mentioned divalent heteroatom-containing linking groups can be suitably used.

[0024] Examples of the monovalent heteroatom-containing substituent include a hydroxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0025] Examples of the heterocyclic group include a group in which one hydrogen atom has been removed from an aromatic heterocyclic structure and a group in which one hydrogen atom has been removed from an aliphatic heterocyclic structure. Five-membered aromatic structures that have aromaticity due to the introduction of heteroatoms are also included in the heterocyclic structure. Examples of heteroatoms include oxygen atoms, nitrogen atoms, and sulfur atoms.

[0026] Examples of the aromatic heterocyclic structure include: oxygen atom-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple heteroatoms such as thiazole, benzothiazole, thiazine, and oxazine.

[0027] Examples of the aliphatic heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; and aliphatic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0028] Examples of cyclic structures corresponding to the heterocyclic groups include lactone structures, cyclic carbonate structures, sultone structures, and structures containing cyclic acetals. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0029]

[0030] In the above formula, m is an integer of 1 to 3.

[0031] In the above formula (1), the cyclic structure is preferably an alicyclic hydrocarbon structure, an aromatic hydrocarbon structure, a lactone structure, a sultone structure, a cyclic acetal structure, a cyclic carbonate structure, a cyclic ether structure, or a combination thereof. Examples of the alicyclic hydrocarbon structure include alicyclic monocyclic structures such as a cyclopentane structure and a cyclohexane structure, and alicyclic polycyclic structures such as an adamantane structure and a norbornane structure. Among these, the alicyclic hydrocarbon structure is preferably an alicyclic polycyclic structure. A structure corresponding to the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms can be suitably employed as the aromatic hydrocarbon structure. When the cyclic organic group has one or more of these structures, the diffusion length of the acid generated by exposure can be appropriately controlled, and the composition can exhibit the above-mentioned resist performances at a high level.

[0032] R ｆ１ and R ｆ２ Examples of the monovalent fluorinated hydrocarbon group represented by the formula (I) include a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms, as well as a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] R ｆ１ and R ｆ２ are each preferably independently a fluorine atom or a trifluoromethyl group. ３ － R on the carbon atom bonded to ｆ１ and R ｆ２ is preferably a fluorine atom.

[0037] m1 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0038] n is preferably 1 or 2, and more preferably 1.

[0039] The onium salt compound is preferably a compound represented by any one of the following formulas (1-a) to (1-e). This increases the rigidity of the anionic structure, and at the same time, the carboxyl group itself has a certain degree of freedom, so it exhibits a high ability to interact with the monocyclic lactone moiety of the polymer. This allows for more precise control of the diffusion length of the generated acid, leading to improvements in various performances such as CDU, LWR, and exposure latitude.

[0040]

[0041] In the above formulas (1-a) to (1-e), W １ and W ２are each independently a substituted or unsubstituted cyclic structure. Ｐ is a single bond or a divalent linking group. Ｑ is a single bond, ＊ -OCO- or ＊ -O-CO-O-. * indicates W １ It is a bond on the side. Ｒ represents a methylene group or a group in which one or both of the hydrogen atoms of a methylene group have been substituted with a hydrocarbon group having 1 to 10 carbon atoms, or ＊ -OCO-R''-. R'' is a methylene group or a group in which one or both of the hydrogen atoms of a methylene group have been substituted with a hydrocarbon group having 1 to 10 carbon atoms. * represents W １ It is a bond on the Z side. １ ＋ is a monovalent radiation-sensitive onium cation. ｆ１ , R ｆ２ , Z ＋ , m1 and n have the same meanings as in formula (1) above.

[0042] W １ and W ２ As the cyclic structure in the formula (1), the cyclic structure shown in A in the formula (1) can be preferably used. １ and W ２ When has 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, an aryloxy 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).

[0043] L Ｐ As the divalent linking group represented by the formula (1), the chain structure shown in A in the formula (1) can be suitably adopted.

[0044] L Ｒ In the formula (I), examples of the hydrocarbon group having 1 to 10 carbon atoms include a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 5 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms.

[0045] Among these, the onium salt compound is preferably a compound represented by the above formula (1-a), (1-b), (1-c) or (1-d), and particularly preferably a compound represented by the above formula (1-b), (1-c) or (1-d).

[0046] Specific examples of the anion portion of the onium salt compound include, but are not limited to, structures of the following formulae (1-1-1) to (1-1-93).

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] In the formula (1), the Z ＋ and Z １ ＋ Examples of the monovalent radiation-sensitive onium cation represented by the formula (I) include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Examples of the radiation-decomposable onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Among these, sulfonium cation or iodonium cation is preferred, and sulfonium cation is more preferred.

[0055] Z ＋The number of fluorine atoms in the compound is 8 or less. This significantly enhances the dissolution-promoting effect during alkaline development and the dissolution-inhibiting effect during organic solvent development. In addition, it is possible to achieve a balance between acid generation efficiency and dispersibility without impairing the polarity of the anion, thereby achieving pattern roughness and shape improvement effects.

[0056] The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-6).

[0057]

[0058] In the above formula (X-1), R ａ１ , R ａ２ and R ａ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group, an alkoxycarbonyloxy group, or a (cyclo)alkoxycarbonylalkoxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or —OSO ２ -R Ｐ , -SO ２ -R Ｑ or -S-R Ｔ or a ring structure formed by combining two or more of these groups. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton. R Ｐ , R Ｑ and R Ｔ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R ａ１ ~R ａ３ and R Ｐ , R Ｑ and R Ｔ If there are multiple R ａ１ ~R ａ３ and R Ｐ , RＱ and R Ｔ may be the same or different.

[0059] In the above formula (X-2), R ｂ１ is a substituted or unsubstituted linear or branched alkyl group having 1 to 20 carbon atoms, an alkoxy group or an alkoxyalkoxy group, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, a hydroxy group, or a halogen atom. ｋ is 0 or 1. ｋ When is 0, k4 is an integer from 0 to 4, and n ｋ When is 1, k4 is an integer from 0 to 7. ｂ１ If there are multiple R ｂ１ may be the same or different, and multiple R ｂ１ may represent a ring structure formed by combining with each other. ｂ２ is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 or 7 carbon atoms. Ｃ is a single bond or a divalent linking group. k5 is an integer of 0 to 4. R ｂ２ If there are multiple R ｂ２ may be the same or different, and multiple R ｂ２ may represent a ring structure formed by combining with each other, and q is an integer of 0 to 3. ＋ The ring structure containing the following may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton.

[0060] In the above formula (X-3), R ｃ１ , R ｃ２ and R ｃ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0061] In the above formula (X-4), R ｇ１is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. ｋ２ is 0 or 1. ｋ２ When is 0, k10 is an integer from 0 to 4, and n ｋ２ When is 1, k10 is an integer from 0 to 7. ｇ１ If there are multiple R ｇ１ may be the same or different, and multiple R ｇ１ may represent a ring structure formed by combining with each other. ｇ２ and R ｇ３ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, or a ring structure formed by combining these groups together. k11 and k12 are each independently an integer of 0 to 4. R ｇ２ and R ｇ３ If there are multiple R ｇ２ and R ｇ３ may be the same or different.

[0062] In the above formula (X-5), R ｄ１ and R ｄ２ are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are each independently an integer of 0 to 5. R ｄ１ and R ｄ２ If there are multiple R ｄ１ and R ｄ２ may be the same or different.

[0063] In the above formula (X-6), R ｅ１ and R ｅ２ are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

[0064] Specific examples of the radiation-sensitive onium cation include, but are not limited to, structures of the following formulae (1-2-1) to (1-2-44).

[0065]

[0066]

[0067]

[0068] The onium salt compound can be obtained by appropriately combining the above-mentioned anion moiety with the above-mentioned radiation-sensitive onium cation. Specific examples include, but are not limited to, structures of the following formulae (1-1) to (1-55).

[0069]

[0070]

[0071]

[0072]

[0073]

[0074] The lower limit of the content of the onium salt compound (the total amount of the onium salt compounds when multiple types of onium salt compounds are contained) is preferably 1 part by mass, more preferably 2 parts by mass, and even more preferably 3 parts by mass, per 100 parts by mass of the polymer described below. The upper limit of the content is preferably 60 parts by mass, more preferably 40 parts by mass, and even more preferably 35 parts by mass. The content of the onium salt compound is appropriately selected depending on the type of polymer used, exposure conditions, required sensitivity, and the like. This allows the resist pattern to exhibit excellent sensitivity, CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude during resist pattern formation.

[0075] (Method for synthesizing onium salt compounds) The target onium salt compounds can be synthesized by carrying out, in an appropriate order, the formation of an organic acid anion skeleton, a reaction of a sulfite with an alkyl halide to introduce a sulfonate structure, and a salt exchange to introduce an onium cation. The formation of the organic acid anion skeleton can be achieved by known reactions such as an esterification reaction, an acetalization reaction between a diol and a ketone, or a cycloaddition reaction between a conjugated diene and an alkene. Various onium salt compounds can be synthesized by appropriately selecting starting materials and precursors corresponding to the organic acid anion and the onium cation.

[0076] (Polymer) The polymer (base polymer) is an aggregate of polymer chains containing the structural unit (I) represented by the above formula (2). The base polymer preferably contains, in addition to the structural unit (I), a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (II)"). The base polymer 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 represented by the following formula (2): The base polymer may contain one or more types of structural unit (I).

[0078] In the above formula (2), R Ａis a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L is a single bond or a divalent linking group. W is a monocyclic lactone structure, a monocyclic carbonate structure, a monocyclic sultone structure, a monocyclic sulfone structure, or a monocyclic ether structure (hereinafter, these are also collectively referred to as "monocyclic polar structures"). R １１ R is a monovalent organic group having 1 to 10 carbon atoms, a cyano group, a nitro group, a hydroxy group, or an amino group. １１ If there are multiple R １１ are the same or different. p is an integer of 0 to 3. q is 0 or 1.

[0079] The above R Ａ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0080] Examples of the divalent linking group represented by L 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, a divalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH-, and -S-.

[0081] L is preferably a single bond or a divalent alkanediyl group having 1 to 10 carbon atoms, more preferably a single bond or a divalent alkanediyl group having 1 to 5 carbon atoms, and even more preferably a single bond or a methanediyl group.

[0082] The lower limit of the number of carbon atoms in the monocyclic polar structure represented by W is preferably 3, more preferably 4. The upper limit of the number of carbon atoms is preferably 6, more preferably 5. This can improve the solubility in an alkaline developer.

[0083] The monocyclic lactone structure represented by W is preferably represented by the above formula (H-3) shown in the anion portion of the onium salt compound. Similarly, the monocyclic carbonate structure represented by W is preferably represented by the above formula (H-4), and the monocyclic sultone structure is preferably represented by the above formula (H-8). Suitable examples of the monocyclic ether structure include an oxirane structure, an oxetane structure, and a tetrahydrofuran structure.

[0084] In the case of development using an alkaline aqueous solution, W preferably has a monocyclic lactone structure from the viewpoint of solubility in the alkaline developer, and in the case of development using an organic solvent, from the viewpoint of dissolution inhibition in the organic solvent developer. This structure reduces bulkiness, facilitates proximity between polymers and between the polymer and the onium salt compound, and improves the ability to interact with each other. These synergistic effects make it possible to specifically shorten the diffusion length of the generated acid, thereby significantly suppressing the occurrence of roughness such as variations in pattern shape and unevenness.

[0085] R １１ As the monovalent organic group having 1 to 10 carbon atoms represented by the formula (1), a chain hydrocarbon group having 1 to 10 carbon atoms, a group having the above-mentioned divalent heteroatom-containing linking group between carbon atoms of the chain hydrocarbon group, a group in which some or all of the hydrogen atoms of the chain hydrocarbon group have been substituted with the above-mentioned monovalent heteroatom-containing substituent, or a combination thereof can be suitably used in addition to or in place of the group corresponding to 1 to 10 carbon atoms among the monovalent cyclic organic groups having 1 to 40 carbon atoms shown in A of the formula (1).

[0086] p is preferably an integer of 0 to 2, and more preferably 0 or 1.

[0087] Specific examples of the structural unit (I) are not particularly limited, but include structures represented by the following formulae (2-1) to (2-34).

[0088]

[0089]

[0090] 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 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of the content is preferably 70 mol%, more preferably 65 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (I) within the above range, it is possible to improve solubility in an alkaline developer and further reduce pattern roughness.

[0091] [Structural Unit (II)] The structural unit (II) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates by the action of an acid. The radiation-sensitive composition has excellent pattern formability due to the polymer having the structural unit (II).

[0092] The structural unit (II) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (3) (hereinafter, also referred to as "structural unit (II-1)") is preferred:

[0093]

[0094] 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 hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ COO- or ＊-COOL １１ａ represents COO-. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0095] The above R １７ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (II-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0096] 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. １１ａ As the alkyl group, a methylene group or an ethanediyl group is preferred.

[0097] 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.

[0098] L １１ａ Examples of the substituent that the arenediyl group represented by the formula (I) may have include 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, and an alkoxy group.

[0099] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a 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.

[0100] The above R １８ ~R ２０ Examples of the chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0101] The above R １８ ~R２０ As the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by A in the formula (1) can be suitably used.

[0102] The above R １８ As the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1), the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by A in the formula (1) can be suitably used.

[0103] 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.

[0104] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining chain hydrocarbon groups or alicyclic hydrocarbon groups represented by the formula (I) together with the carbon atoms to which they are bonded, is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. Note that a fused alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed in such a way that multiple alicyclic rings share a side (a bond between two adjacent carbon atoms).

[0105] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７]decane-2,2-diyl group (adamantane-2,2-diyl group), tricyclo[5.2.1.0 ２，６ ] A decane-8,8-diyl group is preferred.

[0106] Among these, R １８ is an alkyl 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.

[0107] Examples of the structural unit (II-1) include structural units represented by the following formulas (3-1) to (3-15) (hereinafter also referred to as "structural units (II-1-1) to (II-1-15)").

[0108]

[0109]

[0110] In the above formulas (3-1) to (3-7), R １７ ~R ２０ has the same meaning as in formula (3). Ｌ１１ is 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 each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other. a4 is an integer of 1 to 3.

[0111] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, an ethenyl 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 By employing an iodine atom as the aryl group, an iodine group can be suitably introduced into the structural unit (II).

[0112] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (II).

[0113]

[0114] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer of 1 to 4.

[0115] The above R βｆ is preferably a hydrogen atom, a methyl group or an ethyl group. h1 is preferably 1 or 2.

[0116] The base polymer may contain one type of structural unit (II) or a combination of two or more types.

[0117] 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 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of this content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By ensuring that the content of the structural unit (II) falls within this range, the pattern formability of the radiation-sensitive composition can be further improved.

[0118] [Structural Unit (III)] The structural unit (III) is a structural unit containing at least one selected from the group consisting of a polycyclic lactone structure, a polycyclic carbonate structure, and a polycyclic sultone structure. The structural unit (III) is any structural unit. By including the structural unit (III), the base polymer can adjust the solubility in a developer and improve the etching resistance of the resist film.

[0119] Examples of the structural unit (III) include structural units represented by the following formulae (T-1) to (T-6).

[0120]

[0121] In the above formula, R Ｌ１is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｌ２ ~R Ｌ３ 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, or a dimethylamino group. ２ is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3.

[0122] The above L ２ As the divalent linking group represented by the formula (2), the divalent linking group represented by L in the formula (2) can be suitably used.

[0123] Of these, the structural unit (III) 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.

[0124] When the base polymer contains the structural unit (III), the lower limit of the content of the structural unit (III) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 45 mol%. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0125] [Structural Unit (IV)] The structural unit (IV) is a structural unit containing a polar group (excluding those corresponding to the structural unit (III)). The structural unit (IV) is an arbitrary structural unit. By further including the structural unit (IV), 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.

[0126] Examples of the structural unit (IV) include structural units represented by the following formula:

[0127]

[0128] In the above formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0129] When the base polymer has the structural unit (IV) having the polar group, the lower limit of the content of the structural unit (IV) is preferably 5 mol%, more preferably 8 mol%, and even more preferably 10 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (IV) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0130] [Structural Unit (V)] In addition to the structural unit (IV) having the polar group, the base polymer optionally has a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (V)") as another structural unit. The structural unit (V) contributes to improving etching resistance and improving the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, it is suitable for pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In this case, it is preferable that the polymer has structural units (I) and (II) in addition to the structural unit (V).

[0131] The structural unit having a phenolic hydroxyl group is represented by, for example, the following formulas (4-1) and (4-2).

[0132]

[0133] In the above formulas (4-1) to (4-2), R ４１are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Y is a halogen atom, a trifluoromethyl group, a cyano group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or an acyl group, acyloxy group, or alkoxycarbonyl group having 2 to 7 carbon atoms. When there are multiple Ys, the multiple Ys may be the same or different. t is an integer of 0 to 4.

[0134] 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 through hydrolysis. The corresponding monomer may also be polymerized without protecting the phenolic hydroxyl group.

[0135] In the case of a polymer for exposure to radiation having a wavelength of 50 nm or less, the lower limit of the content of the structural unit (V) is preferably 10 mol %, more preferably 20 mol %, based on all structural units constituting the polymer, and the upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0136] [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 (VIII)") 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.

[0137] In the above formula (6), R ２α As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by A in the formula (1) can be suitably used.

[0138] When the base polymer contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 2 mol%, more preferably 5 mol%, and even more preferably 8 mol%, based on the total structural units constituting the base polymer, and the upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%.

[0139] (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.

[0140] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred. These radical initiators can be used alone or in combination of two or more.

[0141] Examples of the solvent used in the polymerization include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; ketones such as acetone, 2-butanone (methyl ethyl ketone), 4-methyl-2-pentanone, 2-heptanone, and cyclohexanone; Examples of the solvent include ethers such as tetrahydrofuran, dimethoxyethanes, diethoxyethanes, and 1,4-dioxane; alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol, and 1-methoxy-2-propanol; and lactones such as γ-butyrolactone. These solvents used in the polymerization may be used alone or in combination of two or more.

[0142] 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.

[0143] 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 25,000, more preferably 15,000, and even more preferably 10,000. When the Mw of the base polymer is within the above range, the resulting resist film can have good heat resistance and developability.

[0144] 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.

[0145] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0146] 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

[0147] The content of the base polymer is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total solid content of the radiation-sensitive composition.

[0148] (Other Polymers) The radiation-sensitive composition of this embodiment may contain, as the other 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 improve 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 the composition within the film. The radiation-sensitive composition may contain one or more high-fluorine-content polymers.

[0149] The high-fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VI)").

[0150]

[0151] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌrepresents 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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 group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0157] When the high-fluorine content polymer has the structural unit (VI), the lower limit of the content of the structural unit (VI) 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. As a result, the water repellency of the surface of the resist film during immersion exposure can be improved, and the surface modification of the resist film during EUV exposure and the distribution of the composition within the film can be controlled to a sufficient level.

[0158] 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 (VII)) in addition to or instead of the structural unit (VI). 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.

[0159]

[0160] The structural unit (VII) 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 simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ At the end of the side, there is an oxygen atom, a sulfur atom, and -NR ｄｄ R has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0161] When the structural unit (VII) has (x) an alkali-soluble group, R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VII) has (x) an alkali-soluble group, it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VII) having (x) an alkali-soluble group, 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.

[0162] When the structural unit (VII) has (y) an alkali-dissociable group, R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A１ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VII) has (y) an alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit (VII) having (y) an alkali-dissociable group, A １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0163] R Ｃ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0164] R Ｅ When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and more preferably a group having a norbornane lactone structure.

[0165] When the high-fluorine-content polymer has the structural unit (VII), the content of the structural unit (VII) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 55 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content is preferably 90 mol%, more preferably 85 mol%, and even more preferably 80 mol%. By setting the content of the structural unit (VII) within the above range, the water repellency and surface modifiability of the resist film can be improved, and the solubility in an alkaline developer can be improved, thereby efficiently suppressing the occurrence of development defects.

[0166] [Other Structural Units] The high fluorine content polymer may contain, as structural units other than the structural units listed above, the structural unit (II) or the structural unit (IV) in the base polymer, or the structural unit (VIII).

[0167] When the high-fluorine content polymer contains the structural unit (II), the lower limit of the content of the structural unit (II) is preferably 2 mol %, more preferably 5 mol %, and even more preferably 8 mol %, based on all structural units constituting the high-fluorine content polymer, and the upper limit of the content is preferably 40 mol %, more preferably 30 mol %, and even more preferably 25 mol %.

[0168] When the high-fluorine content polymer contains the structural unit (IV), the lower limit of the content of the structural unit (IV) is preferably 5 mol %, more preferably 10 mol %, and even more preferably 15 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 %, and even more preferably 35 mol %.

[0169] When the high-fluorine content polymer contains the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 10 mol %, more preferably 20 mol %, and even 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 %, and even more preferably 45 mol %.

[0170] The lower limit of Mw of the high fluorine content polymer is preferably 2,000, more preferably 4,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 12,000, and even more preferably 8,000.

[0171] 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.

[0172] 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 2 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 or less, more preferably 10 parts by mass or less, and even more preferably 6 parts by mass or less.

[0173] (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.

[0174] (Acid Diffusion Controller) The radiation-sensitive composition may contain an acid diffusion controller, if necessary. The acid diffusion controller controls the diffusion phenomenon in the resist film of the acid generated from the onium salt compound upon exposure, thereby suppressing undesirable chemical reactions in unexposed areas. The storage stability of the resulting radiation-sensitive composition is also improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the incubation time from exposure to development can be suppressed, resulting in a radiation-sensitive composition with excellent process stability.

[0175] As the acid diffusion controller, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used. The acid generated by the radiation-sensitive weak acid generator is a weak acid that does not induce dissociation of the acid-dissociable group in the polymer under conditions that dissociate the acid-dissociable group. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

[0176] Examples of the radiation-sensitive weak acid generator include onium salt compounds that decompose upon exposure to light and lose their ability to control acid diffusion. Examples of the onium salt compound include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2). Other examples include compounds containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and compounds containing an iodonium cation and anion in the same molecule represented by the following formula (8-4).

[0177]

[0178] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. ＋ Examples of the sulfonium cation represented by the formula (X-1) to (X-4) include sulfonium cations represented by the formula (X-1) to (X-4), and U ＋ Examples of the iodonium cation represented by the formula (X-5) to (X-6) include the iodonium cation represented by the formula (X-6). － and Q － are each independently OH － , R α -COO － , R α -SO ３ － It is an anion represented by R α is a single bond or a monovalent organic group having 1 to 30 carbon atoms. The monovalent organic group having 1 to 30 carbon atoms includes R １１ A group in which the monovalent organic group having 1 to 10 carbon atoms represented by the following formula (I) is extended to have 1 to 30 carbon atoms can be suitably used.

[0179] Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula:

[0180]

[0181]

[0182]

[0183]

[0184] Of these, the radiation-sensitive weak acid generator is preferably a sulfonium salt, more preferably a triarylsulfonium salt, and even more preferably an onium salt of a triarylsulfonium and a salicylic acid anion which may have a substituent, an onium salt of a triarylsulfonium and a benzoic acid anion which may have a substituent, an onium salt of a triarylsulfonium and a difluorocarboxylic acid anion which may have a substituent, an onium salt of a triarylsulfonium and a dicarboxylic acid monoanion which may have a substituent, an onium salt of a triarylsulfonium and an adamantanecarboxylic acid anion which may have a substituent, and triarylsulfonium 10-camphorsulfonate.

[0185] The lower limit of the content of the acid diffusion controller is preferably 0.5 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 polymer. The upper limit of the content is preferably 30 parts by mass, more preferably 20 parts by mass, and even more preferably 15 parts by mass. By setting the content of the acid diffusion controller within the above range, the lithography performance of the radiation-sensitive composition can be further improved. The radiation-sensitive composition may contain one or more types of acid diffusion controllers.

[0186] (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, the base polymer, and any optional components that may be contained as desired.

[0187] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0188] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 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 polyhydric alcohol-based solvents, such as 3-methoxybutanol and 1-methoxy-2-propanol (propylene glycol monomethyl ether), have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0189] 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.

[0190] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0191] 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.

[0192] 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.

[0193] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0194] Among these, alcohol-based solvents, ester-based solvents, and ether-based solvents are preferred, alcohol acid ester-based solvents, polyhydric alcohol partial ether acetate-based solvents, lactone-based solvents, and polyhydric alcohol partial ether-based solvents are more preferred, and propylene glycol monomethyl ether acetate, γ-butyrolactone, ethyl lactate, and propylene glycol monomethyl ether are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0195] (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 known radiation-sensitive acid generators other than onium salt compounds, crosslinking agents, uneven distribution promoters, surfactants, alicyclic skeleton-containing compounds, and sensitizers. These other optional components may be used alone or in combination of two or more.

[0196] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing an onium salt compound, a polymer, and, if necessary, optional components such as 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% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0197] <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 onto a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film (hereinafter also referred to as a "development step").

[0198] According to the above-described resist pattern forming method, a high-quality resist pattern can be formed because the above-described radiation-sensitive composition is used, which is capable of forming a resist film that is excellent in sensitivity, LWR performance, pattern rectangularity, CDU performance, pattern circularity, and exposure latitude. Each step will be described below.

[0199] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (PB) may be performed to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 150°C, and preferably 80°C to 140°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0200] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure step described below, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0201] 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 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.

[0202] Furthermore, when the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural units (I), (II) and (V) as the base polymer in the composition.

[0203] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is exposed by irradiating it with 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, and ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred.

[0204] 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.

[0205] 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 140°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0206] [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.

[0207] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0208] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0209] 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.

[0210] 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).

[0211] <Onium Salt Compound> The onium salt compound is a compound represented by the following formula (1-d). (In the above formula (1-d), W １ and W ２ are each independently a substituted or unsubstituted cyclic structure. Ｑ is a single bond, ＊ -OCO- or ＊-O-CO-O-. * indicates W １ It is a bond on the R side. ｆ１ and R ｆ２ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ If there are multiple R ｆ１ and R ｆ２ are the same or different, provided that R ｆ１ and R ｆ２ At least one of the groups is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer of 1 to 4. n is an integer of 1 to 3. Z １ ＋ is a monovalent radiation-sensitive onium cation.

[0212] As the onium salt compound, the onium salt compound represented by the formula (1-d) in the radiation-sensitive composition can be suitably used.

[0213] Specific examples of the anion structure of the onium salt compound represented by the above formula (1-d) include compounds represented by the following formulas.

[0214]

[0215]

[0216] Z １ ＋ Specific examples of the monovalent radiation-sensitive onium cation represented by the formula (1) include Z ＋ The structures shown as specific examples of the monovalent radiation-sensitive onium cation represented by the following formula can be suitably employed.

[0217] 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.

[0218] [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.

[0219] [ 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.).

[0220] <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 %.

[0221]

[0222] Synthesis Example 1 Synthesis of Polymer (A-1) Monomer (M-1), monomer (M-10), monomer (M-12), monomer (M-16), and monomer (M-17) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 35 / 40 / 10 / 10 / 5 (mol %), and MAIB (dimethyl-2,2-azobisisobutyrate) (7 mol % relative to 100 mol % of the total monomers used) 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 polymerized 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: 85%). The Mw of the polymer (A-1) was 5,500, and the Mw / Mn was 1.56. １３ As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-10), (M-12), (M-16) and (M-17) were 35.1 mol%, 40.3 mol%, 9.2 mol%, 10.7 mol% and 4.7 mol%, respectively.

[0223] [Synthesis Examples 2 to 12, 101 to 102] (Synthesis of Polymer (A-2) to Polymer (A-12) and Polymer (A-101) to Polymer (A-102)) Polymers (A-2) to (A-12) and Polymer (A-101) to (A-102) 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 obtained 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).

[0224]

[0225] (Synthesis of Polymer (A-13)) Monomer (M-1), monomer (M-10), and monomer (M-21) were dissolved in 1-methoxy-2-propanol (200 parts by mass) so that the molar ratio was 5 / 50 / 45 (mol %), and MAIB (dimethyl-2,2-azobisisobutyrate) (7 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 separated by filtration. The white powder collected by filtration was washed twice with hexane, filtered, and then 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 collected by filtration and dried at 50°C for 13 hours to obtain a white powdery polymer (A-13) (yield: 81%). The Mw of the polymer (A-13) was 5,500, and the Mw / Mn was 1.62. １３As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-10) and (M-21) were 5.2 mol %, 50.2 mol % and 44.6 mol %, respectively.

[0226] [Synthesis Examples 14 to 17, 103] (Synthesis of polymers (A-14) to (A-17) and polymer (A-103)) Polymers (A-14) to (A-17) and polymer (A-103) were synthesized in the same manner as in Synthesis Example 13, 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.

[0227]

[0228] Synthesis Example 18 Synthesis of High Fluorine Content Polymer (F-1) Monomer (M-10) and monomer (M-23) were dissolved in 2-butanone (200 parts by mass) to give a molar ratio of 20 / 80 (mol %), and AIBN (4 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 polymerized solution was cooled with water to 30°C or below. 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 procedure 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: 75%). The high fluorine content polymer (F-1) had an Mw of 6,200 and an Mw / Mn ratio of 1.77. １３ As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-20) were 19.5 mol % and 80.5 mol %, respectively.

[0229] [Synthesis Examples 19 to 22, 104] (Synthesis of high fluorine content polymer (F-2) to high fluorine content polymer (F-5) and high fluorine content polymer (F-101)) High fluorine content polymer (F-2) to high fluorine content polymer (F-5) and high fluorine content polymer (F-101) were synthesized in the same manner as in Synthesis Example 18, except that the types and blending ratios of monomers shown in Table 3 below were used. 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.

[0230]

[0231] <Synthesis of Onium Salt Compound B> [Synthesis Example 23] (Synthesis of Onium Salt Compound (B-1)) Onium salt compound (B-1) as a radiation-sensitive acid generator was synthesized according to the following synthesis scheme.

[0232]

[0233] 20.0 mmol of 3-hydroxy-1-adamantanecarboxylic acid, 20.0 mmol of chloromethyl methyl ether, 20.0 mmol of triethylamine, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 13 hours. After dilution with water, the mixture was extracted with dichloromethane 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 with sodium sulfate, the solvent was distilled off and the mixture was purified by column chromatography to obtain a carboxylic acid protected product in good yield.

[0234] To the above-mentioned carboxylic acid protected compound, 20.0 mmol of the onium salt compound (B-1-a) represented by the above formula (B-1-a), 20.0 mmol of 1,1-carbonyldiimidazole, 20.0 mmol of pyridine, and 50 g of acetonitrile were added, and the mixture was stirred at 50°C for 10 hours. Thereafter, water was added to terminate the reaction, and then dichloromethane was added for extraction, and the organic layer was separated. The obtained 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 residue was purified by column chromatography, yielding the carboxylic acid protected compound onium salt in good yield.

[0235] 50 g of 1 M hydrochloric acid and 50 g of acetonitrile were added to the above-mentioned carboxylic acid-protected onium salt, and the mixture was stirred at room temperature for 24 hours. After dilution with water, the mixture was extracted with dichloromethane 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 with sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the onium salt compound (B-1) represented by the above formula (B-1) in good yield.

[0236] Synthesis Examples 24 to 31 Synthesis of onium salt compounds (B-2) to (B-9) and (B-17) to (B-18) Onium salt compounds (B-2) to (B-9) and (B-17) to (B-18) represented by the following formulas (B-2) to (B-9) and (B-17) to (B-18) were synthesized in the same manner as in Synthesis Example 23, except that the raw materials and precursors were changed as appropriate.

[0237]

[0238]

[0239] Synthesis Example 32 Synthesis of Onium Salt Compound (B-10) Onium salt compound (B-10) was synthesized according to the following synthesis scheme.

[0240]

[0241] 20.0 mmol of 4-bromo-3,3,4,4-tetrafluoro-1-butene, 20.0 mmol of cyclopentadiene, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 3 hours. After that, water was added for dilution, and dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was washed with a saturated aqueous sodium chloride solution and then with water. After drying with sodium sulfate, the solvent was distilled off, and the olefin was obtained in good yield by purifying by column chromatography.

[0242] To the olefin, 40.0 mmol of potassium permanganate and 50 g of acetonitrile were added, followed by stirring at 50°C for 10 hours. Subsequently, a saturated aqueous solution of sodium thiosulfate was added to terminate the reaction, followed by extraction with ethyl acetate and separation of the organic layer. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the diol in good yield.

[0243] To the diol product, 20.0 mmol of 4-acetylbenzoic acid, 2.00 mmol of sulfuric acid, and 50 g of dichloromethane were added, followed by stirring at room temperature for 24 hours. After dilution with water, the mixture was extracted with ethyl acetate 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 with sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain an acetal product in good yield.

[0244] A mixture of acetonitrile and water (1:1 (mass ratio)) was added to the above acetal product to prepare a 1 M solution, and then 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added and reacted at 70°C for 4 hours. After extraction with acetonitrile and distillation of the solvent, a mixture of acetonitrile and water (3:1 (mass ratio)) was added to prepare a 0.5 M solution. 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. A sodium sulfonate salt compound was obtained by extraction with acetonitrile and distillation of the solvent. 20.0 mmol of triphenylsulfonium bromide was added to the above sodium sulfonate salt compound, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare a 0.5 M solution. After vigorously stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the onium salt compound (B-10) represented by the above formula (B-10) in good yield.

[0245] Synthesis Examples 33 to 36 Synthesis of onium salt compounds (B-11) to (B-14) Onium salt compounds (B-11) to (B-14) represented by the following formulas (B-11) to (B-14) were synthesized in the same manner as in Synthesis Example 23, except that the raw materials and precursors were changed as appropriate.

[0246]

[0247] Synthesis Example 37 Synthesis of Onium Salt Compound (B-15) Onium salt compound (B-15) was synthesized according to the following synthesis scheme.

[0248]

[0249] 20.0 mmol of 4-bromo-3,3,4,4-tetrafluoro-1-butene, 40.0 mmol of potassium permanganate, and 50 g of acetonitrile were added to a reaction vessel and stirred at 50°C for 10 hours. Thereafter, a saturated aqueous solution of sodium thiosulfate was added to terminate the reaction, and then ethyl acetate was added for extraction and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off and the mixture was purified by column chromatography to obtain the diol form in good yield.

[0250] To the diol product, 20.0 mmol of cyclohexanone-4-carboxylic acid, 2.00 mmol of sulfuric acid, and 50 g of dichloromethane were added, followed by stirring at room temperature for 24 hours. After dilution with water, the mixture was extracted with ethyl acetate 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 with sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain an acetal product in good yield.

[0251] A mixture of acetonitrile and water (1:1 (mass ratio)) was added to the above acetal product to prepare a 1 M solution, and then 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate were added and reacted at 70°C for 4 hours. After extraction with acetonitrile and distillation of the solvent, a mixture of acetonitrile and water (3:1 (mass ratio)) was added to prepare a 0.5 M solution. 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. A sodium sulfonate salt compound was obtained by extraction with acetonitrile and distillation of the solvent. 20.0 mmol of triphenylsulfonium bromide was added to the above sodium sulfonate salt compound, and a mixture of water and dichloromethane (1:3 (mass ratio)) was added to prepare a 0.5 M solution. After vigorously stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the residue was purified by column chromatography to obtain the onium salt compound (B-15) represented by the above formula (B-15) in good yield.

[0252] Synthesis Example 38 Synthesis of Onium Salt Compound (B-16) An onium salt compound (B-16) represented by the following formula (B-16) was synthesized in the same manner as in Synthesis Example 37, except that the raw materials and precursors were appropriately changed.

[0253]

[0254] Example B1 Synthesis of Onium Salt Compound (B-19) Onium salt compound (B-19) was synthesized according to the following synthesis scheme.

[0255]

[0256] To a reaction vessel, 20.0 mmol of compound (B-19-a), 20.0 mmol of chloromethyl methyl ether, 20.0 mmol of triethylamine, and 50 g of dichloromethane were added, and the mixture was stirred at room temperature for 13 hours. After that, water was added for dilution, and then dichloromethane was added 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 with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain compound (B-19-b) in good yield.

[0257] 20.0 mmol of the onium salt compound (B-1) represented by the above formula (B-1), 20.0 mmol of oxalyl chloride, and 50 g of acetonitrile were added to a reaction vessel and stirred at 50°C for 2 hours. Subsequently, 30.0 mmol of compound (B-19-b), 30.0 mmol of pyridine, and 3.0 mmol of 4-dimethylaminopyridine were added and stirred at 100°C for 10 hours. Water was then added to terminate the reaction, followed by extraction with dichloromethane and separation of the organic layer. 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 residue was purified by column chromatography to obtain the onium salt compound (B-19-c) in good yield.

[0258] 50 g of 1 M hydrochloric acid and 50 g of acetonitrile were added to the onium salt compound (B-19-c) represented by the above formula (B-19-c), and the mixture was stirred at 100°C for 3 hours. After dilution with water, the mixture was extracted with dichloromethane 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 with sodium sulfate, the solvent was distilled off, and the mixture was purified by column chromatography to obtain the onium salt compound (B-19) represented by the above formula (B-19) in good yield.

[0259] Examples B2 to B5 Synthesis of onium salt compounds (B-20) to (B-23) Onium salt compounds (B-20) to (B-23) represented by the following formulas (B-20) to (B-23) were synthesized in the same manner as in Example B1, except that the raw materials and precursors were appropriately changed.

[0260]

[0261] The following compounds were used as components other than the components synthesized above.

[0262] [Radiation-sensitive acid generators other than onium salt compounds (B-1) to (B-23)] b-1 to b-15: compounds represented by the following formulas (b-1) to (b-15) (hereinafter, the compounds represented by formulas (b-1) to (b-15) may be referred to as "compound (b-1)" to "compound (b-15)," respectively).

[0263]

[0264]

[0265] [[D] Acid Diffusion Controller] D-1 to D-12: Compounds represented by the following formulas (D-1) to (D-12).

[0266]

[0267] [[E] Solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-butyrolactone E-4: Ethyl lactate E-5: Diacetone alcohol E-6: Methyl 2-hydroxyisobutyrate

[0268] [Preparation of positive-tone radiation-sensitive composition for ArF immersion exposure] [Example 1] 100 parts by mass of [A] polymer (A-1), 10.0 parts by mass of [B] onium salt compound (B-1), 4.0 parts by mass of [D] acid diffusion controller (D-1), 5.0 parts by mass (solids content) of [F] high-fluorine polymer (F-1), and 3,400 parts by mass of [E] solvent mixed solvent of (E-1) / (E-2) / (E-3), were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare radiation-sensitive composition (J-1).

[0269] [Examples 2 to 47, 101 to 110 and Comparative Examples 1 to 5, 21 to 25] Radiation-sensitive compositions (J-2) to (J-47), (J-101) to (J-110), (CJ-1) to (CJ-5), and (CJ-21) to (CJ-25) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 4 below were used.

[0270]

[0271] <Formation of Resist Pattern Using Positive Radiation-Sensitive Composition for ArF Immersion Exposure> A composition for forming a bottom antireflective 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 antireflective coating with an average thickness of 100 nm. The positive radiation-sensitive composition for ArF immersion 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 160 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 of 80 nm holes and 150 nm pitch contact holes. After exposure, a 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% aqueous TMAH solution as an alkaline developer, and after development, it was washed with water and further dried to form a positive resist pattern (contact hole pattern of 80 nm holes and 150 nm pitch).

[0272] <Evaluation> The resist patterns formed using the above-described positive-working radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity, CDU performance, pattern circularity, and the number of development defects according to the methods described below. The results are shown in Table 5. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0273] [Sensitivity] In forming a resist pattern using the positive radiation-sensitive composition for ArF immersion exposure, the exposure dose required to form 80 nm holes and contact holes with a pitch of 150 nm was defined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm ２ The sensitivity was 30 mJ / cm ２The cases below are "good" and 30 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0274] [CDU Performance] Contact holes with 80 nm holes and a 150 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 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. The CDU performance was evaluated as "good" when it was less than 3.0 nm, and as "poor" when it was 3.0 nm or more.

[0275] [Pattern Circularity] The 80 nm holes and 150 nm pitch contact holes formed by irradiation with the optimum exposure dose determined in the above sensitivity evaluation were observed using the above scanning electron microscope to measure their vertical and horizontal sizes. If the ratio of the vertical size to the horizontal size (aspect ratio) was 0.95 or more and less than 1.05, the result was evaluated as "A" (very good); if it was 0.90 or more and less than 0.95, or 1.05 or more and less than 1.10, the result was evaluated as "B" (good); and if it was less than 0.90 or 1.10 or more, the result was evaluated as "C" (poor).

[0276] [Number of Development Defects] A resist film was exposed to an optimum exposure dose to form a contact hole pattern with 80 nm holes and a 150 nm pitch, which was used as a wafer for defect inspection. The number of defects on this wafer for defect inspection was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 nm or less were determined to be derived from the resist film, and the number of defects was calculated. After development, the number of defects determined to be derived from the resist film was evaluated as "good" when the number of defects was 50 or less, and as "poor" when the number of defects was more than 50.

[0277] [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 hole diameters of each were measured using the scanning electron microscope. From the relationship between the obtained hole diameter and exposure dose, the exposure dose E(88) at which the hole diameter was 88 nm and the exposure dose E(72) at which the hole diameter was 72 nm were determined, and the exposure latitude (%) was calculated using the formula: exposure latitude (EL) = (E(72) - E(88)) x 100 / (optimum exposure dose). The larger the exposure latitude value, the smaller the fluctuation in the dimensions of the pattern obtained when the exposure dose fluctuates, and the higher the yield during device fabrication. EL was evaluated as "good" when it was 10% or more, and as "poor" when it was below 10%.

[0278]

[0279] As is clear from the results in Table 5, when the radiation-sensitive compositions of the Examples were used for ArF exposure, the sensitivity, CDU performance, pattern circularity, development defect suppression, and EL were good, whereas the Comparative Examples were inferior in each property to the Examples. Therefore, when the radiation-sensitive compositions of the Examples are used for ArF exposure, resist patterns with high sensitivity and good CDU performance, pattern circularity, development defect suppression, and EL can be formed.

[0280] [Preparation of negative radiation-sensitive composition for ArF immersion exposure] [Example 48] 100 parts by mass of [A] polymer (A-1), 6.0 parts by mass of [B] onium salt compound (B-1), 3.0 parts by mass of [D] acid diffusion controller (D-2), 3.0 parts by mass of [F] high fluorine content polymer (F-3) (solids content), and 3,230 parts by mass of [E] solvent mixed solvent of (E-1) / (E-2) / (E-3), were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare radiation-sensitive composition (J-48).

[0281] Examples 49 to 61 and Comparative Examples 6 to 10 Radiation-sensitive compositions (J-49) to (J-61) and (CJ-6) to (CJ-10) were prepared in the same manner as in Example 48, except that the types and amounts of each component shown in Table 6 below were used.

[0282]

[0283] <Formation of Resist Pattern Using Negative 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 having an average thickness of 100 nm. The negative radiation-sensitive composition for ArF immersion exposure prepared above was applied to this bottom antireflective coating using the spin coater, and prebaked at 100°C for 60 seconds. The coating was then cooled at 23°C for 30 seconds to form a resist film having an average thickness of 90 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 dipole (σ = 0.9 / 0.7) through a mask pattern with 40 nm holes and a 105 nm pitch. After exposure, a post-exposure bake (PEB) was performed at 100°C for 60 seconds. Thereafter, the resist film was developed using n-butyl acetate as an organic solvent developer, and dried to form a negative resist pattern (40 nm holes, 105 nm pitch).

[0284] <Evaluation> The resist patterns formed using the above-described negative radiation-sensitive composition for ArF immersion exposure were evaluated for sensitivity, CDU performance, and depth of focus 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).

[0285] [Sensitivity] In forming a resist pattern using the negative radiation-sensitive composition for ArF immersion exposure, the exposure dose required to form a resist pattern with 40 nm holes and a 105 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 25 mJ / cm ２ The following cases are considered "good" and 25 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0286] [CDU Performance] A total of 1,800 resist patterns with 40 nm holes and a 105 nm pitch were measured at arbitrary points from the top of the pattern using the scanning electron microscope. The dimensional variation (3σ) was determined and used as the CDU performance (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better performance. CDU performance was evaluated as "good" when it was 4.0 nm or less, and "poor" when it exceeded 4.0 nm.

[0287] [Depth of Focus] In the resist pattern resolved at the optimum exposure dose determined in the above sensitivity evaluation, the dimensions were observed when the focus was changed in the depth direction, and the margin in the depth direction where the pattern dimensions were 90% to 110% of the standard without bridges or residues was measured, and this measured value was taken as the depth of focus (nm). The larger the value of the depth of focus, the better. A depth of focus of 70 nm or more can be evaluated as "good," and a depth of focus of less than 70 nm can be evaluated as "poor."

[0288]

[0289] As is clear from the results in Table 7, when the radiation-sensitive compositions of the Examples were used for ArF exposure, they exhibited good sensitivity, CDU performance, and depth of focus, whereas the Comparative Examples were inferior in each property to the Examples. Therefore, when the radiation-sensitive compositions of the Examples were used for ArF exposure, resist patterns with optimal sensitivity, good CDU performance, and depth of focus could be formed.

[0290] [Preparation of Positive Radiation-Sensitive Composition for Extreme Ultraviolet (EUV) Exposure] [Example 62] [A] 100 parts by mass of (A-13) as a polymer, [B] 20.0 parts by mass of (B-1) as an onium salt compound, [D] 10.0 parts by mass of (D-1) as an acid diffusion controller, [F] 3.0 parts by mass (solids content) of (F-5) as a high fluorine content polymer, and [E] 6,100 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-4) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-62).

[0291] [Examples 63 to 72, 111 to 117 and Comparative Examples 11 to 15, 26 to 27] Radiation-sensitive compositions (J-63) to (J-72), (J-111) to (J-117), (CJ-11) to (CJ-15), and (CJ-26) to (CJ-27) were prepared in the same manner as in Example 62, except that the types and amounts of each component shown in Table 8 below were used.

[0292]

[0293] <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 55 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 (15 nm line and space pattern).

[0294] <Evaluation> The resist patterns formed using the above-described positive radiation-sensitive composition for EUV exposure were evaluated for sensitivity, LWR performance, and pattern rectangularity according to the methods described below. The results are shown in Table 9. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0295] [Sensitivity] In forming a resist pattern using the positive-working radiation-sensitive composition for EUV exposure, the exposure dose required to form a 20 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The sensitivity was 35 mJ / cm ２ The following cases are considered "good" and 35 mJ / cm ２ If it exceeded this, it was rated as "poor".

[0296] [LWR Performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 15 nm line-and-space pattern. 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. This 3 sigma value was defined as the LWR (nm). The smaller the LWR value, the smaller the line chatter and the better the result. The LWR performance was evaluated as "good" when it was 2.5 nm or less, and as "poor" when it exceeded 2.5 nm.

[0297] [Pattern rectangularity] A 15 nm line-and-space resist pattern 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-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the length of the bottom side to the length of the top side in the cross-sectional shape was 1.00 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.

[0298] [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 ２A resist pattern was formed at each exposure dose, and the line width of each was measured using the scanning electron microscope. From the relationship between the obtained line width and exposure dose, the exposure dose E(16.5) at which the line width was 16.5 nm and the exposure dose E(13.5) at which the line width was 13.5 nm were determined, and the exposure latitude (%) was calculated using the formula: exposure latitude (EL) = (E(13.5) - E(16.5)) x 100 / (optimum exposure dose). The larger the exposure latitude value, the smaller the fluctuation in the dimension of the pattern obtained when the exposure dose fluctuates, and the higher the yield during device fabrication can be. EL was evaluated as "good" when it was 7% or more, and as "poor" when it was below 7%.

[0299]

[0300] As is clear from the results in Table 9, when the radiation-sensitive compositions of the Examples were used for EUV exposure, the sensitivity, LWR performance, pattern rectangularity, and EL were good, whereas the Comparative Examples were inferior to the Examples in each of the properties.

[0301] [Preparation of Negative Radiation-Sensitive Composition for EUV Exposure, and Formation and Evaluation of Resist Pattern Using This Composition] [Example 73] 100 parts by mass of [A] (A-16) as a polymer, 30.0 parts by mass of [B] (B-12) as an onium salt compound, 10.0 parts by mass of [D] (D-4) as an acid diffusion controller, 5.0 parts by mass (solids content) of [F] (F-5) as a high fluorine content polymer, and 6,110 parts by mass of [E] a mixed solvent of (E-1) / (E-4) (4280 / 1830 parts by mass) as a solvent were mixed and filtered through a membrane filter having a pore size of 0.2 μm, to prepare a radiation-sensitive composition (J-73).

[0302] 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 negative radiation-sensitive composition for EUV exposure (J-73) prepared above was applied to this bottom antireflective 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 55 nm. Next, this resist film was exposed to light using an EUV exposure system ("NXE3300" from ASML) 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 20 nm holes and a 40 nm pitch).

[0303] The resist pattern formed using the negative-tone radiation-sensitive composition for EUV exposure was evaluated in the same manner as the evaluation of the resist pattern formed using the negative-tone radiation-sensitive composition for ArF exposure. As a result, the radiation-sensitive composition of Example 73 was found to have good sensitivity, CDU performance, and depth of focus, even when a negative-tone resist pattern was formed by EUV exposure.

[0304] 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 CDU performance, pattern circularity, development defect suppression, depth of focus, LWR performance, pattern rectangularity, and exposure latitude. Therefore, these can be suitably used in processing processes for semiconductor devices, which are expected to become increasingly 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 (I) represented by the following formula (2); and a solvent. (In formula (1), A is a (1+n)-valent organic group containing a cyclic structure and having 3 to 40 carbon atoms. However, when A contains a linear alkanediyl group, the linear alkanediyl group has 1 or 2 carbon atoms. A does not contain a cyclohexylcarbonyloxy structure. R ｆ１ and R ｆ２ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ When there are multiple R ｆ１ and R ｆ２ are the same or different, provided that R ｆ１ and R ｆ２ At least one of is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer of 1 to 4. m2 is 0 or 1. n is an integer of 1 to 3. Z ＋ is a monovalent radiation-sensitive onium cation, ＋ The number of fluorine atoms in is 8 or less. (In formula (2), R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L is a single bond or a divalent linking group. W is a monocyclic lactone structure, a monocyclic carbonate structure, a monocyclic sultone structure, a monocyclic sulfone structure, or a monocyclic ether structure. R １１ R is a monovalent organic group having 1 to 10 carbon atoms, a cyano group, a nitro group, a hydroxyl group, or an amino group. １１ When there are multiple R １１ are the same or different. p is an integer of 0 to 3. q is 0 or 1.

2. The radiation-sensitive composition according to claim 1, wherein the cyclic structure is an alicyclic hydrocarbon structure, an aromatic hydrocarbon structure, a lactone structure, a sultone structure, a cyclic acetal structure, a cyclic carbonate structure, a cyclic ether structure, or a combination thereof.

3. The radiation-sensitive composition according to claim 1, wherein in the above formula (1), n ​​is 1 or 2.

4. The radiation-sensitive composition according to claim 1, wherein the content of the onium salt compound is from 1 part by mass to 60 parts by mass based on 100 parts by mass of the polymer.

5. The radiation-sensitive composition according to any one of claims 1 to 4, wherein in the above formula (2), W is a monocyclic lactone structure.

6. The radiation-sensitive composition according to any one of claims 1 to 4, wherein in the above formula (2), L is a single bond or a divalent alkanediyl group having 1 to 10 carbon atoms.

7. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the content of the structural unit (I) in all structural units constituting the polymer is 1 mol % or more and 70 mol % or less.

8. Z above ＋ The radiation-sensitive composition according to any one of claims 1 to 4, wherein the monovalent radiation-sensitive onium cation represented by the formula: is a sulfonium cation or an iodonium cation.

9. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the polymer contains a plurality of types of the structural unit (I).

10. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the polymer further comprises a structural unit (II) having an acid-dissociable group.

11. The radiation-sensitive composition according to any one of claims 1 to 4, wherein the polymer further comprises a structural unit containing at least one structure selected from the group consisting of a polycyclic lactone structure, a polycyclic carbonate structure, and a polycyclic sultone structure.

12. The radiation-sensitive composition according to any one of claims 1 to 4, further comprising an acid diffusion controller.

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

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

15. An onium salt compound represented by the following formula (1-d): (In the above formula (1-d), W １ and W ２ Each of L is independently a substituted or unsubstituted cyclic structure. Ｑ is a single bond, ＊ -OCO- or ＊ -O-CO-O-. * is W １ It is a bond on the R side. ｆ１ and R ｆ２ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２ When there are multiple R ｆ１ and R ｆ２ are the same or different, provided that R ｆ１ and R ｆ２ At least one of is a fluorine atom or a monovalent fluorinated hydrocarbon group. m1 is an integer from 1 to 4. n is an integer from 1 to 3. Z １ ＋ is a monovalent radiation-sensitive onium cation.

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