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

Abstract

The purpose of the present invention is to provide a radiation-sensitive composition, pattern formation method, onium salt compound, and polymer that, during pattern formation, can exhibit a sensitivity, CDU, underexposure CDU, and number of development defects at levels equal to or better than conventional levels. The radiation-sensitive composition comprises a solvent (E) and a polymer (A) that contains a structural unit (I) having an acid-dissociable group. The radiation-sensitive composition contains an onium salt compound (P) having an onium cation represented by formula (1) and a prescribed monovalent anion, or the polymer (A) contains a structural unit (II) containing an acid-generating structure that generates an acid upon exposure and has an onium cation represented by formula (1) and an organic acid anion.

Description

Radiation-sensitive compositions, pattern-forming methods, onium salt compounds, and polymers

[0001] The present invention relates to radiation-sensitive compositions, pattern-forming methods, onium salt compounds, and polymers.

[0002] Photolithography, which uses resist compositions, is employed to form fine circuits in semiconductor devices. A typical procedure involves, for example, generating acid by irradiating a resist composition film with radiation through a mask pattern. This acid then acts as a catalyst, creating a difference in the solubility of the polymer in alkaline or organic solvent-based developers between the exposed and unexposed areas, thereby forming a resist pattern on the substrate.

[0003] The above-mentioned photolithography techniques utilize short-wavelength radiation such as ArF excimer lasers, or combine this radiation with liquid immersion lithography to advance pattern miniaturization. As a next-generation technology, efforts are being made to utilize even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet).

[0004] As pattern miniaturization progresses, there is a demand for improved resist performance, such as sensitivity, and development is progressing on photoacid generators and quenchers, which are the main components of resist compositions (Japanese Patent Publication No. 2023-109731, Japanese Patent Publication No. 2018-155902).

[0005] Japanese Patent Publication No. 2023-109731 Japanese Patent Publication No. 2018-155902

[0006] In deploying the above-mentioned next-generation technologies, the resist composition is required to have resist performance equivalent to or better than conventional resists in terms of sensitivity, CDU (Critical Dimension Uniformity), an indicator of hole diameter uniformity, underexposure CDU, and the number of development defects.

[0007] The present invention aims to provide a radiation-sensitive composition, a pattern-forming method, an onium salt compound, and a polymer that can exhibit sensitivity, CDU, underexposure CDU, and development defect count at a level equivalent to or higher than conventional methods during pattern formation.

[0008] The inventors of this invention conducted extensive research to solve this problem and, as a result, found that the above objective can be achieved by adopting the following configuration, thus completing the present invention.

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising a polymer (A) containing an acid-dissociable structural unit (I) and a solvent (E), wherein the radiation-sensitive composition contains an onium salt compound (P) having an onium cation represented by the following formula (1) and a monovalent anion selected from the group consisting of a sulfonic acid anion, a sulfonimide anion, a carboxylic acid anion (excluding a benzoate anion substituted with four or more fluoro groups), a methide anion, and a substituted or unsubstituted phenolate anion, or the polymer (A) contains an onium cation represented by the following formula (1) and an organic acid anion, and comprises a structural unit (II) that includes an acid-generating structure that generates acid upon exposure. (In the above formula (1), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ (Each of these is either identical or different from the others. m1 and m2 are independent integers between 0 and 5.)

[0010] In the radiation-sensitive composition, by introducing the specific onium cation into at least any one of a polymer, an onium salt compound regardless of whether it is a radiation-sensitive acid generator or an acid diffusion control agent (quencher), it is possible to exhibit sensitivity, CDU, under-exposure CDU, and the number of development defects equal to or higher than those of the conventional ones. Although the reason for this is not clear, it is speculated as follows. The specific onium cation is an iodonium cation, which is highly sensitive and highly polar compared to the sulfonium cation that has been commonly used. Since the iodonium cation has one or more iodine groups, the sensitivity can be further increased, the radiation absorption efficiency is increased, and the secondary electron generation efficiency is increased, thereby improving the sensitivity, CDU, and under-exposure CDU. In addition, since the iodonium cation has higher hydrophilicity compared to the triphenylsulfonium cation that has been commonly used, the number of development defects can be suppressed. It is speculated that the above resist performance and the like can be exhibited by these combined actions.

[0011] In another embodiment, the present invention relates to a patterning method including a step of directly or indirectly applying the radiation-sensitive composition described above to a substrate to form a resist film, a step of exposing the resist film, and a step of developing the exposed resist film with a developer.

[0012] In the patterning method, since the radiation-sensitive composition capable of exhibiting excellent sensitivity, CDU, under-exposure CDU, and the number of development defects during patterning is used, a high-quality resist pattern can be efficiently formed.

[0013] In another embodiment, the present invention relates to an onium salt compound represented by the following formula (1'). (In the above formula (1'), Ar １ is an (n1 + m1 + 1)-valent aromatic ring group having 5 to 20 carbon atoms. Ar ２ is an (n2 + m2 + 1)-valent aromatic ring group having 5 to 20 carbon atoms. n1 and n2 are each independently an integer of 0 to 5. However, 1 ≦ n1 + n2 ≦ 10. R １ and R２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ Each of them is either identical or different from the others. m1 and m2 are each independent integers between 0 and 5. １ - This is a monovalent anion selected from the group consisting of sulfonate anions (excluding trifluoromethanesulfonate anions and toluenesulfonate anions), sulfonimide anions, carboxylic acid anions (excluding benzoate anions substituted with four or more fluoro groups), methide anions, and substituted or unsubstituted phenolate anions.

[0014] The onium salt compound in question possesses a specific onium cation and exhibits hydrophilicity and high secondary electron generation efficiency, making it suitable as a radiation-sensitive acid generator or acid diffusion control agent in radiation-sensitive compositions.

[0015] In yet another embodiment, the present invention relates to a polymer comprising a structural unit (I) having an acid-dissociable group, and a structural unit (II) having an onium cation represented by the following formula (1) and an organic acid anion, and including an acid-generating structure that generates acid upon exposure. (In the above formula (1), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R１ and R ２ (Each of these is either identical or different from the others. m1 and m2 are independent integers between 0 and 5.)

[0016] The polymer in question possesses the specific onium cation described above and exhibits hydrophilicity and high secondary electron generation efficiency, making it suitable as a base polymer in radiation-sensitive compositions.

[0017] In this specification, "organic group" means a group having at least one carbon atom (excluding groups that constitute a functional group or characteristic group on their own, such as -CN, -COOH, -CO-, -COO-, -O-CO-O-, etc.).

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

[0019] <<Radiation-sensitive composition>> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "the composition") contains at least a polymer (A) and a solvent (E). The composition contains an onium salt compound (P) having a specific onium cation and a monovalent anion, or the polymer (A) contains a structural unit (II) having a specific onium cation and an organic acid anion, and including an acid-generating structure that generates acid upon exposure. The composition may contain other optional components as long as they do not impair the effects of the present invention. The components included in the radiation-sensitive composition will be described below.

[0020] <Onium salt compound (P)> The radiation-sensitive composition of the present invention may contain an onium salt compound (P). If the polymer (A) contains the structural unit (II) described later, the inclusion of the onium salt compound (P) in the composition is optional.

[0021] The onium salt compound (P) described above has a form in which the onium salt structure exists as a low molecular weight compound on its own (liberated from the polymer), and is different from the acid-generating structure in polymer (A), where the first organic acid anion or first onium cation is bonded (covalently) to the main chain as a side chain structure of the base polymer, as in structural unit (II).

[0022] The onium salt compound (P) described above is a compound that has the onium cation and generates acid upon exposure. Depending on the structure of the organic acid anion, the onium salt compound (P) functions as a radiation-sensitive acid generator or an acid diffusion controller. The radiation-sensitive acid generator is a compound that generates an acid that dissociates the acid-dissociating group upon exposure. The acid diffusion controller is a compound that generates an acid that does not dissociate the acid-dissociating group upon exposure, and has the function of suppressing the diffusion of acid generated from the radiation-sensitive acid generator, etc., in the unexposed area. The acid generated from the acid diffusion controller can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the radiation-sensitive acid generator, etc. Whether the onium salt compound (P) functions as a radiation-sensitive acid generator or an acid diffusion controller depends on the energy required for the dissociation of the acid-dissociating group of the polymer (A) described later, and the acidity of the acid generated upon exposure, etc. First, we will explain the onium cation represented by formula (1) above, which is a common structure for each function. Then, we will explain the case where the onium salt compound (P) functions as a radiation-sensitive acid generator (onium salt compound (P1)) and the case where the onium salt compound (P) functions as an acid diffusion control agent (onium salt compound (P2)).

[0023] (Onium cation represented by formula (1)) The onium cation of the onium salt compound (P) is represented by the following formula (1). (In the above formula (1), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２(Each of these is either identical or different from the others. m1 and m2 are independent integers between 0 and 5.)

[0024] The above Ar １ As an aromatic ring group with 5 to 20 carbon atoms and an (n1 + m1 + 1) valency, a group obtained by removing (n1 + m1 + 1) hydrogen atoms from an aromatic ring with 5 to 20 carbon atoms can be suitably adopted.

[0025] The above Ar ２ As an aromatic ring group with 5 to 20 carbon atoms and an (n² + m² + 1) valency, a group obtained by removing (n² + m² + 1) hydrogen atoms from an aromatic ring with 5 to 20 carbon atoms can be suitably adopted.

[0026] The above Ar １ Ar ２ The aromatic ring in is not particularly limited as long as it has 5 to 20 carbon atoms and is an aromatic ring structure. Examples of aromatic rings include aromatic hydrocarbon rings such as benzene rings, naphthalene rings, anthracene rings, phenalene rings, phenanthrene rings, pyrene rings, fluorene rings, and perylene rings; aromatic heterocycles such as 1,3-benzodioxole rings, pyridine rings, pyrrole rings, benzopyrrole rings, carbazole rings, thiazole rings, benzothiazole rings, thiophene rings, benzothiophene rings, dibenzothiophene rings, furan rings, benzofuran rings, and dibenzofuran rings; or combinations thereof. Among these, Ar １ Ar ２ The aromatic ring in this compound is preferably a benzene ring, a naphthalene ring, or a 1,3-benzodioxole ring, with the benzene ring being more preferred.

[0027] The above values ​​of n1 and n2 are each independent integers from 0 to 5, preferably from 0 to 3, and more preferably n1 is 1 and n2 is an integer from 0 to 3. Furthermore, from the viewpoint of underexposure CDU, it is preferable that n1 and n2 are each independent integers from 1 to 2, and more preferably that both n1 and n2 are 1.

[0028] n1 + n2 is 1 or more and 10 or less, preferably 1 or more and 5 or less, more preferably 2 or more and 5 or less from the viewpoint of sensitivity and solubility, and even more preferably 2 or 3.

[0029] The above R １ and R ２ Other halogen atoms besides the iodine atom represented by include fluorine, chlorine, and bromine atoms, with fluorine being preferred.

[0030] The above R １ and R ２ Examples of monovalent organic groups having 1 to 20 carbon atoms represented by this formula include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups having a divalent heteroatom-containing group between carbon atoms or at the end of the carbon chain of this hydrocarbon group, groups in which some or all of the hydrogen atoms of the hydrocarbon group are replaced with a monovalent heteroatom-containing group, or combinations thereof.

[0031] Examples of the above-mentioned monovalent hydrocarbon groups having 1 to 20 carbon atoms include chain-like hydrocarbon groups having 1 to 20 carbon atoms, monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms, and monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms.

[0032] Examples of the above-mentioned monovalent linear hydrocarbon groups having 1 to 20 carbon atoms include monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms, or monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms. Examples of the above-mentioned monovalent linear or branched saturated hydrocarbon groups having 1 to 20 carbon atoms include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, isopentyl group, and neopentyl group. Examples of the above-mentioned monovalent linear or branched unsaturated hydrocarbon groups having 2 to 20 carbon atoms include alkenyl groups such as ethenyl group, propenyl group, and butenyl group; and alkynyl groups such as ethynyl group, propynyl group, and butynyl group.

[0033] Examples of monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl groups. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl groups. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norborneyl, tricyclodecenyl, and tetracyclododecenyl groups. A bridged alicyclic hydrocarbon group is a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are bonded together by a linking group containing one or more carbon atoms.

[0034] Examples of the monovalent aromatic hydrocarbon groups having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xyl, naphthyl, and anthyl groups; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl groups.

[0035] Examples of heteroatoms that constitute the monovalent heteroatom-containing groups and divalent heteroatom-containing groups mentioned above include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0036] Examples of the monovalent heteroatom-containing groups mentioned above include hydroxyl groups, carboxyl groups, sulfanyl groups, cyano groups, nitro groups, halogen atoms, and the like.

[0037] Examples of the above-mentioned divalent heteroatom-containing groups include -CO-, -C(=O)O-, -CS-, -NH-, -O-, -S-, -SO-, and -SO ２ - or combinations thereof are examples.

[0038] Among these, the above R１ , R ２ Preferably, the group is a fluoro group, a C1-C5 alkyl group, a C1-C5 alkoxy group, an alkylsulfonyl group, or an alkyloxycarbonyl group, and more preferably a fluoro group, a C1-C5 alkyl group, a C1-C5 alkoxy group, or a substituted or unsubstituted alkyloxycarbonyl group.

[0039] m1 and m2 are each independent integers between 0 and 5, preferably between 0 and 3.

[0040] Among the above onium salt compounds (P), from the viewpoint of development defects, n1 + n2 is 1 and Ar １ and Ar ２ A compound in which is a benzene ring, n1 + n2 is 2 or more, m1 + m2 is 1 or more, R １ , R ２ Compounds in which any of the groups are an alkoxy group, an alkylsulfonyl group, a halogen-substituted alkyloxycarbonyl group, or an unsubstituted alkyloxycarbonyl group are preferred. Furthermore, from the viewpoint of sensitivity, it is preferable that n1 + n2 is 2 or more, or m1 + m2 is 2 or more, and R １ , R ２ A compound containing a fluoro group or a fluorinated alkyl group in either of the following is preferred. From the viewpoint of CDU, m1 + m2 is 3 or more, and R １ , R ２ Compounds containing an alkoxy group or an alkyl group in any of the following are preferred.

[0041] While there are no particular limitations on specific examples of the onium cation of the onium salt compound (P), examples include structures (XI-1) to (XI-67) and (XI-69) to (XI-75) represented by the following formulas. In the following formulas, Me represents a methyl group.

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] (Onium salt compound (P1)) As the monovalent anion of the onium salt compound (P1), it is preferably selected from the group consisting of sulfonic acid anions, sulfonimide anions, and methide anions, and more preferably a sulfonic acid anion. Further, it is preferable that an electron-withdrawing group is bonded to the carbon atom at the α-position or β-position of the sulfur atom of the sulfonic acid anion or sulfonimide anion. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, a cyano group, an alkylsulfonyl group, an alkyloxycarbonyl group, etc. As the fluorinated hydrocarbon group, a perfluoroalkyl group having 1 to 5 carbon atoms is preferable, and a trifluoromethyl group is more preferable.

[0048] As the sulfonic acid anion, an anion represented by the following formula (p1) can be preferably employed. (In formula (p1), ６０ R is a monovalent organic group having 1 to 40 carbon atoms. ｆ１ R ｆ２ and R ｆ１ are each independently a hydrogen atom, a cyano group, a nitro group, a fluorine atom, or a monovalent fluorinated hydrocarbon group. When there are a plurality of R ｆ２ and R ｆ１ and R ｆ２ are present, the plurality of R ｆ１ and R ｆ２ are each the same or different. t is an integer from 0 to 4.)

[0049] As the monovalent organic group having 1 to 40 carbon atoms represented by R ６０ a group obtained by expanding the number of carbon atoms of the monovalent organic group having 1 to 20 carbon atoms represented by R １ and R ２ in the above formula (1) to 1 to 40 can be preferably employed. Among these, as R ６０ from the viewpoint of appropriately controlling the diffusion length of the generated acid, it is preferably a structure containing a cyclic structure.

[0050] The cyclic structure may be monocyclic, polycyclic, or a combination thereof. Furthermore, the cyclic structure may be alicyclic, aromatic, heterocyclic, or a combination thereof. In the case of a combination, the cyclic structures may be linked by a chain structure, and two or more cyclic structures may form a fused ring structure, a bridged ring structure, or a spiro-ring structure. Divalent heteroatom-containing groups may be present between carbon atoms forming the skeleton of the cyclic or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic or chain structure may be substituted with other substituents.

[0051] As a divalent heteroatom-containing group, R in formula (1) above is １ and R ２ The divalent heteroatom-containing group shown can be suitably adopted.

[0052] As substituents that replace some or all of the hydrogen atoms on the carbon atoms of the above-described cyclic or chain structure, substituents (T) described later can be suitably adopted.

[0053] The above alicyclic structure is R in formula (1) above. １ and R ２ Structures corresponding to the alicyclic hydrocarbon groups shown can be suitably adopted.

[0054] The above aromatic ring structure is R in formula (1) above. １ and R ２ The structure corresponding to the aromatic hydrocarbon group shown can be suitably adopted.

[0055] Examples of the above heterocyclic structures 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 thiethane, thiolane, and thian; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0056] Heterocyclic structures include lactone structures, cyclic carbonate structures, sultone structures, cyclic acetals, or combinations thereof.

[0057] Among these, alicyclic structures, aromatic ring structures, and cyclic acetals are preferred as cyclic structures.

[0058] R ｆ１ and R ｆ２ As a monovalent fluorinated hydrocarbon group represented by formula (1), R １ and R ２ Examples include groups in which some or all of the hydrogen atoms of a monovalent hydrocarbon group having 1 to 20 carbon atoms are replaced with fluorine atoms.

[0059] Specific examples of the above-mentioned sulfonate anions include, but are not limited to, the structures shown in the following formulas (XB-1) to (XB-61) and (XB-65) to (XB-70).

[0060]

[0061]

[0062]

[0063]

[0064]

[0065]

[0066] As the sulfonimide anion, a bisaryl sulfonimide anion can be mentioned. Specific examples of the sulfonimide anion include, for example, those described in International Publication No. 2020 / 262692 are preferably mentioned.

[0067] Specific examples of the above sulfonimide anion include, although not limited to, for example, the structures of the following formulas (XB-62) to (XB-63).

[0068]

[0069] As the above methide anion, for example, (CF ３ SO ２ ), (CF ３ C - ), [(CF ３ CF ２ SO ２ ), [(CF ３ C - ), [(CF ３ ), ２ CFSO ２ , ３ C - ), (CF ３ CF ２ CF ２ SO ２ ), ３ C - ), (CF ３ CF ２ CF ２ CF ２ SO ２ ), ３ C - ), [(CF ３ ), ２ CFCF ２ SO ２ , ３ C - ), [CF ３ CF ２ (CF ３ ), ２ , ３ C - ), [(CF ３ ), ３ CSO ２ , ３ C -(FSO ２ ) ３ C - In addition to the above, other examples include the methidoanions described in Japanese Patent Publication No. 2011-145540, U.S. Patent No. 5,554,664, Japanese Patent Publication No. 2005-309408, Japanese Patent Publication No. 2004-085657, Japanese Patent Publication No. 2010-505787, etc. Among these, (CF ３ SO ２ ) ３ C - (Hereafter, this may also be referred to as "XB-64") is preferred.

[0070] In the present invention, from the viewpoint of sensitivity, it is preferable that the above anion contains one or more iodine groups.

[0071] As specific examples of the onium salt compound (P1) above, any combination of the onium cation represented by formula (1) above and the monovalent anion above can be suitably adopted, but there are no limitations. However, specific examples of radiation-sensitive acid generators can be given below (P1-1) to (P1-286).

[0072]

[0073]

[0074]

[0075] The above onium salt compound (P1) can be synthesized by the method described in the examples.

[0076] The above onium salt compound (P1) may be used alone or in combination of two or more types.

[0077] When the above radiation-sensitive composition contains an onium salt compound (P1), the lower limit of the onium salt compound (P1) content (total in the case of multiple types) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass, per 100 parts by mass of the base polymer (A) described later. The upper limit of the above content is preferably 70 parts by mass, more preferably 60 parts by mass, and even more preferably 50 parts by mass. This allows for excellent sensitivity during resist pattern formation.

[0078] (Onium salt compound (P2)) As the anion of the above onium salt compound (P2), among the above anions, sulfonate anions (however, in which an electron-withdrawing group is not bonded to the carbon atom at the α or β position of the sulfur atom in the sulfonate anion), carboxylate anions (however, excluding benzoate anions substituted with four or more fluoro groups), or substituted or unsubstituted phenolate anions or carboxylate anions are preferred, and carboxylate anions are more preferred. Examples of electron-withdrawing groups include those described for onium salt compound (P1).

[0079] As the above carboxylic acid anion, the anion represented by the following formula (ii) can be suitably used. However, the anion represented by the following formula (ii) does not include benzoate anions substituted with four or more fluoro groups. ７０ -COO - (ii) (In formula (ii), R ７０ (This refers to a monovalent organic group having 1 to 40 carbon atoms.)

[0080] R ７０ As a monovalent organic group having 1 to 40 carbon atoms represented by the above formula (1), R １ and R ２ Groups with 1 to 20 carbon atoms represented by the monovalent organic group can be preferably adopted, with the number of carbon atoms extended from 1 to 40. Among these, R ７０ Preferably, the structure includes an aromatic ring structure. The aromatic ring structure is R of formula (1) above. １ and R ２ A structure corresponding to a monovalent aromatic hydrocarbon group having 3 to 20 carbon atoms can be suitably adopted.

[0081] Specific examples of the above carboxylic acid anions include, but are not limited to, the structures shown in the following formulas (XC-1) to (XC-25).

[0082]

[0083]

[0084] Examples of the phenolate anions mentioned above include the phenolate anion described in Japanese Patent Publication No. 2005-029548.

[0085] As the above-mentioned sulfonate anions (provided that no electron-withdrawing group is bonded to the α- or β-carbon atom of the sulfur atom in the sulfonate anion), groups obtained by removing the electron-withdrawing group present on the α- or β-carbon atom of the sulfur atom in the sulfonate anions represented by formulas (XB-1) to (XB-61) above can be suitably adopted. Examples of electron-withdrawing groups include those described in the onium salt compound (P1).

[0086] As specific examples of the onium salt compound (P2) above, any combination of the onium cation represented by formula (1) above and the monovalent anion above can be suitably used, and is not limited to such combinations, but specific examples of acid diffusion control agents are listed below as (P2-1) to (P2-220).

[0087]

[0088]

[0089]

[0090] The above onium salt compound (P2) can be synthesized by the method described in the examples.

[0091] The onium salt compound (P2) used as an acid diffusion control agent may be used alone or in combination of two or more types.

[0092] When the above-mentioned radiation-sensitive composition contains an onium salt compound (P2) as an acid diffusion control agent, the lower limit of the content of the onium salt compound (P2) (total in the case of multiple types) is preferably 10 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total amount of the monomer that gives the structural unit (II) of the base polymer (A) described later, the onium salt compound (P1), and the radiation-sensitive acid generator (X) described later (if all are included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%.

[0093] <Polymer (A)> Polymer (A) is an aggregate of polymerization chains containing a structural unit (I) having an acid-dissociable group (hereinafter also referred to as "base polymer (A)"). In addition to structural unit (I), base polymer (A) may also contain structural units (II) containing an acid-generating structure, structural units (III) having a phenolic hydroxyl group, structural units (IV) containing a lactone structure, structural units (V) containing a polar group, etc.

[0094] (Structural Unit (I)) Structural unit (I) is a structural unit having an acid-dissociable group. An "acid-dissociable group" is a hydrogen atom-substituting group such as a carboxyl group, phenolic hydroxyl group, alcoholic hydroxyl group, or sulfo group, which dissociates upon the action of an acid. When the base polymer contains structural unit (II) due to exposure, the acid generated from the onium salt compound (P1) etc. dissociates the acid-dissociable group in structural unit (I), generating a carboxyl group, etc. This creates a difference in solubility in the developer between the exposed and unexposed areas of the resist film, enabling pattern formation. In this specification, "dissociation" of an acid-dissociable group refers to dissociation when post-exposure baking is performed at 110°C for 60 seconds.

[0095] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is replaced by a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern-forming properties of the radiation-sensitive composition, a structural unit represented by the following formula (i) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0096] (In formula (i), R １７ R is a hydrogen atom, a fluorine atom, or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms. １８ R is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０Each of these independently represents a substituted or unsubstituted monovalent linear hydrocarbon group having 1 to 10 carbon atoms, or a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ -COO-, or ＊ -COOL-L １１ａ Represents -COO-. １１ａ * is a substituted or unsubstituted alkanediyl group or arenediyl group. １７ This is the bonding site with the carbon atom to which it is bonded.

[0097] R １７ Examples of C1-C6 alkyl groups represented by include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, isopentyl group, neopentyl group, and the like.

[0098] R １７ When an alkyl group having 1 to 6 carbon atoms represented by has substituents, examples of substituents include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; hydroxyl groups; carboxyl groups; cyano groups; nitro groups; amino groups; alkoxy groups; alkoxycarbonyl groups; alkoxycarbonyloxy groups; acyl groups; acyloxy groups or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and substituents (T) such as oxo groups (=O).

[0099] R １７Examples of alkoxy groups as substituents include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as methoxy, ethoxy, and propoxy groups. Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as methoxycarbonyl and ethoxycarbonyl groups. Examples of alkoxycarbonyloxy groups include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy groups. Examples of acyl groups include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl groups. Examples of acyloxy groups include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy, propionyloxy, benzoyloxy, and acryloyloxy groups.

[0100] The above R １７ From the viewpoint of copolymerizability of the monomer that gives structural unit (I-1), hydrogen atoms and methyl groups are preferred.

[0101] L １１ａ Examples of alkanediyl groups represented by include divalent alkanediyl groups having 1 to 10 carbon atoms, such as methylene groups, ethanediyl groups, and propanediyl groups. １１ａ The alkanediyl group represented is preferably a methylene group or an ethanediyl group.

[0102] L １１ａ Examples of the arenediyl group represented by include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl groups and naphthalenediyl groups. １１ａ A benzenediyl group is preferred as the allenediyl group represented by .

[0103] L １１ａ When an alkanediyl group or arenediyl group represented by is substituted, the substituent is R １７ The substituents shown above can be preferably adopted. Among them, L １１ａ A hydroxyl group is preferred as the substituent.

[0104] L １１ teeth, ＊ -COO-, ＊ -L １１ａ -COO- is preferred, ＊ -COO- is preferable.

[0105] The above R １８ As a monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the above formula (1), R １ and R ２ Monovalent hydrocarbon groups having 1 to 20 carbon atoms can be suitably used in this material.

[0106] The above R １８ Preferably, the alkyl group has 1 to 10 carbon atoms, or the aryl group has 6 to 20 carbon atoms.

[0107] R １９ and R ２０ As a monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the above formula (1), R １ and R ２ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms, groups with the corresponding number of carbon atoms can be suitably adopted.

[0108] R １９ and R ２０ As a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the above formula (1), R １ and R ２ A monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used in this material.

[0109] The above R １９ and R ２０ Divalent alicyclic groups having 3 to 20 carbon atoms, which are formed by combining these atoms with the carbon atoms to which they are bonded, include groups obtained by removing one hydrogen atom from the above-mentioned monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms.

[0110] The above R １８ ~R ２０ The substituents that it may have include R １７ The substituent (T) shown in can be suitably adopted.

[0111] Among these, R １８The C1-C5 alkyl group or the C6-C10 aryl group is preferred. １９ and R ２０ Preferably, each of these groups is either an independent methyl group or an ethyl group, or they can be combined to form a cycloalkane structure with the carbon atoms to which they are bonded.

[0112] Examples of structural units (I-1) include those represented by the following formulas (i-1) to (i-11) (hereinafter also referred to as "structural units (I-1-1) to (I-1-11)").

[0113]

[0114] In the above equations (i-1) to (i-11), R １７ ~R ２０ This is equivalent to equation (i) above. R Ｌ１１ R is a halogen atom; hydroxyl group; carboxyl group; cyano group; nitro group; amino group; alkoxy group; alkoxycarbonyl group; alkoxycarbonyloxy group; acyl group; acyloxy group, or a group in which a hydrogen atom of any of these groups is substituted with a halogen atom. h, i, and j are each independently integers from 1 to 4. k1, k2, and k3 are each independently 0 or 1. 3a are each independently integers from 0 to 3. If 3a is 2 or more, multiple R Ｌ１１ They are either identical or different from one another.

[0115] h, i, and j are preferably 1 or 2. １８ Preferred groups include methyl, ethyl, isopropyl, ethenyl (vinyl), butenyl, phenyl, and iodophenyl groups. １９ and R ２０ Preferably, the group is a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ Preferred elements include hydroxyl groups, iodine atoms, alkyl groups, and alkoxy groups.

[0116] Furthermore, the polymer may contain structural units (I) represented by the following formulas (1f) to (2f) (hereinafter also referred to as "structural unit (I-2)").

[0117]

[0118] In the above equations (1f) to (2f), R αｆ Each of these is independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ Each of these is independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer between 1 and 4.

[0119] The above R βｆ Preferably, it is a hydrogen atom, a methyl group, or an ethyl group. １ 1 or 2 is preferred.

[0120] While there are no particular limitations on specific examples of structural unit (I) (including structural unit (I-1) and structural unit (I-2)), one example is a structure represented by the following formula.

[0121]

[0122]

[0123]

[0124]

[0125] In the formula, R １７ This is equivalent to equation (i) above.

[0126] The base polymer (A) may contain one or more structural units (I) in combination.

[0127] The lower limit of the content of structural unit (I) (total content if multiple types are included) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 90 mol%, more preferably 80 mol%, and even more preferably 70 mol%. By setting the content of structural unit (I) within the above range, the pattern-forming properties of the radiation-sensitive composition can be further improved. If the acid-dissociable group has an iodine group, the sensitivity can be further improved.

[0128] (Structural Unit (II)) The base polymer (A) may also contain structural unit (II) which has an organic acid anion and an onium cation represented by the following formula (1), and which includes an acid generating structure that generates acid upon exposure. (In the above formula (1), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ (Each of these is either identical or different from the others. m1 and m2 are independent integers between 0 and 5.)

[0129] The case where the onium salt structure formed by an organic acid anion and an onium cation functions as a radiation-sensitive acid-generating structure (first acid-generating structure) is defined as structural unit (II-1) (the organic acid anion in this case is referred to as the first organic acid anion). When the base polymer (A) contains the above-mentioned radiation-sensitive acid-generating structure, the polarity of the base polymer (A) in the exposed area increases, making it soluble in the developer in the case of alkaline aqueous solution development, while it becomes sparingly soluble in the developer in the case of organic solvent development.

[0130] Structural unit (II-2) is defined as the case where an onium salt structure formed by an organic acid anion and an onium cation functions as an acid diffusion control structure (second acid generation structure). Structural unit (II-2) generates an acid by exposure that does not induce the dissociation of the above-mentioned acid-dissociable group (the organic acid anion in this case is defined as the second organic acid anion). Under pattern formation conditions using the above-mentioned radiation-sensitive composition, the second acid generation structure substantially prevents the dissociation of the acid-dissociable group of structural unit (I) and has the function of suppressing the diffusion of acid generated from the first acid generation structure and the onium salt compound (P1), etc., in the unexposed areas by salt exchange. The acid generated from the second acid generation structure can be said to be a relatively weaker acid (an acid with a high pKa) than the acid generated from the first acid generation structure.

[0131] (Structural Unit (II-1)) Structural unit (II-1) has a first organic acid anion and the above onium cation. The base polymer (A) has the above first organic acid anion as a side chain portion. Having as a side chain portion means that the corresponding first organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer (A). The above onium cation is ionically bonded to the first organic acid anion as its counterion.

[0132] The above-mentioned first organic acid anion preferably has at least one selected from the group consisting of sulfonic acid anions and sulfonimide anions as the acid anion portion, and more preferably has a sulfonic acid anion. Examples of acids generated by exposure include sulfonic acid and sulfonimide, corresponding to the above-mentioned acid anion portion.

[0133] The above-mentioned first organic acid anion preferably includes, as a structure other than the acid anion portion, -O-, -CO-, a cyclic structure, or a combination thereof. This combination also includes structures (heterocyclic structures) in which -O- or -CO- are incorporated as ring-forming parts within the cyclic structure.

[0134] As the annular structure, the annular structure described in formula (p1) above can be suitably adopted.

[0135] In the above-described first acid generation structure, the first organic acid anion preferably has a sulfonic acid anion as the acid anion portion, and an electron-withdrawing group is bonded to the carbon atom at the α or β position relative to the sulfur atom in the sulfonic acid anion. This allows the first acid generation structure to efficiently perform the above-described function. Examples of electron-withdrawing groups include those described in the onium salt compound (P1).

[0136] The anion in structural unit (II-1) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (II-1)").

[0137]

[0138] In the formula, R Ｖ This is a hydrogen atom or a methyl group. V １ This is a single bond or an ester group. V ２ This is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and a portion of the methylene groups constituting the alkylene group, the cycloalkylene group, or the arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ This is a single bond, an ether group, an ester group, or a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and a portion of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group. ２ and V ３ Some or all of the hydrogen atoms in the compound may be substituted with heteroatoms, or with monovalent hydrocarbon groups having 1 to 20 carbon atoms that may contain heteroatoms. Rf １ ~Rf ４ Each of these is independently either a hydrogen atom or an electron-withdrawing group, but at least one is an electron-withdrawing group. Examples of electron-withdrawing groups include those described in the onium salt compound (P1).

[0139] V ２ and V ３The C1-C20 monovalent hydrocarbon group in this is preferably a C1-C12 alkyl group, a C3-C12 cycloalkyl group, or a C6-C20 aryl group. Some or all of the hydrogen atoms in these groups may be substituted with heteroatom-containing groups such as hydroxyl groups, carboxyl groups, halogen atoms, oxo groups, cyano groups, amide groups, nitro groups, sultone groups, sulfone groups, or sulfonium salt-containing groups, alkoxy groups, or alkoxycarbonyl groups. Some of the methylene groups constituting these groups may be substituted with ether groups, ester groups, carbonyl groups, carbonate groups, or sulfonic acid ester groups.

[0140] The structural unit (II-1) is preferably represented by the following formula (a1-1).

[0141]

[0142] In the formula, R Ｖ , Rf １ ~Rf ４ and V １ This is equivalent to the above formula (a1). R ４８ m is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxyl group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer from 0 to 4. n is an integer from 0 to 3.

[0143] Examples of primary organic acid anions of monomers that give structural unit (II-1) are listed below, but are not limited to these. Furthermore, among those listed below, those having an iodine group-containing aromatic ring structure can also suitably be used in which the iodine atom in the following formula is replaced with a hydrogen atom or other substituent. In the following formula, R Ｖ This is synonymous with the above.

[0144]

[0145]

[0146]

[0147]

[0148] The onium cation represented by formula (1) above, which is present in structural unit (II-1), can preferably be the same as that of the onium salt compound (P) above.

[0149] When the base polymer has structural unit (II-1), the lower limit of the content of structural unit (II-1) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of structural unit (II-1) within the above range, it is possible to fully exhibit its function as an acid-generating structure and exhibit the above-mentioned resist properties.

[0150] (Structural Unit (II-2)) Structural unit (II-2) has a secondary organic acid anion and the onium cation. The base polymer (A) has the secondary organic acid anion as a side chain portion. Having it as a side chain portion means that the corresponding secondary organic acid anion is bonded (covalently bonded) to the main chain as a side chain structure of the base polymer (A). The onium cation is ionically bonded to the secondary organic acid anion as its counterion.

[0151] The above-mentioned second organic acid anion preferably has a sulfonic acid anion or a carboxylic acid anion as the acid anion portion, and more preferably has a carboxylic acid anion. However, when the above-mentioned second organic acid anion has the above-mentioned sulfonic acid anion, no electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonic acid anion. Examples of electron-withdrawing groups include those described in the onium salt compound (P1). The acid generated by exposure is a carboxylic acid or sulfonic acid, corresponding to the above-mentioned acid anion portion.

[0152] The second organic acid anion described above preferably includes -O-, -CO-, a cyclic structure, or a combination thereof, as a structure other than the acid anion portion. The structure shown for the first organic acid anion described above can be suitably adopted as such a structure.

[0153] The onium cation represented by formula (1) above, which is present in structural unit (II-2), can preferably be the same as that of the onium salt compound (P) above.

[0154] When the base polymer has structural unit (II-2), the lower limit of the content of structural unit (II-2) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 4 mol%, relative to the total amount of the monomer that gives structural unit (II-1), the onium salt compound (P1), and the radiation-sensitive acid generator (X) described later (if all are included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. When the onium salt compound (P2) as an acid diffusion control agent is included, the total amount of the monomer that gives structural unit (II-2) and the onium salt compound (P2) should be within the above range. By setting the content of structural unit (II-2) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0155] (Structural Unit (III)) Structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to structural units (I) to (II)). By including structural unit (III) in the polymer, the solubility in the developer can be adjusted more appropriately, and as a result, the sensitivity of the above-mentioned radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beams, etc. are used as the radiation irradiated in the exposure step in the resist pattern formation method, structural unit (III) contributes to improving etching resistance and improving the difference in developer solubility between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure with radiation of wavelength 50 nm or less, such as electron beams and EUV. Structural unit (III) is preferably represented by the following formula (2).

[0156] (In the above formula (2), R β L is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ This is a single bond, -COO- ＊ , -O- or -CONH-＊ This is the case. * indicates a bond on the aromatic ring side. R １０２ R is a halogen atom, cyano group, nitro group, alkyl group, alkoxycarbonyl group, acyl group, or acyloxy group. １０２ If multiple R １０２ They are either identical or different from each other. ３ m is an integer between 0 and 2. ３ m is an integer from 1 to 8. ４ Each of these is an independent integer between 0 and 8, where 1 ≤ m. ３ +m ４ ≤ 2n ３ (Saves +5.)

[0157] The above R β From the viewpoint of copolymerization of the monomer that gives structural unit (III), it is preferable that the atom be a hydrogen atom or a methyl group.

[0158] L ＣＡ For example, a single bond or -COO- ＊ It is preferable.

[0159] R １０２ In the halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group, or acyloxy group, the groups listed above as substituents (T) can be suitably adopted. １０２ In this mixture, iodine or fluorine atoms are preferred as halogen atoms, with iodine atoms being more preferred.

[0160] The above n ３ As such, 0 or 1 is more preferable, and 0 is even more preferable. ３ If the value is 1 or greater, then -OH and -R in formula (2) above. １０２ Each of these may be bonded to any of the multiple benzene rings that are condensed.

[0161] The above m ３ Preferably, the integer is between 1 and 3, and more preferably 1 or 2.

[0162] The above m ４ Preferably, the integer is between 0 and 3, and more preferably between 0 and 2.

[0163] The above structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-24) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-24)").

[0164]

[0165]

[0166] In the above equations (2-1) to (2-24), R β This is the same as equation (2) above.

[0167] When the base polymer has structural unit (III), the lower limit of the content of structural unit (III) (total if there are multiple types of structural unit (III)) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, relative to the total structural units constituting the polymer. The upper limit of the above content is preferably 85 mol%, more preferably 75 mol%, and even more preferably 70 mol%. By setting the content of structural unit (III) within the above range, the radiation-sensitive composition can achieve further improvements in sensitivity and development contrast.

[0168] (Structural Unit (IV)) Structural Unit (IV) is a structural unit comprising at least one selected from the group consisting of lactone structures, cyclic carbonate structures, and sultone structures. By further comprising structural unit (IV), the solubility of the base polymer in the developer can be adjusted, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between the resist pattern formed from the base polymer (A) and the substrate can be improved.

[0169] Among these, structural units (IV) that include a lactone structure are preferred, and structural units that include a γ-butyrolactone structure, norbornane lactone structure, or adamantane lactone structure are more preferred.

[0170] When the base polymer has structural units (IV), the lower limit of the content of structural units (IV) (total content if multiple types are included) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 55 mol%. By setting the content of structural units (IV) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0171] (Structural Unit (V)) Structural unit (V) is a structural unit containing a polar group (excluding those corresponding to structural units (I) to (IV)). The solubility of the base polymer in the developer can be adjusted by further containing structural unit (V). Examples of the above polar groups include hydroxyl groups, carboxyl groups, cyano groups, nitro groups, sulfo groups, and sulfonamide groups. Among these, hydroxyl groups and carboxyl groups are preferred, and hydroxyl groups are more preferred.

[0172] Examples of structural units (V) include structural units represented by the following formula.

[0173]

[0174]

[0175] In the above formula, R Ｋ This is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0176] When the base polymer (A) has structural units (V) having the polar group described above, the lower limit of the content of structural units (V) (total content if multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, relative to the total structural units constituting the base polymer (A). The upper limit of the above content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%. By setting the content of structural units (V) within the above range, the solubility of the base polymer (A) in the developer can be efficiently adjusted.

[0177] (Method for synthesizing base polymers) Base polymers can be synthesized, for example, by polymerizing monomers that give each structural unit in a suitable solvent using a radical polymerization initiator or the like.

[0178] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight-average molecular weight (Mw) in polystyrene terms, calculated by gel permeation chromatography (GPC), is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 15,000, and even more preferably 10,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0179] The ratio of Mw to the polystyrene-equivalent number-average molecular weight (Mn) of the base polymer (Mw / Mn) determined by GPC is usually between 1 and 5, preferably between 1 and 3, and more preferably between 1 and 2.

[0180] The methods for measuring Mw and Mn of polymers in this specification are as described in the examples.

[0181] The lower limit of the base polymer content is preferably 40% by mass, more preferably 50% by mass, and even more preferably 60% by mass, relative to the total solid content of the radiation-sensitive composition. The upper limit of the above content is preferably 95% by mass, and more preferably 90% by mass.

[0182] (Other Polymers) The radiation-sensitive composition of this embodiment may also contain, as other polymers, polymers with a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as "high-fluorine content polymers"). When the radiation-sensitive composition contains high-fluorine content polymers, they can be unevenly distributed on the surface of the resist film relative to the base polymer, thereby improving the water repellency of the surface of the resist film during immersion exposure, and controlling the surface modification of the resist film and the distribution of the internal composition during EUV exposure. The radiation-sensitive composition may contain one or more high-fluorine content polymers.

[0183] If the radiation-sensitive composition contains a high-fluorine-content polymer, the amount of the high-fluorine-content polymer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the base polymer (A). Furthermore, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0184] (Method for synthesizing high-fluorine content polymers) High-fluorine content polymers can be synthesized by the same method as the synthesis method for the base polymer (A) described above.

[0185] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains solvent (E). Solvent (E) is not particularly limited as long as it is a solvent capable of dissolving or dispersing the base polymer (A) and optionally contained additives.

[0186] Examples of solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0187] Examples of alcohol-based solvents include monoalcohol solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether solvents, such as propylene glycol 1-monomethyl ether, which are obtained by etherifying some of the hydroxyl groups in the above-mentioned polyhydric alcohol solvents.

[0188] In this embodiment, alcohol acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcohol-based solvents.

[0189] Examples of ether-based solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether solvents such as diphenyl ether and anisole (methylphenyl ether); and polyhydric alcohol ether solvents obtained by etherifying the hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

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

[0191] Examples of amide solvents include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain-like amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0192] Examples of ester solvents include polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone solvents such as γ-butyrolactone and valerolactone; carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyhydric carboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoethyl acetate, and diethyl phthalate.

[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-based solvents, polyhydric alcohol partial ether acetate-based solvents, and polyhydric alcohol partial ether-based solvents are more preferred, and methyl 2-hydroxyisobutyrate, propylene glycol monomethyl ether acetate, propylene glycol 1-monomethyl ether, and diacetone alcohol are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0195] <Radiation-sensitive acid generator (X) other than onium salt compound (P1)> The above radiation-sensitive composition may also use a radiation-sensitive acid generator (X) other than the onium salt compound (P1) as the radiation-sensitive acid generator. The radiation-sensitive acid generator (X) represented by the following formula (X1) can be suitably adopted. (In formula (X1), R ６０ R is a monovalent organic group having 1 to 40 carbon atoms. ｆ１ and R ｆ２ Each of these is independently a hydrogen atom, a cyano group, a nitro group, a fluorine atom, or a monovalent fluorinated hydrocarbon group. ｆ１ and R ｆ２If multiple R ｆ１ and R ｆ２ These are either the same or different. t is an integer between 0 and 4. Z ＋ (This refers to a radiation-sensitive onium cation other than the onium cation represented by formula (1) above.)

[0196] The above R ６０ is R ｆ１ , R ｆ２ t is equivalent to the above equation (p1).

[0197] As specific examples of the sulfonate anion mentioned above, those listed as specific examples of formula (p1) above can be suitably adopted.

[0198] Z ＋ Examples of monovalent onium cations represented by (1) include radiodegradable onium cations. Examples of radiodegradable onium cations include sulfonium cations, tetrahydrothiophenium cations, and iodonium cations (excluding the onium cation represented by formula (1)). Among these, sulfonium cations or iodonium cations are preferred, and sulfonium cations are more preferred.

[0199] Z in the above formula (X1) ＋ Preferably, it is a sulfonium cation represented by the following formula (Q-1).

[0200]

[0201] In the above equation (Q-1), R ａ１ and R ａ２ Each of these independently represents a substituent. n1 represents an integer from 0 to 5, and if n1 is 2 or greater, there are multiple R ａ１ They can be the same or different. n² represents an integer from 0 to 5, and if n² is 2 or greater, there are multiple R ａ２ They may be the same or different. ａ３ represents a substituent. n3 represents an integer from 0 to 5, and if n3 is 2 or greater, there are multiple R ａ３ They may be the same or different. ａ１ and R ａ２They may be connected to each other to form a ring. If n1 is 2 or more, multiple R ａ１ They may be connected to each other to form a ring. If n2 is 2 or more, multiple R ａ２ They may be connected to each other to form a ring.

[0202] R ａ１ , R ａ２ and R ａ３ Preferred substituents represented by are alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, alkylsulfonyl groups, hydroxyl groups, halogen atoms, and halogenated hydrocarbon groups.

[0203] R ａ１ and R ａ２ The alkyl group may be a linear alkyl group or a branched alkyl group. Preferably, the alkyl group has 1 to 10 carbon atoms, and examples include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, 2-methylpropyl group, 1-methylpropyl group, t-butyl group, n-pentyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, and n-decyl group. Of these, methyl group, ethyl group, n-butyl group, and t-butyl group are particularly preferred.

[0204] R ａ１ and R ａ２ Examples of cycloalkyl groups include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0205] R ａ１ and R ａ２ For example, the alkyl group portion of the alkoxy group is R ａ１ and R ａ２The alkyl groups listed are examples. Methoxy, ethoxy, n-propoxy, and n-butoxy groups are particularly preferred as alkoxy groups.

[0206] R ａ１ and R ａ２ For example, the cycloalkyl group portion of the cycloalkyloxy group is R ａ１ and R ａ２ The cycloalkyl groups listed are examples of the cycloalkyl groups listed above. Cyclopentyloxy and cyclohexyloxy groups are particularly preferred among these cycloalkyloxy groups.

[0207] R ａ１ and R ａ２ For example, the alkoxy group portion of the alkoxycarbonyl group is R ａ１ and R ａ２ The alkoxy groups listed are examples of those listed. Methoxycarbonyl groups, ethoxycarbonyl groups, and n-butoxycarbonyl groups are particularly preferred among these alkoxycarbonyl groups.

[0208] R ａ１ and R ａ２ For example, the alkyl group portion of the alkylsulfonyl group is R ａ１ and R ａ２ The alkyl groups listed are listed below. Also, R ａ１ and R ａ２ For example, the cycloalkyl group of the cycloalkylsulfonyl group is R ａ１ and R ａ２ The cycloalkyl groups listed above are examples of the alkylsulfonyl groups or cycloalkylsulfonyl groups in particular: methanesulfonyl group, ethanesulfonyl group, n-propanesulfonyl group, n-butanesulfonyl group, cyclopentanesulfonyl group, and cyclohexanesulfonyl group.

[0209] R ａ１ and R ａ２Each of these groups may have further substituents. Examples of these substituents include halogen atoms such as fluorine atoms (preferably fluorine atoms), hydroxyl groups, carboxyl groups, cyano groups, nitro groups, alkoxy groups, cycloalkyloxy groups, alkoxyalkyl groups, cycloalkyloxyalkyl groups, alkoxycarbonyl groups, cycloalkyloxycarbonyl groups, alkoxycarbonyloxy groups, and cycloalkyloxycarbonyloxy groups.

[0210] R ａ１ and R ａ２ Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms, with fluorine and iodine atoms being preferred.

[0211] R ａ１ and R ａ２ As the halogenated hydrocarbon group, halogenated alkyl groups are preferred. The alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among these, fluorinated alkyl groups are preferred, and CF ３ This is preferable.

[0212] As mentioned above, R ａ１ and R ａ２ They may be linked together to form a ring (i.e., a heterocycle containing sulfur atoms). In this case, R ａ１ and R ａ２ It is preferable that these groups bond to each other to form single bonds or divalent linking groups. Examples of divalent linking groups include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２ -, alkylene groups, cycloalkylene groups, alkenylene groups, or combinations of two or more thereof, preferably with a total carbon number of 20 or less. ａ１ and R ａ２ When they are connected to each other to form a ring, R ａ１ and R ａ２ These combine with each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２- or single bond formation is preferable. Among these, -O-, -S-, or single bond formation is more preferable, and single bond formation is particularly preferable. Also, when n1 is 2 or more, multiple R ａ１ They may be connected to each other to form a ring, and if n2 is 2 or more, multiple R ａ２ They may be connected to each other to form a ring. For example, two R ａ１ One embodiment is one in which these elements are linked to one another, and together with the benzene ring to which they are linked, they form a naphthalene ring.

[0213] R ａ３ It is preferable that this is a fluorine atom, a group having one or more fluorine atoms, or an iodine atom. As for groups having fluorine atoms, R ａ１ and R ａ２ Examples of groups in which alkyl groups, cycloalkyl groups, alkoxy groups, cycloalkyloxy groups, alkoxycarbonyl groups, and alkylsulfonyl groups are substituted with a fluorine atom can be cited. Among these, fluorinated alkyl groups are particularly preferred, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ ,CH ２ CF ３ ,CH ２ CH ２ CF ３ ,CH ２ C ２ F ５ ,CH ２ CH ２ C ２ F ５ ,CH ２ C ３ F ７ ,CH ２ CH ２ C ３ F ７ ,CH ２ C４ F ９ and CH ２ CH ２ C ４ F ９ can be further preferably cited, and CF ３ can be particularly preferably cited.

[0214] R ａ３ is preferably a fluorine atom, an iodine atom or CF ３ and more preferably a fluorine atom or an iodine atom.

[0215] n1 and n2 are each independently preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0216] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0217] (n1 + n2 + n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6.

[0218] Specific examples of such a sulfonium cation represented by the above formula (Q-1) include the following. The fluorine atoms and iodine atoms in the following sulfonium cations may be substituted with hydrogen atoms, the above substituent (T), etc.

[0219]

[0220]

[0221]

[0222]

[0223] The above monovalent onium cation may be a substituted or unsubstituted diaryliodonium cation. As the aryl group, the aryl groups in R １ and R ２ in the above formula (1) can be preferably adopted. The aryl group is preferably a phenyl group. As the substituent when the aryl group has a substituent, the above substituent (T) can be preferably adopted. However, those corresponding to the onium cation represented by the formula (1) are excluded.

[0224] Specific examples of such iodonium cations include the following.

[0225]

[0226] The radiation-sensitive acid generator (X) can be obtained by appropriately combining the above anion and the above radiation-sensitive onium cation.

[0227] In the present invention, the radiation-sensitive acid generator (X) can be used alone or in combination of two or more.

[0228] When the radiation-sensitive composition contains the radiation-sensitive acid generator (X), the lower limit of the content of the radiation-sensitive acid generator (X) (in the case of a plurality of types, the total) is preferably 10 parts by mass, more preferably 20 parts by mass, and even more preferably 25 parts by mass with respect to 100 parts by mass of the base polymer (A). Further, the upper limit of the above content is preferably 70 parts by mass, more preferably 60 parts by mass, and even more preferably 50 parts by mass. Thereby, excellent sensitivity can be exhibited during the formation of the resist pattern.

[0229] <Acid diffusion control agent (Y) other than the onium salt compound (P)> The above radiation-sensitive composition can also use an acid diffusion control agent (Y) other than the onium salt compound (P) as the above acid diffusion control agent. As the above acid diffusion control agent (Y), those represented by the following formula (Y1) can be preferably employed.

[0230] As the above carboxylic acid anion, an anion represented by the following formula (Y1) can be preferably employed. R ７０ -COO - Z ＋ (Y1) (In the formula (Y1), R ７０ is a monovalent organic group having 1 to 40 carbon atoms. Z ＋ is a radiation-sensitive onium cation other than the onium cation represented by the above formula (1).)

[0231] The above R ７０ is synonymous with the above formula (ii).

[0232] The above R ７０ -COO- As specific examples, those listed as specific examples of formula (ii) above can be suitably adopted.

[0233] The above Z ＋ This is Z in the above equation (X1). ＋ It is synonymous with [the above].

[0234] The acid diffusion control agent (Y) can be obtained by appropriately combining the above-mentioned anion and the above-mentioned radiation-sensitive onium cation.

[0235] The above-mentioned acid diffusion control agents can also be synthesized by known methods, particularly by salt exchange reactions.

[0236] These acid diffusion control agents (Y) may be used individually or in combination of two or more.

[0237] If the above radiation-sensitive composition contains an acid diffusion control agent (Y), the lower limit of the content of the acid diffusion control agent (Y) (total if there are multiple types) is preferably 10 mol%, more preferably 30 mol%, and even more preferably 40 mol%, relative to the total amount of the monomer that gives the structural unit (II) of the base polymer (A), the onium salt compound (P1), and the radiation-sensitive acid generator (X) (if all are included). The upper limit of the above content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%.

[0238] <Other Optional Components> The above-mentioned radiation-sensitive composition may contain other optional components in addition to the components listed above. Examples of these other optional components include crosslinking agents, localization accelerators, surfactants, alicyclic skeleton-containing compounds, sensitizers, etc. These other optional components may be used individually or in combination of two or more types.

[0239] <Method for preparing a radiation-sensitive composition> The above radiation-sensitive composition can be prepared, for example, by mixing a base polymer (A) and a solvent (E) with an onium salt compound (P) and other optional components in predetermined proportions, if necessary. After mixing, the above radiation-sensitive composition is preferably filtered using a filter with a pore size of approximately 0.05 μm to 0.4 μm. The solid content concentration of the above 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.

[0240] ≪Pattern Forming Method≫ The pattern forming method in this embodiment includes the steps of: applying the above-mentioned radiation-sensitive composition directly or indirectly to a substrate to form a resist film (1) (hereinafter also referred to as the "resist film forming step"), exposing the resist film to light (2) (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with a developer (3) (hereinafter also referred to as the "development step").

[0241] According to the pattern formation method described above, since the above-mentioned radiation-sensitive composition capable of exhibiting excellent sensitivity, CDU, underexposure CDU, and development defects is used during pattern formation, high-quality resist patterns can be efficiently formed. The following describes each step.

[0242] [Resist Film Formation Process] In this process (step (1) above), a resist film is formed using the above-mentioned radiation-sensitive composition. Examples of substrates for forming this resist film include conventionally known materials such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective film disclosed in, for example, Japanese Patent Publication No. 6-12452 or Japanese Patent Publication No. 59-93448 may be formed on the substrate. Examples of coating methods include spin coating, casting, and roll coating. After coating, soft baking (SB) may be performed as needed to volatilize the solvent in the coating film. The PB temperature is usually 60°C to 160°C, with 80°C to 140°C being preferred. The PB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred. The thickness of the formed resist film is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0243] Furthermore, when the subsequent exposure process is carried out with radiation of a wavelength of 50 nm or less, it is preferable to use a polymer having the above structural unit (III) as the base polymer in the above composition.

[0244] [Exposure Process] In this process (process (2) above), the resist film formed in the resist film formation process, which is process (1) above, is exposed by irradiating it with radiation through a photomask. The radiation used for exposure can be electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays, depending on the line width of the desired pattern; electron beams, alpha rays, and other charged particle beams. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0245] After the exposure described above, it is preferable to perform a post-exposure bake (PEB) to promote the dissociation of acid-dissociable groups in polymers, etc., by the first acid-generating structure of structural unit (II), the onium salt compound (P1), and the radiation-sensitive acid generator (X) in the exposed portion of the resist film. This PEB creates a difference in solubility in the developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 180°C, with 80°C to 150°C being preferred. The PEB time is usually 5 seconds to 600 seconds, with 10 seconds to 300 seconds being preferred.

[0246] [Development Process] In this process (step (3) above), the resist film exposed in the exposure process, which is step (2) above, is developed with a developer. This allows a predetermined resist pattern to be formed. After development, it is common to wash with a rinsing solution such as water or alcohol and then dry it.

[0247] Examples of developers used in the above development process include, in the case of alkaline development, an alkaline aqueous solution containing at least one alkaline compound such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0248] In addition, in the case of organic solvent development, examples of organic solvents include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, alcohol solvents, or solvents containing organic solvents. Examples of the above organic solvents include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As for ester solvents, acetic acid ester solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As for ketone solvents, chain ketones are preferred, and 2-heptanone is more preferred. The content of organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than organic solvents in the developer include water and silicone oil.

[0249] Examples of development methods include immersing the substrate in a tank filled with developer solution for a certain period of time (dip method), developing by puddling the developer solution onto the substrate surface using surface tension and letting it remain still for a certain period of time (paddle method), spraying the developer solution onto the substrate surface (spray method), and continuously dispensing the developer solution while scanning a developer solution dispensing nozzle at a constant speed onto a substrate rotating at a constant speed (dynamic dispensing method).

[0250] ≪Onium Salt Compounds≫ The onium salt compounds according to this embodiment are represented by the following formula (1'). (In the above formula (1'), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １and R ２ Each of them is either identical or different from the others. m1 and m2 are each independent integers between 0 and 5. １ - This is a monovalent anion selected from the group consisting of sulfonate anions (excluding trifluoromethanesulfonate anions and toluenesulfonate anions), sulfonimide anions, carboxylic acid anions (excluding benzoate anions substituted with four or more fluoro groups), methide anions, and substituted or unsubstituted phenolate anions.

[0251] As such an onium salt compound, the onium salt compound (P) in the above-mentioned radiation-sensitive composition can be suitably used. However, X １ - In the case of sulfonate anions, this excludes trifluoromethanesulfonate anions and toluenesulfonate anions.

[0252] ≪Polymer≫ The polymer according to this embodiment includes a structural unit (I) having an acid-dissociable group, and a structural unit (II) having an onium cation represented by the following formula (1) and an organic acid anion, and including an acid-generating structure that generates acid upon exposure. (In the above formula (1), Ar １ Ar is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. ２ R is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. n1 and n2 are each independent integers from 0 to 5, where 1 ≤ n1 + n2 ≤ 10. １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ (Each of these is either identical or different from the others. m1 and m2 are independent integers between 0 and 5.)

[0253] As such an onium salt compound, those containing a structural unit (II) including an acid generation structure that generates an acid upon exposure among the polymers (base polymers) (A) in the above-described radiation-sensitive composition can be preferably employed.

[0254] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. Physical property values in the examples were measured as follows.

[0255] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] Using GPC columns (G2000HXL: 2, G3000HXL: 1, G4000HXL: 1) manufactured by Tosoh Corporation, flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40 °C, detector: differential refractometer, gel permeation chromatography (GPC) was performed with monodisperse polystyrene as a standard. Also, the dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0256] <Synthesis of Radiation-Sensitive Acid Generator (P1)> [Synthesis Example X1] 1,4-Diiodobenzene (13.4 g) and dichloromethane (130 g) were added to the reaction vessel for the synthesis of intermediate (XI-1). After stirring under ice cooling, metachloroperbenzoic acid (containing 30% water, 5.0 g) was added little by little to this solution, and the mixture was stirred at room temperature for 4 hours after the addition was complete. After stirring under ice cooling, 4-Fluorophenylboronic acid (3.7 g) was added. Next, boron trifluoride diethyl ether complex (6.0 g) was added dropwise, and the mixture was stirred at room temperature for 24 hours. Ultrapure water (50 g) and lithium trifluoromethanesulfonate (6.3 g) were added, and the mixture was stirred for 10 minutes. After removing the aqueous layer, the organic layer was washed twice with ultrapure water (30 g). The obtained organic layer was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Dichloromethane (10 g) and diisopropyl ether (50 g) were added, and after stirring for 10 minutes, the precipitated solid was filtered off. The obtained solid was dissolved in methanol (110 g), and this solution was passed through ion exchange chromatography (ion exchange resin: Aldrich Sephadex QAE A-25, packing amount: 25 g). The recovered organic layer was concentrated to dryness to obtain a compound (5.0 g) represented by the following formula (XI-1).

[0257] [Synthesis Examples X2 to X20] Compounds represented by the following formulas (XI-2) to (XI-20) were synthesized in the same manner as in Synthesis Example X1, except that the synthetic precursors of intermediates (XI-2) to (XI-20) were appropriately selected.

[0258]

[0259]

[0260] [Synthesis Example X21] 1,4-diiodo-2,5-dimethylbenzene (19.0 g) and THF (100 g) were added to the reaction vessel for the synthesis of intermediate (XI-21), and the mixture was cooled to -20°C while stirring. To this solution, isopropyl magnesium chloride-lithium chloride complex (1.3 M THF solution, 45 ml) was added dropwise, and the mixture was stirred at the same temperature for 1 hour. Triisopropyl borate (19.0 g) was added dropwise to this solution. After the addition was complete, the mixture was stirred at room temperature for 2 hours. Next, hydrochloric acid (1.0 M, 200 g) was added, and the mixture was stirred for 30 minutes. Diethyl ether (100 g) was added, and the mixture was stirred for 10 minutes, after which the organic layer was separated. The aqueous layer was extracted three times with diethyl ether (50 g). The organic layers were mixed, and the solvent was removed by distillation to obtain (4-iodo-2,5-dimethylphenyl)boronic acid (9.9 g).

[0261] 1,4-Diiodobenzene (18.2 g) and dichloromethane (150 g) were added to the reaction vessel. After stirring under ice cooling, metachloroperbenzoic acid (30% water content, 6.8 g) was added little by little to this solution, and the mixture was stirred at room temperature for 4 hours after the addition was complete. After stirring under ice cooling, the (4-iodo-2,5-dimethylphenyl)boronic acid (9.9 g) prepared above was added. Next, boron trifluoride diethyl ether complex (8.2 g) was added dropwise, and the mixture was stirred at room temperature for 24 hours. Ultrapure water (60 g) and lithium trifluoromethanesulfonate (8.6 g) were added, and the mixture was stirred for 10 minutes. After removing the aqueous layer, the organic layer was washed twice with ultrapure water (40 g). The obtained organic layer was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Dichloromethane (20 g) and diisopropyl ether (100 g) were added, and after stirring for 10 minutes, the precipitated solid was filtered off. The obtained solid was dissolved in methanol (160 g), and this solution was passed through ion exchange chromatography (ion exchange resin: Aldrich Sephadex QAE A-25, packing amount: 45 g). The recovered organic layer was concentrated to dryness to obtain a compound (8.5 g) represented by the following formula (XI-21).

[0262] [Synthesis Examples X22 to X29] Compounds represented by the following formulas (XI-22) to (XI-29) were synthesized in the same manner as in Synthesis Example X21, except that the synthetic precursors of intermediates (XI-22) to (XI-29) were appropriately selected.

[0263]

[0264] [Synthesis Example X30] 1,4-Diiodobenzene (9.9 g), 1-Methoxy-2-(methylsulfonyl)benzene (4.2 g), and dichloromethane (70 g) were added to the reaction vessel for the synthesis of intermediate (XI-30). After stirring under ice cooling, metachloroperbenzoic acid (28% water content, 3.6 g) was added little by little to this solution, and the mixture was stirred under ice cooling for 30 minutes after the addition was complete. Trifluoromethanesulfonic acid (6.8 g) was added dropwise, and the mixture was stirred at room temperature for 24 hours. Ultrapure water (20 g) was added and the mixture was stirred for 10 minutes, after which the aqueous layer was removed. The organic layer was washed three times with ultrapure water (40 g), and the resulting organic layer was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Dichloromethane (15 g) and diisopropyl ether (75 g) were added, and after stirring for 10 minutes, the precipitated solid was filtered off. The obtained solid was dissolved in methanol (120 g), and this solution was passed through ion exchange chromatography (ion exchange resin: Aldrich Sephadex QAE A-25, packing amount: 30 g). The recovered organic layer was concentrated to dryness to obtain a compound (5.8 g) represented by the following formula (XI-30).

[0265] [Synthesis Examples X31-X32] Compounds represented by the following formulas (XI-31)-(XI-32) were synthesized in the same manner as in Synthesis Example X30, except that the synthetic precursors of intermediates (XI-31)-(XI-32) were appropriately selected.

[0266]

[0267] [Synthesis Example X33] 1,4-Diiodobenzene (8.8 g) and dichloromethane (70 g) were added to the reaction vessel for the synthesis of intermediate (XI-33). After stirring under ice cooling, metachloroperbenzoic acid (28% water content, 3.2 g) was added little by little to this solution, and the mixture was stirred under ice cooling for 30 minutes after the addition was complete. After adding 1-iodo-2-methoxybenzene (6.3 g), the mixture was cooled to -20°C, and trifluoromethanesulfonic acid (6.0 g) was added dropwise, followed by stirring at room temperature for 24 hours. Ultrapure water (20 g) was added and the mixture was stirred for 10 minutes, after which the aqueous layer was removed. The organic layer was washed three times with ultrapure water (40 g), and the resulting organic layer was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Dichloromethane (10 g) and diisopropyl ether (50 g) were added and the mixture was stirred for 10 minutes, after which the precipitated solid was filtered off. The obtained solid was dissolved in methanol (80 g), and this solution was passed through ion exchange chromatography (ion exchange resin: Aldrich Sephadex QAE A-25, packing amount: 20 g). The recovered organic layer was concentrated to dryness to obtain a compound (3.8 g) represented by the following formula (XI-33).

[0268] [Synthesis Examples X34 to X36] Compounds represented by the following formulas (XI-34) to (XI-36) were synthesized in the same manner as in Synthesis Example X33, except that the synthetic precursors of intermediates (XI-34) to (XI-36) were appropriately selected.

[0269]

[0270] [Synthesis Examples X37-X44] Compounds represented by the following formulas (XI-37) to (XI-44) were synthesized in the same manner as in Synthesis Example X1, except that the synthetic precursors of intermediates (XI-37) to (XI-44) were appropriately selected.

[0271]

[0272] [Synthesis Example X45] 1,3-Diiodobenzene (4.6 g) and dichloromethane (36 g) were added to the reaction vessel for the synthesis of intermediate (XI-45). After stirring under ice cooling, metachloroperbenzoic acid (28% water content, 1.1 g) was added little by little to this solution, and the mixture was stirred under ice cooling for 10 minutes after the addition was complete. Trifluoromethanesulfonic acid (2.1 g) was added dropwise, and the mixture was stirred at 35°C for 24 hours. Ultrapure water (20 g) was added and the mixture was stirred for 10 minutes, after which the aqueous layer was removed. The organic layer was washed with ultrapure water (20 g), the obtained organic layer was dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure. Dichloromethane (5 g) and diisopropyl ether (25 g) were added, and after stirring for 10 minutes, the precipitated solid was filtered off. The obtained solid was dissolved in methanol (30 g), and this solution was passed through ion exchange chromatography (ion exchange resin: Aldrich Sephadex QAE A-25, packing amount: 8 g). The recovered organic layer was concentrated to dryness to obtain a compound (1.5 g) represented by the following formula (XI-45).

[0273] [Synthesis Examples X46-X52] Compounds represented by the following formulas (XI-46) to (XI-52) were synthesized in the same manner as in Synthesis Example X45, except that the synthetic precursors of intermediates (XI-46) to (XI-52) were appropriately selected.

[0274]

[0275] [Synthesis Examples X69 to X73] Compounds represented by the following formulas (XI-69) to (XI-73) were synthesized in the same manner as in Synthesis Example X1, except that the synthetic precursors of intermediates (XI-69) to (XI-73) were appropriately selected.

[0276]

[0277] [Synthesis Example X74] The compound represented by the following formula (XI-74) was synthesized in the same manner as in Synthesis Example X30, except that the synthetic precursor of the intermediate (XI-74) was appropriately selected.

[0278]

[0279] [Synthesis Example X75] The compound represented by the following formula (XI-75) was synthesized in the same manner as in Synthesis Example X45, except that the synthetic precursor of the intermediate (XI-75) was appropriately selected.

[0280]

[0281] [Synthesis Example B1] In a reaction vessel for the synthesis of the radiation-sensitive acid generator (P1-1), 5.0 g of the compound represented by the above formula (XI-1), 5.0 g of the compound represented by the following formula (XB-1), 50 g of dichloromethane, and 50 g of ultrapure water were added and stirred at room temperature for 2 hours. The aqueous layer was removed, and the organic layer was washed five times with 50 g of ultrapure water. The obtained organic layer was concentrated to dryness to obtain 7.4 g of the compound represented by the following formula (P1-1).

[0282]

[0283] [Synthesis Examples B2 to B76] Synthesis of radiation-sensitive acid generators (P1-2) to (P1-75) and (RP1-1) Radiation-sensitive acid generators (P1-2) to (P1-75) and (RP1-1) were synthesized in the same manner as in Synthesis Example B1, except that the components of the types shown in Table 7 below were used.

[0284]

[0285]

[0286]

[0287] <Synthesis of Acid Diffusion Control Agent (P2)> [Synthesis Example C1] In a reaction vessel for the synthesis of the acid diffusion control agent (P2-1), 2.3 g of the compound represented by the following formula (XC-1), 4.6 g of the compound represented by the above formula (XI-1), 30 g of dichloromethane, and 30 g of ultrapure water were added. After stirring at room temperature for 30 minutes, the organic layer was separated. The obtained organic layer was washed five times with 30 g of ultrapure water. The obtained organic layer was concentrated to dryness to obtain 5.9 g of the compound represented by the following formula (P2-1).

[0288]

[0289] [Synthesis Examples C2 to C67] Synthesis of acid diffusion control agents (P2-2) to (P2-66) and (RP2-1) Acid diffusion control agents (P2-2) to (P2-66) and (RP2-1) were synthesized in the same manner as in Synthesis Example C1, except that the types of components shown in Table 8 below were used.

[0290]

[0291]

[0292] [Synthesis Examples M1-M2] Synthesis of monomers (M-15)-(M-16) Monomers represented by the following formulas (M-15)-(M-16) were synthesized in the same manner as in Synthesis Example B1, except that the types of components shown in Table 9 below were used.

[0293]

[0294]

[0295] <Synthesis of Polymer (A)> The monomers used in the synthesis of each polymer in each example and comparative example are shown below.

[0296]

[0297]

[0298] [Synthesis Example A1] Compound (M-1) and compound (M-4) of polymer (A-1) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total amount of monomer) so that the molar ratio in the final polymer was 40 / 60. Next, azobisisobutyronitrile was added as an initiator at a concentration of 6 mol% relative to the total amount of monomer to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total amount of monomer) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for a further 3 hours. After the polymerization reaction was complete, the polymerization solution was cooled to room temperature.

[0299] The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, and then dissolved in 1-methoxy-2-propanol (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and the hydrolysis reaction was carried out at 70°C for 6 hours with stirring.

[0300] After the reaction was complete, the residual solvent was removed by distillation, and the resulting solid was dissolved in acetone (100 parts by mass). This solution was added dropwise to 500 parts by mass of water to solidify the resin, and the resulting solid was filtered off. It was dried at 50°C for 12 hours to obtain a white powdery polymer (A-1).

[0301] [Synthesis Examples A2 to A12] Polymers (A-2) to (A-12) were synthesized in the same manner as in Synthesis Example A1, except that the types of components shown in Table 10 below were used.

[0302] [Synthesis Example A13] The monomers (M-17), (M-4), and (M-15) of polymer (A-13) were dissolved in propylene glycol monomethyl ether (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer was 35 / 55 / 10. Next, azobisisobutyronitrile was added as an initiator at a concentration of 6 mol% relative to the total amount of monomers to prepare a monomer solution. Meanwhile, propylene glycol monomethyl ether (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for another 3 hours. After the polymerization reaction was complete, the polymerization solution was cooled to room temperature.

[0303] The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution), and then dried at 50°C for 12 hours to obtain a white powdery polymer (A-13).

[0304] [Synthesis Example A14] Synthesis of Polymer (A-14) Polymer (A-14) was synthesized in the same manner as in Synthesis Example A13, except that the components of the types shown in Table 10 below were used.

[0305]

[0306] <Organic Solvents (E)> (E-1): PGMEA (Propylene Glycol Monomethyl Ether Acetate) (E-2): HBM (2-Hydroxyisobutyrate Methyl) (E-3): PGME (Propylene Glycol Monomethyl Ether) (E-4): DAA (Diacetone Alcohol)

[0307] <Radiation-sensitive acid generator (B-66)> B-66: Salt represented by formula (B-66)

[0308] <Acid diffusion control agent (C-60)> C-60: Salt represented by formula (C-60)

[0309]

[0310] [Example 1] 100 parts by mass of polymer (A-1), 40 parts by mass of radiation-sensitive acid generator (P1-1), 50 mol% of acid diffusion control agent (C-60) relative to (P1-1), 2,000 parts by mass of organic solvent (E-1), 4,000 parts by mass of (E-2), and 4,000 parts by mass of (E-3) were mixed and then filtered through a filter with a pore size of 0.20 μm to prepare a radiation-sensitive composition (R-1).

[0311] [Examples 2-159 and Comparative Examples 1-2] Radiation-sensitive compositions (R-2) to (R-159) and (CR-1) to (CR-2) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 11-1 to 11-4 below were used.

[0312]

[0313]

[0314]

[0315]

[0316] <Formation of Resist Pattern> (EUV exposure, alkaline development) The radiation-sensitive compositions prepared above were applied to the surface of a 12-inch silicon wafer on which a 20 nm thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, manufactured by Tokyo Electron). After performing SB (soft bake) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 45 nm thick resist film. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3400", manufactured by ASML, NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was subjected to PEB (post-exposure bake) at 110°C for 60 seconds. Next, the image was developed at 23°C for 30 seconds using a 2.38 mass% TMAH aqueous solution to form a positive-type 48 nm pitch, 24 nm contact hole pattern.

[0317] <Evaluation> For each resist pattern formed as described above, the sensitivity, CDU, underexposure CDU, and number of development defects of each radiation-sensitive composition were evaluated by measurement according to the method described below. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the length of the resist patterns. The evaluation results are shown in Tables 12-1 to 12-4 below.

[0318] [Sensitivity] In forming the resist pattern described above, the exposure amount used to form the 24 nm contact hole pattern is set as the optimal exposure amount, and this optimal exposure amount is set as the sensitivity (mJ / cm²). ２ The sensitivity was set to 38 mJ / cm². A smaller value indicates better sensitivity. ２ If the value is less than 38 mJ / cm², it is classified as "A" (very good). ２ More than 41mJ / cm ２ The following cases are classified as "B" (good), 41 mJ / cm². ２ If it exceeded this value, it was judged as "C" (defective).

[0319] [CDU] Using the scanning electron microscope described above, a 24 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at arbitrary points. The dimensional variation (3σ) was determined and defined as CDU (nm). A smaller CDU value indicates less variation in hole diameter over long periods and therefore better quality. CDU values ​​were judged as "A" (excellent) if less than 2.6 nm, "B" (good) if between 2.6 nm and 2.8 nm, and "C" (poor) if 2.8 nm or more.

[0320] [Underexposure CDU Performance] The same procedure as in the [Sensitivity] section above was performed, except that the EUV exposure dose was less than the optimal exposure dose determined in the [Sensitivity] section above, to form a 23 nm contact hole pattern. Using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), the 23 nm contact hole pattern in the resist pattern was observed from above, and the hole diameter was measured at a total of 800 points. The dimensional variation (3σ) was determined and defined as the underexposure CDU (nm). The underexposure CDU performance indicates that the smaller the underexposure CDU value, the smaller the variation in hole diameter over long periods, and the better the performance. The underexposure CDU performance was judged as "A" (excellent) if it was less than 2.6 nm, "B" (good) if it was between 2.6 nm and 2.8 nm, and "C" (poor) if it was 2.8 nm or more.

[0321] [Development Defect] In the resist pattern resolved at the above optimal exposure, 1 cm ２ The number of development defects per unit area was measured using a defect inspection device (KLA-Tencor's "KLA2810"). Defects with a diameter of 50 μm or less were identified as originating from the resist film, and their number was calculated. A lower number of development defects indicates better quality. The development defect rate was 0.05 defects / cm². ２ The following cases are classified as "A" (excellent), with 0.05 particles / cm². ２ Over 0.10 pieces / cm ２ The following cases are classified as "B" (good), with 0.10 particles / cm². ２ Exceeding 0.15 pieces / cm ２ The following cases are classified as "C" (fairly good), with a value of 0.15 particles / cm². ２ If it exceeds this value, it will be classified as "D" (defective).

[0322]

[0323]

[0324]

[0325]

[0326] As is clear from the results in Tables 12-1 to 12-4, all of the radiation-sensitive compositions in the examples showed a superior balance of sensitivity, CDU, underexposure CDU, and development defects compared to the radiation-sensitive compositions in the comparative examples.

[0327] The radiation-sensitive composition, resist pattern formation method, onium salt compound, and polymer of the present invention can improve sensitivity, CDU, and underexposure CDU while ensuring the absence of development defects. Therefore, these can be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

A polymer (A) containing a structural unit (I) having an acid-dissociable group, Solvent (E) and A radiation-sensitive composition containing, The above radiation-sensitive composition contains an onium salt compound (P) having an onium cation represented by the following formula (1), and a monovalent anion selected from the group consisting of a sulfonic acid anion, a sulfonimide anion, a carboxylic acid anion (excluding benzoate anions substituted with four or more fluoro groups), a methide anion, and a substituted or unsubstituted phenolate anion, or The polymer (A) described above has an onium cation represented by the following formula (1) and an organic acid anion, and includes a structural unit (II) that contains an acid-generating structure that generates acid upon exposure. Radiosensitive linear components. (In the above formula (1), Ar １ This is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. Ar ２ This is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. 　 n1 and n2 are independent integers between 0 and 5, where 1 ≤ n1 + n2 ≤ 10. R １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ They are either identical or different from one another. 　 m1 and m2 are each independent integers between 0 and 5. 　 In the above formula (1), Ar １ and Ar ２ are benzene rings, and the radiation-sensitive composition according to claim 1. 　 In the above formula (1), R １ and R ２ The radiation-sensitive composition according to claim 1, wherein at least one of the groups is at least one group selected from the group consisting of a fluoro group, a C1-C5 alkyl group, a C1-C5 alkoxy group, an alkylsulfonyl group, and an alkyloxycarbonyl group. 　 The radiation-sensitive composition according to claim 1, wherein in formula (1) above, n1 is 1 and n2 is 0 to 3. 　 The radiation-sensitive composition according to claim 1, wherein in formula (1) above, n1 + n2 is 2. 　 The monovalent anion of the above onium salt compound (P) is either a sulfonate anion or a sulfonimide anion. The radiation-sensitive composition according to claim 1, wherein an electron-withdrawing group is bonded to the carbon atom at the α or β position of the sulfur atom of the sulfonate anion or sulfonimide anion. 　 The above radiation-sensitive composition contains the above onium salt compound (P), The radiation-sensitive composition according to claim 6, wherein the content of the onium salt compound (P) is 10 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the polymer (A). 　 The radiation-sensitive composition according to claim 1, wherein the monovalent anion of the onium salt compound (P) is a sulfonate anion (provided that an electron-withdrawing group is not bonded to the α or β carbon atom of the sulfur atom in the sulfonate anion), a carboxylate anion (provided that benzoate anions are substituted with four or more fluoro groups), or a substituted or unsubstituted phenolate anion. 　 The above radiation-sensitive composition contains the above onium salt compound (P), The radioactive composition according to claim 8, wherein the content of the above onium salt compound (P) is 10 mol% or more and 80 mol% or less relative to the total amount of the monomer that gives the above structural unit (II) and the radioactive acid generator. 　 The radiation-sensitive composition according to any one of claims 1 to 9, wherein the polymer further comprises a structural unit (III) having a phenolic hydroxyl group. 　 A step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 9 to a substrate, The process of exposing the above-mentioned resist film, The process involves developing the exposed resist film with a developer solution. A pattern formation method, including the following. 　 The pattern forming method according to claim 11, wherein the exposure is performed using extreme ultraviolet light or an electron beam. 　 An onium salt compound represented by the following formula (1'). (In the above formula (1'), Ar １ This is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. Ar ２ This is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. 　 n1 and n2 are independent integers between 0 and 5, where 1 ≤ n1 + n2 ≤ 10. R １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ They are either identical or different from one another. 　 m1 and m2 are independent integers between 0 and 5. X １ - This is a monovalent anion selected from the group consisting of sulfonate anions (excluding trifluoromethanesulfonate anions and toluenesulfonate anions), sulfonimide anions, carboxylic acid anions (excluding benzoate anions substituted with four or more fluoro groups), methide anions, and substituted or unsubstituted phenolate anions. A structural unit (I) having an acid-dissociable group, A structural unit (II) having an onium cation represented by the following formula (1) and an organic acid anion, and containing an acid-generating structure that generates acid upon exposure, A polymer containing [a certain component]. (In the above formula (1), Ar １ This is an aromatic ring group with 5 to 20 carbon atoms and a (n1 + m1 + 1) valency. Ar ２ This is an aromatic ring group with 5 to 20 carbon atoms and a (n² + m² + 1) valency. 　 n1 and n2 are independent integers between 0 and 5, where 1 ≤ n1 + n2 ≤ 10. R １ and R ２ Each of these is independently a halogen atom other than an iodine atom, a hydroxyl group, a nitro group, a thiol group, a cyano group, a carboxyl group, an amino group, or a monovalent organic group having 1 to 20 carbon atoms. １ and R ２ If there are multiple instances of each, then multiple R １ and R ２ They are either identical or different from one another. 　 m1 and m2 are each independent integers between 0 and 5.

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