Radiation-sensitive composition, pattern formation method, and polymer

Abstract

Provided are a radiation-sensitive composition and pattern formation method that can exhibit satisfactory levels of sensitivity, CDU, and development defect suppression during pattern formation; and a polymer that can be advantageously used in said radiation-sensitive composition. This radiation-sensitive composition contains: a polymer (A) comprising a structural unit (I) having an acid-dissociable group, a structural unit (II) that has a first organic acid anion (b1) and a first onium cation (c1) and that contains a first acid-generating structure that upon exposure generates an acid that induces dissociation of the acid-dissociable group, and a structural unit (III) that has a second organic acid anion (b2) and a second onium cation (c2) and that contains a second acid-generating structure that upon exposure generates an acid that does not induce dissociation of the acid-dissociable group; and a solvent (B). The polymer (A) has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

Description

Radiation-sensitive composition, pattern forming method, and polymer

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

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

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

[0004] As patterns become finer, there is a demand for highly controlled acid diffusion, and as one measure, a resist material using a base polymer containing a weak acid sulfonium salt structure has been proposed (JP 2022-115072 A). In addition, resist materials using resins containing a salt structure that can function as an acid generator and a carboxylate salt structure that can function as a carboxylic acid generator have been proposed (JP 2023-098698 A, JP 2023-098703 A, JP 2023-100003 A, JP 2023-100005 A).

[0005] JP 2022-115072 A JP 2023-098698 A JP 2023-098703 A JP 2023-100003 A JP 2023-100005 A

[0006] In developing the above-mentioned next-generation technology, resist performances equivalent to or better than conventional ones are required in terms of sensitivity, critical dimension uniformity (CDU), which is an index of the uniformity of hole diameter, and suppression of development defects.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern-forming method that can exhibit sufficient levels of sensitivity, CDU, and development defect suppression during pattern formation, as well as a polymer that can be suitably used in the radiation-sensitive composition.

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

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer (A) including: a structural unit (I) having an acid-dissociable group; a structural unit (II) having a first acid-generating structure which has a first organic acid anion (b1) and a first onium cation (c1) and which generates, upon exposure, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) having a second organic acid anion (b2) and a second onium cation (c2) and which generates, upon exposure, an acid that does not induce dissociation of the acid-dissociable group; and a solvent (B), wherein the polymer (A) has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

[0010] The radiation-sensitive composition can be used to form a resist film that satisfies the sensitivity, CDU, and development defect suppression requirements. Although the reason for this is not clear, it is presumed to be as follows.

[0011] When the polymer (A) has at least one alcoholic hydroxyl group, the hydrophilicity of the polymer (A) is improved, and the affinity for the developer can be significantly increased, thereby suppressing development defects.

[0012] The first acid generating structure contained in the structural unit (II) in the polymer (A) has a first organic acid anion (b1) and a first onium cation (c1), and generates an acid that induces dissociation of the acid-dissociable group upon exposure. That is, the first acid generating structure functions as a conventional radiation-sensitive acid generator. By incorporating the first acid generating structure into the structural unit (II), the diffusion length of the acid generated upon exposure can be highly controlled, and an excellent CDU can be exhibited.

[0013] The second acid generating structure contained in the structural unit (III) in the polymer (A) has a second organic acid anion (b2) and a second onium cation (c2), and generates an acid upon exposure that does not induce dissociation of the acid-dissociable group. That is, the second acid generating structure behaves as an acid diffusion controller having a conventional quencher function. By incorporating the second acid generating structure into the structural unit (III), the second acid generating structure having a quencher function can be prevented from diffusing into undesired regions, thereby achieving excellent CDU.

[0014] Furthermore, by incorporating such a first acid generating structure and a second acid generating structure into the polymer (A), the content of the radiation-sensitive acid generator and the acid diffusion controller, which have conventionally been added as low-molecular-weight compounds, can be reduced or eliminated, thereby increasing the solubility of each component in the radiation-sensitive composition and increasing the uniformity of the composition of the resulting resist film, thereby improving sensitivity and suppressing development defects.

[0015] It is presumed that the combined effects of these factors enable the above-mentioned resist performance to be exhibited.

[0016] In another embodiment, the present invention relates to a pattern forming method, comprising the steps of: applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; exposing the resist film; and developing the exposed resist film with a developer.

[0017] In this pattern formation method, the radiation-sensitive composition capable of forming a resist film that is excellent in sensitivity, CDU, and suppression of development defects is used, and therefore a high-quality resist pattern can be efficiently formed.

[0018] In another embodiment, the present invention relates to a polymer comprising: a structural unit (I) having an acid-dissociable group; a structural unit (II) having a first acid-generating structure which has a first organic acid anion (b1) and a first onium cation (c1) and which generates, upon exposure, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) having a second organic acid anion (b2) and a second onium cation (c2) and which generates, upon exposure, an acid that does not induce dissociation of the acid-dissociable group, wherein the polymer has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

[0019] A radiation-sensitive composition using the polymer can form a resist film that satisfies the requirements for sensitivity, CDU, and suppression of development defects.

[0020] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0021] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a polymer (A) having a specific structure and a solvent (B). The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0022] <Polymer (A)> The polymer (A) is an assembly of polymer chains including: a structural unit (I) having an acid-dissociable group; a structural unit (II) having a first acid-generating structure which has a first organic acid anion (b1) and a first onium cation (c1) and which generates, upon exposure, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) having a second organic acid anion (b2) and a second onium cation (c2) and which generates, upon exposure, an acid that does not induce dissociation of the acid-dissociable group (hereinafter, this assembly will also be referred to as a "base polymer"), and is a component that generates an acid upon exposure.

[0023] The structural units (I) to (III) are preferably contained in the same polymer chain. In other words, the polymer (A) of the present invention preferably contains the structural unit (I), the structural unit (II), and the structural unit (III). However, the polymer (A) may be a mixture of polymer chains containing an alcoholic hydroxyl group, the structural unit (I), the structural unit (II), and the structural unit (III) in two or more different polymer chains. For example, the polymer (A) may be a mixture of a first polymer chain containing an alcoholic hydroxyl group, the structural unit (I), and the structural unit (II), and a second polymer chain containing the structural unit (III). Alternatively, the polymer (A) may be a mixture of a first polymer chain containing an alcoholic hydroxyl group and the structural unit (II), a second polymer chain containing the structural unit (I), and a third polymer chain containing the structural unit (III). Alternatively, the polymer (A) may be a mixture of a first polymer chain containing an alcoholic hydroxyl group, a second polymer chain containing the structural unit (I), a third polymer chain containing the structural unit (II), and a fourth polymer chain containing the structural unit (III).

[0024] The polymer (A) has at least one alcoholic hydroxyl group. The alcoholic hydroxyl group refers to a hydroxyl group bonded to a chain hydrocarbon group or an alicyclic hydrocarbon group, and is distinguished from a hydroxyl group directly bonded to an aromatic ring (phenolic hydroxyl group).

[0025] The alcoholic hydroxyl group is preferably at least one type of alcoholic hydroxyl group selected from the group consisting of a primary alcoholic hydroxyl group and a secondary alcoholic hydroxyl group.

[0026] The method for introducing an alcoholic hydroxyl group into the polymer (A) is not particularly limited, and examples thereof include a method of using a monomer having an alcoholic hydroxyl group in the polymerization of the polymer (A) and a method of capping the terminal with a partial structure having an alcoholic hydroxyl group in the polymerization of the polymer (A). Examples of the method for capping the terminal of the polymer (A) with a partial structure having an alcoholic hydroxyl group include a method of using a polymerization initiator having an alcoholic hydroxyl group in the polymerization of the polymer (A).

[0027] In the method using a monomer having an alcoholic hydroxyl group, it is sufficient that at least one of the structural units (I) to (VI) described below has an alcoholic hydroxyl group.

[0028] The polymerization initiator having an alcoholic hydroxyl group may be any one that has an alcoholic hydroxyl group and functions as a polymerization initiator, and its structure is not particularly limited. Examples of the polymerization initiator having an alcoholic hydroxyl group include azo polymerization initiators having an alcoholic hydroxyl group, such as 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) and 2,2'-azobis(2-hydroxymethyl(propionitrile)).

[0029] The polymerization initiator having an alcoholic hydroxyl group may be used alone or in combination with a polymerization initiator not having an alcoholic hydroxyl group. When a monomer having an alcoholic hydroxyl group is used in the polymerization of the polymer (A), a polymerization initiator having an alcoholic hydroxyl group may or may not be used, but when a monomer having an alcoholic hydroxyl group is not used in the polymerization of the polymer (A), a polymerization initiator having an alcoholic hydroxyl group must be used.

[0030] The number of alcoholic hydroxyl groups possessed by the polymer (A) is preferably two or more. The polymer (A) having two or more alcoholic hydroxyl groups can be obtained by using a monomer having one or more alcoholic hydroxyl groups in the polymerization, or by having two or more residues having alcoholic hydroxyl groups derived from the polymerization initiator in the base polymer.

[0031] The number of alcoholic hydroxyl groups in the monomer having one or more alcoholic hydroxyl groups is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0032] In terms of sensitivity and CDU, the polymer (A) preferably contains an iodine group. Although the manner in which the iodine group is contained is not particularly limited, it is preferably contained in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodine groups. By containing an iodine group, radiation absorption efficiency can be increased, and secondary electron generation efficiency can be improved, thereby improving sensitivity.

[0033] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0034] The number of iodo groups in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0035] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The acid generated from the structural unit (II) of the polymer upon exposure dissociates the acid-dissociable group in the structural unit (I), generating a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0036] The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (A1) (hereinafter, also referred to as "structural unit (I-1)") is preferred:

[0037]

[0038] In the above formula (A1), R α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ａ１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ａ２ and R Ａ３ are each independently a monovalent chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. m1 and m2 are each independently 0 or 1. However, when m1 is 1, m2 is 1. When m1 is 0, L Ａ１ represents a single bond or a divalent linking group, and when m1 is 1, L Ａ１ represents a divalent linking group. In the above hydrocarbon groups, chain hydrocarbon groups and alicyclic hydrocarbon groups, some or all of the hydrogen atoms on the carbon atoms may be substituted with substituents such as halogen atoms.

[0039] L Ａ１ Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, an arenediyl group, and groups having —CO—, —CS—, —O—, —S—, —SO— between the carbon-carbon bonds of these groups. ２Examples include -, -NR'-, or a group containing a combination of two or more of these, or a group combining these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms in these groups may be substituted with, for example, a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group, or a group in which the hydrogen atoms of these groups have been substituted with halogen atoms.

[0040] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms, such as a methanediyl group, an ethanediyl group, a 1,3-propanediyl group, or a 2,2-propanediyl group.

[0041] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as cyclopentanediyl and cyclohexanediyl groups, and polycyclic cycloalkanediyl groups such as norbornanediyl and adamantanediyl groups. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0042] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0043] Examples of the arenediyl group include a benzenediyl group, a toluenediyl group, a naphthalenediyl group, etc. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0044] The above R Ａ１ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0045] R Ａ１ ~R Ａ３Examples of the monovalent linear hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a 2-methylpropyl group, a 1-methylpropyl group, a t-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 2 to 20 carbon atoms include alkenyl groups such as an ethenyl group, a propenyl group, and a butenyl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0046] The above R Ａ１ ~R Ａ３ Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Examples of monocyclic saturated hydrocarbon groups include cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Examples of polycyclic saturated hydrocarbon groups include bridged alicyclic hydrocarbon groups such as norbornyl, adamantyl, tricyclodecyl, and tetracyclododecyl. Examples of monocyclic unsaturated hydrocarbon groups include monocyclic cycloalkenyl groups such as cyclopropenyl, cyclobutenyl, cyclopentenyl, and cyclohexenyl. Examples of polycyclic unsaturated hydrocarbon groups include polycyclic cycloalkenyl groups such as norbornenyl, tricyclodecenyl, and tetracyclododecenyl. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms that constitute the alicyclic ring are linked by a linking group containing one or more carbon atoms.

[0047] The above R Ａ１ Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (I) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0048] The above R Ａ１ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms is preferred.

[0049] R Ａ２ and R Ａ３ As the divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded, a group in which one hydrogen atom has been removed from the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0050] R Ａ２ and R Ａ３ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R Ａ２ and R Ａ３ are combined together together with the carbon atoms to which they are bonded, a divalent alicyclic group having 3 to 20 carbon atoms is preferred, a monovalent linear hydrocarbon group having 1 to 10 carbon atoms or a divalent alicyclic group having 5 to 10 carbon atoms is more preferred, and a methyl group, an ethyl group, a cyclopentanediyl group, a cyclohexanediyl group, or an adamantanediyl group is even more preferred.

[0051] When m1 is 0, L Ａ１ is preferably a single bond or an arenediyl group. Ａ１ is preferably an alkanediyl group.

[0052] Examples of the structural unit (I) include structural units represented by the following formulas (1-1) to (1-12) (hereinafter also referred to as "structural units (I-1) to (I-12)").

[0053]

[0054] In the above formulas (1-1) to (1-12), R α , R Ａ１ ~R Ａ３has the same meaning as formula (A1) above. X is a hydroxy group, a halogen atom, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are 0 or 1. a1 is an integer of 0 to 3. When a1 is 2 or more, multiple Xs may be the same or different.

[0055] i and j are preferably 1 or 2. Ａ１ R is preferably a methyl group, an ethyl group, a t-butyl group, a phenyl group, or an iodophenyl group. Ａ２ and R Ａ３ As X, a methyl group, an ethyl group, or an isopropyl group is preferable. As X, an iodine atom, an alkyl group, or an alkoxy group is preferable. By employing an iodine atom as X, an iodine group can be suitably introduced into the structural unit (I).

[0056] Specific examples of the structural unit (I) include, but are not limited to, structures represented by the following formulas:

[0057]

[0058] (In the formula, R α has the same meaning as formula (A1) above.

[0059] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0060] The lower limit of the content of the structural unit (I) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0061] (Structural Unit (II)) The structural unit (II) includes a first acid generating structure. The first acid generating structure has a first organic acid anion (b1) and a first onium cation (c1), and generates an acid that induces dissociation of the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion (b1) and the first onium cation (c1) (i.e., the first acid generating structure) functions as a radiation-sensitive acid generating structure. A polymer (A) having a radiation-sensitive acid generating structure (first acid generating structure) is distinguished from a low-molecular-weight compound (radiation-sensitive acid generator) in which the onium salt structure exists alone as a compound (isolated from a polymer).

[0062] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0063] The form in which the first organic acid anion (b1) and the first onium cation (c1) are contained in the structural unit (II) of the base polymer is not particularly limited, and the base polymer may have the first organic acid anion (b1) as a side chain moiety, or may have the first onium cation (c1) as a side chain moiety. "Having as a side chain moiety" means that the corresponding first organic acid anion (b1) or first onium cation (c1) is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the first organic acid anion (b1) is bonded to the main chain of the base polymer as a side chain structure, the first onium cation (c1) is ionically bonded to the first organic acid anion (b1) as a counter ion of the first organic acid anion (b1). On the other hand, when the first onium cation (c1) is bonded to the main chain as a side chain structure of the base polymer, the first organic acid anion (b1) is ionically bonded to the first onium cation (c1) as a counter ion of the first onium cation (c1). From the viewpoint of CDU, it is preferable that the base polymer has the first organic acid anion (b1) as a side chain moiety.

[0064] The first organic acid anion (b1) preferably has at least one selected from the group consisting of sulfonate anions, carboxylic acid anions, and sulfonimide anions as the acid anion moiety. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide, corresponding to the acid anion moiety. Among these, a sulfonate anion is more preferred, and an electron-withdrawing group is more preferably bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. Furthermore, the polymer (A) preferably has the sulfonate anion as a side chain moiety, since this allows the first acid-generating structure to efficiently exhibit the above-mentioned function.

[0065] Examples of the electron-withdrawing group include acyl groups such as an acetyl group, a propionyl group, a benzoyl group, and an acryloyl group; alkylsulfonyl groups such as a methylsulfonyl group; a cyano group, a nitro group; halogen groups such as a fluorine atom and an iodine atom; and monovalent hydrocarbon groups having 1 to 5 carbon atoms in which some or all of the hydrogen atoms have been substituted with at least one of these groups.

[0066] The organic acid anion (b1) preferably contains -O-, -CO-, a cyclic structure, or a combination thereof. Such combinations also include structures (heterocyclic structures) in which -O- or -CO- is incorporated as a ring-forming moiety within a cyclic structure. The organic acid anion (b1) preferably contains an iodine group, and more preferably contains the iodo group-containing aromatic ring structure.

[0067] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0068] The alicyclic structure may be R Ａ１ ~R Ａ３ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0069] As the aromatic ring structure, the aromatic rings (including aromatic hydrocarbon rings and heteroaromatic rings) shown in the iodo group-containing aromatic ring structure can be suitably used.

[0070] Examples of the heterocyclic structure include: oxygen atom-containing aliphatic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; nitrogen atom-containing aliphatic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; sulfur atom-containing aliphatic heterocyclic structures such as thietane, thiolane, and thiane; aliphatic heterocyclic structures containing multiple types of heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane; oxygen atom-containing aromatic heterocyclic structures such as furan and benzofuran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, pyrazole, and triazine; sulfur atom-containing aromatic heterocyclic structures such as thiophene; and aromatic heterocyclic structures containing multiple types of heteroatoms such as oxazole, isothiazole, and thiazine.

[0071] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof. Examples of such structures include structures represented by the following formulas (H-1) to (H-11).

[0072] (In the above formula, g is an integer of 1 to 3.)

[0073] The chain structure may be R Ａ１ ~R Ａ３ A monovalent chain hydrocarbon group having 1 to 10 carbon atoms in the above formula can be suitably used.

[0074] Examples of the divalent heteroatom-containing group include —CO—, —CS—, —NR′—, —O—, —S—, and —SO ２- or a divalent group formed by combining these groups, etc. R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0075] Examples of the substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include L Ａ１ The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0076] The onium cation (c1) may be a radiation-decomposable onium cation. Examples of the radiation-sensitive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0077] The onium cation (c1) in the structural unit (II) may have an iodo group or may contain the above-mentioned iodo group-containing aromatic ring structure.

[0078] The first onium cation (c1) in the structural unit (II) may be a fluoro-group-containing onium cation having a fluoro group. The fluoro-group-containing onium cation preferably has a fluoro-group-containing aromatic ring structure. The fluoro-group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro-group-containing aromatic ring structure can be suitably an aromatic ring in an iodine-group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0079] The number of fluorine atoms in the fluoro group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, and more preferably 1, 2 or 3.

[0080] The structural unit (II) having the above structures in combination can efficiently exhibit the above functions.

[0081] The polymer (A) preferably contains a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (II-1)") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit (II-2)").

[0082]

[0083] In the formula, R Ａ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ X is a linear, branched or cyclic alkanediyl group having 1 to 12 carbon atoms, a cycloalkanediyl group having 3 to 12 carbon atoms, or an arenediyl group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkanediyl group may be substituted with an ether group, an ester group or a lactone ring-containing group. ３ X is a single bond, an ether group, an ester group, a linear or branched alkanediyl group having 1 to 12 carbon atoms, or a cyclic cycloalkanediyl group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkanediyl group may be substituted with an ether group or an ester group. ２ and X ３ Some or all of the hydrogen atoms of X may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. ２ Preferably, the aromatic ring structure contains an iodo group.

[0084] The alkanediyl group, cycloalkanediyl group, and arenediyl group are each selected from the group consisting of L Ａ１ Alkanediyl groups, cycloalkanediyl groups, and arenediyl groups represented by the following formula can be preferably used.

[0085] The above Rf １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a trifluoromethyl group. The above s1 is 0 or 1. R ４３ ~R ４７are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R ４３ and R ４４ and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. ４３ ~R ４５ and R ４６ ~R ４７ Preferably, at least one of the above contains an iodo group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure.

[0086] R ４３ ~R ４７ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (A1) is R Ａ１ Some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0087] The structural units (II-1) and (II-2) are preferably represented by the following formulae (a1-1) to (a1-4) and (a2-1) to (a2-3), respectively.

[0088]

[0089]

[0090] In the formula, R Ａ , R ４３ ~R ４７ , Rf １ ~Rf ４ , X １ , and s1 have the same meanings as in the above formulas (a1) and (a2). ４８is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3, with the proviso that 0≦m+n≦4. s and s2 are integers of 1 to 5.

[0091] Examples of the organic acid anion (b1) of the monomer that gives the structural unit (II) (including the structural unit (II-1) and the structural unit (II-2)) include, but are not limited to, those shown below. Among those shown below, for the structure having an iodo group-containing aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably used.

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] (In the formula, R Ａ has the same meaning as the above formulas (a1) and (a2).

[0106] The onium cation (c1) of the structural unit (II-1) is preferably represented by the following formula (Q-1):

[0107]

[0108] In the above formula (Q-1), Ra1 to Ra3 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or more, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or more, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or more, multiple Ra3s may be the same or different. Ra1 and Ra2 may be linked to each other to form a ring. When n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring. When n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring.

[0109] The substituents represented by Ra1, Ra2, and Ra3 are preferably an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkyloxy group, an alkoxycarbonyl group, an alkylsulfonyl group, a hydroxyl group, a halogen atom, or a halogenated hydrocarbon group.

[0110] The alkyl groups of Ra1, Ra2, and Ra3 may be linear or branched alkyl groups. Ａ１ ~R Ａ３ Preferably, a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms in the following formula can be used. Among these, a methyl group, an ethyl group, an n-butyl group, and a t-butyl group are particularly preferred.

[0111] The cycloalkyl groups of Ra1, Ra2, and Ra3 include monocyclic or polycyclic cycloalkyl groups (preferably cycloalkyl groups having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0112] Examples of the alkyl group moiety of the alkoxy group of Ra1, Ra2, and Ra3 include those previously listed as the alkyl group of Ra1, Ra2, and Ra3. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0113] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1, Ra2, and Ra3 include those previously listed as the cycloalkyl groups of Ra1, Ra2, and Ra3. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0114] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1, Ra2, and Ra3 include those previously listed as the alkoxy groups of Ra1, Ra2, and Ra3. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0115] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1, Ra2, and Ra3 include those previously listed as the alkyl groups of Ra1, Ra2, and Ra3. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1, Ra2, and Ra3 include those previously listed as the cycloalkyl groups of Ra1, Ra2, and Ra3. Particularly preferred of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl.

[0116] Each of the groups Ra1, Ra2, and Ra3 may further have a substituent, such as a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, a cycloalkyloxyalkyl group, an alkoxycarbonyl group, a cycloalkyloxycarbonyl group, an alkoxycarbonyloxy group, and a cycloalkyloxycarbonyloxy group.

[0117] Examples of the halogen atom for Ra1, Ra2, and Ra3 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0118] The halogenated hydrocarbon group of Ra1, Ra2, and Ra3 is preferably a halogenated alkyl group. Examples of the alkyl group and halogen atom constituting the halogenated alkyl group are the same as those described above. Among them, a fluorinated alkyl group is preferred, and CF ３ is more preferred.

[0119] As described above, Ra1 and Ra2 may be bonded to each other to form a ring (i.e., a heterocycle containing a sulfur atom). In this case, it is preferable that Ra1 and Ra2 are bonded to each other to form a single bond or a divalent linking group. Examples of the divalent linking group include -COO-, -OCO-, -CO-, -O-, -S-, -SO-, and -SO ２-, an alkylene group, a cycloalkylene group, an alkenylene group, or a combination of two or more of these, and those having a total carbon number of 20 or less are preferred. When Ra1 and Ra2 are bonded to each other to form a ring, Ra1 and Ra2 are bonded to each other to form -COO-, -OCO-, -CO-, -O-, -S-, -SO-, -SO ２ It is preferable that n1 forms - or a single bond. Among these, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. Furthermore, when n1 is 2 or more, a plurality of Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, a plurality of Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0120] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF ３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７, C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0121] Ra3 is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0122] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0123] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0124] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0125] Specific examples of the onium cation (c1) represented by the above formula (Q-1) include the following:

[0126] (In the formula, tBu represents a t-butyl group, and Me represents a methyl group.)

[0127] (In the formula, Me represents a methyl group.)

[0128]

[0129]

[0130] (In the formula, Me represents a methyl group.)

[0131]

[0132] (In the formula, Me represents a methyl group.)

[0133] Specific examples of the iodonium cation of the structural unit (II-2) include the following: In the onium cation shown below, a hydrogen atom on the aromatic ring may be substituted with an iodine atom, a fluorine atom, a group containing these atoms, or another substituent.

[0134]

[0135] The monomers that give the structural units (II-1) and (II-2) can be synthesized, for example, by a method similar to that for the sulfonium salts having polymerizable anions described in Japanese Patent No. 5201363.

[0136] When a first onium cation (c1) is bonded to the main chain as a side chain structure of the base polymer, and a first organic acid anion (b1) is ionically bonded to the first onium cation (c1) as a counter ion of the first onium cation (c1), it is preferable that the base polymer contains unit structures represented by the following formulas (a3) ​​and (a4) (hereinafter also referred to as "unit structure (II-3)" and "unit structure (II-4)").

[0137]

[0138] In the formula, R Ａ , R ４４ , R ４５ , Rf １ ~Rf ４ , X １ , and s1 have the same meanings as in the above formulas (a1) and (a2). ４８ , m, and n have the same meanings as in the above formulae (a1-1) to (a1-4) and (a2-1) to (a2-3). ４３１ is R in the above formulas (a1) and (a2). ４３ A divalent group obtained by removing one hydrogen atom from L can be preferably used. １１ is a divalent linking group, and L in the above formula (A1) Ａ１ A divalent linking group represented by the following formula can be preferably used.

[0139] Specific examples of the monomers that give the above unit structures (II-3) and (II-4) include the following.

[0140]

[0141] The lower limit of the content of the structural unit (II) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By keeping the content of the structural unit (II) within the above range, the function as an acid generator can be fully exhibited.

[0142] (Structural Unit (III)) The structural unit (III) includes a second acid generating structure. The second acid generating structure has a second organic acid anion (b2) and a second onium cation (c2), and generates an acid that does not induce dissociation of the acid-dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the radiation-sensitive composition, the second acid generating structure does not substantially dissociate the acid-dissociable group of the structural unit (I), and has the function of suppressing the diffusion of the acid generated from the first acid generating structure in unexposed areas through salt exchange. It can be said that the acid generated from the second acid generating structure is a relatively weaker acid (an acid with a higher pKa) than the acid generated from the first acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable group in the base polymer and the acidity of the onium salt structure or the acid generated. A polymer (A) having an acid-diffusion-controlling structure (second acid-generating structure) is distinguished from a low-molecular-weight onium salt structure (an acid diffusion controller) in which the onium salt structure exists alone as a compound (isolated from a polymer).

[0143] The form in which the second organic acid anion (b2) and the second onium cation (c2) are contained in the structural unit (III) of the base polymer is not particularly limited, and the base polymer may have the second organic acid anion (b2) as a side chain moiety, or may have the second onium cation (c2) as a side chain moiety. "Having as a side chain moiety" means that the corresponding second organic acid anion (b2) or second onium cation (c2) is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the second organic acid anion (b2) is bonded to the main chain of the base polymer as a side chain structure, the second onium cation (c2) is ionically bonded to the second organic acid anion (b2) as a counter ion of the second organic acid anion (b2). On the other hand, when the second onium cation (c2) is bonded to the main chain as a side chain structure of the base polymer, the second organic acid anion (b2) is ionically bonded to the second onium cation (c2) as a counter ion of the second onium cation (c2). From the viewpoint of CDU, it is preferable that the base polymer has the second organic acid anion (b2) as a side chain moiety.

[0144] The second organic acid anion (b2) preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety, and more preferably a carboxylate anion. Furthermore, when the second organic acid anion (b2) has the sulfonate anion, it is preferred that no electron-withdrawing group be bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. The electron-withdrawing group can be suitably selected from the electron-withdrawing groups listed for the first organic acid anion (b1). The acid generated by exposure is a carboxylic acid or sulfonic acid corresponding to the acid anion moiety.

[0145] The second organic acid anion (b2) preferably contains, as a structure other than the acid anion moiety, -O-, -CO-, a cyclic structure, or a combination thereof. As such a structure, the structures shown for the first organic acid anion can be suitably employed. Furthermore, the organic acid anion (b2) preferably contains an iodine group or a hydroxy group, and more preferably contains a carboxylate anion and a hydroxy group bonded to the same aromatic ring.

[0146] The second onium cation (c2) is a radiation-sensitive onium cation. A radiation-sensitive onium cation is a cation that decomposes upon exposure to exposure light. Examples of the onium cation (c2) include the radiation-sensitive onium cations listed for the onium cation (c1). Among these, sulfonium cations and iodonium cations are preferred, and sulfonium cations are more preferred.

[0147] The second onium cation (c2) preferably has an iodo group as described above. As a mode of containing the iodo group, the second onium cation (c2) preferably includes the iodo group-containing aromatic ring structure.

[0148] The second onium cation (c2) preferably has the fluoro group-containing aromatic ring structure, which increases the radiation absorption efficiency and thereby improves sensitivity.

[0149] The structural unit (III) having the above structures in combination can efficiently exhibit the above functions.

[0150] The structural unit (III) is preferably a structural unit represented by the following formula (p1) or (p2) (hereinafter also referred to as "structural unit (III-1)" or "structural unit (III-2)").

[0151]

[0152] In formulas (p1) and (p2), R Ａ is a hydrogen atom or a methyl group.

[0153] In formulas (p1) and (p2), X ３１ is a single bond, an ester bond, an ether bond, a phenylene group, or a naphthylene group.

[0154] In formulas (p1) and (p2), X ３２ X is a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the methylene group constituting the saturated hydrocarbylene group may be replaced by an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ３２The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methanediyl group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3 alkanediyl groups having 1 to 12 carbon atoms, such as 1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, and decane-1,10-diyl; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; and groups obtained by combining these.

[0155] In formulas (p1) and (p2), X ３３ is a single bond, an ester bond or an ether bond.

[0156] In formulas (p1) and (p2), R Ｘ is a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

[0157] In formulas (p1) and (p2), R ４３ ~R ４７ has the same meaning as the above formulas (a1) and (a2).

[0158] In formulas (p1) and (p2), x1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R Ｘ are the same or different.

[0159] Examples of the second organic acid anion (b2) of the monomer that gives the structural unit (III) include, but are not limited to, those shown below. All of the second organic acid anions (b2) shown below have a hydroxy group, but the structural unit (III) does not necessarily require a hydroxy group. As the second organic acid anion that does not have a hydroxy group, a structure in which the hydroxy group in the following formula is substituted with a hydrogen atom, other substituents, or the like can be suitably used. Furthermore, among those shown below, for the structure having an iodo group-containing aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably used. In the following formula, R Ａ is the same as above.

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166]

[0167]

[0168] As the second onium cation (c2) in the structural unit (III), the sulfonium cation and iodonium cation in the structural unit (II) can be suitably used.

[0169] It is also possible to adopt an embodiment in which the second onium cation (c2) is bonded to the main chain as a side chain structure of the base polymer, and the second organic acid anion (b2) is ionically bonded to the second onium cation (c2) as a counter ion of the second onium cation (c2). In this case, the second onium cation (c2) is bonded to the main chain via a divalent linking group or a single bond, and X in the above formula (p1) or (p2) ３１ From COO －The structure up to the above is preferably ionically bonded to the second onium cation (c2) as a counter ion. Ａ１ A divalent linking group represented by the following formula can be preferably used.

[0170] The lower limit of the content of the structural unit (III) in the base polymer (the total content when multiple types are included) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%, based on all structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (III) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0171] The lower limit of the total content of the structural unit (II) and the structural unit (III) in the polymer (A) is preferably 10 mol%, more preferably 15 mol%, based on all structural units constituting the polymer (A). The upper limit of the total content is preferably 60 mol%, more preferably 40 mol%. The sum of the content of the structural unit (II) and the content of the structural unit (III) within the above range is preferred from the viewpoints of sensitivity and CDU.

[0172] (Structural Unit (IV)) The polymer (A) can contain a structural unit (IV) having an alcoholic hydroxyl group represented by the following formula (1) (excluding structures corresponding to the structural units (I) to (III)). (In formula (1), R Ａ１１ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or a hydroxyalkyl group having 1 to 5 carbon atoms. １ is a single bond or an ester group. １ R is an (n11+n12+1)-valent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a group containing a divalent heteroatom-containing group between carbon atoms or at the terminal on the bond side of this aliphatic hydrocarbon group. ２ represents a single bond, a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a bond between carbon atoms in this aliphatic hydrocarbon group or R１ is a group containing a divalent heteroatom-containing group at the terminal on the bond side bonding to R ２ If there are multiple R ２ are the same or different. ３ is a halogen atom, a cyano group, a nitro group, or a monovalent organic group. ３ If there are multiple R ３ are the same or different from each other, and n11 is an integer of 0 to 5. Ａ１１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, n11 is an integer of 1 to 5, and n12 is an integer of 0 to 5.

[0173] Examples of the hydroxyalkyl group having 1 to 5 carbon atoms include a hydroxymethyl group, a 1-hydroxyethyl group, and a 2-hydroxyethyl group.

[0174] R １ Examples of the (n11+n12+1)-valent aliphatic hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (1) include an (n11+n12+1)-valent chain hydrocarbon group having 1 to 20 carbon atoms, an (n11+n12+1)-valent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a group formed by combining these groups.

[0175] The chain hydrocarbon group having 1 to 20 carbon atoms and a valence of (n11+n12+1) is, for example, R Ａ１ ~R Ａ３ Preferably usable are groups in which (n11 + n12) hydrogen atoms have been removed from a monovalent chain hydrocarbon group having 1 to 20 carbon atoms in the formula (I) above. Among these, groups in which (n11 + n12) hydrogen atoms have been removed from a monovalent linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms are preferred, and groups in which (n11 + n12) hydrogen atoms have been removed from an alkyl group having 2 to 6 carbon atoms are more preferred.

[0176] The (n11+n12+1)-valent alicyclic hydrocarbon group having 3 to 20 carbon atoms includes R Ａ１ ~R Ａ３Preferably usable are groups in which (n11 + n12) hydrogen atoms have been removed from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the formula (I) above. Among these, groups in which (n11 + n12) hydrogen atoms have been removed from a monovalent monocyclic or polycyclic saturated hydrocarbon group having 3 to 20 carbon atoms are preferred, and groups in which (n11 + n12) hydrogen atoms have been removed from a monovalent cycloalkyl group having 5 to 8 carbon atoms or a monovalent bridged alicyclic hydrocarbon group having 6 to 12 carbon atoms are more preferred.

[0177] R ２ Examples of the divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a divalent chain hydrocarbon group having 1 to 20 carbon atoms and a divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0178] The divalent chain hydrocarbon group having 1 to 20 carbon atoms includes R Ａ１ ~R Ａ３ A group in which one hydrogen atom has been removed from a monovalent chain hydrocarbon group having 1 to 20 carbon atoms can be suitably used.

[0179] The divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms includes R Ａ１ ~R Ａ３ A group in which one hydrogen atom has been removed from a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms can be suitably used.

[0180] Examples of heteroatoms constituting the divalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0181] Examples of the divalent heteroatom-containing group include -CO-, -CS-, -NH-, -O-, -S-, and combinations of these groups.

[0182] The above R １ aliphatic hydrocarbon groups having 1 to 20 carbon atoms and a valence of (n11+n12+1), represented by the formula: ２a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms represented by the formula: １ In the group containing a divalent heteroatom-containing group at the terminal on the bond side bonded to R, some or all of the hydrogen atoms on the carbon atoms may be substituted with halogen atoms such as fluorine atoms. １ or R ２ In each group represented by the formula (I), it is preferred that the hydrogen atoms on the carbon atoms are not substituted with halogen atoms, from the viewpoint of increasing the affinity for the developer and easily suppressing development defects.

[0183] R ２ is a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a carbon-carbon bond in this aliphatic hydrocarbon group or R １ It is preferable that the group contains a divalent heteroatom-containing group at the terminal on the bond side that bonds to the group.

[0184] R ３ Examples of the monovalent organic group represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof. ３ The monovalent organic group represented by the formula (I) may have a salt structure containing an organic acid anion and an onium cation.

[0185] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R Ａ１ As the divalent heteroatom-containing group, R in the above formula (1) can be suitably used. １ , R ２ Preferably, a divalent heteroatom-containing group represented by the formula (I) can be used. Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0186] Examples of the monomer that provides the structural unit (IV) include, but are not limited to, the following: Ａ１１ is the same as the above formula (1).

[0187]

[0188]

[0189]

[0190]

[0191] The base polymer may contain one or more types of structural unit (IV).

[0192] When the base polymer has the structural unit (IV), the lower limit of the content of the structural unit (IV) (when multiple types are contained, the total content) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 5 mol% relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 15 mol%. By setting the content of the structural unit (IV) within the above range, the development defect suppression property can be further improved.

[0193] (Structural Unit (V)) The polymer (A) preferably further contains a structural unit (V) having a phenolic hydroxyl group. When the polymer (A) contains the structural unit (V), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (V) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the present invention is suitable for pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (V) is preferably represented by the following formula (2):

[0194] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊or -O-. * is a bond on the aromatic ring side. R １０１ is an acid-dissociable group. １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ and m ５ are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ +m ５ ≦2n ３ Meets +5.)

[0195] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (V), the substituent is preferably a hydrogen atom or a methyl group.

[0196] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0197] The above R １０１ The acid-dissociable group represented by the formula (I) is not particularly limited, and examples thereof include R １０１ a structure forming a tertiary alkyl ester moiety together with —COO— to which R １０１ a structure that forms, together with —COO— to which —COO— is bonded, a secondary unsaturated alkyl ester moiety having a double bond between the β-position carbon and the γ-position carbon of the terminal oxygen atom of —COO—; １０１ and a structure in which an acetal bond is formed together with —COO— to which —COO— is bonded.

[0198] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the formula (A1) is preferably L Ａ１ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0199] The above n ３is more preferably 0 or 1, and even more preferably 0.

[0200] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0201] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0202] The above m ５ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0203] The structural unit (V) is preferably a structural unit represented by the following formulas (2-1) to (2-30) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-30)"), or the like.

[0204]

[0205]

[0206]

[0207] In the above formulas (2-1) to (2-30), R β is the same as the above formula (2).

[0208] The lower limit of the content of the structural unit (V) (total content when multiple types of structural unit (V) are present) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of the structural unit (V) within the above range, the sensitivity of the radiation-sensitive composition can be further improved.

[0209] (Structural Unit (VI)) The polymer (A) may further contain another structural unit (VI) containing a polar group such as a halogen atom, a carboxy group, a lactone ring, a sultone ring, an ether group, an ester group, a carbonyl group, or a cyano group. Monomers that provide the other structural unit (VI) include, but are not limited to, those shown below. In the following formula, R Ａ is the same as above.

[0210]

[0211]

[0212]

[0213]

[0214]

[0215]

[0216]

[0217]

[0218]

[0219] The base polymer may contain one or more types of structural unit (VI) in combination.

[0220] When the base polymer contains the structural unit (VI), the lower limit of the content of the structural unit (VI) (the total content when multiple types are contained) is preferably 1 mol %, more preferably 3 mol %, based on all structural units constituting the base polymer. The upper limit of the content is preferably 20 mol %, more preferably 15 mol %, and even more preferably 10 mol %. By keeping the content of the structural unit (VI) within the above range, pattern adhesion can be further improved.

[0221] To synthesize the polymer (A), for example, a monomer that provides the structural unit described above may be polymerized by adding a radical polymerization initiator to an organic solvent and heating. A known polymerization initiator can be used for the polymerization. When using a polymerization initiator having an alcoholic hydroxyl group in the polymerization of the polymer (A), the polymerization initiator having an alcoholic hydroxyl group may be used alone or in combination with a polymerization initiator that does not have an alcoholic hydroxyl group. When used in combination, the polymerization initiator having an alcoholic hydroxyl group preferably accounts for 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more of the total polymerization initiators used in the polymerization of the polymer (A).

[0222] The polymer (A) has a polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) using THF as a solvent of preferably 3,000, more preferably 5,000. The upper limit of Mw is preferably 30,000, more preferably 15,000. When Mw is within the above range, the resist material exhibits good pattern formability and heat resistance.

[0223] The molecular weight distribution of the polymer (A) is preferably narrow, ranging from 1.0 to 2.0, particularly from 1.0 to 1.8.

[0224] The polymer (A) may contain two or more polymers having different composition ratios, Mws, and molecular weight distributions.

[0225] The lower limit of the content of the polymer (A) in the radiation-sensitive composition is preferably 75% by mass, more preferably 80% by mass, and even more preferably 85% by mass, based on the amount of the components other than the solvent contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass.

[0226] The radiation-sensitive composition may further contain a radiation-sensitive acid generator (C) and an acid diffusion controller (D) in addition to the polymer (A) and solvent (B).

[0227] <Radiation-Sensitive Acid Generator (C)> From the viewpoints of sensitivity and CDU, the radiation-sensitive composition preferably contains a radiation-sensitive acid generator (C). The radiation-sensitive acid generator (C) has a third organic acid anion (b3) and a third onium cation (c3), has a lower molecular weight than the polymer (A), and generates an acid upon exposure that induces dissociation of the acid-dissociable group in the polymer (A). The acid generated upon exposure has the function of dissociating the acid-dissociable group in the base polymer and generating a carboxy group or the like.

[0228] The radiation-sensitive acid generator containing the third organic acid anion (b3) and the third onium cation (c3) is preferably represented by the following formula (p-1). (In the above formula (p-1), R ｐ１ is a monovalent group containing a ring structure.ｐ２ is a divalent linking group. ｐ３ and R ｐ４ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ｐ５ and R ｐ６ are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ｐ１ is an integer from 0 to 10. ｐ２ is an integer from 0 to 10. ｐ３ is an integer from 0 to 10. ｐ１ +n ｐ２ +n ｐ３ is an integer between 1 and 30. ｐ１ If there are two or more R ｐ２ are the same or different. ｐ２ If there are two or more R ｐ３ are the same or different, and multiple R ｐ４ are the same or different. ｐ３ If there are two or more R ｐ５ are the same or different, and multiple R ｐ６ are the same or different. ＋ is a monovalent onium cation.

[0229] R ｐ１ Examples of the monovalent group containing a ring structure represented by the formula (I) include a monovalent group containing an alicyclic structure having 5 or more ring members, a monovalent group containing an aliphatic heterocyclic structure having 5 or more ring members, a monovalent group containing an aromatic ring structure having 6 or more ring members, and a monovalent group containing an aromatic heterocyclic structure having 6 or more ring members. ｐ１ Among these, a monovalent group containing an alicyclic structure having five or more ring members or a monovalent group containing an aromatic heterocyclic structure having six or more ring members is preferable, and specifically, an adamantyl group, a phenyl group, or a naphthyl group is more preferable, and an adamantyl group is particularly preferable.

[0230] R ｐ１ A part or all of the hydrogen atoms in the ring structure may be substituted with a substituent. Examples of the substituent include L in the above formula (A1). Ａ１The substituents that can be contained in the divalent linking group represented by the following formula (I) can be preferably used. Among these, an iodo group is preferred.

[0231] R ｐ２ Examples of the divalent linking group represented by the formula (A1) include L Ａ１ A divalent linking group represented by the following formula can be preferably used.

[0232] R ｐ３ and R ｐ４ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (A1) is Ａ１ A monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the following formula can be preferably used. ｐ３ , R ｐ４ , R ｐ５ and R ｐ６ Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include groups in which some or all of the hydrogen atoms in the monovalent hydrocarbon group having 1 to 20 carbon atoms have been replaced with fluorine atoms.

[0233] Examples of the third organic acid anion (b3) of the radiation-sensitive acid generator (C) represented by the above formula (p-1) include, but are not limited to, the following: Among the following, for the organic acid anion having an iodo group-containing aromatic ring structure, a structure in which the iodine atom is substituted with an atom or group other than the iodine atom, such as a hydrogen atom or another substituent, can also be suitably used.

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242] In the formula (p-1), the Z ＋ As the third onium cation (c3) represented by the formula: the sulfonium cation and iodonium cation in the unit structure (II) can be suitably used.

[0243] The radiation-sensitive acid generator (C) includes any combination of the third organic acid anion (b3) and the third onium cation (c3). Among these, the following are preferred:

[0244]

[0245] The radiation-sensitive acid generator (C) can be synthesized by a known method, particularly a salt exchange reaction. A known radiation-sensitive acid generator other than the radiation-sensitive acid generator (C) can be used in combination with the radiation-sensitive acid generator (C) as long as the effects of the present invention are not impaired.

[0246] These radiation-sensitive acid generators (C) may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator (C), the lower limit of the content of the radiation-sensitive acid generator (C) (total content when multiple types are used) is preferably 1 part by mass, more preferably 2 parts by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass, per 100 parts by mass of the polymer (A). This allows for excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0247] <Acid Diffusion Controller (D)> From the viewpoints of sensitivity and CDU, the radiation-sensitive composition preferably contains an acid diffusion controller (D). The acid diffusion controller (D) has a fourth organic acid anion (b4) and a fourth onium cation (c4), has a lower molecular weight than the polymer (A), and generates, upon exposure, a weak acid that does not induce dissociation of the acid-dissociable group in the polymer (A). That is, upon exposure to radiation, it generates an acid having a higher pKa than the acid generated from the first acid-generating structure of the polymer (A) or the radiation-sensitive acid generator (C). The acid diffusion controller (D) containing the fourth organic acid anion (b4) and the fourth onium cation (c4) is preferably represented by any of the following formulas (8-1) to (8-4).

[0248]

[0249] In the above formula (8-1) and formula (8-2), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. E in the above formula (8-1) and formula (8-2) － and Q － are each independently R ８ SO ３ － , R ８ COO － , and (R ８ SO ２ ) N － Preferably, R is at least one selected from the group consisting of ８ COO － Further, examples of the compound include a compound represented by the above formula (8-3) containing a sulfonium cation and an anion in the same molecule, and a compound represented by the above formula (8-4) containing an iodonium cation and an anion in the same molecule. In the above formulas (8-3) and (8-4), J' ＋ is a monovalent group having a sulfonium cation structure, and U' ＋ is a monovalent group having an iodonium cation structure. － and Q' － are each independently -R ８１ SO ３ － , -R ８１ COO － , and -R ８１ SO ２ N － SO ２ R ８ Preferably, the group is at least one selected from the group consisting of -R ８１ COO － It is more preferable that the above R ８ is a monovalent organic group, and the R ８１ is a single bond or a divalent organic group.

[0250] From the viewpoint of sensitivity, the fourth organic acid anion (b4) is preferably an organic acid anion containing iodine or fluorine, and more preferably an organic acid anion containing an iodo group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure.

[0251] Examples of the third organic acid anion (b4) include anions represented by the following formulas: Among the structures shown below, for the structures having an iodo group-containing aromatic ring structure, structures in which the iodine atom in the following formula is substituted with an atom or group other than an iodine atom, such as a hydrogen atom or other substituent, can also be suitably used.

[0252]

[0253]

[0254]

[0255]

[0256]

[0257]

[0258]

[0259]

[0260] J ＋ sulfonium cation, U ＋ As the iodonium cation, the sulfonium cation and iodonium cation in the unit structure (II) can be suitably used.

[0261] The acid diffusion controller (D) includes any combination of the quaternary organic acid anion (b4) and the quaternary onium cation (c4).

[0262] The acid diffusion controller (D) can be synthesized by a known method, particularly a salt exchange reaction. Known acid diffusion controllers other than those mentioned above can also be used as long as they do not impair the effects of the present invention.

[0263] These acid diffusion controllers (D) may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (D) (total amount when multiple types are used) is preferably 1 part by mass, more preferably 3 parts by mass, and even more preferably 5 parts by mass, per 100 parts by mass of the polymer (A). The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass, per 100 parts by mass of the polymer (A). This allows excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0264] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, it is possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film.

[0265] <Solvent (B)> The radiation-sensitive composition according to this embodiment contains a solvent (B). The solvent (B) is not particularly limited as long as it is a solvent that can dissolve or disperse the base polymer and optional additives.

[0266] Examples of the solvent (B) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0267] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0268] Examples of ether-based solvents include dialkyl ether-based solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether-based solvents such as tetrahydrofuran and tetrahydropyran; aromatic ring-containing ether-based solvents such as diphenyl ether and anisole (methyl phenyl ether); and polyhydric alcohol ether-based solvents obtained by etherifying the hydroxy groups of the above-mentioned polyhydric alcohol-based solvents.

[0269] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0270] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0271] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate; polyhydric alcohol partial ether acetate-based solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; lactone-based solvents such as γ-butyrolactone and valerolactone; carbonate-based solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; and polyvalent carboxylic acid diester-based solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, and diethyl phthalate.

[0272] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0273] Among these, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether-based solvents, polyhydric alcohol partial ether-based solvents, lactone-based solvents, monoalcohol-based solvents, and alcoholic acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, γ-butyrolactone, diacetone alcohol, ethyl lactate, and methyl 2-hydroxyisobutyrate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0274] <Other Optional Components> The radiation-sensitive composition may contain other optional components in addition to the components described above. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0275] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A) and the solvent (B) with, as necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0276] <<Pattern Forming Method>> The pattern forming method of the present embodiment includes: a step (1) of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as an "exposure step"); and a step (3) of developing the exposed resist film with a developer (hereinafter also referred to as a "development step").

[0277] According to the pattern forming method, since the radiation-sensitive composition capable of forming a resist film excellent in sensitivity, CDU, and suppression of development defects is used, a high-quality resist pattern can be formed.

[0278] [Resist Film Forming Step] In this step (step (1) above), a resist film is formed from the radiation-sensitive composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of coating methods include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 160°C, and preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0279] When the subsequent exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a polymer (A) having the structural unit (V) as the base polymer in the composition.

[0280] [Exposure Step] In this step (step (2) above), the resist film formed in the resist film formation step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0281] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of the acid-dissociable groups of the polymer (A) by the acid generated from the first acid-generating structure of the polymer (A) or the radiation-sensitive acid generator (C) in the exposed portions of the resist film. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0282] [Development Step] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed with a developer. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0283] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass aqueous TMAH solution is more preferred.

[0284] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive composition. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As the ketone solvent, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0285] Examples of the developing method include a method of immersing a substrate in a tank filled with a developer for a certain period of time (dip method), a method of piling up a developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time to develop (puddle method), a method of spraying the developer onto the surface of the substrate (spray method), and a method of continuously discharging the developer while scanning a developer discharging nozzle at a constant speed onto a substrate that is rotating at a constant speed (dynamic dispense method).

[0286] <Polymer> The polymer in this embodiment comprises: a structural unit (I) having an acid-dissociable group; a structural unit (II) having a first acid-generating structure which has a first organic acid anion (b1) and a first onium cation (c1) and which, upon exposure, generates an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) having a second organic acid anion (b2) and a second onium cation (c2) and which, upon exposure, generates an acid that does not induce dissociation of the acid-dissociable group, wherein the polymer has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

[0287] As the polymer, the polymer (A) in the radiation-sensitive composition can be suitably used.

[0288] The present invention will be specifically explained below with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the following Examples. Measurement methods for various physical properties are shown below.

[0289] [Mw and Mn] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns (two "Super AW2500", one "Super AW3000", and one "Super AW4000") manufactured by Tosoh Corporation under the following conditions: Eluent: N,N-dimethylformamide (manufactured by Wako Pure Chemical Industries, Ltd.) Additive: 0.2 mass% lithium bromide Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40°C Detector: differential refractometer Standard material: monodisperse polystyrene

[0290] [Synthesis Example] Synthesis of base polymers (A-1) to (A-29) and (CA-1) to (CA-2) The monomers shown below were combined and copolymerized in N,N-dimethylformamide (DMF) solvent to obtain base polymers (A-1) to (A-29) and (CA-1) to (CA-2) having the compositions shown in Table 1. The polymerization initiators shown in Table 1 were used in the polymerization reactions. The compositions of the obtained base polymers were as follows: １ Mw and dispersity (Mw / Mn) were confirmed by H-NMR and the above-mentioned GPC (solvent: DMF, standard: polystyrene). For example, in Synthesis Example 17, the structural unit (III) "mb-1 / mb-6 = 5 / 10" and "cat5 / cat5 = 5 / 10" mean that mb-1 (counter ion is cat5) was used at 5 mol% and mb-6 (counter ion is cat5) at 10 mol%, and in Synthesis Example 1, the structural unit (I) "ma-1 / ma-2 = 30 / 10" means that ma-1 and ma-2 are contained at 30 mol% and 10 mol%, respectively, for a total of 40 mol%. In Table 1, "-" indicates that the corresponding component was not used.

[0291]

[0292] (In the formula, X + , Y －represent a counter cation and a counter anion, respectively, and the counter cation is cat1, cat2, cat5, or cat9 below, and the counter anion is ani1 or ani3.

[0293] (In the formula, X + , Y － represent a counter cation and a counter anion, respectively, and the counter cation is cat1, cat2, cat5, or cat9 below, and the counter anion is ani1 or ani3.

[0294]

[0295]

[0296]

[0297]

[0298]

[0299]

[0300]

[0301]

[0302] [Examples and Comparative Examples] Radiation-sensitive compositions were prepared by dissolving each component in the composition shown in Table 2 in a solvent containing 100 ppm of FC-4430 (manufactured by 3M) as a surfactant, and filtering the resulting solution through a 0.2 μm nylon filter. In Table 2, "-" indicates that the corresponding component was not used.

[0303] In Table 2, the components other than the base polymer are as follows:

[0304] (Radiation-Sensitive Acid Generators (PAG1) to (PAG2) and Acid Diffusion Controller (Q-1))

[0305] (Organic solvent) PGMEA: Propylene glycol monomethyl ether acetate PGME: Propylene glycol monomethyl ether EL: Ethyl lactate GBL: γ-butyrolactone DAA: Diacetone alcohol HBM: Methyl 2-hydroxyisobutyrate

[0306] (High Fluorine Content Polymer (E)) A polymer having a structural unit represented by the following formula (E-1) (the subscripts of the structural units indicate the molar ratio when the total number of structural units is taken as 1). E-1: Mw=8,900, Mw / Mn=2.0

[0307]

[0308]

[0309] <Formation of Contact Hole (CH) Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which an underlayer film (Brewer Science's "AL412") with an average thickness of 20 nm had been formed, using a spin coater (Tokyo Electron Limited's "CLEAN TRACK ACT12"). Prebaking was performed at 130°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a resist film with an average thickness of 50 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (ASML's "NXE3400", NA = 0.33, σ 0.9 / 0.6, quadrupole illumination conditions). After irradiation, the resist film was subjected to post-exposure baking (PEB) at 130°C for 60 seconds. Next, development was carried out using a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) at 23° C. for 30 seconds to form a positive contact hole pattern (diameter 25 nm, pitch 50 nm).

[0310] <Evaluation> The sensitivity, CDU, and development residues of each CH pattern formed above were evaluated according to the following methods. A scanning electron microscope ("CG-4100" manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the pattern. The evaluation results are shown in Table 3 below.

[0311] [Sensitivity] In forming the CH pattern, the exposure amount for forming a CH pattern with a diameter of 25 nm is defined as the optimum exposure amount, and this optimum exposure amount is expressed as Eop (mJ / cm ２ The smaller the Eop value, the higher the sensitivity and the better the sensitivity.

[0312] [CDU] The CH pattern was observed from above using the scanning electron microscope, and the diameter of a total of 800 CH patterns was measured at random locations. The 3 sigma value was determined from the distribution of the measured values, and this was designated as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, and the better. Using the CDU of Comparative Example 1 as the standard, an improvement of more than 6% was designated "A," an improvement of more than 2% to 6% was designated "B," an improvement of more than 0% to 2% was designated "C," and no improvement was designated "D." The CDU of Comparative Example 1 was designated "-."

[0313] [Development Residue] A wafer having a resist film formed thereon was produced by carrying out the same operations as in the CH pattern formation method described above up to the operation of forming a resist film with an average thickness of 50 nm. Next, without carrying out pattern exposure using an EUV exposure machine, the wafer was post-baked for 60 seconds on a hot plate at 130°C. Next, development was carried out for 30 seconds with a 2.38 mass% TMAH aqueous solution to produce a wafer for evaluation of development residue. This wafer was observed with a defect inspection device (Applied Materials' "COMPLUS"), and the number of residual defects was counted using a defect review SEM (Hitachi High-Technologies Corporation's "RS-5500"). Depending on the number of residual defects counted, the wafer was evaluated according to the following evaluation criteria: A: 5 or less B: 6 to 10 C: 11 to 20 D: 21 to 50 E: 51 or more

[0314]

[0315] As a result of evaluating the resist patterns formed via the above-described EUV exposure, the radiation-sensitive compositions of the Examples all had better CDU than Comparative Example 1 or better development residue than Comparative Example 2. In addition to CDU, the compositions of Examples 14 to 18, 20, 23, and 26 had better sensitivity than Comparative Example 1. In addition to development residue, the compositions of Examples 14 to 21, 23 and 24, and 26 and 27 had better sensitivity than Comparative Example 2.

[0316] The radiation-sensitive composition and the method for forming a resist pattern described above enable the formation of a resist pattern that exhibits good CDU and suppresses development defects, and also has excellent sensitivity. Therefore, these compositions can be suitably used in the fabrication processes of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer (A) including: a structural unit (I) having an acid dissociable group; a structural unit (II) including a first acid generating structure having a first organic acid anion (b1) and a first onium cation (c1), and which generates, upon exposure to light, an acid that induces dissociation of the acid dissociable group; and a structural unit (III) including a second organic acid anion (b2) and a second onium cation (c2), and which generates, upon exposure to light, an acid that does not induce dissociation of the acid dissociable group; and a solvent (B), wherein the polymer (A) has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

2. The radiation-sensitive composition according to claim 1, wherein the sum of the content of the structural unit (II) and the content of the structural unit (III) in the polymer (A) is 10 mol % or more based on all structural units constituting the polymer (A).

3. The radiation-sensitive composition according to claim 1, wherein the alcoholic hydroxyl group is at least one type of alcoholic hydroxyl group selected from the group consisting of a primary alcoholic hydroxyl group and a secondary alcoholic hydroxyl group.

4. The radiation-sensitive composition according to claim 1, wherein the polymer (A) contains a structural unit represented by the following formula (1): (In formula (1), R Ａ１１ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or a hydroxyalkyl group having 1 to 5 carbon atoms. １ is a single bond or an ester group. １ R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms and a valence of (n11+n12+1), or a group containing a divalent heteroatom-containing group between the carbon atoms or at the bond-side terminal of this aliphatic hydrocarbon group. ２ represents a single bond, a divalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, or a carbon-carbon bond in this aliphatic hydrocarbon group or R １ is a group containing a divalent heteroatom-containing group at the terminal on the bond side bonded to R ２ When there are multiple R ２ are the same or different. ３ R is a halogen atom, a cyano group, a nitro group, or a monovalent organic group. ３ When there are multiple R ３ are the same or different. n11 is an integer of 0 to 5. Ａ１１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, n11 is an integer of 1 to 5. n12 is an integer of 0 to 5.

5. The radiation-sensitive composition according to claim 1, wherein the polymer (A) is end-capped with a partial structure having an alcoholic hydroxyl group.

6. The radiation-sensitive composition according to claim 1, wherein the polymer (A) has an aromatic ring structure containing an iodine group.

7. The radiation-sensitive composition according to claim 1, wherein the first organic acid anion (b1) has an iodine group.

8. The radiation-sensitive composition according to claim 1, wherein the first organic acid anion (b1) has a sulfonate anion, and the polymer (A) has the sulfonate anion as a side chain moiety.

9. The radiation-sensitive composition according to claim 1, wherein the first organic acid anion (b1) has a sulfonate anion, and an electron-withdrawing group is bonded to a carbon atom adjacent to a sulfur atom in the sulfonate anion.

10. The radiation-sensitive composition according to claim 1, wherein the second organic acid anion (b2) has an iodine group or a hydroxyl group.

11. The radiation-sensitive composition according to claim 1, wherein the second organic acid anion (b2) has a sulfonate anion or a carboxylate anion (provided that, when the second organic acid anion (b2) has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion), and the polymer has the second organic acid anion (b2) as a side chain moiety.

12. The radiation-sensitive composition according to claim 1, wherein the second organic acid anion (b2) has a carboxylate anion and a hydroxyl group, and the carboxylate anion and the hydroxyl group are bonded to the same aromatic ring.

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

14. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (II) in all structural units constituting the polymer (A) is from 1 mol % to 30 mol %.

15. The radiation-sensitive composition according to claim 1, wherein the content of the structural unit (III) in all structural units constituting the polymer (A) is from 1 mol % to 30 mol %.

16. The radiation-sensitive composition according to claim 4, wherein the content of the structural unit represented by formula (1) in all structural units constituting the polymer (A) is from 1 mol % to 40 mol %.

17. The radiation-sensitive composition according to claim 1, further comprising a radiation-sensitive acid generator which has a third organic acid anion (b3) and a third onium cation (c3), has a lower molecular weight than said polymer (A), and generates, upon exposure to light, an acid that induces dissociation of the acid-dissociable group in said polymer (A).

18. The radiation-sensitive composition according to claim 1, further comprising an acid diffusion controller which has a fourth organic acid anion (b4) and a fourth onium cation (c4), has a lower molecular weight than the polymer (A), and generates, upon exposure to light, a weak acid that does not induce dissociation of the acid-dissociable group in the polymer (A).

19. A pattern forming method comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 18 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

20. The pattern forming method according to claim 19, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

21. A polymer comprising: a structural unit (I) having an acid dissociable group; a structural unit (II) having a first organic acid anion (b1) and a first onium cation (c1), and including a first acid generating structure that generates, upon exposure to light, an acid that induces dissociation of the acid dissociable group; and a structural unit (III) having a second organic acid anion (b2) and a second onium cation (c2), and including a second acid generating structure that generates, upon exposure to light, an acid that does not induce dissociation of the acid dissociable group, wherein the polymer has at least one alcoholic hydroxyl group, and the second onium cation (c2) is a radiation-sensitive onium cation.

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