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

Abstract

The purpose of the present invention is to provide a radiation-sensitive composition and a pattern formation method that enable formation of a resist film that, when a next-generation technology is applied, can exhibit sufficient levels of sensitivity and CDU and suppress development defects. Another purpose of the present invention is to provide a polymer and a compound applicable to the radiation-sensitive composition.　The present invention relates to a radiation-sensitive composition containing a solvent and a polymer containing a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by formula (1). (In the formula (1), R1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R2 is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R3 is a single bond or an organic group having 1 to 5 carbon atoms. Rf1 and Rf2 are each independently a hydrogen atom, a fluorine atom, or a fluorinated hydrocarbon group, and at least one thereof is a fluorine atom or a fluorinated hydrocarbon group. When there are multiple Rf1s and multiple Rf2s, the multiple Rf1s and the multiple Rf2s are each the same or different. n is an integer of 1 to 3. M+ is a monovalent onium cation.)

Description

Radiation-sensitive composition, pattern forming method, polymer, and compound

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

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

[0003] In the photolithography technology, pattern miniaturization is promoted by using short-wavelength radiation such as an ArF excimer laser or by combining this radiation with liquid immersion lithography. As a next-generation technology, the use of even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is being considered, and resist materials containing acid-generating compounds with structures that enhance the absorption efficiency of such radiation are also being investigated (Japanese Patent Laid-Open Publication No. 2010-134279).

[0004] JP 2010-134279 A

[0005] The above-mentioned next-generation technology also requires resist performance equal to or better than conventional ones in terms of sensitivity, critical dimension uniformity (CDU) which is an index of uniformity of hole diameter, and development defects.

[0006] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that are capable of forming a resist film that exhibits sufficient sensitivity and CDU and can suppress development defects when next-generation technologies are applied. Another object of the present invention is to provide a polymer or compound that can be used in the radiation-sensitive composition.

[0007] 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.

[0008] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer including a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by the following formula (1); and a solvent: (In the above formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or an organic group having 1 to 5 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0009] This radiation-sensitive composition makes it possible to construct a resist film that satisfies the sensitivity and CDU requirements and suppresses the occurrence of development defects. While the reason for this is unclear, it is presumed to be as follows: The inclusion of an amide bond in the polymer controls the diffusion of acid generated from the polymer upon exposure. This makes it possible to improve the CDU. Furthermore, the polymer contains a specific structural unit (II) having an amide bond, which increases the hydrophilicity of the polymer and its affinity with the developer. As a result, the occurrence of development defects is suppressed. It is presumed that these combined effects enable the resist performance and development defect suppression described above to be exhibited.

[0010] In another embodiment, the present invention relates to a pattern forming method, comprising: a step of applying the radiation-sensitive composition directly or indirectly to a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

[0011] The pattern formation method uses the radiation-sensitive composition described above, which is capable of forming a resist film that has excellent sensitivity and CDU and is capable of suppressing the occurrence of development defects, and therefore can efficiently form a high-quality resist pattern.

[0012] In another embodiment, the present invention relates to a polymer including a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by the following formula (1): (In the above formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or an organic group having 1 to 5 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0013] By preparing a radiation-sensitive composition containing the polymer, it is possible to form a resist film that has excellent sensitivity and CDU and in which the occurrence of development defects is suppressed.

[0014] In another embodiment, the present invention relates to a compound represented by the following formula (2): (In the above formula (2), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a single bond or a divalent linking group. W is a substituted or unsubstituted organic group having a ring structure and having 3 to 40 carbon atoms. n1 is 0 or 1. R ４ , R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. ４ and R ５If there are multiple R ４ and R ５ are the same or different. m1 is an integer of 0 to 8. R ６ is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0015] By preparing a radiation-sensitive composition containing a polymer having structural units derived from this compound, it is possible to form a resist film that is excellent in sensitivity and CDU and in which the occurrence of development defects is suppressed.

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

[0017] <Radiation-Sensitive Composition> The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") comprises a polymer (P) containing a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by the above formula (1), and a solvent (E). The composition may contain other optional components as long as the effects of the present invention are not impaired. By including the polymer (P) having a specific structure, the radiation-sensitive composition can provide a resist film obtained from the radiation-sensitive composition with higher levels of sensitivity, CDU, and suppression of development defects.

[0018] <Polymer (P)> The polymer (P) is an assembly of polymer chains containing a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by the above formula (1) (hereinafter, this assembly will also be referred to as a "base polymer"). The structural unit (I) and the structural unit (II) may be contained in the same polymer chain, or the structural unit (I) may be contained in one polymer chain and the structural unit (II) may be contained in another polymer chain. It is sufficient that the entire polymer chain constituting the polymer (P) contains the structural unit (I) and the structural unit (II). The polymer (P) may contain structural units other than the structural unit (I) and the structural unit (II).

[0019] The polymer (P) preferably contains iodine atoms. The manner in which the iodine atoms are contained is not particularly limited, and the iodine atoms may be contained as iodo groups or iodonium cations. By containing iodine atoms, the radiation absorption efficiency can be increased, and the secondary electron generation efficiency can be improved, thereby improving sensitivity.

[0020] Although the manner in which the iodo group is contained is not particularly limited, it is preferably contained in the form of an iodo group-containing aromatic ring structure, which is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with iodo groups.

[0021] 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.As the aromatic ring, for example, aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, coronene ring, etc., 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, dibenzofuran ring, benzofuran ring, indole ring, benzothiophene ring, etc., heteroaromatic rings, or combinations thereof, etc.Among them, benzene ring and thiophene ring are preferred as the aromatic ring.

[0022] 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, even more preferably 1 or 2, and from the viewpoint of the number of development defects, more preferably 1.

[0023] The iodonium cation may be contained in the form of M ＋ It is preferable that the monovalent onium cation represented by the following formula (I) is contained in the form of an iodonium cation.

[0024] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. However, in this specification, a monomer corresponding to both the structural unit (I) and the structural unit (III) described later is included in the structural unit (I). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The acid generated from the polymer (P) or the radiation-sensitive acid generator (A) described later upon exposure dissociates the acid-dissociable group in the structural unit (I) to generate a carboxy group or the like. This creates a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0025] 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 (P1) (hereinafter, also referred to as "structural unit (I-1)") is preferred.

[0026]

[0027] In the above formula (P1), 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 Ａ３are 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. m11 and m12 are each independently 0 or 1. However, when m11 is 1, m12 is 1. When m11 is 0, L Ａ１ represents a single bond or a divalent linking group; when m11 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.

[0028] 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. ２ Examples of such groups include -, -NR'-, and groups containing a combination of two or more of these, or groups 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 a substituent such as a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an alkyl group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group, or a group in which the hydrogen atoms of these groups are substituted with halogen atoms.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] R Ａ１ ~R Ａ３ Examples 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.

[0035] The above R Ａ１ ~R Ａ３Examples 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.

[0036] 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.

[0037] The above R Ａ１ is preferably a hydrogen atom, 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.

[0038] 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.

[0039] R Ａ２ and R Ａ３ is a monovalent chain hydrocarbon group having 1 to 10 carbon atoms, or R Ａ２ and R Ａ３are combined 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, a cyclopentanediyl group, a cyclohexanediyl group, or a cyclohexenediyl group is even more preferred.

[0040] When m11 is 0, L Ａ１ is preferably a single bond or an arenediyl group. Ａ１ is preferably an alkanediyl group.

[0041] Examples of the structural unit (I) include structural units represented by the following formulas (1-1) to (1-14) (hereinafter also referred to as "structural units (I-1) to (I-14)").

[0042]

[0043]

[0044] In the above formulas (1-1) to (1-14), R α , R Ａ１ ~R Ａ３ has the same meaning as formula (P1) 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 are the same or different. a4 is an integer of 1 to 3.

[0045] i, j, k, and l are preferably 1 or 2. a4 is preferably 1. R 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, a hydroxy group, an iodine atom, or an alkyl group is preferable. By employing an iodine atom as X, an iodine group can be suitably introduced into the structural unit (I).

[0046] Furthermore, the polymer (P) may contain, as the structural unit (I), structural units represented by the following formulae (1f) to (2f).

[0047]

[0048] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. h1 is an integer of 1 to 4.

[0049] The above R βｆ is preferably a hydrogen atom, a methyl group or an ethyl group. h1 is preferably 1 or 2.

[0050] Specific examples of the structural unit (I) include, but are not limited to, those shown below.

[0051] (In the formula, R α has the same meaning as formula (P1) above.

[0052] (In the formula, R α has the same meaning as formula (P1) above.

[0053] The base polymer may contain one type of structural unit (I) or a combination of two or more types.

[0054] 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 30 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 65 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.

[0055] (Structural Unit (II)) The structural unit (II) is represented by the following formula (1): The structural unit (II) contains an acid-generating structure, and generates an acid that induces dissociation of the acid-dissociable group upon exposure. That is, it functions as a radiation-sensitive acid-generating structure. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds. (In the above formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or a divalent organic group having 1 to 5 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0056] When the base polymer contains the radiation-sensitive acid generating structure, the polarity of the base polymer in the exposed area increases, making it soluble in the developer when developed with an aqueous alkaline solution, but making it poorly soluble in the developer when developed with an organic solvent.

[0057] R in the above formula (1) ２ Examples of the divalent organic group having 1 to 50 carbon atoms represented by the formula (I) include a divalent chain hydrocarbon group having 1 to 50 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 50 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 50 carbon atoms, or a group having -CO-, -C(=O)-O-, -CS-, -O-, -S-, -SO between the carbon-carbon bonds of these groups or at the terminals of these groups. ２Examples of the substituent include -, -NR'-, 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 of these groups may be substituted with a substituent. Examples of the substituent include L in formula (P1) above. Ａ１ The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0058] The above R ２ As the divalent chain hydrocarbon group having 1 to 50 carbon atoms represented by the formula (P1), 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, represented by the following formula, can be suitably used.

[0059] The above R ２ The divalent alicyclic hydrocarbon group having 3 to 50 carbon atoms represented by the formula (P1) is 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, represented by the following formula, can be suitably used.

[0060] The above R ２ As the divalent aromatic hydrocarbon group having 6 to 50 carbon atoms represented by the formula (P1), Ａ１ A group in which one hydrogen atom has been removed from a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, represented by the following formula, can be suitably used.

[0061] The above R ３ The divalent organic group having 1 to 5 carbon atoms represented by the above R ２ Among divalent organic groups having 1 to 50 carbon atoms represented by the following formula, those having the corresponding number of carbon atoms can be suitably used.

[0062] R in the above formula (1) ２ and R ３ From the viewpoint of CDU, it is preferable that at least one of R ２ More preferably, it has a substituted or unsubstituted ring structure.

[0063] The ring structure may be a monocycle, a polycycle, or a combination thereof. The ring 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 ring structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the ring structure or chain structure may be substituted with other substituents.

[0064] 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.

[0065] As the aromatic ring structure, the aromatic rings (including aromatic hydrocarbon rings and aromatic heterocycles) shown in the iodo group-containing aromatic ring structure can be suitably used.

[0066] 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.

[0067] 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).

[0068]

[0069] In the above formula, γ is an integer of 1 to 3.

[0070] The chain structure may be R Ａ１ ~R Ａ３ A structure corresponding to the monovalent chain hydrocarbon group having 1 to 20 carbon atoms in the above formula can be suitably employed.

[0071] 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.

[0072] Examples of the substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the ring 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.

[0073] The ring structure is preferably an aromatic ring having 6 to 20 carbon atoms or an alicyclic hydrocarbon having 5 to 20 carbon atoms, more preferably an aromatic ring having 6 to 10 carbon atoms or an alicyclic hydrocarbon having 5 to 10 carbon atoms, and further preferably benzene, naphthalene, adamantane, or cyclopentane.

[0074] The above R ２ When R has a substituted or unsubstituted ring structure, ２ As the alkyl group, a substituted or unsubstituted benzenediyl group, a substituted or unsubstituted naphthalenediyl group, a substituted or unsubstituted cycloalkanediyl group, a substituted or unsubstituted adamantanediyl group, or a group containing -C(=O)-O-** on the polymer main chain side of these groups is preferred, where ** represents a bond on the ring structure side.

[0075] The amide bond represented by Z is *-NR １１ -C(=O)-, *-C(=O)-NR １１ -, *-NR １１ -C(=O)- is preferred. １１ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R ２Represents the bond on the side.

[0076] The above R １１ The monovalent hydrocarbon group having 1 to 10 carbon atoms represented by the formula (P1) is Ａ１ Among monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by the following formula, those having the corresponding number of carbon atoms can be suitably used.

[0077] The above Rf １ , Rf ２ Examples of the fluorinated hydrocarbon group represented by the formula (I) include a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms and a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0078] Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include fluorinated alkyl groups such as a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a heptafluoro-n-propyl group, a heptafluoro-i-propyl group, a nonafluoro-n-butyl group, a nonafluoro-i-butyl group, a nonafluoro-t-butyl group, a 2,2,3,3,4,4,5,5-octafluoro-n-pentyl group, a tridecafluoro-n-hexyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group; fluorinated alkenyl groups such as a trifluoroethenyl group and a pentafluoropropenyl group; and fluorinated alkynyl groups such as a fluoroethynyl group and a trifluoropropynyl group.

[0079] Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as a fluorocyclopentyl group, a difluorocyclopentyl group, a nonafluorocyclopentyl group, a fluorocyclohexyl group, a difluorocyclohexyl group, an undecafluorocyclohexylmethyl group, a fluoronorbornyl group, a fluoroadamantyl group, a fluorobornyl group, a fluoroisobornyl group, and a fluorotricyclodecyl group; and fluorinated cycloalkenyl groups such as a fluorocyclopentenyl group and a nonafluorocyclohexenyl group.

[0080] The fluorinated hydrocarbon group is preferably the monovalent fluorinated linear hydrocarbon group having 1 to 20 carbon atoms, more preferably a monovalent fluorinated linear hydrocarbon group having 1 to 5 carbon atoms, and even more preferably a trifluoromethyl group.

[0081] The above Rf １ , Rf ２ is preferably a fluorine atom or a fluorinated hydrocarbon group.

[0082] The above n is an integer of 1 to 3, and is preferably 1 or 2.

[0083] The structural unit (II) is preferably a structural unit represented by the following formula (1-1): (In the above formula (1-1), L １ is a single bond or a divalent linking group. W is a substituted or unsubstituted organic group having a ring structure and having 3 to 40 carbon atoms. n1 is 0 or 1. R ４ , R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. ４ and R ５ If there are multiple R ４ and R ５ are the same or different. m1 is an integer of 0 to 8. R ６ is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. １ , Rf １ , Rf ２ , n, M ＋ has the same meaning as the above formula (1).

[0084] L １ Examples of the divalent linking group represented by the formula: ２ Examples of the substituent include -, -NR'-, an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, an arenediyl group, or a combination of two or more of these. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Some or all of the hydrogen atoms of these groups may be substituted with a substituent. Examples of the substituent include L in formula (P1) above. Ａ１The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0085] The alkanediyl group, cycloalkanediyl group, alkenediyl group, and arenediyl group are each selected from the group consisting of L Ａ１ In the divalent linking group represented by the following formula, a cycloalkanediyl group, an alkenediyl group, or an arenediyl group can be preferably used.

[0086] The above L １ As the group, a single bond, —COO—, or —CONH— is preferred, a single bond or —COO— is more preferred, and from the viewpoint of the number of development defects, —COO— is even more preferred.

[0087] Examples of the ring structure contained in the organic group having 3 to 40 carbon atoms represented by W include the ring structure in the formula (1). Ａ１ The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0088] The above n1 is 0 or 1.

[0089] The above R ４ , R ５ The hydrocarbon group having 1 to 5 carbon atoms represented by the formula (P1) is Ａ１ Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by the following formula, those having the corresponding carbon number can be suitably used. ４ , R ５ is preferably a hydrogen atom.

[0090] The above m1 is an integer of 0 to 8, preferably an integer of 0 to 5, and more preferably an integer of 0 to 3.

[0091] The above R ６ The hydrocarbon group having 1 to 3 carbon atoms represented by the formula (P1) is Ａ１ Among the monovalent hydrocarbon groups having 1 to 20 carbon atoms represented by the following formula, those having the corresponding carbon number can be suitably used. ６ is preferably a hydrogen atom.

[0092] The above R １, Rf １ , Rf ２ , n, M ＋ has the same meaning as the above formula (1).

[0093] The number of iodo groups in the organic acid anion of the monomer that provides the structural unit (II) is not particularly limited, but from the viewpoint of the number of development defects, it is preferably 0 to 3, more preferably 0 to 2, and even more preferably 0 or 1.

[0094] Examples of organic acid anions of the monomers that provide the structural unit (II) include, but are not limited to, those shown below.

[0095] (In the formula, R １ are synonymous with the above formulas (1) and (2).

[0096] (In the formula, R １ are synonymous with the above formulas (1) and (2).

[0097] (In the formula, R １ are synonymous with the above formulas (1) and (2).

[0098] (In the formula, R １ are synonymous with the above formulas (1) and (2).

[0099] The above M ＋ Examples of the monovalent onium cation represented by the formula (I) include a radiation-decomposable onium cation. Examples of the radiation-sensitive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, an iodonium cation, etc. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0100] From the viewpoint of sensitivity, the onium cation preferably has an iodo group, and more preferably contains the iodo group-containing aromatic ring structure.

[0101] The onium cation is preferably 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 or trifluoromethyl groups. The aromatic ring in the fluoro-group-containing aromatic ring structure can be suitably the same as the aromatic ring in the iodine-group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0102] The sulfonium cation is preferably represented by the following formula (Q-1).

[0103]

[0104] In the above formula (Q-1), Ar １ , Ar ２ and Ar ３ are each independently a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 5 to 20 carbon atoms.

[0105] The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms includes R Ａ１ As the aromatic heterocyclic group having 5 to 20 carbon atoms, a group in which one hydrogen atom has been removed from the heterocyclic structure in the ring structure of the formula (1) can be suitably used. Among these, Ar １ , Ar ２ and Ar ３ As the alkyl group, benzene and thiophene are preferred, and benzene is more preferred.

[0106] In the above formula (Q-1), Ra1 to Ra3 each independently represent a substituent. n11 represents an integer of 0 to 5, and when n11 is 2 or greater, multiple Ra1s may be the same or different. n12 represents an integer of 0 to 5, and when n12 is 2 or greater, multiple Ra2s may be the same or different. n13 represents an integer of 0 to 5, and when n13 is 2 or greater, multiple Ra3s may be the same or different. Ra1 and Ra2 may be bonded to each other to form a ring. When n11 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n12 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0107] 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.

[0108] 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.

[0109] The cycloalkyl group of Ra1, Ra2, and Ra3 includes a monocyclic or polycyclic cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms), such as a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclododecanyl group, a cyclopentenyl group, a cyclohexenyl group, and a cyclooctadienyl group. Among these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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 n11 is - 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 n11 is 2 or more, multiple Ra1s may be linked to each other to form a ring, and when n12 is 2 or more, multiple Ra2s may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1s are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0118] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF３ , C ２ F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0119] Ra3 is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0120] n11 and n12 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0121] n13 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0122] (n11+n12+n13) 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.

[0123] Specific examples of such onium cations represented by the above formula (Q-1) include the following:

[0124] (In the formula, tBu represents a t-butyl group, and Me represents a methyl group.)

[0125]

[0126] (In the formula, Me represents a methyl group.)

[0127]

[0128]

[0129] (In the formula, Me represents a methyl group.)

[0130]

[0131] (In the formula, Me represents a methyl group.)

[0132] Specific examples of the iodonium cation include the following:

[0133] The monomer that provides the structural unit (II) can be obtained by appropriately combining the above organic acid anion and the above onium cation. Specific examples include, but are not limited to, structures of the following formulas:

[0134]

[0135]

[0136]

[0137]

[0138] 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 polymer is preferably 1 mol%, more preferably 5 mol%, and even more preferably 8 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.

[0139] (Structural Unit (III)) The polymer (P) preferably further contains a structural unit (III) having a phenolic hydroxyl group. Examples of monomers that provide the structural unit (II) include, but are not limited to, those shown below. In the following formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0140]

[0141]

[0142] When the polymer (P) contains the structural unit (III), the lower limit of the content of the structural unit (III) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 10 mol%, more preferably 15 mol%, even more preferably 20 mol%, and particularly 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 (III) within the above range, the pattern formability of the radiation-sensitive composition can be further improved.

[0143] (Structural Unit (IV)) The polymer (P) may further contain another structural unit (IV) containing a polar group such as an alcoholic hydroxyl group, a carboxyl 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 (IV) include, but are not limited to, those shown below. In the following formula, R Ａ is the same as above.

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154] When the polymer (P) contains the structural unit (IV), the lower limit of the content of the structural unit (IV) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol% relative to all structural units constituting the base polymer. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%. By setting the content of the structural unit (III) within the above range, pattern adhesion can be further improved.

[0155] (Method for synthesizing polymer (P)) The polymer (P) can be synthesized, for example, by adding a radical polymerization initiator to a monomer that provides the structural unit described above in an organic solvent and heating the mixture to polymerize it. A known polymerization initiator can be used for the polymerization.

[0156] The polymer (P) has a polystyrene-equivalent weight average molecular weight (Mw) of preferably 2,000, more preferably 4,000, as determined by gel permeation chromatography (GPC) using THF as a solvent. 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.

[0157] Furthermore, if the polymer (P) has a broad molecular weight distribution (Mw / Mn), the presence of low-molecular-weight and high-molecular-weight polymers may result in the appearance of foreign matter on the pattern after exposure, or the shape of the pattern may be deteriorated. As the pattern rule becomes finer, the effects of Mw and molecular weight distribution tend to become greater. Therefore, in order to obtain a resist material that is suitable for use with fine pattern dimensions, it is preferable that the molecular weight distribution of the polymer (P) is narrow, i.e., 1.0 to 2.0, and particularly 1.0 to 1.8.

[0158] The polymer (P) may contain two or more polymers having different composition ratios, Mws, and molecular weight distributions.

[0159] The lower limit of the content of the polymer (P) in the radiation-sensitive composition is preferably 40% by mass, more preferably 50% by mass, based on the amount of the components other than the solvent (E) contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass.

[0160] <Radiation-sensitive acid generator (A)> From the viewpoint of sensitivity, the radiation-sensitive composition preferably contains a radiation-sensitive acid generator (A) that has a first organic acid anion and a first onium cation and that generates, upon exposure, an acid that induces dissociation of the acid-dissociable group in the polymer (P). The radiation-sensitive acid generator (A) has a lower molecular weight than the polymer (P). 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.

[0161] The radiation-sensitive acid generator (A) containing the first organic acid anion and the first onium cation is preferably represented by the following formula (a-1): (In the above formula (a-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 ｐ６are 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 primary onium cation.

[0162] R ｐ１ Examples of the ring structure in the monovalent group containing a ring structure represented by the formula (1) include the ring structure in the above formula (1). Among these, the ring structure preferably contains an alicyclic structure having 5 or more ring members, an aliphatic heterocyclic structure having 5 or more ring members, or an aromatic ring structure having 6 or more ring members.

[0163] The ring structure may have a substituent, and examples of the substituent include L in formula (P1). Ａ１ The substituents that can be possessed by the divalent linking group represented by the following formula can be suitably employed.

[0164] R ｐ２ Examples of the divalent linking group represented by the formula (P1) include L Ａ１ A divalent linking group represented by the following formula can be preferably used.

[0165] R ｐ３ and R ｐ４ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (P1) is Ａ１ A monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the following formula can be preferably used. ｐ３ , R ｐ４ , Rｐ５ 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.

[0166] The first organic acid anion of the radiation-sensitive acid generator (A) represented by formula (a-1) may have an iodine group. The number of iodine groups in the first organic acid anion is preferably 1 to 5, and from the viewpoint of preventing development defects, preferably 2 or less.

[0167] Examples of the first organic acid anion of the radiation-sensitive acid generator (A) represented by formula (a-1) above include, but are not limited to, the following.

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177] In the formula (a-1), the Z ＋ The sulfonium cation and iodonium cation in the unit structure (II) can be suitably used as the monovalent first onium cation represented by the following formula: Among these, a sulfonium cation or iodonium cation containing an iodo group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure is preferred.

[0178] The radiation-sensitive acid generator (A) includes any combination of the first organic acid anion and the first onium cation. Among these, the following are preferred.

[0179]

[0180]

[0181] The radiation-sensitive acid generator (A) 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 (A) can be used in combination as long as the effects of the present invention are not impaired.

[0182] These radiation-sensitive acid generators (A) may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator (A), the lower limit of the content of the radiation-sensitive acid generator (A) (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 (P). 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 (P). This allows excellent sensitivity to be exhibited during resist pattern formation.

[0183] <Acid Diffusion Controller (Q)> From the viewpoint of CDU, the composition according to this embodiment preferably contains an acid diffusion controller (Q). The acid diffusion controller (Q) contains a second organic acid anion and a second onium cation, and generates, upon exposure, a weak acid that does not induce dissociation of the acid-dissociable group contained in the polymer (P). The acid diffusion controller (Q) containing the second organic acid anion and the second onium cation is preferably represented by any of the following formulae (8-1) to (8-4).

[0184]

[0185] 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 ８SO 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.

[0186] From the viewpoint of sensitivity, the second organic acid anion may have an iodo group, and more preferably contains the iodo group-containing aromatic ring structure.

[0187] Examples of the second organic acid anion include anions represented by the following formula:

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195] J ＋ As the sulfonium cation, the sulfonium cation represented by the above formula (Q-1) can be suitably used.

[0196] U ＋ The iodonium cation of the formula (1) is M ＋ The monovalent onium cations represented by the following formula (I) can be suitably used.

[0197] The acid diffusion controller (Q) 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.

[0198] These acid diffusion controllers (Q) may be used alone or in combination of two or more. The lower limit of the content of the acid diffusion controller (Q) (total amount when multiple types are used) is preferably 5 parts by mass, more preferably 10 parts by mass, and even more preferably 15 parts by mass, per 100 parts by mass of the polymer (P). The upper limit of the content is preferably 80 parts by mass, more preferably 70 parts by mass, and even more preferably 60 parts by mass. This allows excellent sensitivity and CDU to be exhibited during resist pattern formation.

[0199] <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 (F)"). When the radiation-sensitive composition contains the high-fluorine-content polymer (F), the high-fluorine-content polymer (F) can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to desired states.

[0200] The high fluorine content polymer (F) preferably has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (V)"): In addition, for example, the high fluorine content polymer (F) may have at least one of the structural units (I), (III), and (IV) in the base polymer, if necessary.

[0201] In the above formula (6), R ７３ is a hydrogen atom, a methyl group, or a trifluoromethyl group. Ｌ represents a single bond, an oxygen atom, a sulfur atom, -COO-, or -SO ２ ONH-, -CONH- or -OCONH-. ７４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0202] The above R ７３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0203] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and —COO— are preferred, and —COO— is more preferred.

[0204] The above R ７４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0205] The above R ７４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0206] The above R ７４As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 1-(trifluoromethyl)-2,2,2-trifluoroethyl group or a 4,4,4-trifluoro-3-hydroxy-3-trifluoromethylbutyl group is even more preferable.

[0207] When the high-fluorine content polymer (F) has the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine content polymer (F). The upper limit of the content is preferably 100 mol%, more preferably 95 mol%, and even more preferably 90 mol%. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, thereby further promoting uneven distribution of fluorine atoms in the surface layer of the resist film.

[0208] The lower limit of Mw of the high fluorine content polymer (F) is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 4,000. The upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 20,000, and particularly preferably 15,000.

[0209] The Mw / Mn of the high fluorine content polymer (F) is usually at least 1, and more preferably at least 1.1. The Mw / Mn is usually at most 5, preferably at most 3, more preferably at most 2.5, and even more preferably at most 2.2.

[0210] The lower limit of the content of the high fluorine content polymer (F) is preferably 0.5 parts by mass, more preferably 1 part by mass, and even more preferably 1.5 parts by mass, relative to 100 parts by mass of the polymer (P). The upper limit of the content is preferably 10 parts by mass, more preferably 8 parts by mass, and even more preferably 5 parts by mass. By setting the content of the high fluorine content polymer (F) within the above range, the high fluorine content polymer (F) can be more effectively localized to the surface layer of the resist film, thereby suppressing elution from the upper part of the pattern during development and improving the rectangularity of the pattern. The radiation-sensitive composition may contain one or more high fluorine content polymers (F).

[0211] (Method for synthesizing high fluorine content polymer (F)) The high fluorine content polymer (F) can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0212] <Solvent (E)> The radiation-sensitive composition according to this embodiment contains a solvent (E). The solvent (E) is not particularly limited as long as it is a solvent that can dissolve or disperse the polymer (P) and other components that may be contained as desired.

[0213] Examples of the solvent (E) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0214] 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, diacetone alcohol, and methyl 2-hydroxyisobutyrate; 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 partially etherified solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] Among these, ester-based solvents, ketone-based solvents, alcohol-based solvents, and ether-based solvents are preferred, with polyhydric alcohol partial ether acetate-based solvents, cyclic ketone-based solvents, lactone-based solvents, monoalcohol-based solvents having 1 to 18 carbon atoms, alcoholic acid ester-based solvents, polyhydric alcohol partial ether-based solvents, and monocarboxylic acid ester-based solvents being more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone, γ-butyrolactone, propylene glycol monomethyl ether, diacetone alcohol, ethyl lactate, and methyl 2-hydroxy-2-methylpropionate being even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0222] <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.

[0223] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing the polymer (P), the solvent (E), and, if necessary, other optional components in a predetermined ratio. After mixing, the radiation-sensitive composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.4 μm. The solids concentration of the radiation-sensitive composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0224] <<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").

[0225] 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.

[0226] [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, preferably 80°C to 140°C. The PB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, more preferably 10 nm to 500 nm.

[0227] When the subsequent exposure step is carried out using radiation having a wavelength of 50 nm or less, it is preferable to use a polymer having the structural unit (III) as the base polymer in the composition.

[0228] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is exposed by irradiating it with radiation through a photomask (or, in some cases, through an immersion 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.

[0229] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0230] [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.

[0231] 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.

[0232] 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.

[0233] 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).

[0234] <Polymer> The polymer of the present embodiment includes a structural unit (I) having an acid-dissociable group, and a structural unit (II) represented by the following formula (1). (In the above formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or an organic group having 1 to 5 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf１ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0235] The polymer may be the polymer (P). The polymer preferably contains an iodine atom.

[0236] <Compound> The compound according to the present embodiment is represented by the following formula (2). (In the above formula (2), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a single bond or a divalent linking group. W is a substituted or unsubstituted organic group having a ring structure and having 3 to 40 carbon atoms. n1 is 0 or 1. R ４ , R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. ４ and R ５ If there are multiple R ４ and R ５ are the same or different. m1 is an integer of 0 to 8. R ６ is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

[0237] As the compound, a monomer that gives the unit structure (II) in the radiation-sensitive composition can be suitably used.

[0238] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0239] [Measurement of Weight-Average Molecular Weight (Mw) and Number-Average Molecular Weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns (two "G2000HXL", one "G3000HXL", and one "G4000HXL" columns) manufactured by Tosoh Corporation under the following conditions: Elution solvent: tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40° C. Detector: differential refractometer Standard material: monodisperse polystyrene

[0240] <Synthesis of Radiation-Sensitive Acid Generator (A)> [Synthesis Example A-1: ​​Synthesis of Compound (A-1)] Compound (A-1) was synthesized according to the following reaction scheme.

[0241] Compound (PA-1) (20 mmol), compound (PC-1) (20 mmol), methylene chloride (50 mL), and ultrapure water (50 mL) were added to a recovery flask and stirred at room temperature for 2 hours. The organic layer was washed three times with ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was distilled off to obtain compound (A-1).

[0242] [Synthesis Examples A-2 to A-8: Synthesis of Compounds (A-2) to (A-8)] By appropriately selecting precursors and selecting the same recipe as in Synthesis Example (A-1), compounds (A-2) to (A-8) were synthesized. Compounds (A-1) to (A-8) are shown below.

[0243]

[0244] <Synthesis of Radiation-Sensitive Acid Generator Monomer (B)> [Synthesis Example B-1: Synthesis of Monomer (B-1)] Monomer (B-1) was synthesized according to the following reaction scheme.

[0245] Compound (PB-1) (120 mmol), acetonitrile (80 mL), and 1,1'-carbonyldiimidazole (120 mmol) were added to a recovery flask and stirred at room temperature for 1 hour. Compound (PPB-1) (100 mmol) and triethylamine (100 mmol) were added and stirred at room temperature for 3 hours. Methylene chloride (200 mL) was added, followed by washing with a 2 mol / L aqueous hydrochloric acid solution and ultrapure water. Compound (PPC-1) (100 mmol) and ultrapure water (200 mL) were added and stirred at room temperature for 2 hours. The organic layer was washed three times with ultrapure water. The organic layer was dried over sodium sulfate and filtered. The solvent was distilled off, and the resulting mixture was purified by silica gel column chromatography to obtain monomer (B-1).

[0246]

[0247] [Synthesis Examples B-2 to B-20: Synthesis of Monomers (B-2) to (B-20)] By appropriately selecting precursors and selecting the same recipe as in Synthesis Example (B-1), monomers (B-2) to (B-20) were synthesized. Compounds (B-1) to (B-20) are shown below.

[0248]

[0249]

[0250] <Synthesis of Polymer (P)> Polymers (P-1) to (P-33) and polymers (CP-1) to (CP-2) were synthesized as polymer (P) according to the following method. The above-mentioned monomers (B-1) to (B-20) and the following monomers (M-1) to (M-15) were used in the synthesis of the polymers. In the following synthesis examples, unless otherwise specified, "parts by mass" means a value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0251]

[0252] Synthesis Example P-1: Synthesis of Polymer (P-1) Monomer (B-1), monomer (M-1), and monomer (M-11) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 10 / 60 / 30. Azobisisobutyronitrile (AIBN) was added as an initiator in an amount of 6 mol % relative to the total monomers to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours. The mixture was then heated at 80°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the obtained polymerization solution and stirred. The lower layer was recovered, and the solvent was removed to obtain Polymer (P-1). The Mw and Mw / Mn of the obtained polymer are shown in Table 1.

[0253] [Synthesis Examples P-2 to P-33 and CP-1 to CP-2: Synthesis of Polymers (P-2) to (P-33) and Polymers (CP-1) to (CP-2)] Polymers (P-2) to (P-33) and Polymers (CP-1) to (CP-2) were obtained in the same manner as in Synthesis Example P-1, except that the types and amounts of monomers shown in Table 1 were blended in the specified amounts. The Mw and Mw / Mn of each of the obtained polymers are shown in Table 1.

[0254]

[0255] <Preparation of Radiation-Sensitive Composition> The polymer (P), radiation-sensitive acid generator (A), acid diffusion controller (Q), and solvent (E) used in preparing the radiation-sensitive compositions of the following Examples and Comparative Examples are shown below. In the following Examples and Comparative Examples, unless otherwise specified, "parts by mass" means a value when the mass of the polymer (P) used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of anions of the radiation-sensitive acid generator (A) and polymer (P) used is taken as 100 mol %.

[0256] [Polymer (P)] As the polymer, polymers (P-1) to (P-33) synthesized in Synthesis Examples P-1 to P-33 and polymers (CP-1) to (CP-2) synthesized in Synthesis Examples CP-1 to CP-2 were used.

[0257] [Radiation-Sensitive Acid Generator (A)] The compounds (A-1) to (A-8) synthesized in the above Synthesis Examples A-1 to A-8 were used as radiation-sensitive acid generators.

[0258] [Acid Diffusion Controller (Q)] As the acid diffusion controller, compounds represented by the following formulae (Q-1) to (Q-6) were used.

[0259]

[0260] [Solvent (E)] The following solvents were used as solvent (E): E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether

[0261] Example 1 Preparation of Radiation-Sensitive Composition (R-1) 100 parts by mass of (P-1) as the polymer (P), 7.5 parts by mass of (A-1) as the radiation-sensitive acid generator (A), (Q-1) as the acid diffusion controller (Q) in an amount of 43 mol % based on the total anions of (A-1) and (P-1), 5,000 parts by mass of (E-1) as the solvent (E), and 1,500 parts by mass of (E-2) were mixed together. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0262] Examples 2 to 63 and Comparative Examples 1 to 6: Preparation of Radiation-Sensitive Compositions (R-2) to (R-63) and Radiation-Sensitive Compositions (CR-1) to (CR-6) Radiation-sensitive compositions (R-2) to (R-63) and Radiation-Sensitive Compositions (CR-1) to (CR-6) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 2-1 and 2-2 below were used. In Tables 2-1 and 2-2, "-" indicates that the corresponding component was not used.

[0263]

[0264]

[0265] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) had been formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After soft baking (SB) at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 35 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300," ASML, NA=0.33, illumination conditions: Conventional s=0.89). The resist film was then post-exposure baked (PEB) at 100°C for 60 seconds. Next, development was carried out using a 2.38 wt % aqueous solution of TMAH at 23° C. for 30 seconds to form a positive resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as a “25 nm contact hole pattern”).

[0266] <Evaluation> The radiation-sensitive compositions prepared above were used to evaluate sensitivity, CDU, and the number of development defects according to the following methods. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist pattern. The evaluation results are shown in Tables 3-1 and 3-2 below.

[0267] [Sensitivity] In forming the resist pattern, the exposure dose for forming a 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the sensitivity, the better. The sensitivity was 48 mJ / cm ２ If it is less than 48 mJ / cm, it is rated as "A" (very good). ２ 51mJ / cm or more ２ The following cases are rated as "B" (good) and 51 mJ / cm ２ If the value exceeded this, it was evaluated as "C" (poor).

[0268] [CDU] Using the scanning electron microscope, a 25 nm contact hole pattern was observed from above, and a total of 800 lengths were measured at random points. The dimensional variation (3σ) was calculated and recorded as CDU (nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating better results. CDU was rated as "A" (very good) for values ​​less than 3.4 nm, "B" (good) for values ​​between 3.4 nm and 3.6 nm, and "C" (poor) for values ​​3.6 nm or greater.

[0269] [Number of Development Defects] A resist film was exposed to an optimum exposure dose and developed to form a 25 nm contact hole pattern. The number of defects on the wafer was measured using a defect inspection system (KLA-Tencor's "KLA2810"). Of the defects measured, defects with a diameter of 0.5 μm or less were determined to be originating from the resist film. The number of development defects was determined as "A" (very good) if the number of defects determined to be originating from the resist film was less than 35, "B" (good) if the number was 35 to 60, and "C" (poor) if the number was more than 60.

[0270]

[0271]

[0272] As is clear from the results in Tables 3-1 and 3-2, the radiation-sensitive compositions of the examples all exhibited good performance in terms of sensitivity, CDU, and number of development defects.

[0273] The radiation-sensitive composition and method for forming a resist pattern of the present invention can improve sensitivity, CDU, and the number of development defects compared to conventional methods, and therefore can be suitably used for forming fine resist patterns in lithography processes for various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition comprising: a polymer including a structural unit (I) having an acid-dissociable group and a structural unit (II) represented by the following formula (1); and a solvent. (In the above formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or an organic group having 1 to 5 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

2. R in the above formula (1) ２ The radiation-sensitive composition according to claim 1 , wherein has a substituted or unsubstituted ring structure.

3. The radiation-sensitive composition according to claim 1, wherein the structural unit (II) is a structural unit represented by the following formula (1-1). (In the above formula (1-1), L １ is a single bond or a divalent linking group. W is an organic group having 3 to 40 carbon atoms having a substituted or unsubstituted ring structure. n1 is 0 or 1. R ４ , R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. When there are a plurality of R ４ and R ５ , the plurality of R ４ and R ５ are the same or different from each other. m1 is an integer of 0 to 8. R ６ is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. R １ , Rf １ , Rf ２ , n, M ＋ have the same meanings as in the above formula (1).) 4. The radiation-sensitive composition according to claim 2 or 3, wherein the ring structure is an aromatic ring having 6 to 20 carbon atoms or an alicyclic hydrocarbon having 5 to 20 carbon atoms.

5. n is 1, and Rf １ , Rf ２ is, independently of each other, a fluorine atom or a fluorinated hydrocarbon group, the radiation-sensitive composition according to any one of claims 1 to 3.

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the monovalent onium cation is a sulfonium cation or an iodonium cation.

7. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the content ratio of the structural unit (I) in all the structural units constituting the polymer is 10 mol% or more and 80 mol% or less.

8. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the content ratio of the structural unit (II) in all the structural units constituting the polymer is 1 mol% or more and 30 mol% or less.

9. The radiation-sensitive composition according to any one of claims 1 to 3, comprising a radiation-sensitive acid generator that has a first organic acid anion and a first onium cation and generates an acid that induces dissociation of the acid-dissociable group of the polymer upon exposure.

10. The radiation-sensitive composition according to any one of claims 1 to 3, comprising an acid diffusion control agent that has a second organic acid anion and a second onium cation and generates a weak acid that does not induce dissociation of the acid-dissociable group of the polymer upon exposure.

11. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the polymer further comprises a structural unit (III) having a phenolic hydroxyl group.

12. A pattern forming method comprising: a step of forming a resist film by directly or indirectly applying the radiation-sensitive composition according to any one of claims 1 to 3 onto a substrate; a step of exposing the resist film; and a step of developing the exposed resist film with a developer.

13. The pattern forming method according to claim 12, wherein the exposure is performed using extreme ultraviolet rays or an electron beam.

14. A polymer comprising a structural unit (I) having an acid dissociable group and a structural unit (II) represented by the following formula (1). (In the above formula (1), １ R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R ２ is a divalent organic group having 1 to 50 carbon atoms. Z is an amide bond. R ３ is a single bond or an organic group having 1 to 5 carbon atoms. Rf １ , Rf ２ are each independently a hydrogen atom, a fluorine atom, or a fluorinated hydrocarbon group, provided that at least one of them is a fluorine atom or a fluorinated hydrocarbon group. Rf １ and Rf ２ When there are a plurality of them, the plurality of Rf １ and Rf ２ are the same or different from each other. n is an integer of 1 to 3. M ＋ is a monovalent onium cation.) 15. A compound represented by the following formula (2): (In the above formula (2), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a single bond or a divalent linking group. W is a substituted or unsubstituted organic group having a ring structure and having 3 to 40 carbon atoms. n1 is 0 or 1. R ４ , R ５ are each independently a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. ４ and R ５ If there are multiple R ４ and R ５ are the same or different. m1 is an integer from 0 to 8. ６ is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. １ , Rf ２ are each independently a hydrogen atom, a fluorine atom or a fluorinated hydrocarbon group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. １ and Rf ２ When there are a plurality of Rf １ and Rf ２ are the same or different, and n is an integer of 1 to 3. ＋ is a monovalent onium cation.

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