Radiation-sensitive composition and pattern formation method

Abstract

Provided are a radiation-sensitive composition and a pattern formation method capable of exhibiting, at sufficient levels, sensitivity, development contrast, development defect suppression property, and limit resolution when forming patterns. This radiation-sensitive composition contains a polymer and a solvent. The polymer includes: a structural unit (I) that has an iodo group and that also has an acid-dissociable group; a structural unit (II) that has a first organic acid anion and a first onium cation and that includes a first acid-generating structure for generating, through exposure to light, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) that has a second organic acid anion and a second onium cation, and that includes a second acid-generating structure for generating, through exposure to light, an acid that does not induce dissociation of the acid-dissociable group.

Description

Radiation-sensitive composition and pattern forming method

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

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

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

[0004] As patterns become finer, it is necessary to highly control acid diffusion. As one measure to achieve this, a resist material using a base polymer containing a sulfonium salt structure of a weak acid has been proposed (JP 2022-115072 A).

[0005] Japanese Patent Application Laid-Open No. 2022-115072

[0006] In developing the above-mentioned next-generation technologies, resist performances equivalent to or better than conventional ones are required in terms of sensitivity, development contrast, suppression of development defects, limiting resolution, and the like.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method which have excellent sensitivity during pattern formation and can exhibit development contrast, development defect suppression, and limiting resolution at levels equal to or higher than those of conventional compositions.

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

[0009] In one embodiment, the present invention relates to a radiation-sensitive composition comprising: a polymer; and a solvent, wherein the polymer comprises: a structural unit (I) having an iodine group and further having an acid-dissociable group; a structural unit (II) including a first acid-generating structure having a first organic acid anion and a first onium cation, and which generates, upon exposure, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) including a second organic acid anion and a second onium cation, which generates, upon exposure, an acid that does not induce dissociation of the acid-dissociable group.

[0010] The radiation-sensitive composition can exhibit excellent sensitivity during resist pattern formation, as well as development contrast, development defect suppression, and limiting resolution that are equal to or better than those of conventional compositions. Although the reason for this is unclear, it is presumed to be as follows.

[0011] Radiation such as EUV having a wavelength of 13.5 nm is largely absorbed by iodine groups (iodine atoms), which increases the efficiency of secondary electron generation and makes the resulting resist film highly sensitive.

[0012] The first acid generating structure contained in the structural unit (II) in the polymer has a first organic acid anion and a first onium cation, and generates an acid that induces dissociation of the acid-dissociable group upon exposure. That is, the first acid generating structure functions as a conventional radiation-sensitive acid generator. By incorporating the first acid generating structure into the structural unit (II), the diffusion length of the acid generated upon exposure can be highly controlled, and development contrast and limiting resolution equivalent to or better than those of conventional structures can be achieved.

[0013] The second acid generating structure contained in the structural unit (III) in the polymer has a second organic acid anion and a second onium cation, and generates an acid upon exposure that does not induce dissociation of the acid-dissociable group. That is, the second acid generating structure behaves as an acid diffusion controller having a conventional quencher function. By incorporating the second acid generating structure into the structural unit (III), it is possible to suppress the diffusion of the second acid generating structure having a quencher function into undesired regions, and it is possible to achieve development contrast and limiting resolution that are equal to or better than those of conventional structures.

[0014] Furthermore, by incorporating such a first acid generating structure and a second acid generating structure into the polymer, the content of the radiation-sensitive acid generator and the acid diffusion controller, which have conventionally been added as low-molecular-weight compounds, can be reduced or eliminated. This increases the solubility of each component in the radiation-sensitive composition and improves the uniformity of the composition of the resulting resist film. As a result, the resist film can exhibit not only excellent sensitivity but also development contrast, development defect suppression, and limiting resolution that are equal to or better than those of conventional resist films.

[0015] It is presumed that the above resist performance can be achieved by the combined effects of these factors.

[0016] 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.

[0017] The pattern formation method uses the radiation-sensitive composition, which is capable of exhibiting excellent sensitivity during resist pattern formation, as well as development contrast, suppression of development defects, and limiting resolution that are equal to or better than those of conventional compositions, and therefore can efficiently form high-quality resist patterns.

[0018] In yet another embodiment, the present invention relates to a polymer comprising: a structural unit (I) having an iodo group and further having an acid dissociable group; a structural unit (II) including a first acid generating structure having a first organic acid anion and a first onium cation, and which generates, upon exposure, an acid that induces dissociation of the acid dissociable group; and a structural unit (III) including a second organic acid anion and a second onium cation, which generates, upon exposure, an acid that does not induce dissociation of the acid dissociable group.

[0019] The polymer, which contains an iodine group, a first acid-generating structure, and a second acid-generating structure, is suitable for use in a radiation-sensitive composition that is required to have excellent sensitivity during resist pattern formation, as well as development contrast, development defect suppression, and limiting resolution that are equal to or better than those of conventional compositions.

[0020] 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.

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

[0022] <Polymer> The polymer (i.e., base polymer) is an assembly of polymer chains having an iodine group and further including the structural units (I), (II), and (III). In addition to these structural units, the base polymer may also include a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)") or a structural unit including a lactone structure (hereinafter also referred to as "structural unit (V)"). While the polymer of this embodiment preferably includes the iodine group, the structural unit (I), the structural unit (II), and the structural unit (III) in the same polymer chain, it may also include the iodine group, the structural unit (I), the structural unit (II), and the structural unit (III) in two or more different polymer chains. For example, the polymer may be a mixture of a first polymer chain including the iodine group, the structural unit (I), and the structural unit (II) and a second polymer chain including the structural unit (III). Alternatively, the polymer may be a mixture of a first polymer chain containing an iodo group and the structural unit (II), a second polymer chain containing the structural unit (I), and a third polymer chain containing the structural unit (III). Alternatively, the polymer may be a mixture of a first polymer chain containing an iodo group, a second polymer chain containing the structural unit (I), a third polymer chain containing the structural unit (II), and a fourth polymer chain containing the structural unit (III). The polymer may contain an iodo group, a structural unit (I), a structural unit (II), and a structural unit (III) in any combination in one or more polymer chains.

[0023] By incorporating iodine groups into the base polymer, the radiation absorption efficiency increases, and the secondary electron generation efficiency increases, thereby improving sensitivity.

[0024] The form in which the base polymer contains an iodine group is not particularly limited, but in the base polymer, the acid-dissociable group preferably contains an iodine group.

[0025] The base polymer preferably contains an iodine group in the form of an iodine group-containing aromatic ring structure. The iodine group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in an aromatic ring are substituted with iodine groups. Any structural unit constituting the base polymer may contain the iodine group-containing aromatic ring structure.

[0026] In particular, the acid-dissociable group preferably contains an iodine group-containing aromatic ring structure. Generally, the introduction of an iodine group tends to reduce removability with a developer. In contrast, the acid-dissociable group dissociates with acid upon exposure to generate an acid group, which is easily removed during development. By introducing an iodine group or an iodine group-containing aromatic ring structure into the acid-dissociable group that is easily removed during development, good development defect suppression properties can be achieved.

[0027] The aromatic ring in the iodo group-containing aromatic ring structure is not particularly limited as long as it is a ring structure having aromaticity.Examples of the aromatic ring include aromatic hydrocarbon rings such as benzene ring, naphthalene ring, anthracene ring, phenalene ring, phenanthrene ring, pyrene ring, fluorene ring, perylene ring, and coronene ring, heteroaromatic rings such as furan ring, pyrrole ring, thiophene ring, phosphole ring, pyrazole ring, oxazole ring, isoxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, triazine ring, carbazole ring, and dibenzofuran ring, or combinations thereof.Among these, the aromatic ring is preferably a benzene ring.

[0028] The number of iodine atoms in the iodo group-containing aromatic ring structure is not particularly limited, but is preferably 1 to 4, more preferably 1, 2 or 3, and even more preferably 1 or 2.

[0029] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group (excluding structures corresponding to the structural unit (IV)). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The acid generated from the structural unit (II) of the polymer upon exposure dissociates the acid-dissociable group in the structural unit (I), generating a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0030] The structural unit (I) is not particularly limited as long as it has an acid-dissociable group, and examples thereof include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. In the base polymer, it is preferable that the acid-dissociable group contains the above-mentioned iodine group-containing aromatic ring structure. From the viewpoint of improving the pattern formability of the radiation-sensitive composition, a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0031]

[0032] In the above formula (1), R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １８ is a monovalent substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms. １９ and R ２０ L each independently represents a monovalent substituted or unsubstituted chain hydrocarbon group having 1 to 10 carbon atoms, a monovalent substituted or unsubstituted alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded. １１ teeth, ＊ -COO-, ＊ -L １１ａ -COO- or ＊ -COO-L １１ａ represents —COO—. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R１７ is the bond to the carbon atom to which it is bonded.

[0033] The above R １７ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0034] L １１ａ Examples of the alkanediyl group represented by the formula (I) include divalent alkanediyl groups having 1 to 10 carbon atoms, such as methanediyl, ethanediyl, and propanediyl. １１ａ The alkanediyl group represented by the formula (I) is preferably a methanediyl group or an ethanediyl group.

[0035] L １１ａ Examples of the arenediyl group represented by the formula (I) include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl and naphthalenediyl groups. １１ａ As the arenediyl group represented by the formula:

[0036] L １１ａ Examples of the substituent that the alkanediyl group or arenediyl group represented by the formula (I) may have include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, and an alkoxy group.

[0037] L １１ａExamples of the alkyl group as a substituent include linear or branched alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, and propyl. Examples of the fluorinated alkyl group include linear or branched fluorinated alkyl groups having 1 to 8 carbon atoms, such as trifluoromethyl and pentafluoroethyl. Examples of the alkoxycarbonyloxy group include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as methoxycarbonyloxy, butoxycarbonyloxy, and adamantylmethyloxycarbonyloxy. Examples of the acyl group include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as acetyl, propionyl, benzoyl, and acryloyl. Examples of the acyloxy group include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as acetyloxy, propionyloxy, benzoyloxy, and acryloyloxy. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, and a propoxy group.

[0038] The above R １８ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 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.

[0039] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, and isopentyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0040] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group; polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group; monocyclic alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group and a cyclohexenyl group; and polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group.

[0041] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl groups, and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl groups.

[0042] The above R １８ As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0043] R １９ and R ２０ The monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula １８ Among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms in the above formula, groups having 1 to 10 carbon atoms are exemplified.

[0044] R １９ and R ２０ The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula １８ Examples of the monovalent alicyclic hydrocarbon group include those having 3 to 20 carbon atoms.

[0045] The above R １９ and R ２０The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded is not particularly limited as long as it is a group in which two hydrogen atoms have been removed from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above number of carbon atoms. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0046] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, such as bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. ３，７ ] Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0047] Among these, R １８ is an alkyl group, an alkenyl group, or a phenyl group having 1 to 4 carbon atoms, and R １９ and R ２０ are combined with each other, and the alicyclic structure formed together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0048] The above R １８ ~R ２０ Examples of the substituent that may be possessed by L include １１ａ Substituents that can be possessed by an alkanediyl group or arenediyl group represented by the following formula can be suitably employed.

[0049] Examples of the structural unit (I-1) include structural units represented by the following formulas (1-1) to (1-15) (hereinafter also referred to as "structural units (I-1-1) to (I-1-11)").

[0050]

[0051]

[0052] In the above formulas (1-1) to (1-15), R １７ ~R ２０ has the same meaning as in formula (1). Ｌ１１ is 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 each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other.

[0053] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, an ethenyl group, a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ is preferably an iodine atom, an alkyl group, or an alkoxy group. Ｌ１１ By employing an iodine atom as R , an iodine group can be suitably introduced into the structural unit (I). Ｌ１１ It is preferable to use an iodine atom as the ion source in terms of suppressing development defects.

[0054] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0055]

[0056] In the above formulas (1f) to (2f), R αｆ R are each independently a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. βｆ are each independently a hydrogen atom or a chain alkyl group having 1 to 5 carbon atoms. １ is an integer from 1 to 4.

[0057] The above R βｆis preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0058] Specific examples of the structural unit (I) (including the structural unit (I-1)) are not particularly limited, but include structures represented by the following formulae (1-1) to (1-33).

[0059]

[0060]

[0061] In the formula, R １７ is synonymous with the above formula (1).

[0062] 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 60 mol%, and even more preferably 50 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. When the acid-dissociable group has an iodine group, sensitivity can be further improved.

[0063] (Structural Unit (II)) The structural unit (II) includes a first acid-generating structure. The first acid-generating structure has a first organic acid anion and a first onium cation, and generates an acid that induces dissociation of the acid-dissociable group upon exposure. The onium salt structure formed by the first organic acid anion and the first onium cation (i.e., the first acid-generating structure) functions as a radiation-sensitive acid-generating structure.

[0064] In this specification, the term "dissociation" of an acid-dissociable group means dissociation upon post-exposure baking at 110° C. for 60 seconds.

[0065] 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.

[0066] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (II) of the base polymer is not particularly limited. The base polymer may have the first organic acid anion as a side chain moiety, or the first onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding first organic acid anion or first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the first organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the first onium cation is ionically bonded to the first organic acid anion as a counter ion of the first organic acid anion. On the other hand, when the first onium cation is bonded to the main chain of the base polymer as a side chain structure, the first organic acid anion is ionically bonded to the first onium cation as a counter ion of the first onium cation. From the viewpoint of controlling the acid diffusion length, it is preferable that the base polymer have the first organic acid anion as a side chain moiety.

[0067] The first organic acid anion preferably has, as an acid anion moiety, at least one selected from the group consisting of a sulfonate anion, a carboxylate anion, and a sulfonimide anion. Examples of the acid generated by exposure include sulfonic acid, carboxylic acid, and sulfonimide, corresponding to the acid anion moiety.

[0068] The first organic acid anion preferably includes, as a structure other than the acid anion moiety, —O—, —CO—, a cyclic structure, or a combination thereof. The combination also includes a structure (heterocyclic structure) in which —O— or —CO— is incorporated into the cyclic structure as a ring-forming moiety.

[0069] The cyclic structure may be a monocycle, a polycycle, or a combination thereof. The cyclic structure may be an alicyclic structure, an aromatic ring structure, a heterocyclic structure, or a combination thereof. In the case of a combination, the ring structures may be bonded to form a chain structure, or two or more ring structures may form a fused ring structure, a bridged ring structure, or a spiro ring structure. A divalent heteroatom-containing group may be present between carbon atoms forming the skeleton of the cyclic structure or chain structure, and some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure may be substituted with other substituents.

[0070] The alicyclic structure may be R １８ A structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula can be suitably employed.

[0071] 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.

[0072] 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.

[0073] 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).

[0074]

[0075] In the above formula, γ is an integer of 1 to 3.

[0076] The chain structure may be R １９ and R ２０ A structure corresponding to the monovalent chain hydrocarbon group having 1 to 10 carbon atoms in the formula (I) can be suitably employed.

[0077] 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.

[0078] The substituents that substitute a part or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure include L １１ａ Substituents that can be possessed by the alkanediyl group or arenediyl group represented by the following formula can be suitably employed.

[0079] In the first acid generating structure, the first organic acid anion preferably has a sulfonate anion as the acid anion moiety, and an electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion. This allows the first acid generating structure to efficiently exhibit the above-mentioned function. Examples of the electron-withdrawing group include a fluorine atom, a fluorinated hydrocarbon group, a nitro group, and a cyano group. The fluorinated hydrocarbon group is preferably a perfluoroalkyl group having 1 to 5 carbon atoms.

[0080] The first organic acid anion preferably has an iodo group. The first organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0081] The first onium cation may be a radioactive onium cation. Examples of the radioactive onium cation include a sulfonium cation, a tetrahydrothiophenium cation, and an iodonium cation. Among these, a sulfonium cation or an iodonium cation is preferred, and a sulfonium cation is more preferred.

[0082] The first onium cation preferably has an iodo group. The first onium cation preferably contains the iodo group-containing aromatic ring structure.

[0083] The first onium cation in the structural unit (II) 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. As the aromatic ring in the fluoro-group-containing aromatic ring structure, an aromatic ring in an iodine-group-containing aromatic ring structure can be suitably used. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0084] The structural unit (II) having the above structures in combination can efficiently exhibit the above functions.

[0085] The structural unit (II) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (II-1)") or a structural unit represented by the following formula (a2) (hereinafter also referred to as "structural unit (II-2)").

[0086]

[0087] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２ is a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, or an arylene group having 6 to 10 carbon atoms, or a combination thereof, and some of the methylene groups constituting the alkylene group, cycloalkylene group, or arylene group may be substituted with an ether group, an ester group, or a lactone ring-containing group. ３ represents a single bond, an ether group, an ester group, a linear or branched alkylene group having 1 to 12 carbon atoms, or a cyclic cycloalkylene group having 3 to 12 carbon atoms, and some of the methylene groups constituting the alkylene group may be substituted with an ether group or an ester group.２ and V ３ Some or all of the hydrogen atoms in Rf may be substituted with a heteroatom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom. １ ~Rf ４ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, provided that at least one is a fluorine atom or a fluorinated hydrocarbon group. ４３ ~R ４７ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain a heteroatom, and R ４３ and R ４４ and may be bonded to each other to form a ring together with the sulfur atom to which they are attached. ４３ ~R ４５ and R ４６ ~R ４７ Preferably, at least one of the above contains an iodo group-containing aromatic ring structure or a fluoro group-containing aromatic ring structure.

[0088] V ２ and V ３ , R ４３ ~R ４７ The monovalent hydrocarbon group having 1 to 20 carbon atoms in the formula (I) is preferably an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with a heteroatom-containing group such as a hydroxy group, a carboxy group, a halogen atom, an oxo group, a cyano group, an amide group, a nitro group, a sultone group, a sulfone group, or a sulfonium salt-containing group, an alkoxy group, or an alkoxycarbonyl group, and some of the methylene groups constituting these groups may be substituted with an ether group, an ester group, a carbonyl group, a carbonate group, or a sulfonate ester group.

[0089] The structural units (II-1) and (II-2) are preferably represented by the following formulae (a1-1) and (a2-1), respectively.

[0090]

[0091] In the formula, R Ｖ , R ４３ ~R４７ , Rf １ ~Rf ４ and V １ has the same meaning as in formula (a1) or (a2). ４８ is a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms, a halogen atom other than iodine, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms. m is an integer of 0 to 4. n is an integer of 0 to 3.

[0092] Examples of the first organic acid anion of the monomer that gives the structural unit (II) (including the structural unit (II-1) and the structural unit (II-2)) include, but are not limited to, those shown below. Of the first organic acid anions shown below, all of the first organic acid anions that contain an aromatic ring structure have an iodine group-containing aromatic ring structure, but the structural unit (II) does not necessarily require an iodine group-containing aromatic ring structure. As the first organic acid anion that does not have an iodine group-containing aromatic ring structure, a structure in which the iodine atom in the following formula is substituted with a hydrogen atom or another substituent can be suitably used. In the following formula, R Ｖ is synonymous with the above.

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] The first onium cation of the structural unit (II-1) is preferably represented by the following formula (Q-1).

[0099]

[0100] In the above formula (Q-1), Ra1 and Ra2 each independently represent a substituent. n1 represents an integer of 0 to 5, and when n1 is 2 or greater, multiple Ra1s may be the same or different. n2 represents an integer of 0 to 5, and when n2 is 2 or greater, multiple Ra2s may be the same or different. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra3 represents a substituent. Ra1 and Ra2 may be bonded to each other to form a ring. When n1 is 2 or greater, multiple Ra1s may be bonded to each other to form a ring. When n2 is 2 or greater, multiple Ra2s may be bonded to each other to form a ring.

[0101] 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.

[0102] The alkyl groups of Ra1 and Ra2 may be linear or branched. The alkyl groups preferably have 1 to 10 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, and n-decyl. Of these, methyl, ethyl, n-butyl, and t-butyl are particularly preferred.

[0103] The cycloalkyl group of Ra1 and Ra2 includes a monocyclic or polycyclic cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms), such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecanyl, cyclopentenyl, cyclohexenyl, and cyclooctadienyl groups. Of these, cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups are particularly preferred.

[0104] Examples of the alkyl group moiety of the alkoxy group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. As the alkoxy group, a methoxy group, an ethoxy group, an n-propoxy group, and an n-butoxy group are particularly preferred.

[0105] Examples of the cycloalkyl group moiety of the cycloalkyloxy group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. As this cycloalkyloxy group, a cyclopentyloxy group and a cyclohexyloxy group are particularly preferred.

[0106] Examples of the alkoxy group moiety of the alkoxycarbonyl group of Ra1 and Ra2 include those previously listed as the alkoxy group of Ra1 and Ra2. As the alkoxycarbonyl group, a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group are particularly preferred.

[0107] Examples of the alkyl group moiety of the alkylsulfonyl group of Ra1 and Ra2 include those previously listed as the alkyl groups of Ra1 and Ra2. Furthermore, examples of the cycloalkyl group moiety of the cycloalkylsulfonyl group of Ra1 and Ra2 include those previously listed as the cycloalkyl groups of Ra1 and Ra2. Particularly preferred of these alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl groups.

[0108] Each of the groups Ra1 and Ra2 may further have a substituent, such as a halogen atom such as a fluorine atom (preferably a fluorine 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.

[0109] Examples of the halogen atom for Ra1 and Ra2 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and an iodine atom being preferred.

[0110] The halogenated hydrocarbon group of Ra1 and Ra2 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.

[0111] 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 they form - or a single bond. Among these, it is more preferable that they form -O-, -S- or a single bond, and it is particularly preferable that they form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1's may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2's may be linked to each other to form a ring. Such an example includes an embodiment in which two Ra1's are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0112] Ra3 is preferably a fluorine atom or a group having one or more fluorine atoms. Examples of the group having a fluorine atom include groups in which the alkyl group, cycloalkyl group, alkoxy group, cycloalkyloxy group, alkoxycarbonyl group, and alkylsulfonyl group represented by Ra1 and Ra2 are substituted with a fluorine atom. Among these, fluorinated alkyl groups are preferred, and CF ３ , C ２ F５ , 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 are particularly preferred.

[0113] Ra3 is a fluorine atom or CF ３ is preferably, and a fluorine atom is more preferably.

[0114] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0115] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0116] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is an iodine atom, a fluorine atom, or CF ３When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ and n3=2 and Ra3 is an iodine atom, a fluorine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ and n3=5 and each Ra3 is independently an iodine atom, a fluorine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently an iodine atom, a fluorine atom, or CF ３ A combination in which:

[0117] Specific examples of such onium cations represented by the above formula (Q-1) include the following: The fluorine atom or iodine atom in the onium cations below may be substituted with a hydrogen atom or another substituent.

[0118]

[0119]

[0120]

[0121]

[0122] The onium cation of the structural unit (II-2) is preferably a diaryliodonium cation having one or more fluorine atoms or iodine atoms, and at least one of the aryl groups of the onium cation of the structural unit (II-2) preferably has a fluoro- or iodo-containing aromatic ring structure.

[0123] It is also possible to adopt an embodiment in which a first onium cation is bonded to the main chain as a side chain structure of the base polymer, and a first organic acid anion is bonded to the first onium cation by an ionic bond as a counter ion of the first onium cation. In this case, the first onium cation is bonded to the main chain via a divalent linking group or a single bond, and V in the above formula (a1) or (a2) ２ From SO ３ － The structure up to the first onium cation is preferably ionically bonded to the first onium cation as a counter ion. １ A divalent linking group represented by the following formula can be preferably used.

[0124] When the base polymer contains the structural unit (II), the lower limit of the content of the structural unit (II) (when multiple types are contained, the total content) relative to all structural units constituting the radiation-sensitive acid-generating 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 setting the content of the structural unit (II) within the above range, the function as an acid-generating structure can be fully exhibited, and the above-mentioned resist performances can be exhibited.

[0125] The monomers that give the structural units (II-1) and (II-2) can be synthesized, for example, by a method similar to that for the sulfonium salts having polymerizable anions described in Japanese Patent No. 5201363.

[0126] (Structural Unit (III)) The structural unit (III) includes a second acid generating structure. The second acid generating structure has a second organic acid anion and a second onium cation, and generates an acid that does not induce dissociation of the acid-dissociable group upon exposure. The onium salt structure formed by the second organic acid anion and the second onium cation (i.e., the second acid generating structure) functions as an acid diffusion control structure. Specifically, under pattern formation conditions using the radiation-sensitive composition, the second acid generating structure does not substantially dissociate the acid-dissociable group of the structural unit (I), and has the function of suppressing the diffusion of the acid generated from the first acid generating structure in unexposed areas through salt exchange. It can be said that the acid generated from the second acid generating structure is a relatively weaker acid (an acid with a higher pKa) than the acid generated from the first acid generating structure. Whether the onium salt structure functions as a radiation-sensitive acid-generating structure or an acid-diffusion-controlling structure depends on the energy required to dissociate the acid-dissociable group of the base polymer and the acidity of the onium salt structure or the acid generated.

[0127] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (III) of the base polymer is not particularly limited. The base polymer may have the second organic acid anion as a side chain moiety, or the second onium cation as a side chain moiety. "Having as a side chain moiety" means that the corresponding second organic acid anion or second onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure. When the second organic acid anion is bonded to the main chain of the base polymer as a side chain structure, the second onium cation is ionically bonded to the second organic acid anion as a counter ion of the second organic acid anion. On the other hand, when the second onium cation is bonded to the main chain of the base polymer as a side chain structure, the second organic acid anion is ionically bonded to the second onium cation as a counter ion of the second onium cation. From the viewpoint of development contrast, it is preferable that the base polymer have the second organic acid anion as a side chain moiety.

[0128] The second organic acid anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety, and more preferably a carboxylate anion. However, when the second organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom at the α- or β-position relative to the sulfur atom in the sulfonate anion. Examples of the electron-withdrawing group include electron-withdrawing groups that the first organic acid anion may have in the first acid-generating structure. The acid generated by exposure is a carboxylic acid or sulfonic acid corresponding to the acid anion moiety.

[0129] The second organic acid anion preferably includes, as a structure other than the acid anion moiety, —O—, —CO—, a cyclic structure, or a combination thereof. As such a structure, the structures shown for the first organic acid anion can be suitably adopted.

[0130] The second organic acid anion preferably has an iodo group or a hydroxy group. The second organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0131] Examples of the second onium cation include radiolytic and non-radiolytic onium cations. Examples of the radiolytic and non-radiolytic onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, and ammonium cation. Among these, sulfonium cation and iodonium cation are preferred, and sulfonium cation is more preferred.

[0132] The second onium cation preferably has an iodo group. The second onium cation preferably contains the iodo group-containing aromatic ring structure.

[0133] The second onium cation in the structural unit (III) preferably has the above-mentioned fluoro group-containing aromatic ring structure, which increases the radiation absorption efficiency and thereby improves sensitivity.

[0134] The structural unit (II) having the above structures in combination can efficiently exhibit the above functions.

[0135] The structural unit (III) is preferably a structural unit represented by the following formula (p1) (hereinafter also referred to as "structural unit (III-1)").

[0136]

[0137] In formula (p1), R A is a hydrogen atom or a methyl group.

[0138] In formula (p1), X 1 is a single bond, an ester bond, an ether bond, a phenylene group, or a naphthylene group.

[0139] In formula (p1), X ２ represents a single bond, a saturated hydrocarbylene group having 1 to 12 carbon atoms, or a phenylene group, and the saturated hydrocarbylene group may contain an ether bond, an ester bond, an amide bond, a lactone ring, or a sultone ring. ２ The hydrocarbylene group represented by the formula (I) may be linear, branched or cyclic, and specific examples thereof include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,2-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a butane-1,2-diyl group, a butane-1,3-diyl group, a butane-1,4-diyl group, a butane-2,2-diyl group, a butane-2,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a 2-methylpropane-2 ... alkanediyl groups having 1 to 12 carbon atoms, such as diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group; cyclic saturated hydrocarbylene groups having 3 to 12 carbon atoms, such as cyclopentanediyl group, cyclohexanediyl group, norbornanediyl group, and adamantanediyl group; and groups obtained by combining these.

[0140] In formula (p1), X 3 is a single bond, an ester bond or an ether bond.

[0141] In formula (p1), RＸ is a linear, branched, or cyclic alkyl group having 1 to 5 carbon atoms, a halogen atom, a hydroxy group, a linear, branched, or cyclic alkoxy group having 1 to 4 carbon atoms, or a linear, branched, or cyclic alkoxycarbonyl group having 2 to 5 carbon atoms.

[0142] In formula (p1), R ４３ ~R ４５ has the same meaning as the above formula (a1).

[0143] In formula (p1), x1 is an integer of 0 to 3. When x1 is 2 or more, a plurality of R Ｘ are the same or different.

[0144] Instead of the sulfonium cation in the above formula (p1), an iodonium cation can also be used. As the iodonium cation, the diaryliodonium cation shown as the onium cation of the structural unit (II-2) can be suitably used.

[0145] Examples of the second organic acid anion of the monomer that gives the structural unit (III) include, but are not limited to, those shown below. Note that although all of the second organic acid anions shown below have an iodine group or a hydroxy group, the structural unit (III) does not necessarily require an iodine group or a hydroxy group. As the second organic acid anion that does not have an iodine group or a hydroxy group, a structure in which the iodine group or the hydroxy group in the following formula is substituted with a hydrogen atom or other substituent can be suitably used. In the following formula, R Ａ is the same as above. The second organic acid anion preferably has a carboxylate anion and a hydroxy group. In this case, it is preferable that the carboxylate anion and the hydroxy group are bonded to the same aromatic ring in the second organic acid anion, and it is more preferable that the carbon atom to which the carboxylate anion is bonded and the carbon atom to which the hydroxy group is bonded are directly bonded to each other in the same aromatic ring.

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155] As the second onium cation of the structural unit (III), a sulfonium cation represented by the above formula (Q-1) can be suitably used.

[0156] It is also possible to adopt an embodiment in which a second onium cation is bonded to the main chain as a side chain structure of the base polymer, and a second organic acid anion is bonded to the second onium cation by an ionic bond as a counter ion of the second onium cation. In this case, the second onium cation is bonded to the main chain via a divalent linking group or a single bond, and X in the above formula (p1) １ From COO － The structure up to is preferably ionically bonded to the second onium cation as a counter ion. １ A divalent linking group represented by the following formula can be preferably used.

[0157] When the base polymer contains the structural unit (III), the lower limit of the content of the structural unit (III) (the total content when multiple types are contained) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 10 mol%, based on all structural units constituting the radiation-sensitive acid-generating polymer. The upper limit of the content is preferably 30 mol%, more preferably 25 mol%, and even more preferably 20 mol%. By keeping the content of the structural unit (III) within the above range, the function of the acid diffusion control structure can be fully exhibited.

[0158] When the content of the structural unit (II) is taken as 100 mol%, the lower limit of the content of the structural unit (III) relative to the content of the structural unit (II) is preferably 50 mol%, more preferably 80 mol%, and even more preferably 100 mol%. The upper limit of the content is preferably 300 mol%, more preferably 250 mol%, and even more preferably 200 mol%. By setting the content of the structural unit (III) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0159] (Structural Unit (IV)) The structural unit (IV) is a structural unit having a phenolic hydroxyl group. When the polymer contains the structural unit (IV), the solubility in a developer can be more appropriately adjusted, and as a result, the sensitivity of the radiation-sensitive composition can be further improved. Furthermore, when KrF excimer laser light, EUV, electron beam, or the like is used as the radiation to be irradiated in the exposure step of the resist pattern formation method, the structural unit (IV) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (IV) is suitably applied to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (IV) is preferably represented by the following formula (2):

[0160] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ represents a single bond, -COO- ＊ or -O-. * is a bond on the aromatic ring side. R １０１ is an acid-dissociable group. １０２ R is a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxycarbonyl group, an acyl group, or an acyloxy group. １０２ If there are multiple R １０２ are the same or different. ３ is an integer from 0 to 2, and m ３ is an integer from 1 to 8, and m ４ and m ５ are each independently an integer of 0 to 8, provided that 1≦m３ +m ４ +m ５ ≦2n ３ Meets +5.)

[0161] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (IV), it is preferably a hydrogen atom or a methyl group.

[0162] L ＣＡ is a single bond or —COO— ＊ is preferred.

[0163] The above R １０１ The acid-dissociable group represented by the formula (I) is not particularly limited, and examples thereof include R １０１ a structure forming a tertiary alkyl ester moiety together with —COO— to which R １０１ a structure that forms, together with —COO— to which —COO— is bonded, a secondary unsaturated alkyl ester moiety having a double bond between the β-position carbon and the γ-position carbon of the terminal oxygen atom of —COO—; １０１ and a structure in which an acetal bond is formed together with —COO— to which —COO— is bonded.

[0164] R １０２ The halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in the formula (1) is preferably L １ The groups listed as the substituents of R can be suitably used. １０２ The halogen atom in is preferably an iodine atom.

[0165] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0166] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0167] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0168] The above m ５ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0169] The structural unit (IV) is preferably a structural unit represented by the following formulas (2-1) to (2-26) (hereinafter also referred to as "structural unit (2-1) to structural unit (2-26)").

[0170]

[0171]

[0172]

[0173] In the above formulas (2-1) to (2-26), R β is the same as the above formula (2).

[0174] The lower limit of the content of the structural unit (IV) (total content when multiple types of structural unit (IV) are present) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%. The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, and even more preferably 50 mol%. By setting the content of the structural unit (IV) within the above range, the radiation-sensitive composition can further improve the sensitivity and development contrast.

[0175] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is polymerized, it is preferable to polymerize the monomer in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group (e.g., an acyl group), and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis. The hydroxystyrene may also be polymerized without protecting the phenolic hydroxyl group.

[0176] (Structural Unit (V)) The structural unit (V) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (V), the base polymer can adjust its solubility in a developer, and as a result, the radiation-sensitive composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base polymer and a substrate can be improved.

[0177] When the base polymer contains the structural unit (V), the lower limit of the content of the structural unit (V) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 20 mol%, more preferably 16 mol%, and even more preferably 12 mol%. By setting the content of the structural unit (V) within the above range, the radiation-sensitive composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0178] (Structural Unit (VI)) The base polymer optionally has other structural units. Examples of the other structural units include structural units (VI) containing a polar group (excluding those corresponding to the structural unit (V)). By further including the structural unit (VI), the base polymer can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0179] Examples of the structural unit (VI) include structural units represented by the following formula:

[0180]

[0181] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0182] When the base polymer has the structural unit (VI) having the polar group, the lower limit of the content of the structural unit (VI) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on the total structural units constituting the base polymer. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%. By setting the content of the structural unit (VI) within the above range, the lithography performance such as resolution of the radiation-sensitive composition can be further improved.

[0183] The polymer may further contain a structural unit derived from styrene or iodostyrene (hereinafter also referred to as "structural unit (VII)"). When the base polymer contains the structural unit (VII) having the polar group, the lower limit of the content of the structural unit (VII) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, based on all structural units constituting the base polymer. The upper limit of the content is preferably 15 mol%, more preferably 10 mol%, and even more preferably 8 mol%.

[0184] (Method of Synthesizing Base Polymer) The base polymer can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a radical polymerization initiator or the like.

[0185] Examples of the radical polymerization initiator include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Of these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0186] As the solvent used in the polymerization, the solvents described below can be suitably used. These solvents used in the polymerization may be used alone or in combination of two or more kinds.

[0187] The reaction temperature in the polymerization is usually 40° C. to 150° C., preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, preferably 1 hour to 24 hours.

[0188] The molecular weight of the base polymer is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 3,000, more preferably 4,000, and even more preferably 5,000. The upper limit of Mw is preferably 20,000, more preferably 12,000, and even more preferably 10,000. By setting the Mw of the base polymer within the above range, the resulting resist film can exhibit good heat resistance and developability.

[0189] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0190] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0191] The lower limit of the content of the base polymer is preferably 60% by mass, more preferably 70% by mass, and even more preferably 80% by mass, based on the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 98% by mass, more preferably 95% by mass, and even more preferably 92% by mass.

[0192] <Other Polymers> The radiation-sensitive composition of the present embodiment may contain, as another polymer, a polymer having a higher mass content of fluorine atoms than the base polymer (hereinafter also referred to as a "high-fluorine content polymer"). When the radiation-sensitive composition contains a high-fluorine content polymer, the high-fluorine content polymer can be unevenly distributed in the surface layer of the resist film relative to the base polymer, and as a result, it is possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film.

[0193] The high fluorine content polymer preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (VIII)").

[0194]

[0195] In the above formula (5), R １３ is a hydrogen atom, a methyl group, or a trifluoromethyl group.Ｌ represents a single bond, an alkanediyl group having 1 to 5 carbon atoms, an oxygen atom, a sulfur atom, —COO—, or —SO ２ ONH-, -CONH-, -OCONH- or a combination thereof. １４ is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0196] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VIII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0197] Above G Ｌ As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VIII), a single bond and —COO— are preferred, and —COO— is more preferred.

[0198] The above R １４ Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0199] The above R １４ Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0200] The above R １４ As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropan-2-yl group, a 5,5,5-trifluoro-1,1-diethylpentyl group, and a 1,1,1,2,2,3,3-heptafluoro-6-methylheptan-4-yl group are even more preferable.

[0201] When the high-fluorine content polymer has the structural unit (VIII), the lower limit of the content of the structural unit (VIII) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content may be 100 mol%, 90 mol%, or 80 mol%. By setting the content of the structural unit (VIII) 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. As a result, the surface modification properties, component distribution controllability, and water repellency of the resist film can be further improved.

[0202] The high-fluorine-containing polymer preferably contains at least one structural unit (hereinafter collectively referred to as "structural unit (IX)") selected from the group consisting of a structural unit represented by the following formula (f-1) (hereinafter also referred to as "structural unit (IX-1)") and a structural unit represented by the following formula (f-2) (hereinafter also referred to as "structural unit (IX-2)"):

[0203] In the above formula (f-1), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １１ is a single bond or a divalent linking group. ｆ１１ and R ｆ１２ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ｆ１１ and Y １１ may be bonded to each other to form a ring structure having 3 to 15 carbon atoms. ｆ１３ and R ｆ１４ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. １１ is a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ｆ１３ , R ｆ１４ , and X １１Any two or three of R may together form a ring structure having 3 to 15 carbon atoms. ｆ１１ , R ｆ１２ , R ｆ１３ , R ｆ１４ , or X １１ At least one of the groups is a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group.

[0204] In the above formula (f-2), R ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２１ is a divalent linking group. ｆ２１ and R ｆ２２ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ２１ is a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms, a cyano group, or a nitro group. ｆ２１ , R ｆ２２ , and X ２１ Any two or three of R may together form a ring structure having 3 to 15 carbon atoms. ｆ２１ , R ｆ２２ , or X ２１ At least one of the groups is a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group.

[0205] (Structural unit (IX-1)) In the above formula (f-1), R １１ As the alkyl group, a hydrogen atom or a methyl group is preferred from the viewpoint of copolymerizability of the monomer that gives the structural unit (IX-1).

[0206] Y １１ Examples of the divalent linking group represented by the formula (I) include a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms.

[0207] Y １１ The divalent hydrocarbon group having 1 to 20 carbon atoms in the formula (1) is R １８A group in which one hydrogen atom has been removed from a monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula:

[0208] Y １１ In the formula (I), the divalent fluorinated hydrocarbon groups having 1 to 20 carbon atoms each independently include, for example, a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms and a divalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms. Examples of the chain hydrocarbon group and alicyclic hydrocarbon group constituting such a divalent fluorinated chain hydrocarbon group and fluorinated alicyclic hydrocarbon group include the divalent hydrocarbon groups described above.

[0209] R ｆ１１ , R ｆ１２ , R ｆ１３ , R ｆ１４ and X １１ Examples of the monovalent hydrocarbon group having 1 to 5 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 5 carbon atoms and a monovalent alicyclic hydrocarbon group having 3 to 5 carbon atoms.

[0210] Examples of the monovalent chain hydrocarbon group having 1 to 5 carbon atoms include a monovalent linear or branched saturated hydrocarbon group having 1 to 5 carbon atoms, or a monovalent linear or branched unsaturated hydrocarbon group having 1 to 5 carbon atoms. Examples of the monovalent linear or branched saturated hydrocarbon group having 1 to 5 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, and a t-butyl group. Examples of the monovalent linear or branched unsaturated hydrocarbon group having 1 to 5 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.

[0211] The monovalent alicyclic hydrocarbon group having 3 to 5 carbon atoms includes a monovalent saturated hydrocarbon group or a monovalent unsaturated hydrocarbon group having a monocyclic or polycyclic ring. A cyclopentyl group is preferred as the monovalent saturated hydrocarbon group.

[0212] R ｆ１１ , R ｆ１２ , R ｆ１３ , R ｆ１４ and X１１ Examples of the monovalent fluorinated hydrocarbon groups having 1 to 5 carbon atoms represented by the formula (I) each independently include a monovalent fluorinated chain hydrocarbon group having 1 to 5 carbon atoms and a monovalent fluorinated alicyclic hydrocarbon group having 3 to 5 carbon atoms.

[0213] In the above formula (1), R ｆ１１ and Y １１ may be bonded to each other to form a ring structure having 3 to 15 carbon atoms. ｆ１３ , R ｆ１４ , and X １１ Any two or three of these may together form a ring structure having 3 to 15 carbon atoms.

[0214] In addition, in the above formula (f-1), R ｆ１１ , R ｆ１２ , R ｆ１３ , R ｆ１４ , or X １１ At least one of the groups is preferably a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group.

[0215] Examples of the structural unit (IX-1) include structural units represented by the following formula: １１ In addition, Rf in the following formula is a monovalent chain hydrocarbon group which may have a fluorine atom.

[0216]

[0217]

[0218]

[0219]

[0220]

[0221] Examples of the monomer that forms the structural unit (IX-1) include monomers represented by the following formula:

[0222]

[0223]

[0224]

[0225] (Structural unit (IX-2)) R ２１ As the alkyl group, a hydrogen atom or a methyl group is preferred from the viewpoint of copolymerizability of the monomer that gives the structural unit (IX-2).

[0226] Y ２１ Examples of the divalent linking group represented by the formula (I) include a divalent hydrocarbon group having 1 to 20 carbon atoms and a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms, which may contain an ether group or an ester group.

[0227] Y ２１ When the divalent hydrocarbon group and fluorinated hydrocarbon group having 1 to 20 carbon atoms as the group contains an ether group or an ester group, the hydrocarbon group may contain one or more ether groups or ester groups within the group.

[0228] Y ２１ The divalent hydrocarbon group having 1 to 20 carbon atoms and the divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms in the formula (f-1) are, respectively, Y １１ In the above formula, a divalent hydrocarbon group having 1 to 20 carbon atoms and a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms can be suitably used.

[0229] R ｆ２１ and R ｆ２２ The hydrocarbon group having 1 to 5 carbon atoms and the fluorinated hydrocarbon group having 1 to 5 carbon atoms represented by the formula (f-1) are ｆ１１ and R ｆ１２ Monovalent hydrocarbon groups having 1 to 5 carbon atoms and monovalent fluorinated hydrocarbon groups having 1 to 5 carbon atoms can be suitably used.

[0230] X ２１ The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (1) is １８ A monovalent hydrocarbon group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0231] X ２１Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms 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.

[0232] X ２１ The monovalent hydrocarbon group having 1 to 20 carbon atoms and the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms as the above may contain a divalent linking group containing a heteroatom between the carbon-carbon bond. Examples of such a divalent linking group containing a heteroatom include -O-, -CO-, -COO-, -NH-, -CONH-, -S-, -SO-, and -SO ２ - and others.

[0233] In addition, in the above formula (f-2), R ｆ２１ , R ｆ２２ , and X ２１ Any two or three of these may together form a ring structure having 3 to 15 carbon atoms.

[0234] In addition, in the above formula (f-2), R ｆ２１ , R ｆ２２ , or X ２１ At least one of the groups is a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group.

[0235] Examples of the structural unit (IX-2) include a structural unit represented by the following formula: ２１ has the same meaning as the above formula (f-2).

[0236]

[0237] Examples of the monomer that gives the structural unit (IX-2) include the monomers represented by the following formula:

[0238]

[0239]

[0240] When the high-fluorine-content polymer has the structural unit (IX), the lower limit of the content of the structural unit (IX) is preferably 10 mol%, more preferably 20 mol%, and even more preferably 30 mol%, based on all structural units constituting the high-fluorine-content polymer. The upper limit of the content may be 100 mol%, 90 mol%, or 80 mol%. By setting the content of the structural unit (IX) within the above range, the solubility in an alkaline developer can be improved, thereby suppressing the occurrence of development defects.

[0241] (Other Structural Units) The high fluorine content polymer may contain the structural unit (I) or the structural unit (VI) in the base polymer as a structural unit other than the structural units listed above. When the high fluorine content polymer contains the structural unit (VI), the structural unit (VI) is preferably a structure containing a fluorine atom.

[0242] The lower limit of Mw of the high fluorine content polymer is preferably 4,000, more preferably 6,000, and even more preferably 8,000. The upper limit of Mw is preferably 20,000, more preferably 14,000, and even more preferably 12,000.

[0243] The lower limit of Mw / Mn of the high fluorine content polymer is usually 1, more preferably 1.1. The upper limit of Mw / Mn is usually 5, preferably 3, more preferably 2.

[0244] When the radiation-sensitive composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the base polymer, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less.

[0245] By setting the content of the high fluorine-containing polymer within the above range, the high fluorine-containing polymer can be more effectively localized in the surface layer of the resist film, which in turn makes it possible to modify the surface of the resist film during EUV exposure and control the distribution of the composition within the film. The radiation-sensitive composition may contain one or more high fluorine-containing polymers.

[0246] (Method for synthesizing high fluorine content polymer) The high fluorine content polymer can be synthesized by the same method as the above-mentioned method for synthesizing the base polymer.

[0247] <Radiation-Sensitive Acid Generator> The radiation-sensitive composition may contain a radiation-sensitive acid generator. The radiation-sensitive acid generator contains a third organic acid anion and a third onium cation to form an onium salt structure. The radiation-sensitive acid generator is a component that generates an acid upon exposure. The acid generated upon exposure has the function of dissociating an acid-dissociable group in the base polymer to generate a carboxyl group or the like. The radiation-sensitive acid generator has a form in which the onium salt structure exists alone as a low-molecular-weight compound (free from the polymer), and is different from a radiation-sensitive acid-generating structure in which the first organic acid anion or the first onium cation is bonded (covalently bonded) to the main chain of the base polymer as a side chain structure, such as the structural unit (II) in the base polymer.

[0248] At least one selected from the group consisting of the third organic acid anion and the third onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0249] The structure of the third organic acid anion of the radiation-sensitive acid generator is V in the above formula (a1) or (a2) of the base polymer. ２ From SO ３ － The above structures can be suitably adopted.

[0250] Examples of the third organic acid anion of the radiation-sensitive acid generator include, but are not limited to, those shown below. Note that, instead of the first organic acid anion having an iodo group-containing aromatic ring structure, a third organic acid anion not having an iodo group-containing aromatic ring structure can suitably be a structure in which the iodo group in the following formula is substituted with a hydrogen atom or another substituent.

[0251]

[0252]

[0253] The structure of the third onium cation in the radiation-sensitive acid generator can suitably be the same as the structure of the first onium cation in the structural unit (II) in the base polymer.

[0254] The above-mentioned radiation-sensitive acid generator can be synthesized by a known method, particularly by a salt exchange reaction. Known radiation-sensitive acid generators can also be used as long as they do not impair the effects of the present invention.

[0255] These radiation-sensitive acid generators may be used alone or in combination of two or more. When the radiation-sensitive composition contains a radiation-sensitive acid generator, the lower limit of the content of the radiation-sensitive acid generator (total content when multiple types are used) is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and even more preferably 1 part by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 10 parts by mass, more preferably 6 parts by mass, and even more preferably 4 parts by mass. This allows excellent sensitivity to be exhibited during resist pattern formation.

[0256] <Acid Diffusion Controller> The radiation-sensitive composition may contain an acid diffusion controller. The acid diffusion controller contains a quaternary organic acid anion and a quaternary onium cation, and generates an acid having a higher pKa than the acid generated from the radiation-sensitive acid generator upon irradiation with radiation. The acid diffusion controller does not substantially dissociate the acid-dissociable group of the base polymer under pattern formation conditions using the radiation-sensitive composition, and has the function of suppressing the diffusion of the acid generated from the radiation-sensitive acid generator in unexposed areas through salt exchange.

[0257] By including the acid diffusion controller in the radiation-sensitive composition, it is possible to suppress the diffusion of acid in unexposed areas, and to form a resist pattern with superior resolution and development contrast.

[0258] At least one selected from the group consisting of the quaternary organic acid anion and the quaternary onium cation preferably has an iodo group, and more preferably has the iodo group-containing aromatic ring structure.

[0259] The structure of the fourth organic acid anion is not particularly limited, but preferably includes -O-, -CO-, a cyclic structure, or a combination thereof. As the cyclic structure, the cyclic structure in the first organic acid anion of the structural unit (II) of the base polymer can be suitably used.

[0260] In the acid diffusion controller, it is preferable that the second organic anion has a sulfonate anion or a carboxylate anion as the acid anion moiety (provided that when the fourth organic acid anion has the sulfonate anion, neither a fluorine atom nor a fluorinated hydrocarbon group is bonded to the carbon atom at the α-position or β-position relative to the sulfur atom of the sulfonate anion), which allows the acid diffusion controller to efficiently exhibit the above-mentioned function.

[0261] Examples of the acid diffusion controller include a sulfonium salt compound represented by the following formula (8-1), an iodonium salt compound represented by the following formula (8-2), etc. Further examples include a compound containing a sulfonium cation and an anion in the same molecule represented by the following formula (8-3), and a compound containing an iodonium cation and an anion in the same molecule represented by the following formula (8-4).

[0262]

[0263] In the above formulas (8-1) to (8-4), J ＋ is a sulfonium cation, and U ＋ is an iodonium cation. － and Q － are each independently OH － , R α -COO － , R α -SO ３ － In the above formulas (8-1) and (8-2), R α is a monovalent organic group having 1 to 30 carbon atoms. αis a single bond or a divalent organic group having 1 to 30 carbon atoms. Examples of this organic group include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group having a divalent heteroatom-containing group between carbon atoms of this hydrocarbon group or at the carbon chain terminal, a group in which some or all of the hydrogen atoms of the hydrocarbon group have been substituted with a monovalent heteroatom-containing group, or a combination thereof.

[0264] The monovalent hydrocarbon group having 1 to 20 carbon atoms in the organic group is R １８ Preferably, a monovalent hydrocarbon group having 1 to 20 carbon atoms, represented by the following formula: can be used. As the divalent heteroatom-containing group, preferably, a divalent heteroatom-containing group in the first organic acid anion of the structural unit (II) of the base polymer can be used. Examples of monovalent heteroatom-containing groups include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom.

[0265] Examples of the fourth organic acid anion of the acid diffusion controller include, but are not limited to, those shown below. Examples also include compounds containing an iodonium cation and an anion in the same molecule and compounds containing a sulfonium cation and anion in the same molecule. As the organic acid anion without an iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with an atom or group other than the iodo group, such as a hydrogen atom or another substituent, can be suitably used.

[0266]

[0267]

[0268] As the quaternary onium cation in the acid diffusion controller, the structure of the first onium cation in the structural unit (II) in the base polymer can be suitably adopted.

[0269] When the quaternary onium cation is an iodonium cation, it is preferably a diaryliodonium cation, more preferably having one or more fluoro or iodo groups.

[0270] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0271] These acid diffusion controllers may be used alone or in combination of two or more. When the radiation-sensitive composition contains an acid diffusion controller, the lower limit of the content of the acid diffusion controller (total content when multiple types are used) is preferably 1 part by mass, more preferably 2 parts by mass, and even more preferably 3 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, and even more preferably 8 parts by mass.

[0272] <Solvent> The radiation-sensitive composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the base polymer and optional additives.

[0273] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0274] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; and polyhydric alcohol partial ether-based solvents in which some of the hydroxy groups in the above-mentioned polyhydric alcohol-based solvents have been etherified. In the present embodiment, alcoholic acid ester solvents such as methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, i-butyl 2-hydroxyisobutyrate, and n-butyl 2-hydroxyisobutyrate are also included in the alcoholic solvents.

[0275] 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.

[0276] 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.

[0277] 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.

[0278] 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.

[0279] 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.

[0280] Among these, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether-based solvents, polyhydric alcohol partial ether-based solvents, lactone-based solvents, monoalcohol-based solvents, and alcoholic acid ester-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, γ-butyrolactone, diacetone alcohol, ethyl lactate, and methyl 2-hydroxyisobutyrate are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0281] <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.

[0282] <Method for Preparing Radiation-Sensitive Composition> The radiation-sensitive composition can be prepared, for example, by mixing a base polymer, a solvent, 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 approximately 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.

[0283] <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").

[0284] According to the pattern formation method, a high-quality resist pattern can be formed because the radiation-sensitive composition is used, which is capable of exhibiting excellent sensitivity, development contrast, suppression of development defects, and limiting resolution during pattern formation. Each step will be described below.

[0285] [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.

[0286] 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 (IV) as the base polymer in the composition.

[0287] [Exposure Step] In this step (the above step (2)), the resist film formed in the above step (1), the resist film formation step, is irradiated with radiation through a photomask to expose it. Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), 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, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0288] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the polymer, etc., due to the acid generated by the structural unit (II) or the radiation-sensitive acid generator added as needed in the exposed portions of the resist film. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is typically 50°C to 180°C, preferably 80°C to 150°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0289] [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.

[0290] 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.

[0291] 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.

[0292] 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).

[0293] <<Polymer>> The polymer comprises: a structural unit (I) having an iodine group and further having an acid-dissociable group; a structural unit (II) including a first acid-generating structure having a first organic acid anion and a first onium cation, and generating, upon exposure, an acid that induces dissociation of the acid-dissociable group; and a structural unit (III) including a second organic acid anion and a second onium cation, and generating, upon exposure, an acid that does not induce dissociation of the acid-dissociable group.

[0294] As such a polymer, the polymer in the radiation-sensitive composition can be suitably used.

[0295] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Measurement methods for various physical properties are shown below.

[0296] [Mw and Mn] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using GPC columns manufactured by Tosoh Corporation (two "Super AW2500", one "Super AW3000", and one "Super AW4000") under the following conditions: Eluent: N,N-dimethylformamide (DMF) (manufactured by Wako Pure Chemical Industries, Ltd.) Additive: 0.2 mass% lithium bromide Flow rate: 1.0 mL / min Sample concentration: 1.0 mass% Sample injection amount: 100 μL Column temperature: 40°C Detector: differential refractometer Standard material: monodisperse polystyrene

[0297] [Example] Synthesis of base polymers (A-1) to (A-27) and (CA-1) The monomers shown below were combined and copolymerized in N,N-dimethylformamide (DMF) solvent to obtain base polymers (A-1) to (A-27) and (CA-1) having the compositions shown in Table 1. The solvent used in the polymerization was methyl isobutyl ketone, and the polymerization initiators used were AIBN and 2,2'-azobis(2,4-dimethylvaleronitrile) in a molar ratio of 1:3. The polymerization temperature was 73°C, and the polymerization time was 5 hours. The composition of the obtained base polymer was: １The Mw and dispersity (Mw / Mn) were confirmed by H-NMR and the above-mentioned GPC (solvent: DMF, standard: polystyrene). For example, Synthesis Example 26 means that 5 mol % of mb-1 (counter ion: cat 5) and 10 mol % of mb-1 (counter ion: cat 1) were used as monomers that provide the structural unit (III). In the following formula, X ＋ is an onium cation as a counter ion, Y － indicates an organic acid anion as a counter ion.

[0298]

[0299]

[0300]

[0301]

[0302]

[0303]

[0304]

[0305]

[0306]

[0307]

[0308]

[0309]

[0310] [Examples and Comparative Examples] Radiation-sensitive compositions were prepared by dissolving each component in the composition shown in Table 2 below in a solvent containing 100 ppm of FC-4430 (manufactured by 3M) as a surfactant, and filtering the resulting solution through a 0.2 μm nylon filter. In the table, "-" indicates that the corresponding component was not used.

[0311] In Table 2, the components other than the base polymer are as follows: The content of each component is the amount relative to 100 parts by mass of the base polymer.

[0312] (Radiation-sensitive acid generator PAG1 and acid diffusion controller Q-1)

[0313]

[0314] (Solvent) PGMEA: Propylene glycol monomethyl ether acetate PGME: Propylene glycol monomethyl ether EL: Ethyl lactate GBL: γ-butyrolactone DAA: Diacetone alcohol HBM: Methyl 2-hydroxyisobutyrate

[0315] (High Fluorine Content Polymer) Polymers having structural units represented by the following formulae (F-1) to (F-13) (the subscripts of the structural units indicate the molar ratio when all structural units are taken as 1): F-1: Mw = 8,900, Mw / Mn = 2.0 F-2: Mw = 9,100, Mw / Mn = 2.0 F-3: Mw = 9,200, Mw / Mn = 2.0 F-4: Mw = 9,100, Mw / Mn = 2.0 F-5: Mw = 10,500, Mw / Mn = 1.8 F-6: Mw = 9,100, Mw / Mn = 1.9 F-7: Mw = 10,400, Mw / Mn = 1.8 F-8: Mw = 8,800, Mw / Mn = 2.0 F-9: Mw=8,900, Mw / Mn=2.0 F-10: Mw=9,700, Mw / Mn=2.0 F-11: Mw=9,400, Mw / Mn=1.9 F-12: Mw=8,300, Mw / Mn=2.1 F-13: Mw=10,100, Mw / Mn=1.9

[0316]

[0317]

[0318]

[0319] <Formation of Contact Hole (CH) Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which an underlayer film (Brewer Science's "AL412") with an average thickness of 20 nm had been formed, using a spin coater (Tokyo Electron Limited's "CLEAN TRACK ACT12"). Prebaking was performed at 130°C for 60 seconds, followed by cooling at 23°C for 30 seconds to form a resist film with an average thickness of 50 nm. Next, this resist film was irradiated with EUV light using an EUV exposure machine (ASML's "NXE3400", NA = 0.33, σ 0.9 / 0.6, quadrupole illumination conditions). After irradiation, the resist film was subjected to post-exposure baking (PEB) at 130°C for 60 seconds. Next, development was carried out using a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) at 23° C. for 30 seconds to form a positive contact hole pattern (diameter 25 nm, pitch 50 nm).

[0320] <Evaluation> Each of the CH patterns formed above was evaluated for sensitivity, development contrast, development residue, and limiting resolution according to the following methods. A scanning electron microscope (CG-4100 manufactured by Hitachi High-Technologies Corporation) was used to measure the length of the pattern. The evaluation results are shown in Table 2 below.

[0321] [Sensitivity] In forming the CH pattern, the exposure amount for forming a CH pattern with a diameter of 25 nm is defined as the optimum exposure amount, and this optimum exposure amount is expressed as Eop (mJ / cm ２ The smaller the Eop value, the higher the sensitivity and the better the sensitivity.

[0322] [Development Contrast] Each of the radiation-sensitive compositions prepared above was spin-coated onto a 12-inch silicon wafer and pre-baked on a hot plate at 130°C for 60 seconds to form a resist film with a thickness of 100 nm. Next, this resist film was exposed to 10 mm x 10 mm light using a KrF scanner exposure device (Nikon Corporation's "NSR-S210D") at various exposure doses. ２The resist film was exposed to 18 shots of 1800 nm. This was then post-baked at 100°C for 60 seconds. Using a resist development analyzer (RDA-812WR, manufactured by Litho Tech Japan Co., Ltd.), the resist was developed at 23°C for 60 seconds with a 2.38% by mass aqueous solution of tetramethylammonium hydroxide. In this way, the development rate of the resist film during development at each exposure dose was measured.

[0323] Based on the obtained data, the horizontal axis shows the exposure dose (mJ / cm ２ A curve (hereinafter referred to as an exposure dose-development rate curve) was created by plotting the exposure dose with the development rate (nm / s) of the resist film during development on the vertical axis. Rmax, Rmin and γ value were then determined using the following method. The larger the γ value, the better the development contrast.

[0324] Rmax: maximum development rate (nm / s) when exposed to excessive light Rmin: minimum dissolution rate (nm / s) in unexposed areas γ value: in the exposure dose-development rate curve, the exposure dose at which the development rate is 50% of Rmax is defined as R50 (mJ / cm ２ The exposures at which the tangent at R50 of the exposure dose-development rate curve intersects with the line of Rmax and the line of Rmin are defined as R100 and R0, respectively. The γ value was calculated using the following formula: γ=1 / {log(R0 / R100)}

[0325] The larger the γ value, the better the development contrast. The γ value of Comparative Example 1 was taken as γstd, and the development contrast was evaluated using γstd as the standard according to the following evaluation criteria. In Table 2, the development contrast of Comparative Example 1 is indicated as "-". A: (γ-γstd)×100 / γstd is 15 or more B: (γ-γstd)×100 / γstd is 5 or more and less than 15 C: (γ-γstd)×100 / γstd is less than 5

[0326] [Development Residue] A wafer on which a resist film was formed was prepared by carrying out the same operations as in the CH pattern formation method described above up to the step of forming a resist film with an average thickness of 50 nm. Next, without carrying out pattern exposure using an EUV exposure machine, the wafer was post-baked for 60 seconds on a hot plate at 130°C. Next, development was carried out for 30 seconds with a 2.38 mass% TMAH aqueous solution to prepare a wafer for evaluation of development residue. This wafer was observed with a defect inspection device (Applied Materials' "COMPLUS"), and the number of residual defects was counted using a defect review SEM (Hitachi High-Technologies Corporation's "RS-5500"). Depending on the number of residual defects counted, the wafer was evaluated according to the following evaluation criteria: A: 5 or less B: 6 to 10 C: 11 to 20 D: 21 to 50 E: 51 or more

[0327] [Limiting Resolution] In forming the CH pattern, the exposure dose was gradually reduced from the optimum exposure dose to form the CH pattern. The obtained CH pattern was observed using the scanning electron microscope, and the maximum dimension at which the pattern resolved was defined as the limiting resolution (nm). The limiting resolution was evaluated according to the following evaluation criteria. The smaller the limiting resolution value, the finer the pattern that can be formed, and the better. A: Limiting resolution diameter is less than 21 nm B: Limiting resolution diameter is 21 nm or more and less than 22 nm C: Limiting resolution diameter is 22 nm or more and less than 23 nm D: Limiting resolution diameter is 23 nm or more and less than 24 nm E: Limiting resolution diameter is 24 nm or more

[0328]

[0329] As a result of evaluating the resist patterns formed via the above-mentioned EUV exposure, the radiation-sensitive resin compositions of all of the Examples had better sensitivity than the Comparative Examples. In addition to sensitivity, the compositions of Examples 1 to 5, 8 to 12, 14 to 18, 21, 23 to 24, 26, and 28 to 39 had better development contrast than the Comparative Examples. In addition to sensitivity, the compositions of Examples 3 to 5, 21, and 23 to 39 had less development residue than the Comparative Examples. In addition to sensitivity, the compositions of Examples 4 to 5 and 23 to 27 had better limiting resolution than the Comparative Examples.

[0330] The radiation-sensitive resin composition and the method for forming a resist pattern described above can form a resist pattern that has good sensitivity to exposure light and is excellent in development contrast, development residue, and limiting resolution. Therefore, these compositions can be suitably used in the processing of semiconductor devices, which are expected to become even more miniaturized in the future.

Claims

1. A radiation-sensitive composition comprising: a polymer; and a solvent, the polymer comprising: a structural unit (I) having an iodine group and further having an acid dissociable group; a structural unit (II) including a first acid generating structure having a first organic acid anion and a first onium cation, and generating an acid that induces dissociation of the acid dissociable group upon exposure; and a structural unit (III) including a second organic acid anion and a second onium cation, and generating an acid that does not induce dissociation of the acid dissociable group upon exposure.

2. The radiation-sensitive composition according to claim 1, wherein the acid-dissociable group has an iodine group.

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

4. The radiation-sensitive composition according to claim 1 or 3, wherein the first organic acid anion has a sulfonate anion, and the polymer has the first organic acid anion as a side chain moiety.

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

6. The radiation-sensitive composition according to claim 1 or 5, wherein the second organic acid anion has a sulfonate anion or a carboxylate anion (provided that, when the second organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to the carbon atom adjacent to the sulfur atom in the sulfonate anion), and the polymer has the second organic acid anion as a side chain moiety.

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

8. The radiation-sensitive composition according to claim 1 or 2, wherein at least one selected from the group consisting of the first onium cation and the second onium cation contains a fluoro group.

9. The radiation-sensitive composition according to claim 1 or 2, wherein the content of the structural unit (I) in all structural units constituting the polymer is 10 mol % or more and 80 mol % or less.

10. The radiation-sensitive composition according to claim 1 or 2, wherein the content of the structural unit (II) in all structural units constituting the polymer is 1 mol % or more and 30 mol % or less.

11. The radiation-sensitive composition according to claim 1 or 2, wherein the content of the structural unit (III) in all structural units constituting the polymer is 1 mol % or more and 30 mol % or less.

12. The radiation-sensitive composition according to claim 1 or 2, wherein the content of the structural unit (III) relative to the content of the structural unit (II), where the content of the structural unit (II) is taken as 100 mol %, is 50 mol % or more and 200 mol % or less.

13. The radiation-sensitive composition according to claim 1 or 2, wherein the polymer further contains a structural unit (IV) having a phenolic hydroxyl group.

14. The radiation-sensitive composition according to claim 1 or 2, further comprising a high-fluorine content polymer having a higher mass content of fluorine atoms than the polymer, the high-fluorine content polymer comprising at least one structural unit selected from the group consisting of a structural unit represented by the following formula (f-1) and a structural unit represented by the following formula (f-2): (In formula (f-1), R １１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. １１ R is a single bond or a divalent linking group. ｆ１１ and R ｆ１２ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ｆ１１ and Y １１ may be bonded to each other to form a ring structure having 3 to 15 carbon atoms. ｆ１３ and R ｆ１４ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. １１ R is a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ｆ１３ , R ｆ１４ , and X １１ Any two or three of R may together form a ring structure having 3 to 15 carbon atoms. ｆ１１ , R ｆ１２ , R ｆ１３ , R ｆ１４ , or X １１ At least one of R is a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ２１ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms. ２１ is a divalent linking group. ｆ２１ and R ｆ２２ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 5 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group. ２１ R is a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms, a cyano group, or a nitro group. ｆ２１ , R ｆ２２ , and X ２１ Any two or three of R may together form a ring structure having 3 to 15 carbon atoms. ｆ２１ , R ｆ２２ , or X ２１ At least one of is a fluorine atom, a monovalent fluorinated hydrocarbon group having 1 to 5 carbon atoms, a cyano group, or a nitro group.

15. A method for forming a pattern, comprising the steps of: applying the radiation-sensitive composition according to claim 1 or 2 directly or indirectly to a substrate to form a resist film; exposing the resist film to light; and developing the exposed resist film with a developer.

16. The pattern forming method according to claim 15, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

17. A polymer comprising: a structural unit (I) having an iodine group and further having an acid dissociable group; a structural unit (II) including a first acid generating structure having a first organic acid anion and a first onium cation, and generating an acid that induces dissociation of the acid dissociable group upon exposure; and a structural unit (III) including a second organic acid anion and a second onium cation, and generating an acid that does not induce dissociation of the acid dissociable group upon exposure.

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