Radiation-sensitive composition, pattern forming method, and method for producing polymer

Abstract

The present invention provides: a radiation-sensitive composition which is capable of exhibiting sensitivity, CDU, overexposure CDU, and underexposure CDU at levels equal to or higher than conventional levels when forming a pattern; and a pattern forming method. This radiation-sensitive composition contains a first polymer and a solvent, wherein the first polymer comprises a structural unit (I) that has an acid dissociable group, a structural unit (II) that has an organic acid anion and an onium cation and comprises an acid-generating structure which generates an acid upon exposure to light, and a partial structure (a) that is represented by formula (a). (In formula (a), Z represents a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1-20 carbon atoms, and * is an atomic bond with another structure of the polymer.)

Description

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

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

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the 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 pattern miniaturization continues, there is a demand for resist compositions with higher functionality. In order to control the molecular weight of the polymer, which is also the main component of the resist composition, a technology has been proposed that utilizes RAFT (Reversible Addition-Fragmentation Chain Transfer) polymerization, which is a type of living radical polymerization (Japanese Patent No. 4964763).

[0005] Patent No. 4964763

[0006] In developing the above-mentioned next-generation technologies, resist compositions are required to have various resist performances that are equal to or better than conventional ones in terms of sensitivity, CDU, overexposure CDU, underexposure CDU, and the like.

[0007] An object of the present invention is to provide a radiation-sensitive composition and a pattern forming method which, when forming a pattern, can exhibit sensitivity, CDU, overexposure CDU, and underexposure CDU 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 first polymer; and a solvent, wherein the first polymer comprises: a structural unit (I) having an acid-dissociable group; a structural unit (II) including an acid-generating structure that has an organic acid anion and an onium cation and generates an acid upon exposure; and a partial structure (a) represented by the following formula (a): (In formula (a), Z represents a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.)

[0010] The radiation-sensitive composition can exhibit excellent sensitivity, CDU, overexposure CDU, and underexposure CDU during resist pattern formation. Although the reason for this is not clear, it is presumed to be as follows.

[0011] The acid generating structure contained in the structural unit (II) in the first polymer has an organic acid anion and an onium cation, and generates an acid upon exposure. That is, the acid generating structure can function as a radiation-sensitive acid generating structure that generates an acid that dissociates an acid-dissociable group upon exposure, and can also function as an acid diffusion control structure that generates an acid that does not dissociate the acid-dissociable group upon exposure and suppresses the diffusion of acid in unexposed areas. By incorporating the acid generating structure into the structural unit (II) in this way, the diffusion length of the acid generated upon exposure can be highly controlled, and even if exposure fluctuations occur, a dissolution contrast equal to or greater than that of conventional polymers can be exhibited.

[0012] Furthermore, by incorporating such an acid-generating structure into the first polymer, the content of the radiation-sensitive acid generator or acid diffusion controller, which have conventionally been added as low-molecular-weight compounds, can be reduced or eliminated, thereby increasing the solubility of each component in the radiation-sensitive composition and improving the uniformity of the composition of the resulting resist film, thereby enabling the resist film to exhibit not only excellent sensitivity but also CDU, overexposure CDU, and underexposure CDU that are equal to or greater than those of conventional resist films.

[0013] Furthermore, the first polymer contains the partial structure (a) derived from a chain transfer agent characteristic of RAFT polymerization, which allows the first polymer to have a narrow molecular weight distribution and exhibit high homogeneity as a polymer, thereby enabling the above-mentioned resist performances to be exhibited at a high level.

[0014] Generally, polymers obtained by RAFT polymerization are often subjected to a modification treatment such that the structure derived from the chain transfer agent is substantially eliminated. In contrast, the partial structure (a) derived from the chain transfer agent is intentionally left in the first polymer. Since the partial structure (a) can be decomposed by EUV exposure, post-exposure bake (PEB), light or heat during development, or other physical or chemical energy, the physical properties of the first polymer can be controlled by designing the partial structure (a) so that it imparts desired changes in physical properties before and after decomposition.

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

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

[0017] The pattern formation method uses the radiation-sensitive composition, which is capable of exhibiting excellent sensitivity, CDU, overexposure CDU, and underexposure CDU during resist pattern formation, and therefore can efficiently form a high-quality resist pattern.

[0018] In yet another embodiment, the present invention relates to a method for producing a polymer, comprising a polymerization step of reacting a monomer (i) that provides a structural unit (I) having an acid-dissociable group with a monomer (ii) that provides a structural unit (II) that has an organic acid anion and an onium cation and includes an acid-generating structure that generates an acid upon exposure, in the presence of a compound (A) represented by the following formula (A): (In formula (A), R is a monovalent organic group having 1 to 20 carbon atoms. Z is a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms.)

[0019] According to the method for producing a polymer, a polymer is obtained through RAFT polymerization of predetermined monomers including a monomer (ii) that provides a structural unit (II) having an acid-generating structure in the presence of compound (A) that is a chain transfer agent. This allows for efficient production of a polymer that has a highly controlled molecular weight distribution and is capable of exhibiting controllability in terms of solubility contrast, acid diffusion length, and physical properties.

[0020] In this specification, the term "organic group" refers to a group containing at least one carbon atom. Organic groups include cyano groups and carboxy groups. The term "fused ring structure" refers to a structure in which adjacent rings share one edge (two adjacent atoms). The term "bridged ring hydrocarbon group" refers to a polycyclic cyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the ring are linked by a linking group containing one or more carbon atoms.

[0021] 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.

[0022] Radiation-Sensitive Composition The radiation-sensitive composition according to this embodiment (hereinafter also simply referred to as "composition") contains a first polymer and a solvent. The composition may contain other optional components as long as the effects of the present invention are not impaired.

[0023] The composition preferably includes a second polymer containing a partial structure (b) different from the partial structure (a) and having the same structure as the first polymer except for the partial structure (b). As described below, the first polymer has a partial structure (a) derived from a chain transfer agent for RAFT polymerization. While the partial structure (a) may be maintained as is in the first polymer, it is preferable to perform a modification treatment to form a partial structure (b) different from the partial structure (a). A polymer containing this partial structure (b) is referred to as a second polymer. The second polymer contains a partial structure (b) different from the partial structure (a), but has the same structure as the first polymer except for the partial structure (b). In other words, by performing a modification treatment of the partial structure (a), the composition becomes a mixture of a first polymer containing the partial structure (a) and a second polymer containing the partial structure (b).

[0024] As the modification treatment of the partial structure (a) proceeds, the amount of the first polymer decreases, while the amount of the second polymer increases. The content ratio of the second polymer to the total amount of the first polymer and the second polymer is, so to speak, an index of the modification rate, which indicates the extent to which the partial structure (a) has been converted to the partial structure (b). The lower limit of the content ratio of the second polymer (i.e., the modification rate) is preferably 5 mol%, more preferably 10 mol%, even more preferably 15 mol%, and particularly preferably 20 mol%. The upper limit of the content ratio of the second polymer is preferably 85 mol%, more preferably 75 mol%, even more preferably 55 mol%, and particularly preferably 45 mol%.

[0025] The first polymer and the second polymer differ in that they have the partial structure (a) and the partial structure (b) as described above, but share other structures in common. Therefore, both the first polymer and the second polymer will be treated as polymers that are the main components of the composition (hereinafter, both will be collectively referred to as "base polymers"). Details of each structural unit (structure, content ratio, etc.) can be applied to both the first polymer and the second polymer, so they will be described without distinguishing which polymer the structural unit belongs to.

[0026] <Base Polymer> The base polymer is an aggregate of polymer chains containing the structural unit (I), the structural unit (II), and the partial structure (a) or the partial structure (b). In addition to these structural units, the base polymer may also contain a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (III)") or a structural unit containing a lactone structure (hereinafter also referred to as "structural unit (V)").

[0027] The base polymer preferably contains an iodine group, which increases the radiation absorption efficiency and secondary electron generation efficiency, thereby improving sensitivity.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] (Partial structure (a)) The partial structure (a) in the first polymer is a structure represented by the following formula (a): The partial structure (a) is a structure derived from a chain transfer agent for RAFT polymerization (RAFT agent), and is mainly bonded to the terminal of the polymer, but may be bonded to a part other than the terminal. (In formula (a), Z represents a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.)

[0034] Examples of the monovalent organic group having 1 to 20 carbon atoms and represented by Z include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group (a) having a divalent heteroatom-containing group between carbon atoms of the hydrocarbon group (between two adjacent or non-adjacent carbon atoms) or at the end of the hydrocarbon group, a group in which some or all of the hydrogen atoms of the hydrocarbon group or the group (a) have been substituted with a monovalent heteroatom-containing group, and combinations thereof.

[0035] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and combinations thereof.

[0036] Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group; 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.

[0037] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include cycloalkyl groups such as a cyclopentyl group and a cyclohexyl group; cycloalkenyl groups such as a cyclopropenyl group, a cyclopentenyl group and a cyclohexenyl group; bridged ring saturated hydrocarbon groups such as a norbornyl group, an adamantyl group and a tricyclodecyl group; and bridged ring unsaturated hydrocarbon groups such as a norbornenyl group and a tricyclodecenyl group.

[0038] 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.

[0039] Examples of heteroatoms constituting the divalent or monovalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, halogen atoms, etc. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0040] Examples of the divalent heteroatom-containing group include -CO-, -CS-, -NR'-, -O-, -S-, and combinations thereof, where R' is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0041] Examples of the monovalent heteroatom-containing group include a hydroxy group, a carboxy group, a sulfanyl group, a cyano group, a nitro group, and a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0042] In the above formula (a), Z is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a substituted or unsubstituted linear hydrocarbon group having 1 to 20 carbon atoms or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, even more preferably a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and particularly preferably a substituted or unsubstituted phenyl group.

[0043] When Z has a substituent, examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; a hydroxy group; a carboxy group; a cyano group; a nitro group; an amino group; an alkoxy group; an alkoxycarbonyl group; an alkoxycarbonyloxy group; an acyl group; an acyloxy group or a group in which the hydrogen atom of any of these groups has been substituted with a halogen atom; and an oxo group (═O).

[0044] Examples of alkoxy groups as the substituent for Z include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group, an ethoxy group, and a propoxy group. Examples of alkoxycarbonyl groups include alkoxycarbonyl groups having 1 to 6 carbon atoms, such as a methoxycarbonyl group and an ethoxycarbonyl group. Examples of alkoxycarbonyloxy groups include linear or alicyclic alkoxycarbonyloxy groups having 2 to 16 carbon atoms, such as a methoxycarbonyloxy group, a butoxycarbonyloxy group, and an adamantylmethyloxycarbonyloxy group. Examples of acyl groups include aliphatic or aromatic acyl groups having 2 to 12 carbon atoms, such as an acetyl group, a propionyl group, a benzoyl group, and an acryloyl group. Examples of acyloxy groups include aliphatic or aromatic acyloxy groups having 2 to 12 carbon atoms, such as an acetyloxy group, a propionyloxy group, a benzoyloxy group, and an acryloyloxy group.

[0045] Specific examples of the partial structure (a) include, but are not limited to, the following structures:

[0046] (Partial structure (b)) The partial structure (b) in the second polymer is a structure different from the partial structure (a) and is generated by a modification treatment of the partial structure (a). The specific structure of the partial structure (b) is not particularly limited, and a known structure depending on the method of modification treatment can be appropriately adopted. Typical structures include a hydrogen atom, a mercapto group, and a structure derived from a polymerization initiator. Among these, the partial structure (b) is preferably a hydrogen atom.

[0047] (Structural Unit (I)) The structural unit (I) is a structural unit having an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and dissociates under the action of an acid. The acid generated from the structural unit (II) of the polymer upon exposure dissociates the acid-dissociable group in the structural unit (I), generating a carboxy group or the like. This results in a difference in solubility in a developer between the exposed and unexposed areas of the resist film, making it possible to form a pattern.

[0048] 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 an ester moiety derived from a secondary alcohol having an aromatic ring group and an aliphatic hydrocarbon group, 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.

[0049]

[0050] 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 ２０L 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 ＊ -COOL １１ａ COO-. １１ａ is a substituted or unsubstituted alkanediyl group or arenediyl group. * is R １７ is the bond to the carbon atom to which it is bonded.

[0051] The above R １７ As the alkyl group, 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.

[0052] L １１ａ Examples of the alkanediyl group represented by the formula (I) include alkanediyl groups having 1 to 10 carbon atoms, such as a methylene group, an ethanediyl group, a 1,3-propanediyl group, and a 2,2-propanediyl group. １１ａ As the alkyl group, a methylene group or an ethanediyl group is preferred.

[0053] L １１ａ Examples of the arenediyl group represented by the formula (I) include divalent aromatic hydrocarbon groups having 6 to 20 carbon atoms, such as benzenediyl and naphthalenediyl groups. １１ａ As the alkyl group, a benzenediyl group is preferred.

[0054] L １１ａ Examples of the substituent that the arenediyl group represented by the formula (I) may have include a halogen atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, and an alkoxy group.

[0055] The above R １８ As the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (a), the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by Z in the formula (a) above can be suitably used.

[0056] 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.

[0057] R １９ and R ２０ As the monovalent chain hydrocarbon group having 1 to 10 carbon atoms in Z in formula (a), a group corresponding to a carbon number of 1 to 10 among the monovalent chain hydrocarbon groups having 1 to 20 carbon atoms shown in Z in formula (a) above can be suitably used.

[0058] R １９ and R ２０ As the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above formula (a), the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown as Z in the above formula (a) can be suitably used.

[0059] The above R １９ and R ２０ The divalent alicyclic group having 3 to 20 carbon atoms constituted by combining these together with the carbon atoms to which they are bonded can suitably be a group obtained by removing one hydrogen atom from the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown as Z in formula (a) above.

[0060] 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 The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0061] The above R １８ ~R ２０ Examples of the substituent that may be possessed by L include １１ａ Substituents that can be possessed by the arenediyl group represented by the following formula can be suitably employed.

[0062] 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 (II-1-15)").

[0063]

[0064]

[0065] 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 hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, or an alkoxy group. i and j are each independently an integer of 1 to 4. k and l are each 0 or 1. 3a are each independently an integer of 0 to 3. When 3a is 2 or more, multiple R Ｌ１１ are the same or different from each other. a4 is an integer of 1 to 3.

[0066] i and j are preferably 1. １８ R is preferably a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a cyclopentyl group, an ethenyl group, a phenyl group, or an iodophenyl group. １９ and R ２０ R is preferably a methyl group, an ethyl group, or an isopropyl group. Ｌ１１ By employing an iodine atom as the aryl group, an iodine group can be suitably introduced into the structural unit (I).

[0067] Furthermore, the polymer may contain structural units represented by the following formulae (1f) to (2f) as the structural unit (I).

[0068]

[0069] 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.

[0070] The above R βｆ is preferably a hydrogen atom, a methyl group, or an ethyl group. １ As the number, 1 or 2 is preferred.

[0071] Specific examples of the structural unit (I) (including the structural unit (I-1)) are not particularly limited, but include structures represented by the following formulas (1-1) to (1-39).

[0072]

[0073]

[0074]

[0075] In the formula, R １７ is synonymous with the above formula (1).

[0076] 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 25 mol%, and even more preferably 40 mol%. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, and even more preferably 60 mol%. By setting the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive composition can be further improved. When the acid-dissociable group has an iodine group, sensitivity can be further improved.

[0077] (Structural Unit (II)) The structural unit (II) includes an acid generating structure which is an onium salt structure having an organic acid anion and an onium cation and which generates an acid upon exposure. The acid generating structure functions as a radiation-sensitive acid generating structure or an acid diffusion-controlling structure. When the acid generating structure of the structural unit (II) functions as a radiation-sensitive acid generating structure, it is also called structural unit (IIa), and when it functions as an acid diffusion-controlling structure, it is also called structural unit (IIb). The distinction between these functions is determined by the organic acid anion. Each structural unit will be described below.

[0078] (Structural Unit (IIa)) The structural unit (IIa) 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. 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 in the case of aqueous alkaline development, but sparingly soluble in the developer in the case of organic solvent development.

[0079] The form in which the first organic acid anion and the first onium cation are contained in the structural unit (IIa) 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.

[0080] 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.

[0081] 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 as a ring-forming moiety in the cyclic structure.

[0082] 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.

[0083] As the alicyclic structure, a structure corresponding to the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms shown as Z in the above formula (a) can be suitably adopted.

[0084] 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.

[0085] 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.

[0086] The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, a cyclic acetal structure, or a combination thereof, such as those represented by the following formulas (H-1) to (H-11).

[0087]

[0088] In the above formula, γ is an integer of 1 to 3.

[0089] 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.

[0090] As the divalent heteroatom-containing group, the divalent heteroatom-containing group shown as Z in the above formula (a) can be suitably used.

[0091] As the substituents that substitute some or all of the hydrogen atoms on the carbon atoms of the cyclic structure or chain structure, the substituents that Z in the formula (a) can have can be suitably used.

[0092] 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 at the α- or β-position of 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.

[0093] The first organic acid anion preferably has an iodo group. The first organic acid anion preferably contains the iodo group-containing aromatic ring structure.

[0094] 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.

[0095] The first onium cation preferably has an iodo group. The first onium cation preferably contains the iodo group-containing aromatic ring structure.

[0096] The first onium cation in the structural unit (IIa) is preferably a fluoro-group-containing onium cation having a fluoro group in addition to or instead of an iodo group. The fluoro-group-containing onium cation preferably has a fluoro-group-containing aromatic ring structure. The fluoro-group-containing aromatic ring structure is a structure in which some or all of the hydrogen atoms in the aromatic ring are substituted with fluoro groups. The aromatic ring in the fluoro-group-containing aromatic ring structure can be suitably the same as the aromatic ring in the iodo-group-containing aromatic ring structure. This increases the radiation absorption efficiency, thereby improving sensitivity.

[0097] The structural unit (IIa) having the above structures in combination can efficiently exhibit the above functions.

[0098] The structural unit (IIa) is preferably a structural unit represented by the following formula (a1) (hereinafter also referred to as "structural unit (IIa-1)").

[0099]

[0100] In the formula, R Ｖ is a hydrogen atom or a methyl group. １ is a single bond or an ester group. ２is 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, or an amide bond, 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 ２ are each independently a hydrogen atom, a fluorine atom, or a trifluoromethyl group, but at least one is a fluorine atom or a fluorinated hydrocarbon group. kk is an integer of 1 to 4. X １ ＋ is a sulfonium cation or an iodonium cation.

[0101] V ２ and V ３ 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.

[0102] The structural unit (IIa-1) is preferably a structural unit represented by the following formula (a1-1).

[0103]

[0104] In the formula, R Ｖ , Rf １ ~Rf ２ , V １ , kk and X １ ＋ has the same meaning as in formula (a1) above. 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.

[0105] Examples of the first organic acid anion of the monomer that gives the structural unit (IIa) (including the structural unit (IIa-1)) include, but are not limited to, those shown below. Note that in the following, the iodo group of the iodo group-containing aromatic ring structure may be substituted with a hydrogen atom or the substituent shown for Z in the above formula (a), etc.

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] In the above formula, R Ｖ has the same meaning as the above formula (a1).

[0113] The first onium cation is preferably a sulfonium cation represented by the following formula (Q-1):

[0114]

[0115] 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. Ra3 represents a substituent. n3 represents an integer of 0 to 5, and when n3 is 2 or greater, multiple Ra3s may be the same or different. Ra1 and Ra2 may be bonded to each other to form a ring. When 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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. Also, 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 alkylsulfonyl groups or cycloalkylsulfonyl groups are methanesulfonyl, ethanesulfonyl, n-propanesulfonyl, n-butanesulfonyl, cyclopentanesulfonyl, and cyclohexanesulfonyl.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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 thereof, and preferably has a total carbon number of 20 or less. 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 to form - or a single bond. Among these, it is more preferable to form -O-, -S- or a single bond, and it is particularly preferable to form a single bond. Furthermore, when n1 is 2 or more, multiple Ra1s may be linked to each other to form a ring, and when n2 is 2 or more, multiple Ra2s may be linked to each other to form a ring. Such an example includes, for example, an embodiment in which two Ra1s are linked to each other to form a naphthalene ring together with the benzene ring to which they are bonded.

[0127] Ra3 is preferably a fluorine atom, a group having one or more fluorine atoms, or an iodine atom. 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 ２F ５ , C ３ F ７ , C ４ F ９ , C ５ F １１ , C ６ F １３ , C ７ F １５ , C ８ F １７ , C.H. ２ CF ３ , C.H. ２ CH ２ CF ３ , C.H. ２ C ２ F ５ , C.H. ２ CH ２ C ２ F ５ , C.H. ２ C ３ F ７ , C.H. ２ CH ２ C ３ F ７ , C.H. ２ C ４ F ９ and CH ２ CH ２ C ４ F ９ More preferred examples include CF ３ can be particularly preferably mentioned.

[0128] Ra3 is a fluorine atom, an iodine atom, or CF ３ is preferably, and more preferably, a fluorine atom or an iodine atom.

[0129] n1 and n2 each independently represent an integer of 0 to 3, preferably an integer of 0 to 2.

[0130] n3 is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0131] (n1+n2+n3) is preferably an integer of 1 to 15, more preferably an integer of 1 to 9, still more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 6. When (n1+n2+n3) is 1, n3=1 and Ra3 is a fluorine atom, an iodine atom, or CF ３When (n1 + n2 + n3) is 2, n1 = n3 = 1, and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=2 and Ra3 is a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 3, n1=n2=n3=1 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1 + n2 + n3) is 4, n1 = n3 = 2 and Ra1 and Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 5, n1=n2=1 and n3=3, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ a combination in which n1=n2=2 and n3=1, and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ and n3=5 and each Ra3 is independently a fluorine atom, an iodine atom, or CF ３ When (n1+n2+n3) is 6, n1=n2=n3=2 and Ra1 to Ra3 are each independently a fluorine atom, an iodine atom, or CF ３ A combination in which:

[0132] Specific examples of such sulfonium cations represented by the above formula (Q-1) include the following: The fluorine atom or iodine atom in the following sulfonium cations may be substituted with a hydrogen atom or the substituent shown for Z in the above formula (a).

[0133]

[0134]

[0135]

[0136]

[0137] The first onium cation of the structural unit (IIa) may be a diaryliodonium cation. The diaryliodonium cation preferably has one or more fluorine atoms or iodine atoms. At least one of the aryl groups of the iodonium cation preferably has a fluoro- or iodine-containing aromatic ring structure. The aryl group is preferably a phenyl group.

[0138] 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 as a counter ion through an ionic bond. 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) ２ From SO ３ - The structure up to is preferably ionically bonded to the first onium cation as a counter ion. １１ The group represented by the following formula (I), the above divalent heteroatom-containing group, or a combination thereof can be suitably employed.

[0139] When the base polymer has the structural unit (IIa), the lower limit of the content of the structural unit (IIa) (when a plurality of types are contained, the total content) is preferably 1 mol%, more preferably 5 mol%, and even more preferably 10 mol% based on the total structural units constituting the base polymer.The upper limit of the content is preferably 30 mol%, more preferably 25 mol%, and even more preferably 20 mol%.By making the content of the structural unit (IIa) within the above range, it can fully exhibit the function as an acid generating structure and exhibit the above resist properties.

[0140] The monomer that provides the structural unit (IIa-1) can be synthesized, for example, by a method similar to that for the sulfonium salt having a polymerizable anion described in Japanese Patent No. 5201363.

[0141] (Structural Unit (IIb)) The base polymer may contain a structural unit (IIb) including a second acid generating structure having a second organic acid anion and a second onium cation, which generates an acid that does not dissociate 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 acid generated from the first acid generating structure or the radiation-sensitive acid generator (if included) in unexposed areas through salt exchange. The acid generated from the second acid generating structure can be said to be 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.

[0142] The form in which the second organic acid anion and the second onium cation are contained in the structural unit (IIb) 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.

[0143] 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 either the α- or β-position carbon atom of the sulfonate anion. Examples of the electron-withdrawing group include the electron-withdrawing group 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.

[0144] The second organic acid anion preferably contains, as a structure other than the acid anion moiety, -O-, -CO-, a cyclic structure, or a combination thereof. As such a structure, the structures shown for the first organic acid anion can be suitably adopted.

[0145] 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.

[0146] 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.

[0147] The second onium cation preferably has an iodo group. The second onium cation preferably contains the iodo group-containing aromatic ring structure.

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

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

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

[0151]

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

[0153] In formula (p1), X 1 represents a single bond, an ester bond, an ether bond, a phenylene group, a naphthylene group, or a combination thereof.

[0154] 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 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.

[0155] In formula (p1), X 3 represents a single bond, an ester bond, an ether bond, an alkylene group, a phenylene group, or a combination thereof.

[0156] In formula (p1), X 1 ~X ３ Some or all of the hydrogen atoms in X may be substituted with a substituent. As the substituent, the substituent shown for Z in the above formula (a) can be suitably used. 1 ~X ３ When has a phenylene group, it is preferred that some or all of the hydrogen atoms of at least one phenylene group are substituted with fluorine atoms or iodine atoms.

[0157] In formula (p1), X ２ ＋ is X in the above formula (a1). １ ＋ is synonymous with.

[0158] The second onium cation in the formula (p1) may be an iodonium cation, such as the diaryliodonium cation shown as the onium cation in the structural unit (IIa-1).

[0159] Examples of the second organic acid anion of the monomer that gives the structural unit (IIb) (including the structural unit (IIb-1)) 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 (IIb) 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 iodo group or hydroxy group in the following formula is substituted with a hydrogen atom or the substituent shown in Z in the above formula (a) can be suitably used. Note that 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.

[0160]

[0161]

[0162]

[0163] In the formula, R A has the same meaning as the above formula (p1).

[0164] As the second onium cation of the structural unit (IIb), a sulfonium cation represented by the above formula (Q-1) can be suitably used.

[0165] 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. １１ or the above-mentioned divalent heteroatom-containing group can be suitably employed.

[0166] When the base polymer contains the structural unit (IIb), the lower limit of the content of the structural unit (IIb) (when multiple types are contained, the total content) relative to all structural units constituting the base polymer is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%. The upper limit of the content is preferably 30 mol%, more preferably 20 mol%, and even more preferably 10 mol%. By setting the content of the structural unit (IIb) within the above range, the function as an acid diffusion control structure can be fully exhibited.

[0167] (Structural Unit (III)) The structural unit (III) is a structural unit having a phenolic hydroxyl group (excluding structures corresponding to the structural units (I) and (II)). When the polymer contains the structural unit (III), 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 (III) contributes to improving the etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the structural unit (III) is suitable for use in pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beam or EUV. The structural unit (III) is preferably represented by the following formula (2):

[0168] (In the above formula (2), R β is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＣＡ is a single bond, -COO- ＊ , —O— or —CONH— ＊ * is a bond on the aromatic ring side. 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 are each independently an integer of 0 to 8, provided that 1≦m ３ +m ４ ≦2n ３ Meets +5.)

[0169] The above R β From the viewpoint of copolymerizability of the monomer that gives the structural unit (III), it is preferable that the alkyl group is a hydrogen atom or a methyl group.

[0170] L ＣＡ is a single bond or -COO- ＊ is preferred.

[0171] R １０２ As the halogen atom, alkyl group, alkoxycarbonyloxy group, acyl group or acyloxy group in R, the groups exemplified as the substituent of Z in the above formula (a) can be suitably used. １０２ The halogen atom in is preferably an iodine atom or a fluorine atom, more preferably an iodine atom.

[0172] The above n ３ is more preferably 0 or 1, and even more preferably 0.

[0173] The above m ３ is preferably an integer of 1 to 3, more preferably 1 or 2.

[0174] The above m ４ is preferably an integer of 0 to 3, and more preferably an integer of 0 to 2.

[0175] The structural unit (III) is preferably a structural unit represented by the following formulas (2-1) to (2-24) (hereinafter also referred to as "structural unit (III-1) to structural unit (III-24)").

[0176]

[0177]

[0178] In the above formulas (2-1) to (2-24), R β is the same as the above formula (2).

[0179] When the base polymer has the structural unit (III), the lower limit of the content of the structural unit (III) (total content when multiple types of structural unit (III) are present) relative to all structural units constituting the polymer is preferably 10 mol%, more preferably 20 mol%, and even more preferably 25 mol%. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 40 mol%. By setting the content of the structural unit (III) within the above range, the radiation-sensitive composition can further improve the sensitivity and development contrast.

[0180] (Structural Unit (IV)) The structural unit (IV) 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 (IV), 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.

[0181] When the base polymer has the structural unit (IV), the lower limit of the content of the structural unit (IV) (the total content when multiple types are contained) relative to all structural units constituting the base polymer is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. By setting the content of the structural unit (IV) 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.

[0182] (Structural Unit (V)) The structural unit (V) is a structural unit containing a polar group (excluding those corresponding to the structural units (I) to (IV)). By further including the structural unit (V), the base polymer can adjust its solubility in a developer. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, a sulfo group, and a sulfonamide group. Of these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0183] Examples of the structural unit (V) include structural units represented by the following formula:

[0184]

[0185]

[0186] In the above formula, R Ｋ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0187] When the base polymer has the structural unit (V), the lower limit of the content of the structural unit (V) (when multiple types are contained, the total content) is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol% relative to the total structural units constituting the base polymer. The upper limit of the content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%. By setting the content of the structural unit (V) within the above range, the solubility of the base polymer in the developer can be efficiently adjusted.

[0188] The polymer may further contain a structural unit derived from styrene or iodostyrene (hereinafter also referred to as "structural unit (VI)"). When the base polymer contains 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%.

[0189] (Method for Producing First Polymer) The method for producing the first polymer includes a polymerization step of reacting, in the presence of a compound (A) represented by the following formula (A), a monomer (i) that provides a structural unit (I) having an acid-dissociable group with a monomer (ii) that provides a structural unit (II) that has an organic acid anion and an onium cation and includes an acid-generating structure that generates an acid upon exposure, to obtain a polymer. (In formula (A), R is a monovalent organic group having 1 to 20 carbon atoms. Z is a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms.)

[0190] Compound (A) is used as a chain transfer agent (RAFT agent) for RAFT polymerization, and monomers that provide at least the structural unit (I) and the structural unit (II) are subjected to a radical polymerization reaction in an appropriate solvent under an inert atmosphere such as nitrogen, whereby a polymer having a controlled molecular weight distribution can be efficiently produced.

[0191] In the above formula (A), the monovalent organic group having 1 to 20 carbon atoms represented by R can preferably be a monovalent organic group having 1 to 20 carbon atoms represented by Z in the above formula (a). R is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a substituted or unsubstituted alkyl group or a substituted or unsubstituted aralkyl group, and even more preferably a substituted or unsubstituted methyl group, ethyl group, propyl group, isobutyl group, or substituted or unsubstituted benzyl group. When the hydrocarbon group represented by R has a substituent, the substituent that Z in the above formula (a) can preferably have can be used as the substituent. Among these, a cyano group, a carboxy group, or a methoxycarbonyl group is preferred as the substituent.

[0192] As specific examples of Z in the above formula (A), the structures shown as Z in the above formula (a) can be suitably adopted.

[0193] Examples of the compound (A) include compounds represented by the following formula:

[0194]

[0195] The lower limit of the amount of compound (A) is preferably 1 mol%, more preferably 2 mol%, and even more preferably 3 mol%, relative to the total moles of the monomers, and the upper limit of the amount is preferably 8 mol%, more preferably 6 mol%, and even more preferably 5 mol%.

[0196] Examples of radical polymerization initiators used in the polymerization 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. Among 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.

[0197] The lower limit of the amount of the radical polymerization initiator to be blended is preferably 0.1 mol%, more preferably 0.3 mol%, and even more preferably 0.5 mol%, relative to the total moles of the monomers, and the upper limit of the amount to be blended is preferably 5 mol%, more preferably 3 mol%, and even more preferably 1 mol%.

[0198] 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.

[0199] The lower limit of the reaction temperature in the polymerization is preferably 40° C., more preferably 50° C. The upper limit of the reaction temperature is preferably 150° C., more preferably 120° C. The lower limit of the reaction time is preferably 1 hour, more preferably 2 hours. The upper limit of the reaction time is preferably 48 hours, more preferably 24 hours.

[0200] After the polymerization reaction, the first polymer can be obtained by performing filtration, washing, drying, etc. When the second polymer is synthesized by modifying the partial structure (a) of the first polymer, it is preferable to pour the reaction solution into a poor solvent (hexane, etc.) to precipitate the polymer, and then to disperse or dissolve the filtered first polymer in a solvent to subject the first polymer to the modification treatment in the form of a solution.

[0201] (Method for Producing Second Polymer) The method for producing the second polymer further includes a modification treatment step of modifying the partial structure (a) so that the content of the partial structure (a) represented by the following formula (a) in the polymer after the polymerization step is 100 mol % but less than 1 mol %: (In formula (a), Z represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.)

[0202] The second polymer can be produced by converting the partial structure (a) of the first polymer into a partial structure (b) different from the partial structure (a) through a modification treatment step. The partial structure (a) of the first polymer represented by the above formula (a) and the partial structure (b) of the second polymer can each preferably be the same as those described above.

[0203] In the modification treatment step, it is preferable to perform modification treatment of the partial structure (a) so that the content of the partial structure (a) represented by the following formula (a) in the polymer is 5 mol% or more and 95 mol% or less, assuming that the content of the partial structure (a) in the polymer is 100 mol%. In other words, it is preferable to perform modification treatment so that the content of the partial structure (b) in the second polymer is 5 mol% or more and 95 mol% or less (i.e., modification rate). The lower limit of the modification rate is more preferably 10 mol%, and even more preferably 15 mol%. The upper limit of the modification rate is more preferably 90 mol%, and even more preferably 85 mol%.

[0204] As the denaturation treatment, known denaturation treatments can be used, such as denaturation with a denaturing agent and denaturation by heating.

[0205] The modifying agent is not particularly limited, and known modifying agents can be used. Examples of the modifying agent include thiols, polymerization initiators, and combinations thereof. Examples of the thiols include n-butanethiol, n-octanethiol, n-decanethiol, t-dodecanethiol, and n-dodecanethiol. The radical polymerization initiators shown in the method for producing the first polymer can be suitably used as the polymerization initiator.

[0206] When thiols are used as the modifying agent, the lower limit of the amount of thiols to be blended is preferably 0.5 mol%, more preferably 1.5 mol%, and even more preferably 2 mol%, relative to the total moles of the monomers, and the upper limit of the amount to be blended is preferably 15 mol%, more preferably 8 mol%, and even more preferably 5 mol%.

[0207] When a polymerization initiator is used as a modifier, the lower limit of the amount of the polymerization initiator to be blended is preferably 0.5 mol%, more preferably 1.5 mol%, and even more preferably 2 mol%, relative to the total moles of the monomers, and the upper limit of the amount to be blended is preferably 20 mol%, more preferably 15 mol%, even more preferably 8 mol%, and particularly preferably 5 mol%.

[0208] When a thiol and a polymerization initiator are used in combination as a modifier, the lower limit of the amount of each of them is preferably 2 mol%, more preferably 4 mol%, and even more preferably 6 mol%, relative to the total moles of the monomers, and the upper limit of the amount is preferably 30 mol%, more preferably 20 mol%, and even more preferably 10 mol%.

[0209] The lower limit of the reaction temperature in the modification treatment with the modifying agent is preferably 40° C., more preferably 50° C. The upper limit of the reaction temperature is preferably 150° C., more preferably 120° C. The lower limit of the reaction time is preferably 0.5 hours, more preferably 1 hour. The upper limit of the reaction time is preferably 12 hours, more preferably 6 hours.

[0210] The lower limit of the reaction temperature in the modification by heating is preferably 80°C, more preferably 100°C. The upper limit of the reaction temperature is preferably 160°C, more preferably 140°C. The lower limit of the reaction time is preferably 0.5 hours, more preferably 1 hour. The upper limit of the reaction time is preferably 12 hours, more preferably 6 hours.

[0211] As the solvent used for the modification, the solvents described below can be suitably used. These solvents used for polymerization may be used alone or in combination of two or more kinds.

[0212] 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 4,000, more preferably 5,000, and even more preferably 6,000. The upper limit of Mw is preferably 20,000, more preferably 14,000, 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.

[0213] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base polymer as determined by GPC is preferably 1 or more and 3 or less, more preferably 1 or more and 2 or less, even more preferably 1 or more and 1.8 or less, and particularly preferably 1.5 or less.

[0214] The method for measuring Mw and Mn of the polymer in this specification is as described in the Examples.

[0215] The lower limit of the content of the base polymer is preferably 20% by mass, more preferably 30% by mass, and even more preferably 35% by mass, relative to the total solid content of the radiation-sensitive composition, and the upper limit of the content is preferably 95% by mass, more preferably 80% by mass, and even more preferably 60% by mass.

[0216] <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.

[0217] 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 (VII)").

[0218]

[0219] 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.

[0220] The above R １３ As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0221] Above G ＬAs the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VII), a single bond and -COO- are preferred, and -COO- is more preferred.

[0222] 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.

[0223] 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.

[0224] The above R １４ As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl-2-yl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0225] When the high-fluorine content polymer has the structural unit (VII), the lower limit of the content of the structural unit (VII) is preferably 50 mol%, more preferably 60 mol%, and even more preferably 70 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 95 mol%, more preferably 90 mol%, and even more preferably 85 mol%. By setting the content of the structural unit (VII) within the above range, the mass content of fluorine atoms in the high-fluorine content polymer can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film. As a result, the water repellency of the surface of the resist film during immersion exposure can be improved, and the surface modification of the resist film during EUV exposure and the distribution of the composition within the film can be controlled to a sufficient level.

[0226] The high-fluorine content polymer may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VIII)) in addition to or instead of the structural unit (VII): By having the structural unit (f-2), the high-fluorine content polymer has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0227]

[0228] The structural unit (VIII) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter, also simply referred to as an "alkali-dissociable group"). In both (x) and (y), R Ｃ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｄ is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R Ｅ Oxygen atom, sulfur atom, -NR at the end of ｄｄ R has a structure in which -, a carbonyl group, -COO-, -OCO-, or -CONH- is bonded, or a structure in which some of the hydrogen atoms in this hydrocarbon group are substituted with an organic group having a hetero atom. ｄｄ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0229] When the structural unit (VIII) has (x) an alkali-soluble group, R Ｆ is a hydrogen atom, and A １ is an oxygen atom, -COO-* or -SO ２ O-*. * is R Ｆ The binding site of W is shown. １ represents a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. １ is an oxygen atom, W １ is A １ is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple RＥ , W １ , A １ and R Ｆ may be the same or different. When the structural unit (VIII) has (x) an alkali-soluble group, it is possible to increase affinity for an alkaline developer and suppress development defects. As the structural unit (VIII) having (x) an alkali-soluble group, A １ is an oxygen atom and W １ It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0230] When the structural unit (VIII) has (y) an alkali-dissociable group, R Ｆ is a monovalent organic group having 1 to 30 carbon atoms, and A １ is an oxygen atom, -NR ａａ -, -COO-*, -OCO-* or -SO ２ O-*. R ａａ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R Ｆ The binding site of W is shown. １ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. Ｅ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １ is -COO-*, -OCO-* or -SO ２ If O-*, then W １ or R Ｆ is A １ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １ is an oxygen atom, W １ , R Ｅ is a single bond, and R Ｄ is a hydrocarbon group having 1 to 20 carbon atoms. Ｅ A carbonyl group is bonded to the end of the R Ｆ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R Ｅ , W １ , A １ and R Ｆmay be the same or different. When the structural unit (VIII) has an alkali-dissociable group (y), the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. As a result, affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. Examples of the structural unit (VI) having an alkali-dissociable group (y) include: １ is -COO-*, and R Ｆ Or W １ It is particularly preferred that both of them have a fluorine atom.

[0231] R Ｃ 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.

[0232] When the high-fluorine content polymer has the structural unit (VIII), the content of the structural unit (VIII) is preferably 40 mol%, more preferably 50 mol%, and even more preferably 60 mol%, based on all structural units constituting the high-fluorine content polymer. The upper limit of the content is preferably 98 mol%, more preferably 96 mol%, and even more preferably 94 mol%. By setting the content of the structural unit (VIII) within the above range, the water repellency and surface modifiability of the resist film can be improved, and the solubility in an alkaline developer can be improved, thereby efficiently suppressing the occurrence of development defects.

[0233] [Other Structural Units] The high fluorine content polymer may contain structural units other than the structural units listed above, such as the structural units (I), (II) and (V) of the base polymer.

[0234] The lower limit of Mw of the high fluorine content polymer is preferably 6,000, more preferably 12,000, and even more preferably 16,000.The upper limit of Mw is preferably 40,000, more preferably 32,000, and even more preferably 26,000.

[0235] 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.

[0236] 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 8 parts by mass or less.

[0237] (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.

[0238] <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 (IIa) in the base polymer.

[0239] 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.

[0240] The structure of the third organic acid anion of the radiation-sensitive acid generator is V in the above formula (a1) of the base polymer. ２ From SO ３ - The above structures can be suitably adopted.

[0241] 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 be used. As the third organic acid anion not having an iodo group-containing aromatic ring structure, a structure in which the iodo group in the following formula is substituted with a hydrogen atom or another substituent can be suitably used.

[0242]

[0243]

[0244] 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 (IIa) in the base polymer.

[0245] 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.

[0246] 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 10 parts by mass, more preferably 20 parts by mass, and even more preferably 30 parts by mass, relative to 100 parts by mass of the base polymer. The upper limit of the content is preferably 100 parts by mass, more preferably 80 parts by mass, and even more preferably 60 parts by mass. This allows excellent sensitivity to be exhibited during resist pattern formation.

[0247] <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.

[0248] 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.

[0249] 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.

[0250] 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 (IIa) of the base polymer can be suitably used.

[0251] In the acid diffusion controller, the fourth organic anion preferably has a sulfonate anion or a carboxylate anion as the acid anion moiety (however, when the fourth organic acid anion has the sulfonate anion, no electron-withdrawing group is bonded to either the α- or β-position carbon atom of the sulfonate anion). Examples of the electron-withdrawing group include the electron-withdrawing groups listed for the first organic acid anion. This allows the acid diffusion controller to efficiently exhibit the above-mentioned function.

[0252] The structure of the fourth organic acid anion of the acid diffusion controller is X in the above formula (p1) of the base polymer. １ From COO - Structure (q) up to or COO of said structure (q) - SO ３ - A structure in which the above is replaced can be preferably adopted.

[0253] 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.

[0254]

[0255]

[0256] As the quaternary onium cation in the acid diffusion controller, the structure of the first onium cation in the structural unit (IIa) in the base polymer can be suitably adopted.

[0257] 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.

[0258] The acid diffusion controller can also be synthesized by known methods, particularly by salt exchange reaction.

[0259] 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 when multiple types are used) is preferably 20 mol%, more preferably 40 mol%, and even more preferably 60 mol%, based on the total amount of the monomer that provides the structural unit (IIa) and the radiation-sensitive acid generator (when both are included). The upper limit of the content is preferably 100 mol%, more preferably 90 mol%, and even more preferably 80 mol%.

[0260] <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.

[0261] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0262] Examples of alcohol-based solvents include monoalcohol-based solvents having 1 to 18 carbon atoms, such as isopropanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol-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, such as propylene glycol monomethyl ether. In this 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.

[0263] 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.

[0264] Examples of the ketone solvent include chain ketone solvents such as acetone, butanone, and methyl isobutyl ketone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone; and 2,4-pentanedione, acetonylacetone, and acetophenone.

[0265] 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.

[0266] 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.

[0267] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, diisopropylbenzene, and n-amylnaphthalene.

[0268] Among these, ester-based solvents, ether-based solvents, and alcohol-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, polyhydric alcohol partial ether-based solvents, and monoalcohol-based solvents are more preferred, and propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, and diacetone alcohol are even more preferred. The radiation-sensitive composition may contain one or more solvents.

[0269] <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.

[0270] <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.

[0271] <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").

[0272] 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, CDU, overexposure CDU, and underexposure CDU during pattern formation. Each step will be described below.

[0273] [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 80°C to 180°C, preferably 100°C to 150°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.

[0274] [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.

[0275] 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 from the structural unit (IIa) or the radiation-sensitive acid generator upon exposure 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 150°C, preferably 80°C to 120°C. The PEB time is typically 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0276] [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.

[0277] In the case of alkaline development, the developer used in the development may be, for example, 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, or 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.

[0278] 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.

[0279] 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).

[0280] <<Method for Producing Polymer>> The method for producing the polymer includes a polymerization step of reacting, in the presence of a compound (A) represented by the following formula (A), a monomer (i) that provides a structural unit (I) having an acid-dissociable group with a monomer (ii) that provides a structural unit (II) that has an organic acid anion and an onium cation and includes an acid-generating structure that generates an acid upon exposure, to obtain a polymer: (In formula (A), R is a monovalent organic group having 1 to 20 carbon atoms. Z is a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms.)

[0281] It is preferable that the method further includes a modification treatment step of modifying the partial structure (a) so that the content of the partial structure (a) represented by the following formula (a) in the polymer after the polymerization step is 15 mol % or more and 85 mol % or less, assuming that the content of the partial structure (a) in the polymer after the polymerization step is 100 mol %: (In formula (a), Z represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.)

[0282] As a method for producing such a polymer, the methods for producing the first polymer and the second polymer shown above in relation to the radiation-sensitive composition can be suitably employed.

[0283] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0284] The methods for measuring the physical properties of the polymer are shown below. [Measurement of weight average molecular weight (Mw), number average molecular weight (Mn), and dispersity (Mw / Mn)] Measurements were carried out by gel permeation chromatography (GPC) using Tosoh GPC columns (one "TSKGel SuperAW4000", one "SuperAW3000", and two "SuperAW2500") under the following analytical conditions: flow rate: 0.6 mL / min, elution solvent: LiBr DMF solution (20 mM), column temperature: 40°C, with monodisperse polystyrene as the standard. The Mw and Mw / Mn of the obtained polymer are shown in Table 1.

[0285] <Synthesis of Polymer [A]> Polymers (A-1) to (A-14) and (AX-1) to (AX-3) were synthesized as Polymer [A] according to the following method. Compounds represented by the following formulae (M-1) to (M-10) and (CT-1) to (CT-2) (hereinafter also referred to as "monomers (M-1) to (M-10)" and "chain transfer agents (CT-1) to (CT-2)") were used in the synthesis of Polymer [A]. In the following synthesis examples, unless otherwise specified, "parts by mass" means a value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %. In Table 1, "-" indicates that the corresponding component was not used.

[0286]

[0287]

[0288] Example A1 (Synthesis of Polymer (A-1)) The following procedure was carried out as the polymerization step. Monomer (M-1), monomer (M-2), and monomer (M-5) were dissolved in 60 parts by mass of propylene glycol monomethyl ether in a reaction vessel so that the molar ratio in the final polymer obtained was 35 / 50 / 15. Next, 3.5 mol % of a chain transfer agent (CT-1) and 0.7 mol % of AIBN (azobisisobutyronitrile) as an initiator were added to a separate vessel to prepare solution A. The reaction vessel was purged with nitrogen for 30 minutes, and then solution A was added. The mixture was then heated to 80°C with stirring. The time when the solution temperature reached 80°C was defined as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After completion of the polymerization reaction, the polymerization reaction solution was cooled to below 30°C with water. The cooled polymerization reaction solution was poured into hexane (500 parts by mass per 100 parts by mass of the polymerization reaction solution), and the precipitated yellow powder was filtered off. The filtered yellow powder was dissolved in 300 parts by mass of propylene glycol monomethyl ether to prepare a polymer solution.

[0289] Next, the following operation was carried out as the modification treatment step. 3.5 mol % of t-dodecanethiol and 3.5 mol % of AIBN were added to a separate vessel to prepare solution B. After purging the polymer solution with nitrogen for 30 minutes, solution B was added to the polymer solution. The mixture was then heated to 80°C with stirring, and the time when the solution temperature reached 80°C was set as the start time of the reaction. The modification treatment was carried out for 3 hours. After completion of the treatment, the reaction solution was cooled with water to below 30°C. The cooled reaction solution was poured into hexane (500 parts by mass per 100 parts by mass of the reaction solution) to coagulate the polymer. The obtained solid was filtered and dried at 50°C for 12 hours to synthesize a white powdery polymer (A-1).

[0290] Example A2 (Synthesis of Polymer (A-2)) Polymer (A-2) was synthesized in the same manner as in Example A1, except that in preparing Solution B, 7 mol % of t-dodecanethiol and 7 mol % of AIBN were used.

[0291] Example A3 Synthesis of Polymer (A-3) Polymer (A-3) was synthesized in the same manner as in Example A1, except that in preparing Solution B, 10.5 mol % of t-dodecanethiol and 10.5 mol % of AIBN were used.

[0292] Example A4 (Synthesis of Polymer (A-4)) Polymer (A-4) was synthesized in the same manner as in Example A1, except that the steps subsequent to the preparation of Solution B (modification treatment steps) were omitted.

[0293] Example A5 Synthesis of Polymer (A-5) Polymer (A-5) was synthesized in the same manner as in Example A1, except that t-dodecanethiol was not used and 17.5 mol % of AIBN was used in preparing Solution B.

[0294] [Example A6] (Synthesis of Polymer (A-6)) Polymer (A-6) was synthesized in the same manner as in Example A1, except that solution B was not added and only the polymer solution was heated to 120°C and subjected to modification treatment for 3 hours.

[0295] [Examples A7 to A14] (Synthesis of Polymers (A-7) to (A-14)) Polymers (A-7) to (A-14) were synthesized in the same manner as in Example A1, except that the types and amounts of monomers and chain transfer agents shown in Table 1 below were used.

[0296] Comparative Example A1 Synthesis of Polymer (AX-1) Polymer (AX-1) was synthesized in the same manner as in Example A1, except that no chain transfer agent was used in the preparation of Solution A, and a solution containing only AIBN was prepared, and the steps (modification treatment steps) subsequent to the preparation of Solution B were omitted. Comparative Example A1 was a free radical polymerization, and the column for modification rate in Table 1 is marked with "-".

[0297] Comparative Example A2 Synthesis of Polymer (AX-2) Polymer (AX-2) was synthesized in the same manner as in Example A1, except that 17.5 mol % of t-dodecanethiol and 17.5 mol % of AIBN were used in preparing Solution B.

[0298] Comparative Example A3 Synthesis of Polymer (AX-3) Polymer (AX-3) was synthesized in the same manner as in Example A1, except that the monomers (M-1), (M-2) and (M-3) were used in such a way that the molar ratio in the final polymer obtained was 35 / 50 / 15.

[0299] [Measurement of Modification Rate] The polymer before modification was dissolved in 200 parts by mass of a deuterated acetone solution, and 1.3 parts by mass of tris(2,4-pentanedionato)chromium(III) was further added to prepare a measurement sample. Samples of the modified polymer were also prepared in the same manner. The NMR spectrum of each sample was measured using a nuclear magnetic resonance spectrometer. １３ C-NMR was measured, and the modification rate was calculated from the decrease in the peak intensity (content) of the carbon atom of —S—(C═S)— in the partial structure (a) before and after modification.

[0300]

[0301] <Synthesis of [E] Additive (High-Fluorine Content Polymer)> [Synthesis Examples 1-2] Synthesis of High-Fluorine Content Polymers (E-1) to (E-2) Monomers (M-11), (M-12), and (F-1) were combined according to the compositions shown in Table 2 and copolymerized in tetrahydrofuran (THF) solvent. After polymerization, the solvent was replaced with acetonitrile and the resulting mixture was washed with hexane. The solvent was then replaced with propylene glycol monomethyl ether acetate to obtain high-fluorine content polymers (E-1) and (E-2) having the compositions shown below. The amounts of each monomer used, Mw, and Mw / Mn of the resulting polymers are also shown in Table 2.

[0302]

[0303]

[0304] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive acid generator [B], acid diffusion controller [C], solvent [D], and additive [E] used in the preparation of the radiation-sensitive composition are shown below. In the following examples and comparative examples, unless otherwise specified, "parts by mass" means a value relative to 100 parts by mass of the polymer [A] used in the preparation of the radiation-sensitive composition. "Mol %" means a value relative to 100 mol % of the number of moles of the radiation-sensitive acid generator [B] used in the preparation of the radiation-sensitive composition.

[0305] [B] Radiation-sensitive Acid Generator Compounds represented by the following formulae (B-1) to (B-3) were used as radiation-sensitive acid generators.

[0306]

[0307] [C] Acid Diffusion Controller Compounds represented by the following formulae (C-1) to (C-3) were used as acid diffusion controllers.

[0308]

[0309] [D] Solvent The following organic solvents were used as the solvent: (D-1): Propylene glycol monomethyl ether acetate (D-2): Propylene glycol monomethyl ether (D-3): Diacetone alcohol

[0310] [Example 1] Preparation of Radiation-Sensitive Composition (R-1) [A] 100 parts by mass of (A-1) as a polymer, [B] 60 parts by mass of (B-1) as a radiation-sensitive acid generator, [C] 70 mol% of (C-1) as an acid diffusion controller relative to the total amount of the acid generator (B-1) and the component (M-5) in the polymer (A-1), [E] 5 parts by mass of (E-1) as an additive, [D] 1,500 parts by mass of (D-1) and 5,500 parts by mass of (D-2) as a solvent were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare a radiation-sensitive composition (R-1).

[0311] [Examples 2 to 20 and Comparative Examples 1 to 3] Preparation of Radiation-Sensitive Compositions (R-2) to (R-20) and (RX-1) to (RX-3) Radiation-sensitive compositions (R-2) to (R-20) and (RX-1) to (RX-3) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 3 were used. The amount of acid diffusion controller [C] was as follows: - For (R-2) to (R-8), (R-14) to (R-18), (R-20), and (RX-1) to (RX-2), 70 mol % was blended based on the total amount of radiation-sensitive acid generator [B] and component (M-5) in the polymer [A]. - For (R-9), 70 mol % was blended based on the total amount of radiation-sensitive acid generator (B-1) and component (M-6) in the polymer (A-9). In (R-10) to (R-13), 60 mol % was blended based on the total amount of the radiation-sensitive acid generator (B-1) and the component (M-5) in the polymer [A]. In (R-19), 70 mol % was blended based on the total amount of the radiation-sensitive acid generator (B-1), the component (M-5) in the polymer (A-1), and the component (M-11) in the polymer (E-2). In (RX-3), 50 mol % was blended based on the radiation-sensitive acid generator (B-1).

[0312]

[0313] <Evaluation> Using the radiation-sensitive compositions prepared above, the sensitivity, CDU, overexposure CDU, and underexposure CDU were evaluated according to the following methods. The evaluation results are shown in Table 4.

[0314] [Sensitivity] Each radiation-sensitive composition shown in Table 3 was applied using a spin coater to the surface of a 12-inch silicon wafer on which a 70-nm-thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, and the wafer was prebaked (PB) at 130°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 50 nm. This resist film was exposed using an EUV scanner (ASML's "NXE3300" (NA 0.33, σ 0.9 / 0.6, quadruple-pole illumination, a mask with a hole pattern having a 50-nm pitch on the wafer and a +20% bias)). Post-exposure baking (PEB) was performed on a hot plate at 100°C for 60 seconds, and development was performed in a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) for 30 seconds to form a resist pattern with 25 nm holes and a 50 nm pitch (hereinafter also referred to as a "25 nm contact hole pattern"). The exposure dose required to form the 25 nm contact hole pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the value, the better the sensitivity. ２ "A" (very good) if less than 60 mJ / cm ２ More than 63mJ / cm ２ "B" (good) in the following cases: 63 mJ / cm ２ When the test result exceeded this, the test result was evaluated as "C" (poor).

[0315] [CDU] A 25 nm contact hole pattern was formed in the same manner as in the [Sensitivity] section above by irradiating EUV with the optimal exposure dose determined in the [Sensitivity] section above. Using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), the 25 nm contact hole pattern in the resist pattern was observed from above, and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and this was taken as CDU (nm). A smaller CDU value indicates a smaller and better long-period hole diameter variation (i.e., diameter variation between different holes). CDU was evaluated as "A" (very good) when the value was less than 3.3 nm, "B" (good) when it was 3.3 nm or more but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or more.

[0316] [Over-exposure CDU] A 27-nm contact hole pattern was formed using the same procedure as in the [Sensitivity] section above, except that the exposure dose was increased above the optimal exposure dose determined in the [Sensitivity] section above. Using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), the 27-nm contact hole pattern in the resist pattern was observed from above, and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and used as the over-exposure CDU (nm). The smaller the over-exposure CDU value, the smaller the hole diameter variation over a long period, and the better the result. Over-exposure CDU was evaluated as "S" (very good) when the value was less than 3.2 nm, "A" (good) when it was 3.2 nm or more but less than 3.3 nm, "B" (fair) when it was 3.3 nm or more but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or more.

[0317] [Under-exposure CDU] A 23 nm contact hole pattern was formed using the same procedure as in the [Sensitivity] section above, except that the exposure dose was lower than the optimal exposure dose determined in the [Sensitivity] section above. Using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-5000"), the 23 nm contact hole pattern in the resist pattern was observed from above, and a total of 800 hole diameters were measured at random points. The dimensional variation (3σ) was determined and this was taken as the under-exposure CDU (nm). The smaller the under-exposure CDU value, the smaller the hole diameter variation over a long period, and the better the result. Under-exposure CDU was evaluated as "S" (very good) when the value was less than 3.2 nm, "A" (good) when it was 3.2 nm or more but less than 3.3 nm, "B" (fair) when it was 3.3 nm or more but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or more.

[0318]

[0319] As is clear from the results in Table 4, the radiation-sensitive compositions of Examples 1 to 20 all showed well-balanced improvements in sensitivity, CDU performance, overexposure CDU performance, and underexposure CDU performance compared to the radiation-sensitive compositions of Comparative Examples 1 to 3, and were favorable.

[0320] The radiation-sensitive composition, pattern formation method, and polymer production method of the present invention can improve sensitivity, CDU, overexposure CDU, and underexposure CDU, thereby enabling the widening of the process window, and therefore can be suitably used for the formation of fine resist patterns in the lithography processes of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A radiation-sensitive composition comprising a first polymer and a solvent, the first polymer comprising: a structural unit (I) having an acid-dissociable group; a structural unit (II) including an acid-generating structure having an organic acid anion and an onium cation, and which generates an acid upon exposure; and a partial structure (a) represented by the following formula (a): (In formula (a), Z represents a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.) 2. The radiation-sensitive composition according to claim 1, further comprising a second polymer which contains a partial structure (b) different from the partial structure (a), and which has the same structure as the first polymer except for the partial structure (b).

3. The radiation-sensitive composition according to claim 2, wherein the content of the second polymer in the total amount of the first polymer and the second polymer is 15 mol % or more and 85 mol % or less.

4. The radiation-sensitive composition according to any one of claims 1 to 3, wherein in the formula (a), Z is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms.

5. The radiation-sensitive composition according to any one of claims 1 to 3, wherein in the above formula (a), Z is a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

6. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the acid-dissociable group has an iodine group.

7. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the structural unit (II) is a structural unit (IIa) having a first organic acid anion and a first onium cation, and including a first acid-generating structure that generates an acid that dissociates the acid-dissociable group upon exposure.

8. The radiation-sensitive composition according to claim 7, wherein the first organic acid anion has a sulfonate anion, an electron-withdrawing group is bonded to a carbon atom at the α- or β-position to a sulfur atom in the sulfonate anion, and the polymer has the first organic acid anion as a side chain moiety.

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

10. The radiation-sensitive composition according to claim 7, wherein the first onium cation is a sulfonium cation or an iodonium cation.

11. The radiation-sensitive composition according to any one of claims 1 to 3, wherein the structural unit (II) is a structural unit (IIb) including a second acid-generating structure that has a second organic acid anion and a second onium cation and that generates, upon exposure, an acid that does not dissociate the acid-dissociable group.

12. The radiation-sensitive composition according to claim 11, 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 either the α- or β-position carbon atom of the sulfonate anion), and the polymer has the second organic acid anion as a side chain moiety.

13. The radiation-sensitive composition according to claim 11, wherein the second organic acid anion has an iodine group.

14. The radiation-sensitive composition according to claim 11, wherein the second onium cation is a sulfonium cation or an iodonium cation.

15. The radiation-sensitive composition according to any one of claims 1 to 3, 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.

16. The radiation-sensitive composition according to claim 7, wherein the content of the structural unit (IIa) in all structural units constituting the polymer is 1 mol % or more and 30 mol % or less.

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

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

19. The radiation-sensitive composition according to any one of claims 1 to 3, further comprising a radiation-sensitive acid generator that generates an acid that dissociates the acid-dissociable group upon exposure.

20. The radiation-sensitive composition according to any one of claims 1 to 3, further comprising an acid diffusion controller.

21. The radiation-sensitive composition according to any one of claims 1 to 3, further comprising a high-fluorine content polymer having a higher mass content of fluorine atoms than the polymer.

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

23. The pattern forming method according to claim 22, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

24. A method for producing a polymer, comprising a polymerization step of reacting, in the presence of a compound (A) represented by the following formula (A), a monomer (i) that provides a structural unit (I) having an acid-dissociable group with a monomer (ii) that provides a structural unit (II) that has an organic acid anion and an onium cation and includes an acid-generating structure that generates acid upon exposure to light, to obtain a polymer: (In formula (A), R is a monovalent organic group having 1 to 20 carbon atoms. Z is a hydrogen atom, a halogen atom, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms.) 25. A method for producing a polymer according to claim 24, further comprising a modification treatment step of modifying the partial structure (a) so that the content of the partial structure (a) represented by the following formula (a) in the polymer after the polymerization step is 100 mol % but less than 1 mol %: (In formula (a), Z represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, or a monovalent organic group having 1 to 20 carbon atoms. * represents a bond to another structure of the polymer.)

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