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

Abstract

Provided is a radiation-sensitive composition which contains a polymer (A) that includes: a first structural unit that is at least one type selected from the group consisting of a structural unit represented by formula (1-1) and a structural unit represented by formula (1-2); a second structural unit represented by formula (2); and a third structural unit having an acid-dissociable group, and which satisfies one or more of a first requirement, a second requirement and a third requirement. At least one selected from the group consisting of the polymer (A), a structural unit (b1) and a radiation-sensitive onium salt (C) has an iodine atom. First requirement: the polymer (A) also includes a fourth structural unit derived from a radiation-sensitive onium salt. Second requirement: a polymer (E1) which is different from the polymer (A) and which includes the structural unit (b1) derived from a radiation-sensitive onium salt is also contained. Third requirement: a non-polymer radiation-sensitive onium salt (C) is also contained.

Description

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

[0001] [Cross-Reference to Related Applications] This application claims priority to Japanese Patent Application No. 2024-054819, filed on March 28, 2024, the entire contents of which are incorporated herein by reference. The present disclosure relates to a radiation-sensitive composition, a method for forming a resist pattern, a polymer, and a compound.

[0002] In lithography techniques used in the manufacturing processes of various electronic devices such as semiconductor devices and liquid crystal devices, a radiation-sensitive composition is irradiated with far ultraviolet rays such as those from an ArF excimer laser, extreme ultraviolet rays (EUV), electron beams, or the like to generate an acid in the exposed area, and a chemical reaction involving the generated acid causes a difference in the dissolution rate in a developer between the exposed area and the unexposed area, thereby forming a resist pattern on a substrate.

[0003] As the structures of various electronic devices become finer, there is a demand for even finer resist patterns in lithography processes. Furthermore, in response to the demand for even finer resist patterns, various efforts have been made to improve the resolution and resist pattern shape of radiation-sensitive compositions used in lithographic microfabrication (see, for example, Patent Document 1). Patent Document 1 discloses a radiation-sensitive resin composition containing a resin including a structural unit having a phenolic hydroxyl group or a protective structure that generates a phenolic hydroxyl group upon the action of an acid and an acid-dissociable group, a radiation-sensitive acid generator consisting of a sulfonate anion and an onium cation, and a solvent.

[0004] Japanese Patent Application Laid-Open No. 2022-007909

[0005] In recent years, attempts have been made to form fine patterns with line widths of, for example, 40 nm or less. Radiation-sensitive compositions for forming resist films are required to exhibit high sensitivity while also further improving CDU (Critical Dimension Uniformity), which is an index of pattern quality.

[0006] Furthermore, with further miniaturization of resist patterns and increased sensitivity of radiation-sensitive compositions, slight differences in process conditions such as exposure conditions and development conditions are more likely to affect the shape of the resist pattern, the occurrence of defects, etc. Therefore, radiation-sensitive compositions used in forming resist patterns are required to have a margin capable of absorbing slight differences in process conditions while maintaining good sensitivity and resist pattern quality, i.e., a wide range of process conditions (hereinafter also referred to as "process window") that allows the formation of a pattern without bridge defects or collapse in the resist pattern formation step.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and a primary object of the present disclosure is to provide a radiation-sensitive composition that has high sensitivity to radiation, excellent CDU performance, and a wide process window, and a method for forming a resist pattern. Another object of the present disclosure is to provide a polymer and a compound that can be used to obtain a radiation-sensitive composition that has high sensitivity to radiation, excellent CDU performance, and a wide process window.

[0008] The present inventors have found that the above-mentioned problems can be solved by a radiation-sensitive composition that contains a polymer having a specific structural unit, and that also contains a component derived from a radiation-sensitive onium salt and an iodine atom. Specifically, the present disclosure provides the following radiation-sensitive composition, method for forming a resist pattern, polymer, and compound.

[0009] In one aspect, the present disclosure provides a radiation-sensitive composition comprising a polymer (A) including a first structural unit which is at least one type selected from the group consisting of structural units represented by the following formula (1-1) and structural units represented by the following formula (1-2), a second structural unit represented by the following formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit), and which satisfies one or more of the following first, second, and third requirements: first requirement: the polymer (A) further includes a fourth structural unit derived from a radiation-sensitive onium salt; second requirement: the polymer (A) further includes a polymer (E1) which is a polymer different from the polymer (A) and includes a structural unit (b1) derived from a radiation-sensitive onium salt; and third requirement: the polymer (A) further includes a non-polymeric radiation-sensitive onium salt (C), and at least one selected from the group consisting of the polymer (A), the structural unit (b1) in the polymer (E1), and the radiation-sensitive onium salt (C) contains an iodine atom. (In formula (1-1) and formula (1-2), R １ is a hydrogen atom or a monovalent organic group. ２ Is -COOR １ m1 is an integer of 1 to 3. m2 is an integer of 0 to 5, and m1+m2≦6. When m1 is 2 or more, multiple R １ When m2 is 2 or more, a plurality of R ２ are the same or different. In formula (2), R ３ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ represents a single bond, —COO—, or —CONH—. １ is an aromatic ring group. ４ is a substituent that is a group other than a hydroxyl group and does not have an acid-dissociable group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.)

[0010] In another aspect, the present disclosure provides a method for forming a resist pattern, the method including the steps of applying the radiation-sensitive composition onto a substrate to form a resist film, exposing the resist film to light, and developing the exposed resist film.

[0011] In another aspect, the present disclosure provides a polymer including a first structural unit which is at least one selected from the group consisting of structural units represented by the above formula (1-1) and structural units represented by the above formula (1-2), a second structural unit represented by the above formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit).

[0012] In another aspect, the present disclosure provides a compound represented by the following formula (1B-1) or (1B-2): (In formula (1B-1) and formula (1B-2), R １Ａ is a monovalent organic group having 6 or more carbon atoms. ２Ａ Is -COOR １Ａ m3 is an integer of 1 to 3. m4 is an integer of 0 to 5, and m3+m4≦6. When m3 is 2 or more, multiple R １Ａ When m4 is 2 or more, a plurality of R ２Ａ are the same or different.)

[0013] According to the present disclosure, it is possible to obtain a radiation-sensitive composition that is highly sensitive to radiation, has excellent CDU performance, and has a wide process window. Also, according to the present disclosure, it is possible to obtain a polymer and a compound that can give a radiation-sensitive composition that is highly sensitive, has excellent CDU performance, and has a wide process window.

[0014] Matters related to the implementation of the present disclosure will be described in detail below. In this specification, a numerical range described using "to" means that the numerical values ​​before and after "to" are included as the lower limit and upper limit.

[0015] In this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain hydrocarbon group" refers to a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure and is composed only of a chain structure. However, the chain hydrocarbon group may be saturated or unsaturated. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, the alicyclic hydrocarbon group does not necessarily have to be composed only of an alicyclic hydrocarbon structure and may also have a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, the aromatic hydrocarbon group does not necessarily have to be composed only of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The term "aromatic ring group" refers to an n-valent group obtained by removing n hydrogen atoms (where n is an integer of 1 or more) from an aromatic ring. The term "organic group" refers to an atomic group formed by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound). The term "aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles.

[0016] The "main chain" of a polymer refers to the "backbone" portion of the polymer, which is the longest chain of atoms. It is acceptable for this "backbone" portion to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes part of the main chain of the polymer. A "side chain" refers to a portion branched from the "backbone" of the polymer. A "structural unit" refers to a unit that primarily constitutes the main chain structure, and at least two or more of which are contained in the main chain structure. A structural unit is typically a monomer unit. However, a "structural unit" also includes a unit obtained by reacting a monomer unit having a reactive group with a compound having a functional group capable of reacting with the reactive group, and a unit obtained by polymerizing a monomer protected with a protecting group such as an alkali-labile group and then deprotecting the monomer by hydrolysis. "(Meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate."

[0017] The expression "substituted or unsubstituted p-valent hydrocarbon group (where p is an integer of 1 or more)" encompasses p-valent hydrocarbon groups (i.e., unsubstituted p-valent hydrocarbon groups) and groups in which p hydrogen atoms have been removed from the hydrocarbon structural portion of a substituted hydrocarbon group. Examples of substituted or unsubstituted p-valent hydrocarbon groups include alkyl groups and fluoroalkyl groups where p=1, and alkanediyl groups and fluoroalkanediyl groups where p=2. Of these, fluoroalkyl groups are categorized as "substituted monovalent hydrocarbon groups," and fluoroalkanediyl groups are categorized as "substituted divalent hydrocarbon groups." The same applies to other groups to which "substituted or unsubstituted" is attached.

[0018] <Radiation-Sensitive Composition> The radiation-sensitive composition of the present disclosure (hereinafter also referred to as "the composition") contains a polymer (A) including a first structural unit which is at least one type selected from the group consisting of structural units represented by the following formula (1-1) and structural units represented by the following formula (1-2), a second structural unit represented by the following formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit). (In formula (1-1) and formula (1-2), R １ is a hydrogen atom or a monovalent organic group. ２ Is -COOR １ m1 is an integer of 1 to 3. m2 is an integer of 0 to 5, and m1+m2≦6. When m1 is 2 or more, multiple R １ When m2 is 2 or more, a plurality of R ２ are the same or different. In formula (2), R ３ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ represents a single bond, —COO—, or —CONH—. １ is an aromatic ring group. ４ is a substituent that is a group other than a hydroxyl group and does not have an acid-dissociable group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.)

[0019] The present composition contains a radiation-sensitive onium salt or a component having a radiation-sensitive onium salt structure (hereinafter, these are collectively referred to as the "onium salt component"). The onium salt component may be polymeric or non-polymeric. Furthermore, the present composition may contain both polymeric and non-polymeric onium salt components. Specifically, the present composition satisfies one or more of the following first, second, and third requirements. First requirement: Polymer (A) further contains a fourth structural unit derived from a radiation-sensitive onium salt. Second requirement: The composition further contains a polymer (E1) that is different from Polymer (A) (referred to as "Polymer (E)") and contains a structural unit (b1) derived from a radiation-sensitive onium salt. Third requirement: The composition further contains a non-polymeric radiation-sensitive onium salt (C).

[0020] The structural units contained in the polymer (A) are not particularly limited as long as the radiation-sensitive composition satisfies one or more of the first, second, and third requirements. Specifically, the polymer (A) may be a polymer containing the first structural unit, the second structural unit, and the third structural unit but not the fourth structural unit (referred to as "polymer (A1)"), or a polymer containing the first structural unit, the second structural unit, the third structural unit, and the fourth structural unit (referred to as "polymer (A2)"). Furthermore, the polymer (A1) and the polymer (A2) may further contain structural units different from the first to fourth structural units (hereinafter also referred to as "other structural units").

[0021] Polymer (E) is a component that is optionally blended into the composition, and differs from polymer (A) in that it does not contain either the structural unit represented by formula (1-1) or the structural unit represented by formula (1-2). Similarly, the chemical structure of polymer (E) is not particularly limited as long as the composition satisfies one or more of the first, second, and third requirements. Specifically, polymer (E) may be a polymer that contains the structural unit (b1) but does not contain either the structural unit represented by formula (1-1) or the structural unit represented by formula (1-2) (referred to as "polymer (E1)"), or a polymer that does not contain either the structural unit represented by formula (1-1) or the structural unit represented by formula (1-2) and does not contain the structural unit (b1) (referred to as "polymer (E2)"). From the viewpoint of further improving the lithography properties of the present composition by incorporating polymer (E), polymer (E) preferably contains at least one selected from the group consisting of a structural unit having a fluorine atom (this will be referred to as "structural unit (f)"), a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (this will be referred to as "structural unit (b2)"), and a structural unit having an acid-dissociable group (this will be referred to as "structural unit (b3)").

[0022] When the polymer (E) contains the structural unit (f), it is preferable that the polymer is a polymer having a higher mass content of fluorine atoms than the polymer (A) (hereinafter also referred to as a "high-fluorine content polymer"). The high-fluorine content polymer is, for example, a component blended into the present composition as a water-repellent additive. The high-fluorine content polymer may also be blended into the present composition as a surface modifier for adjusting the hydrophilicity / hydrophobicity of the surface of the resist film, or as a modifier for further improving lithography performance. When the polymer (E) contains at least one of the structural unit (b2) and the structural unit (b3), the polymer may constitute a base resin together with the polymer (A). When the polymer (E) is blended into the present composition as a base resin, it is preferable that the polymer (E) contains the structural unit (b2) and the structural unit (b3).

[0023] Here, in this specification, the "base resin" refers to the main polymer component contained in the composition, and is a component that accounts for, for example, 30% by mass or more of the total amount of the polymer components. The base resin is preferably a component that contributes to the solubility of the composition in a developer by containing a structural unit having an acid-dissociable group in a predetermined proportion or more (for example, 10 mol% or more). The base resin may be composed of two or more polymers. When the base resin is composed of two or more polymers, the total amount thereof is preferably 60% by mass or more of the total amount of the polymer components contained in the composition.

[0024] The radiation-sensitive onium salt (C), like the polymer (E), is a component that is optionally blended into the composition. The radiation-sensitive onium salt (C) is a substance that generates an acid upon irradiation with radiation, and typically has a radiation-sensitive onium cation and an organic anion that is the conjugate base of the acid. The organic anion is usually an anion obtained by removing a proton from the acid group of an organic acid. Herein, the term "radiation" encompasses electron beams (visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), etc.) and electromagnetic waves (X-rays, gamma rays, etc.).

[0025] The radiation-sensitive onium salt (C) may be a so-called radiation-sensitive acid generator or an acid diffusion controller. The present composition may contain both an acid generator and an acid diffusion controller as the radiation-sensitive onium salt (C). The acid generator is a substance that, upon exposure, generates a strong acid in the present composition that is capable of cleaving an acid-dissociable group from a component in the radiation-sensitive composition. The acid diffusion controller is a substance that inhibits the diffusion of an acid derived from the acid generator generated upon exposure within the resist film, thereby inhibiting chemical reactions caused by the acid in unexposed regions. The radiation-sensitive onium salt (C) is classified as an acid generator or an acid diffusion controller depending on the strength of its acid relative to the components in the present composition (specifically, the monomer that provides the fourth structural unit in the polymer (A2) and other radiation-sensitive onium salts (C) in the case where two or more types of radiation-sensitive onium salts (C) are contained). The acidity can be evaluated by the acid dissociation constant (pKa). For example, the acid dissociation constant of the acid generated by the acid diffusion controller is usually −3 or more, preferably −1≦pKa≦7, and more preferably 0≦pKa≦5.

[0026] The radiation-sensitive onium salt (C) is a component different from the polymer (A). The composition preferably contains a radiation-sensitive onium salt (C) as an onium salt component, from the viewpoints of ease of adjusting the sensitivity and lithography properties of the composition and high freedom of selection. The molecular weight of the radiation-sensitive onium salt (C) is preferably 1,000 or less, more preferably 800 or less, and even more preferably 600 or less.

[0027] Specific embodiments of the radiation-sensitive composition that satisfy one or more of the first, second, and third requirements include the following embodiments [1] to [6] and combinations of two or more of these embodiments. Embodiment [1]: Contains a polymer (A1) and a radiation-sensitive onium salt (C). Embodiment [2]: Contains a polymer (A2), with the polymer (A2) constituting the base resin. Embodiment [3]: Contains a polymer (A1) and a polymer (E1), with the polymer (E1) being a high-fluorine-containing polymer. Embodiment [4]: ​​Contains a polymer (A1) and a polymer (E1), with the polymer (A1) and the polymer (E1) constituting the base resin. Embodiment [5]: Contains a polymer (A2) and a polymer (E2), with the polymer (E2) being a high-fluorine-containing polymer. Embodiment [6]: Contains a polymer (A2) and a polymer (E2), with the polymer (A2) and the polymer (E2) constituting the base resin.

[0028] In addition, in the above embodiments [1] to [6], in addition to the components included in each embodiment, other solid components (such as an acid generator, an acid diffusion controller, or a high-fluorine-containing polymer) may be further blended. In this specification, the term "solid components" refers to components other than the solvent contained in the composition.

[0029] Furthermore, in the present composition, at least one selected from the group consisting of the polymer (A), the structural unit (b1) in the polymer (E1), and the radiation-sensitive onium salt (C) contains an iodine atom. The present composition, which contains the polymer (A), satisfies one or more of the first, second, and third requirements, and in which at least one selected from the group consisting of the polymer (A), the structural unit (b1) in the polymer (E1), and the radiation-sensitive onium salt (C) contains an iodine atom, can ensure a wider process window. The present composition contains a relatively rigid acenaphthylene skeleton or indene skeleton in the polymer (A) and an iodine atom in the radiation-sensitive composition, which is thought to contribute to high sensitivity, thereby improving the CDU performance against overexposure and the CDU performance against underexposure in a well-balanced manner. As a result, it is believed that a radiation-sensitive composition with a wide process window can be obtained by maintaining stable performance against variations in exposure dose.

[0030] In the present composition, the component having an iodine atom may be one or more of the polymer (A), the structural unit (b1) in the polymer (E1), and the radiation-sensitive onium salt (C). Therefore, for example, only the polymer (A) may have an iodine atom, only the structural unit (b1) in the polymer (E1) may have an iodine atom, or only the radiation-sensitive onium salt (C) may have an iodine atom. Alternatively, both the polymer (A) and the radiation-sensitive onium salt (C) may have an iodine atom, or both the structural unit (b1) in the polymer (E1) and the radiation-sensitive onium salt (C) may have an iodine atom. From the viewpoints of further enhancing the sensitivity of the present composition and facilitating sensitivity adjustment, it is preferred that the present composition contain a radiation-sensitive onium salt (C), and that at least a portion of the radiation-sensitive onium salt (C) contained in the present composition contain an iodine atom.

[0031] The bonding position of the iodine atom in the present composition is not particularly limited. In terms of further improving the sensitivity and CDU performance of the present composition, the present composition preferably contains an iodine atom bonded to an aromatic ring. Examples of aromatic rings to which iodine atoms are bonded include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Of these, a benzene ring or a naphthalene ring is preferred, and a benzene ring is more preferred. Furthermore, the number of iodine atoms bonded to one aromatic ring is not particularly limited. In consideration of ease of synthesis, the number of iodine atoms bonded to one aromatic ring is, for example, 1 to 8, and preferably 1 to 5.

[0032] Next, the components contained in the composition and the optional components will be described in detail. Unless otherwise specified, each component contained in the composition may be used alone or in combination of two or more.

[0033] <Polymer (A)> (First structural unit) The first structural unit has an acenaphthylene skeleton or an indene skeleton. The first structural unit has a structure in which one or both of a carboxy group and a group in which a hydrogen atom in the carboxy group is replaced with a monovalent organic group are bonded to an aromatic ring in the acenaphthylene skeleton or the indene skeleton. In the above formulas (1-1) and (1-2), R １ Examples of the monovalent organic group represented by the formula (I) include a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and a monovalent group having a heterocyclic structure.

[0034] R １ When R is a monovalent hydrocarbon group, examples of the monovalent hydrocarbon group include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms. １ When is a substituted monovalent hydrocarbon group, examples of the substituent include a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.; the same applies hereinafter), a hydroxyl group, an alkoxy group having 1 to 3 carbon atoms, etc.

[0035] R １ is a monovalent group having a heterocyclic structure, examples of the heterocyclic structure include an oxygen-containing heterocyclic structure, a sulfur-containing heterocyclic structure, and a nitrogen-containing heterocyclic structure. The monovalent group having a heterocyclic structure may have a substituent. Examples of the substituent include a monovalent hydrocarbon group having 1 to 6 carbon atoms, a halogen atom, a hydroxyl group, and an alkoxy group having 1 to 3 carbon atoms.

[0036] Due to the action of acid, R １ R in the above formula (1-1) or (1-2) is preferred in that it can eliminate R, thereby increasing the change in the solubility of the polymer (A) in a developer. １ It is preferable that at least one of m1 is an acid-dissociable group. １ is preferably an acid-dissociable group. When m1 is 2 or more, a plurality of R １ At least one of the groups is preferably an acid-dissociable group.

[0037] R １ is an acid-dissociable group, R １The acid-dissociable group represented by the formula "-COOR" may be any group that dissociates under the action of an acid to generate a carboxy group. １ Specific examples of the group represented by " include R １ but having a tertiary carbon atom, a benzylic carbon atom, or an allylic carbon atom and bonding to the oxygen atom in the oxycarbonyl group (-COO-) via such a carbon atom; a group having an acetal ester structure of a carboxylic acid; a group having a ketal ester structure of a carboxylic acid; etc. Examples of the group having an acetal ester structure of a carboxylic acid include a 1-methoxyethoxycarbonyl group, a 1-cyclohexyloxyethoxycarbonyl group, and a 2-tetrahydropyranyloxycarbonyl group. Examples of the group having a ketal ester structure of a carboxylic acid include a 1-methyl-1-methoxyethoxycarbonyl group, a 1-methyl-1-cyclohexyloxyethoxycarbonyl group, and a 2-(2-methyltetrahydropyranyl)oxycarbonyl group.

[0038] R １ The acid-dissociable group represented by the formula (I) preferably has a tertiary carbon atom, a benzylic carbon atom or an allylic carbon atom, and is bonded to the oxygen atom in the oxycarbonyl group via one of these carbon atoms.

[0039] R １ When is an acid-dissociable group, preferred specific examples include groups represented by the following formula (r-1): (In formula (r-1), R ２１ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. ２２ and R ２３ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R ２２ and R ２３ are aligned with each other and R ２２ and R ２３ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. ２１ When is a hydrogen atom, R ２２ and R ２３or both of which are, independently of each other, a substituted or unsubstituted monovalent alicyclic unsaturated hydrocarbon group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a monovalent aromatic heterocyclic group, or R ２２ and R ２３ are aligned with each other and R ２２ and R ２３ represents an alicyclic unsaturated hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which it is bonded. "*" represents a bond to an oxygen atom.)

[0040] R ２１ ~R ２３ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0041] The monovalent chain hydrocarbon group having 1 to 20 carbon atoms may be saturated or unsaturated, and may be linear or branched. Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, and t-butyl; alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl. Among these, R ２１ ~R ２３ The monovalent chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) is preferably an alkyl group or an alkenyl group, more preferably an alkyl group having 1 to 4 carbon atoms or an alkenyl group having 2 to 4 carbon atoms.

[0042] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monovalent monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a methylcyclopentyl group, an ethylcyclopentyl group, a methylcyclohexyl group, and an ethylcyclohexyl group; monovalent monocyclic unsaturated hydrocarbon groups such as a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, and a methylcyclohexenyl group; monovalent polycyclic saturated alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, and a tricyclodecyl group; and monovalent polycyclic unsaturated alicyclic hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group, and an indanyl group.

[0043] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, mesityl, naphthyl, methylnaphthyl, anthryl, methylanthryl, and indenyl; and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl. Examples of the monovalent aromatic heterocyclic group include furyl and thienyl.

[0044] R ２２ and R ２３ are aligned with each other and R ２２ and R ２３ Examples of the alicyclic hydrocarbon structure having 3 to 20 carbon atoms constituted together with the carbon atom to which it is bonded include monocyclic saturated aliphatic hydrocarbon structures such as a cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, and cyclooctane structure; monocyclic unsaturated aliphatic hydrocarbon structures such as a cyclopentene structure and cyclohexene structure; and polycyclic aliphatic hydrocarbon structures such as a norbornane structure, adamantane structure, tricyclodecane structure, and tetracyclododecane structure.

[0045] R ２１ ~R ２３ In the case where the group represented by the formula (r-1) has a substituent, examples of the substituent include a halogen atom, a hydroxyl group, and an alkoxy group having 1 to 3 carbon atoms. ２１ , R ２２ and R ２３ is preferably a tertiary carbon atom, a benzylic carbon atom, or an allylic carbon atom, and is preferably bonded to the oxygen atom in the above formula (1-1) and formula (1-2) via these carbon atoms.

[0046] R in the above formula (1-1) and formula (1-2) １ has preferably 6 or more carbon atoms, more preferably 7 or more carbon atoms, and even more preferably 8 or more carbon atoms. １ The number of carbon atoms in R is preferably 20 or less, more preferably 15 or less, and even more preferably 12 or less. １When the number of carbon atoms is within the above range, the solubility in the developer can be prevented from becoming excessively high or low, and as a result, the process window can be made wider.

[0047] In addition, from the viewpoint of enhancing the effect of widening the process window, R １ Preferably, R has a cyclic structure. The cyclic structure is not particularly limited, and examples thereof include an alicyclic hydrocarbon structure, an aromatic hydrocarbon structure, and an aromatic heterocyclic structure. Specific examples of these include R ２１ ~R ２３ Examples of the ring structures include those exemplified in the description of the group represented by the formula:

[0048] R in the above formula (1-1) １ When R has 6 or more carbon atoms, the above formula (1-1) is represented by the following formula (1A-1). １ When the number of carbon atoms is 6 or more, the above formula (1-2) is represented by the following formula (1A-2). (In formula (1A-1) and formula (1A-2), R １Ａ is a monovalent organic group having 6 or more carbon atoms. ２Ａ Is -COOR １Ａ m3 is an integer of 1 to 3. m4 is an integer of 0 to 5, and m3+m4≦6. When m3 is 2 or more, multiple R １Ａ When m4 is 2 or more, a plurality of R ２Ａ are the same or different.)

[0049] In the above formula (1A-1) and formula (1A-2), R １Ａ The monovalent organic group having 6 or more carbon atoms represented by the formula (1-1) and the formula (1-2) includes R １ Among the groups exemplified in the description of R, groups having 6 or more carbon atoms can be mentioned. １Ａ Preferably, has a cyclic structure.

[0050] R in the above formula (1A-1) and formula (1A-2) ２ The substituent represented by "-COOR １ In addition, R in the above formula (1A-1) and formula (1A-2) ２The substituent represented by "-COOR １Ａ " may be any group different from the group represented by R ２ and R ２Ａ Specific examples of R include a halogen atom, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, a halogenated alkyl group having 1 to 12 carbon atoms, a hydroxyalkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a halogenated alkoxy group having 1 to 12 carbon atoms, a hydroxyalkoxy group having 1 to 12 carbon atoms, a cyano group, a nitro group, a cycloalkyl group having 3 to 12 carbon atoms, a halogenated cycloalkyl group having 3 to 12 carbon atoms, a hydroxycycloalkyl group having 3 to 12 carbon atoms, an alkylsulfonyl group, and a cycloalkylsulfonyl group. ２Ａ may be a carboxy group or an alkoxycarbonyl group.

[0051] In the above formulas (1-1) and (1-2), m1 is an integer of 1 to 3, preferably 1 or 2. m2 is an integer of 0 to 5, preferably 0 to 2, more preferably 0 or 1, and even more preferably 0. In the above formulas (1A-1) and (1A-2), m3 is preferably 1 or 2. m4 is preferably 0 to 2, more preferably 0 or 1, and even more preferably 0. In the above formulas (1-1) and (1-2), -COOR relative to the benzene ring １Ａ The bonding position of -COOR is not particularly limited. １Ａ In the benzene ring to which -COOR is bonded, the bonding position of the main chain and -COOR １Ａ The positional relationship with the carbon atom may be any of the ortho, meta and para positions.

[0052] When at least a part of the first structural units contained in the polymer (A) has an iodine atom, it is preferable in that the sensitivity and CDU performance of the present composition can be improved in a well-balanced manner and the process window can be expanded. From the viewpoint of sufficiently enhancing the effect of improving the sensitivity of the present composition, it is preferable that the iodine atom in the first structural unit is bonded to an aromatic ring. Furthermore, from the viewpoint of further enhancing the effect of improving CDU performance, it is more preferable that the acid-dissociable group in the first structural unit has an aromatic ring and that the iodine atom is bonded to the aromatic ring. Specifically, R in the above formulas (1-1) and (1-2) １is a group represented by the above formula (r-1), and R ２１ is preferably an iodophenyl group. In this specification, when an "iodophenyl group" is referred to, it is sufficient that the number of iodine atoms bonded to the benzene ring is one or more.

[0053] Specific examples of the first structural unit include structural units represented by the following formulas: However, the first structural unit is not limited to these specific examples.

[0054] The content of the first structural unit in the polymer (A) is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total amount of structural units contained in the polymer (A). The content of the first structural unit is preferably 40 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less, based on the total amount of structural units contained in the polymer (A). By keeping the content of the first structural unit within the above range, the sensitivity and CDU performance of the composition can be maintained at a good level, and the process window can be expanded.

[0055] (Second structural unit) The second structural unit has an aromatic ring and a hydroxyl group bonded to the aromatic ring. When the polymer (A) contains the second structural unit, the composition can be preferably used in pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beams or EUV.

[0056] In the above formula (2), R ３ is preferably a hydrogen atom or a methyl group from the viewpoint of copolymerizability of the monomer that provides the second structural unit.

[0057] A １ is a group obtained by removing (n1+n2+1) hydrogen atoms from the ring portion of a substituted or unsubstituted aromatic ring. The aromatic ring is preferably an aromatic hydrocarbon ring, such as a benzene ring, a naphthalene ring, an anthracene ring, or a phenanthrene ring. From the viewpoint of ease of synthesis of a monomer that provides the second structural unit and sensitivity, A １The aromatic ring contained in the second structural unit is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring. The position of the hydroxyl group bonded to the aromatic ring is not particularly limited. For example, when the second structural unit has a hydroxyl group bonded to a benzene ring, the bonding position of the hydroxyl group on the benzene ring in the second structural unit may be any of the ortho-position, meta-position, and para-position relative to other groups.

[0058] R ４ is a group other than a hydroxyl group, and may be a substituent that does not have an acid-dissociable group. ４ Specific examples of ２ and R ２Ａ Specific examples of the groups exemplified above include groups other than a hydroxyl group. n1 is preferably 1 to 3, and more preferably 1 or 2. n2 is preferably 0 to 5, and more preferably 0 to 2, and even more preferably 0 or 1.

[0059] Specific examples of the second structural unit include structural units represented by the following formulae: However, the second structural unit is not limited to these specific examples. (In the formula, R ３ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0060] In the polymer (A), the content of the second structural unit is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on the total amount of structural units contained in the polymer (A). Furthermore, the content of the second structural unit is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, based on the total amount of structural units contained in the polymer (A). By setting the content of the second structural unit within the above range, the CDU performance of the present composition can be made even better.

[0061] (Third Structural Unit) The third structural unit has an acid-dissociable group. The third structural unit is introduced into the polymer (A) together with the first structural unit in order to adjust the sensitivity of the polymer (A) and its solubility in a developer. The acid-dissociable group of the third structural unit is a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxyl group, and may be a group that is eliminated by the action of an acid. However, the third structural unit differs from the first structural unit in that it does not have either an acenaphthylene skeleton or an indene skeleton, and differs from the second structural unit in that it has an acid-dissociable group. The polymer (A) may contain a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring. In this specification, a structural unit having an acid-dissociable group and a hydroxyl group bonded to an aromatic ring is classified as a third structural unit.

[0062] The third structural unit is not particularly limited as long as it has an acid-dissociable group and is different from the first structural unit and the second structural unit. Examples of the third structural unit include a structural unit represented by the following formula (3-1) (hereinafter also referred to as "structural unit (3A)"), a structural unit represented by the following formula (3-2) (hereinafter also referred to as "structural unit (3B)"), and a structural unit represented by the following formula (3-3) (hereinafter also referred to as "structural unit (3C)"). (In formula (3-1), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ２ R is a divalent chain organic group or an alicyclic hydrocarbon group. ３１ is a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. ３２ and R ３３ are each independently a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which R is bonded. ３１ When is a hydrogen atom, R ３２ and R ３３or both of which are, independently of each other, a substituted or unsubstituted monovalent alicyclic unsaturated hydrocarbon group, a substituted or unsubstituted monovalent aromatic hydrocarbon group, or a monovalent aromatic heterocyclic group, or R ３２ and R ３３ are aligned with each other and R ３２ and R ３３ represents an alicyclic unsaturated hydrocarbon structure having 3 to 20 carbon atoms, which is formed together with the carbon atom to which it is bonded. g1 is 0 or 1. In formula (3-2), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ３ represents a single bond, -O-, -CO-, * ２ -COO- or * ２ -CONH-. ２ " represents a bond to the main chain. ３４ , R ３５ and R ３６ are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ２８ is -OR ３４ R ３５ R ３６ g2 is an integer of 0 to 4. In formula (3-3), R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ４ represents a single bond, -O-, -CO-, * ３ -COO- or * ３ -CONH-. ３ " represents a bond to the main chain. ３７ R is a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms. ３８ and R ３９ are each independently a hydrogen atom, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, or a substituted or unsubstituted monovalent oxyhydrocarbon group having 1 to 20 carbon atoms, or R ３８ and R ３９ are aligned with each other and R ３８ and R３９ represents an alicyclic hydrocarbon structure having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded. ２９ Is -COOR ３７ R ３８ R ３９ g3 is an integer of 0 to 4.

[0063] In the above formula (3-1), R ３０ In view of the copolymerizability of the monomer that gives the structural unit (3A), R is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. ３０ is preferably a hydrogen atom from the viewpoint of copolymerizability of the monomer that gives the structural unit (3B). ３０ is preferably a hydrogen atom or a methyl group. ３ Or L in formula (3-3) ４ is preferably a single bond, —COO— or —CONH—.

[0064] L in the above formula (3-1) ２ The divalent chain organic group represented by the formula (I) includes a linear or branched saturated hydrocarbon group having 1 to 20 carbon atoms, a linear or branched saturated hydrocarbon group in which a methylene group is replaced with a heteroatom-containing group (for example, -O-, -S-, -CO-, -COO-, -NH-, -NHCO-, -SO ２ -), and a divalent group having 2 to 20 carbon atoms. ２ Specific and preferred examples of the divalent alicyclic hydrocarbon group represented by the formula (r-1) include R ２１ ~R ２３ Examples of the monovalent alicyclic hydrocarbon group include groups in which one hydrogen atom has been removed from the groups exemplified as the monovalent alicyclic hydrocarbon group represented by the formula: ２ is preferably a chain organic group.

[0065] R in the above formulas (3-1) to (3-3) ３１ ~R ３３ , R ３４ ~R ３６ or R ３７ ~R ３９ Specific examples of the group represented by the formula (r-1) include R ２１ ~R ２３In addition, the R ２８ , R in the above formula (3-3) ２９ Specific examples of R in the above formula (1-1) and formula (1-2) include ２ and R in the above formula (1A-1) and formula (1A-2) ２Ａ Specific examples of g2 and g3 include the same groups as those exemplified above. Each of g2 and g3 is preferably 0 to 2.

[0066] In terms of being able to improve the sensitivity and CDU performance of the present composition in a well-balanced manner and to widen the process window, it is preferable that at least a part of the third structural units contained in the polymer (A) have an iodine atom. From the viewpoint of sufficiently enhancing the effect of improving the sensitivity of the present composition, it is preferable that the iodine atom in the third structural unit is bonded to an aromatic ring. Furthermore, from the viewpoint of further enhancing the effect of improving CDU performance, it is more preferable that the acid-dissociable group in the third structural unit has an aromatic ring, and that the iodine atom is bonded to the aromatic ring. Specifically, as the third structural unit, R in the above formula (3-1) ３１ is a structural unit in which R is an iodophenyl group or an iodonaphthyl group, ３４ is an iodophenyl group or an iodonaphthyl group, and R ３７ It is preferable that the compound contains at least one structural unit in which the structural unit is an iodophenyl group or an iodonaphthyl group.

[0067] Specific examples of the structural unit (3A) among the third structural units include structural units represented by the following formula. However, the third structural unit is not limited to the specific examples shown below. In the formula, R ３０ is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0068] Specific examples of the structural unit (3B) include structural units represented by the following formulas:

[0069] Specific examples of the structural unit (3C) include structural units represented by the following formulas:

[0070] In the polymer (A), the content of the third structural unit is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of structural units contained in the polymer (A). Furthermore, the content of the third structural unit is preferably 60 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less, based on the total amount of structural units contained in the polymer (A). By setting the content of the third structural unit within the above range, the difference in dissolution rate in a developer between an exposed portion and an unexposed portion can be appropriately increased while maintaining good sensitivity of the composition, thereby improving the CDU performance of the composition.

[0071] In the polymer (A), the total proportion of the structural units having an acid-dissociable group among the first structural units and the third structural units is preferably less than 50 mol% relative to the total amount of structural units contained in the polymer (A). By setting the content ratio of the acid-dissociable group contained in the polymer (A) within the above range, the process window can be sufficiently widened. From the viewpoint of preventing the process window from narrowing, the total proportion of the structural units having an acid-dissociable group among the first structural units and the third structural units is preferably 30 mol% or more, more preferably 40 mol% or more, relative to the total amount of structural units contained in the polymer (A).

[0072] (Fourth Structural Unit) The fourth structural unit is a structural unit derived from a radiation-sensitive onium salt. Specifically, it is a structural unit derived from a monomer having an onium salt structure formed by a radiation-sensitive onium cation and an organic anion. The fourth structural unit is thought to be formed by the radiation-sensitive onium cation being decomposed by the action of radiation to liberate an organic anion, which then bonds with hydrogen abstracted from components contained in the composition (e.g., a radiation-sensitive acid generator, an acid diffusion controller, a solvent, etc.) to generate an acid derived from the organic anion. Examples of the organic anion include a sulfonate anion and a carboxylate anion.

[0073] When the organic anion in the fourth structural unit is a sulfonate anion, the fourth structural unit is considered to function primarily as a radiation-sensitive acid generator by generating a strong acid that induces dissociation of the acid-dissociable group under normal conditions. On the other hand, when the organic anion in the fourth structural unit is a carboxylate anion, the fourth structural unit is considered to function primarily as an acid diffusion controller by generating a weak acid that does not induce dissociation of the acid-dissociable group under normal conditions. Here, "normal conditions" refers to conditions in which post-exposure baking (PEB) is performed at 110°C for 60 seconds.

[0074] The fourth structural unit is typically a structural unit derived from a monomer having a radiation-sensitive onium cation, an organic anion, and a group participating in polymerization. ３ － Ya-COO － ) may be bonded to the main chain of the polymer via a linking group, and the radiation-sensitive onium cation may form a counter ion. Alternatively, the radiation-sensitive onium cation may be bonded to the main chain of the polymer via a linking group, and the organic anion may form a counter ion. In order to further improve the CDU performance of the present composition, it is preferable that the fourth structural unit be bonded to the main chain of the polymer via a linking group, and that the organic anion be a sulfonate anion (—SO ３ － ) is more preferably bonded to the main chain of the polymer via a linking group.

[0075] The radiation-sensitive cation in the fourth structural unit is preferably a sulfonium cation or an iodonium cation, more preferably a triarylsulfonium cation or a diaryliodonium cation, from the viewpoint of enhancing the sensitivity of the present composition. From the viewpoint of further enhancing the sensitivity of the present composition, the aromatic ring (i.e., S ＋ or I ＋ Preferably, at least one of an iodo group, a fluoro group, and a fluoroalkyl group is bonded to the aromatic ring bonded to the aromatic ring. The fluoroalkyl group is preferably a trifluoromethyl group.

[0076] It is preferable that at least a portion of the fourth structural units contained in the polymer (A) have an iodo group in the structural unit, since this can further increase the sensitivity while maintaining good CDU performance of the present composition. When the fourth structural unit has an iodo group, it is preferable that the iodo group is bonded to an aromatic ring. Furthermore, when the fourth structural unit has an iodo group, the radiation-sensitive onium cation may have an iodo group, the organic anion may have an iodo group, or both the radiation-sensitive onium cation and the organic anion may have an iodo group.

[0077] Specific examples of the fourth structural unit include structural units represented by the following formulas: However, the fourth structural unit is not limited to these specific examples. (In the formula, R ３０ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ＋ is a radiation-sensitive onium cation. － is a sulfonate anion or a carboxylate anion.

[0078] When the polymer (A) contains a fourth structural unit (i.e., when it is a polymer (A2)), the content of the fourth structural unit in the polymer (A) is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of structural units contained in the polymer (A). Furthermore, the content of the fourth structural unit in the polymer (A) is preferably 25 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (A). By setting the content of the fourth structural unit within the above range, the CDU performance of the composition can be appropriately improved and the process window can be widened.

[0079] Examples of other structural units contained in the polymer (A) include the following fifth structural unit and sixth structural unit.

[0080] (Fifth Structural Unit) The fifth structural unit is a structural unit having a lactone structure, a cyclic carbonate structure, a sultone structure, or a ring structure formed by combining two or more of these (excluding those corresponding to the first to fourth structural units).

[0081] Specific examples of the fifth structural unit include structural units represented by the following formulas: However, the fifth structural unit is not limited to these specific examples. (In the formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0082] When the polymer (A) contains the fifth structural unit, the content of the fifth structural unit is preferably 1 mol% or more, more preferably 2 mol% or more, based on the total amount of structural units contained in the polymer (A). The content of the fifth structural unit in the polymer (A) is preferably 30 mol% or less, more preferably 20 mol% or less, and even more preferably 15 mol% or less, based on the total amount of structural units contained in the polymer (A).

[0083] (Sixth Structural Unit) The sixth structural unit is a structural unit having an alcoholic hydroxyl group (excluding those corresponding to the first to fifth structural units). By introducing the sixth structural unit into the polymer (A), the effect of suppressing development defects can be enhanced when a resist pattern is formed using the present composition. Here, in this specification, an "alcoholic hydroxyl group" refers to a group having a structure in which a hydroxy group is directly bonded to an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a chain hydrocarbon group or an alicyclic hydrocarbon group.

[0084] The sixth structural unit is preferably a structural unit derived from an unsaturated monomer having an alcoholic hydroxyl group. The structure of the unsaturated monomer that provides the sixth structural unit is not particularly limited. Specific examples of the sixth structural unit include structural units represented by the following formulas. However, the sixth structural unit is not limited to these specific examples. (In the formula, R Ａ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0085] When the polymer (A) contains the sixth structural unit, from the viewpoint of enhancing the effect of suppressing development defects in the resist pattern, the content of the sixth structural unit is preferably 1 mol% or more, more preferably 3 mol% or more, based on the total amount of structural units contained in the polymer (A), and the content of the sixth structural unit is preferably 30 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (A).

[0086] In addition to the above, other structural units contained in the polymer (A) include, for example, structural units containing a cyano group, a nitro group, or a sulfonamide group (specifically, a structural unit derived from 2-cyanomethyladamantan-2-yl(meth)acrylate); structural units containing a non-acid-dissociable hydrocarbon group (specifically, a structural unit derived from styrene or a halogenated styrene (e.g., a styrene unit, a bromostyrene unit), a structural unit derived from vinylnaphthalene, a structural unit derived from n-pentyl(meth)acrylate, etc.). The content ratio of these structural units can be appropriately set depending on each structural unit, as long as the effects of the present invention are not impaired.

[0087] From the viewpoint of obtaining a radiation-sensitive composition having excellent sensitivity, the polymer (A) preferably contains an iodine atom. When the polymer (A) contains an iodine atom, only one of the first to sixth structural units described above may contain an iodine atom, or two or more of them may contain an iodine atom. Furthermore, for example, when the first structural unit in the polymer (A) contains an iodine atom, some of the first structural units contained in the polymer (A) may contain an iodine atom, or all of the first structural units contained in the polymer (A) may contain an iodine atom.

[0088] Among these, it is preferable that at least one selected from the group consisting of the first structural unit and the third structural unit in the polymer (A) contains an iodine atom, since this can further increase the difference in solubility in a developer between the exposed and unexposed areas, thereby further widening the process window of the radiation-sensitive composition. Furthermore, it is preferable that the polymer (A) contains an acid-dissociable group having an iodine atom, since this can fully achieve the effect of widening the process window. Furthermore, it is preferable that the polymer (A) contains a polymer (A2), and the fourth structural unit in the polymer (A2) contains an iodine atom, since this can further increase the sensitivity of the composition.

[0089] The weight average molecular weight (Mw) of the polymer (A) measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of the polymer (A) is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and even more preferably 15,000 or less. By setting the Mw of the polymer (A) within the above range, the coatability of the composition can be improved and development defects can be sufficiently suppressed, which is advantageous.

[0090] The ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer (A) measured by GPC (Mw / Mn, hereinafter also referred to as "dispersity") is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. Mw / Mn is usually 1.0 or more.

[0091] The polymer (A) is preferably blended into the composition as at least a part of the base resin, and the content of the polymer (A) in the composition is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 85% by mass or more, based on the total amount of solids contained in the composition.

[0092] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide each structural unit in an appropriate solvent using a known radical polymerization initiator. Examples of the radical polymerization initiator include azo radical initiators (e.g., azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)), peroxide radical initiators (e.g., benzoyl peroxide), and the like. Examples of the solvent used in the polymerization include linear alkanes, cycloalkanes, aromatic hydrocarbons, halogenated hydrocarbons, saturated carboxylic acid esters, ketones, ethers, and alcohols. The reaction temperature in the polymerization is preferably 40 to 150°C, more preferably 50 to 120°C. The reaction time is preferably 1 to 48 hours, more preferably 2 to 24 hours.

[0093] <Polymer (E)> The polymer (E) is preferably blended in the present composition as one or both of the high fluorine content polymer and the base resin.

[0094] (High-fluorine content polymer) The high-fluorine content polymer is a polymer having a higher mass content of fluorine atoms than the polymer (A). The high-fluorine content polymer may be a polymer containing a structural unit having a fluorine atom (structural unit (f)) and the structural unit (b1) (i.e., polymer (E1)), or may be a polymer containing the structural unit (f) but not the structural unit (b1) (i.e., polymer (E2)).

[0095] When the high-fluorine content polymer is polymer (E1), specific examples of the structural unit (b1) include the same structural units as those exemplified in the description of the fourth structural unit that may be contained in polymer (A). In polymer (E1), the content of the structural unit (b1) is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of structural units contained in polymer (E1). Furthermore, the content of the structural unit (b1) in polymer (E1) is preferably 25 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in polymer (E1).

[0096] The fluorine atom content of the high fluorine content polymer is not particularly limited as long as it is larger than that of the polymer (A). The fluorine atom content of the high fluorine content polymer is preferably 1% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more. The fluorine atom content of the high fluorine content polymer is preferably 60% by mass or less, more preferably 40% by mass or less. The fluorine atom content (% by mass) of the polymer is １３ The polymer structure can be determined by C-NMR spectrum measurement or the like, and the amount can be calculated from the structure.

[0097] Examples of the structural unit (f) contained in the high fluorine content polymer include the structural unit (f1) and the structural unit (f2) shown below. The high fluorine content polymer may have either the structural unit (f1) or the structural unit (f2) as the structural unit (f), or may have both the structural unit (f1) and the structural unit (f2).

[0098] Structural unit (f1) The structural unit (f1) is a structural unit represented by the following formula (9-1): The fluorine atom content of the high fluorine content polymer can be adjusted by adjusting the content ratio of the structural unit (f1) in the high fluorine content polymer. (In formula (9-1), R Ｃ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, —COO—, or —SO ２ -O-NH-, -CONH- or -O-CO-NH-. Ｅ 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.

[0099] In the above formula (9-1), R C From the viewpoint of copolymerizability of the monomer that provides the structural unit (f1), G is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. From the viewpoint of copolymerizability of the monomer that provides the structural unit (f1), G is preferably a single bond or —COO—, and more preferably —COO—.

[0100] R ＥExamples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (R) 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. E Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic alicyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. Ｅ is preferably a monovalent fluorinated chain hydrocarbon group, more preferably a monovalent fluorinated alkyl group, and even more preferably a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group or a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0101] When the high-fluorine content polymer contains the structural unit (f1), the content of the structural unit (f1) is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on the total amount of structural units contained in the high-fluorine content polymer. The content of the structural unit (f1) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on the total amount of structural units contained in the high-fluorine content polymer. By setting the content of the structural unit (f1) 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. This can further improve the water repellency of the resist film during immersion exposure.

[0102] Structural unit (f2) The structural unit (f2) is a structural unit represented by the following formula (9-2): When the high fluorine content polymer contains the structural unit (f2), the solubility of the high fluorine content polymer in an alkaline developer is improved, thereby further suppressing the occurrence of development defects. (In formula (9-2), R Ｆ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. ５９ is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), or R ６０is a group in which an oxygen atom, a sulfur atom, —NR′—, a carbonyl group, —CO—O—, or —CO—NH— is bonded to the terminal of the R ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １２ represents a single bond, a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. １１ represents an oxygen atom, —NR″—, —CO—O—*, or —SO ２ -O-*. R" is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" is R ６１ The binding site that binds to R ６１ is a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms. s is an integer of 1 to 3. However, when s is 2 or 3, multiple R ６０ , X １２ , A １１ and R ６１ are the same or different.)

[0103] The structural unit (f2) can be divided into a case where it has an alkali-soluble group and a case where it has a group that dissociates under the action of an alkali to increase its solubility in an alkaline developer (hereinafter simply referred to as an "alkali-dissociable group"). In this specification, "alkali-soluble" means that it is soluble in a 2.38 mass% aqueous solution of tetramethylammonium hydroxide (TMAH) at 23°C. The "alkali-dissociable group" means a group that substitutes a hydrogen atom of an acid group such as a carboxy group or a hydroxyl group, and that is dissociated in a 2.38 mass% aqueous solution of TMAH at 23°C for 1 minute.

[0104] When the structural unit (f2) has an alkali-soluble group, R ６１ is a hydrogen atom, and A １１ represents an oxygen atom, —COO—*, or —SO ２ O-*. "*" is R ６１ indicates the binding site to X １２ represents a single bond, a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. １１ is an oxygen atom, X １２ A １１is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R ６０ , X １２ , A １１ and R ６１ When the structural unit (f2) has an alkali-soluble group, the affinity for an alkali developer can be increased, and development defects can be suppressed.

[0105] When the structural unit (f2) has an alkali-dissociable group, R ６１ is a monovalent organic group having 1 to 30 carbon atoms, and A １１ is an oxygen atom, —NR″—, —COO—*, or —SO ２ O-*. "*" is R ６１ indicates the binding site to X １２ is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ６０ is a single bond or a divalent organic group having 1 to 20 carbon atoms. １１ -COO-* or -SO ２ If O-*, then X １２ or R ６１ Is A １１ A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. １１ is an oxygen atom, X １２ or R ６０ is a single bond, and R ５９ is a hydrocarbon group having 1 to 20 carbon atoms. ６０ A carbonyl group is bonded to the end of the R ６１ is an organic group having a fluorine atom. When s is 2 or 3, a plurality of R ６０ , X １２ , A １１ and R ６１ are the same or different. When the structural unit (f2) has an alkali dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. This can increase affinity to the developer and more efficiently suppress development defects. Examples of the structural unit (f2) having an alkali dissociable group include A１１ is -COO-*, and R ６１ or X １２ It is particularly preferred that both of them have a fluorine atom.

[0106] When the high-fluorine content polymer contains the structural unit (f2), the content of the structural unit (f2) is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, based on the total amount of structural units contained in the high-fluorine content polymer. Furthermore, the content of the structural unit (f2) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on the total amount of structural units contained in the high-fluorine content polymer. By setting the content of the structural unit (f2) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0107] In addition to the structural unit (f1) and the structural unit (f2), the high fluorine content polymer may also contain a structural unit having an acid-dissociable group (i.e., the structural unit (b3)) or a structural unit having an alicyclic hydrocarbon structure represented by the following formula (10) (hereinafter also referred to as "structural unit (g)"). (In the above formula (10), R Ｇ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｇ２ is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0108] When the high-fluorine content polymer contains the structural unit (g), the content of the structural unit (g) is preferably 10 mol % or more, more preferably 20 mol % or more, and even more preferably 30 mol % or more, based on the total amount of structural units contained in the high-fluorine content polymer. The content of the structural unit (g) is preferably 70 mol % or less, more preferably 60 mol % or less, and even more preferably 50 mol % or less, based on the total amount of structural units contained in the high-fluorine content polymer.

[0109] The Mw of the high fluorine content polymer measured by GPC is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of the high fluorine content polymer is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 20,000 or less. The polydispersity (Mw / Mn) of the high fluorine content polymer measured by GPC, which is expressed as the ratio of Mn to Mw, is preferably 1.0 or more and 5.0 or less, and more preferably 1.0 or more and 3.0 or less.

[0110] When the present composition contains a high-fluorine-containing polymer, the content of the high-fluorine-containing polymer in the present composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of polymer (A). The content of the high-fluorine-containing polymer is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, per 100 parts by mass of polymer (A).

[0111] (Base Resin) The polymer (E) as the base resin may be a polymer containing the structural unit (b1) (i.e., polymer (E1)), or may be a polymer not containing the structural unit (b1) (i.e., polymer (E2)). The polymer (E) as the base resin preferably contains a structural unit having an aromatic ring and a hydroxyl group bonded to the aromatic ring (i.e., structural unit (b2)), and a structural unit having an acid-dissociable group (i.e., structural unit (b3)). Specific examples of the structural unit (b2) include the same structural units as those shown as specific examples of the second structural unit in the polymer (A). Specific examples of the structural unit (b3) include the same structural units as those shown as specific examples of the third structural unit in the polymer (A).

[0112] The content of the structural unit (b2) in the polymer (E) as the base resin is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on the total amount of structural units contained in the polymer (E), and is preferably 75 mol% or less, more preferably 65 mol% or less, based on the total amount of structural units contained in the polymer (E).

[0113] The content of the structural unit (b3) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of structural units contained in the polymer (E) as the base resin, and is preferably 60 mol% or less, more preferably 55 mol% or less, based on the total amount of structural units contained in the polymer (E).

[0114] Furthermore, when the polymer (E) as the base resin is the polymer (E1), specific examples of the structural unit (b1) include the same structural units as those exemplified in the description of the fourth structural unit that the polymer (A) may contain. In the polymer (E1), the content of the structural unit (b1) is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 5 mol% or more, based on the total amount of structural units contained in the polymer (E1). Furthermore, the content of the structural unit (b1) in the polymer (E1) as the base resin is preferably 25 mol% or less, more preferably 20 mol% or less, based on the total amount of structural units contained in the polymer (E1).

[0115] When the present composition contains polymer (E) as a base resin, the content of polymer (E) is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, per 100 parts by mass of polymer (A).

[0116] <Radiation-Sensitive Onium Salt (C)> From the viewpoint of ensuring high sensitivity and excellent CDU performance, the present composition preferably contains a radiation-sensitive onium salt (C). That is, the present composition preferably satisfies the third requirement. In particular, when the present composition contains at least an acid diffusion controller as the radiation-sensitive onium salt (C), the effect of widening the process window can be further enhanced. Specifically, the present composition preferably contains, as the radiation-sensitive onium salt (C), a first radiation-sensitive onium salt and a second radiation-sensitive onium salt that generates an acid with a lower acidity than the first radiation-sensitive onium salt, or the present composition preferably contains a polymer (A2) and a radiation-sensitive onium salt (C), and the radiation-sensitive onium salt (C) is a component that generates an acid with a lower acidity than the monomer that provides the fourth structural unit in the polymer (A2). In the above description, the "first radiation-sensitive onium salt" corresponds to the acid generator, and the "second radiation-sensitive onium salt" corresponds to the acid diffusion controller.

[0117] Acid Generator There are no particular restrictions on the type of acid generator to be incorporated into the composition, and any known radiation-sensitive acid generator used in resist pattern formation can be used as appropriate. The acid generator is preferably a compound that generates, under the above-mentioned normal conditions, an acid in the composition that is more acidic than the acid generated by the acid diffusion controller (preferably a strong acid such as a sulfonic acid, an imidic acid, or a methide acid), thereby inducing dissociation of the acid-dissociable group.

[0118] From the viewpoint of increasing the sensitivity of the present composition and forming a resist film with excellent lithography performance, the acid generator preferably has a sulfonium cation or an iodonium cation as the radiation-sensitive onium cation, and more preferably has an arylsulfonium cation or an aryliodonium cation. Specific examples of the radiation-sensitive cation contained in the acid generator include cations represented by the following formula (4), cations represented by the following formula (5), and cations represented by the following formula (6). (In formula (4), R １ａ and R ２ａ are each independently a monovalent substituent, or R １ａ and R２ａ are combined together to represent a single bond or a divalent group connecting the rings to which they are attached. ３ａ is a monovalent substituent. a1 and a2 are each independently an integer of 0 to 5. a3 is an integer of 0 to (2×r+5). r is 0 or 1. In formula (5), R ４ａ and R ５ａ are each independently a monovalent substituent. a4 and a5 are each independently an integer of 0 to 5. In formula (6), a6 is an integer of 0 to 7. When a6 is 1, R ６ａ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group. ６ａ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group, or a plurality of R ６ａ When two of the groups are combined together, they represent a ring structure having 4 to 20 ring members, which is formed together with the carbon atoms to which they are attached. a7 is an integer of 0 to 6. When a7 is 1, R ７ａ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogen group. ７ａ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogen group, or a plurality of R ７ａ Two of these are combined together to form a ring structure having 3 to 20 ring members together with the carbon atoms to which they are attached. t1 is an integer of 0 to 3. R ８ａ is a single bond or a divalent organic group having 1 to 20 carbon atoms. t2 is 0 or 1.

[0119] In the above formulas (4) and (5), R １ａ , R ２ａ , R ３ａ , R ４ａ and R ５ａ (Hereinafter referred to as “R １ａ ~R ５ａ") include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkyloxy group, an ester group, an alkylsulfonyl group, a cycloalkylsulfonyl group, a hydroxy group, a carboxy group, a cyano group, and a nitro group.

[0120] R １ａ ~R ５ａ The alkyl group represented by the formula (I) may be linear or branched. The alkyl group preferably has 1 to 10 carbon atoms. １ａ ~R ５ａ The alkyl group represented by the formula (I) preferably has 1 to 5 carbon atoms, and more preferably is a methyl group, an ethyl group, an n-butyl group, or a t-butyl group. １ａ ~R ５ａ Specific examples of when is an alkoxy group include groups having the alkyl group exemplified above in the alkyl group moiety that constitutes the alkoxy group. The alkoxy group is preferably a methoxy group, an ethoxy group, an n-propoxy group, or an n-butoxy group.

[0121] R １ａ ~R ５ａ The cycloalkyl group represented by the formula (I) may be either monocyclic or polycyclic. Among these, examples of monocyclic cycloalkyl groups include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cyclooctyl group. Examples of polycyclic cycloalkyl groups include a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. R １ａ ~R ５ａ Specific examples of when R is a cycloalkyloxy group include groups having the above-mentioned cycloalkyl groups in the cycloalkyl group moiety that constitutes the cycloalkyloxy group. １ａ ~R ５ａ The cycloalkyloxy group represented by the following formula is preferably a cyclopentyloxy group or a cyclohexyloxy group.

[0122] R １ａ ~R ５ａWhen has a substituent, examples of the substituent include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a hydroxy group, a carboxy group, a cyano group, a nitro group, and an alkoxy group having 1 to 5 carbon atoms.

[0123] R １ａ ~R ５ａ When R is an ester group (—COOR), examples of the hydrocarbon portion (R) of the ester group include the substituted or unsubstituted alkyl groups or substituted or unsubstituted cycloalkyl groups exemplified above. １ａ ~R ５ａ is an ester group, R １ａ ~R ５ａ is preferably a methoxycarbonyl group, an ethoxycarbonyl group, or an n-butoxycarbonyl group. １ａ ~R ５ａ When R is an alkylsulfonyl group, examples of the alkyl group moiety constituting the alkylsulfonyl group include the substituted or unsubstituted alkyl groups exemplified above. １ａ ~R ５ａ When is a cycloalkylsulfonyl group, the cycloalkyl group moiety constituting the cycloalkylsulfonyl group includes the substituted or unsubstituted cycloalkyl groups exemplified above.

[0124] R １ａ and R ２ａ When these are combined together to represent a divalent group connecting the rings to which they are bonded, examples of the divalent group include -COO-, -OCO-, -CO-, -O-, -SO-, and -SO ２ -, -S-, an alkanediyl group having 1 to 3 carbon atoms, an alkenediyl group having 2 or 3 carbon atoms, -O-, -S-, -COO-, -OCO-, -CO-, -SO-, or -SO between the carbon-carbon bonds of the ethylene group ２ Among these, groups having R １ａ and R ２ａ is preferably a single bond connecting the rings, or forms —O— or —S—.

[0125] Each of a1, a2, and a3 is preferably an integer of 0 to 2. １ａ, R ２ａ and R ３ａ At least one of a4 and a5 is preferably a fluorine atom, an iodine atom, or a trifluoromethyl group. Each of a4 and a5 is preferably an integer of 0 to 2. ４ａ and R ５ａ At least one of the groups is preferably a fluorine atom, an iodine atom, or a trifluoromethyl group.

[0126] In the above formula (6), R ６ａ and R ７ａ The monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) includes a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, -OR ｋ , -COOR ｋ , —O—CO—R ｋ , -O-R ｋｋ -COOR ｋ , -R ｋｋ -CO-R ｋ , -OSO ２ -R ｋ or -SO ２ -R ｋ etc. ｋ is a monovalent hydrocarbon group having 1 to 10 carbon atoms. ｋｋ is a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include the same groups as those exemplified in the above formula (r-1). ６ａ and R ７ａ In the above, examples of the substituents that substitute hydrogen atoms of the hydrocarbon group include the above R １ａ ~R ５ａ Examples of the substituents that the group represented by the formula (R) has include the same groups as those exemplified above. ８ａ Examples of the divalent organic group represented by the formula: ６ａ and R ７ａ Examples of such groups include groups in which one hydrogen atom has been removed from the monovalent organic groups having 1 to 20 carbon atoms exemplified above.

[0127] R ６ａ and R ７ａ is a linear or branched monovalent alkyl group, a monovalent fluoroalkyl group, a monovalent aromatic hydrocarbon group, or —OSO２ -R ｋ or -SO ２ -R ｋ a6 is preferably an integer of 0 to 2, more preferably 0 or 1. a7 is preferably an integer of 0 to 2, more preferably 0 or 1. t2 is preferably 0. t1 is preferably 2 or 3.

[0128] Specific examples of the radiation-sensitive onium cation include cations represented by the following formulas: However, the radiation-sensitive onium cation is not limited to these specific examples.

[0129] The organic anion contained in the acid generator is not particularly limited. In terms of increasing the sensitivity of the present composition, a sulfonate anion, an imide anion, or a methide anion is preferred. For example, specific examples of sulfonate anions include anions represented by the following formula:

[0130]

[0131]

[0132] When an acid generator is incorporated into the composition, the content of the acid generator is preferably 1 part by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of polymer (A), from the viewpoint of fully obtaining the effect of improving sensitivity due to the incorporation of the acid generator. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the acid generator, the content of the acid generator is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, per 100 parts by mass of polymer (A).

[0133] Acid Diffusion Controller The acid diffusion controller is a component that can suppress acid-induced chemical reactions in unexposed areas by inhibiting the diffusion of acid generated in the resist film upon exposure of the present composition within the resist film. The acid diffusion controller generates a weak acid upon exposure that does not induce dissociation of acid-dissociable groups under the above-mentioned normal conditions. Adding such an acid diffusion controller to the present composition can improve the CDU performance of the present composition and expand the process window. The acid diffusion controller (hereinafter also referred to as "photodegradable base") having a radiation-sensitive onium cation and an organic anion that is the conjugate base of the acid is preferably an onium salt that generates a carboxylic acid, sulfonic acid, or sulfonamide upon exposure. Furthermore, in terms of forming a resist film with superior lithography performance, an onium salt having a sulfonium cation or an iodonium cation is preferably used as the photodegradable base.

[0134] Specific examples of the radiation-sensitive onium cation contained in the photodecomposable base include the same onium cations as those exemplified as the radiation-sensitive onium cation that may be contained in the acid generator.

[0135] Examples of the organic anion contained in the photodegradable base include anions represented by the following formula:

[0136] When an acid diffusion controller is blended in the composition, the content of the acid diffusion controller is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of polymer (A) from the viewpoint of sufficiently obtaining the effects of improving sensitivity, CDU performance, and process window. Furthermore, from the viewpoint of suppressing the occurrence of development defects due to the acid diffusion controller, the content of the acid diffusion controller is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, per 100 parts by mass of polymer (A).

[0137] When an acid diffusion controller is incorporated into the composition, the content of the acid diffusion controller in the composition is preferably 5 mol % or more, more preferably 10 mol % or more, and even more preferably 20 mol % or more, based on the total amount of the acid generator, the monomer that provides the fourth structural unit in the polymer (A2), and the monomer that provides the structural unit (b1) in the polymer (E1) contained in the composition. Furthermore, the content of the acid diffusion controller is preferably 90 mol % or less, more preferably 80 mol % or less, based on the total amount of the acid generator, the monomer that provides the fourth structural unit in the polymer (A2), and the monomer that provides the structural unit (b1) in the polymer (E1) contained in the composition. By setting the content of the acid diffusion controller within the above range, the CDU performance of the composition can be further improved.

[0138] At least a portion of the radiation-sensitive onium salt (C) blended in the present composition preferably contains an iodine atom, which is preferable in that the CDU performance of the present composition can be further improved and the process window can be widened by incorporating a compound having an iodine atom as the radiation-sensitive onium salt (C) in the present composition.

[0139] When the radiation-sensitive onium salt (C) has an iodine atom, the radiation-sensitive cation or the organic anion of the radiation-sensitive onium salt (C) may have an iodine atom. Alternatively, both the radiation-sensitive cation and the organic anion may have an iodine atom. In the radiation-sensitive onium salt (C), when the organic anion has an iodine atom, this is preferred because it can improve the sensitivity and CDU performance of the composition in a well-balanced manner. Furthermore, when the radiation-sensitive onium cation has an iodine atom, this is preferred because it can further enhance the CDU performance of the composition. Furthermore, radiation-sensitive onium salts composed of a radiation-sensitive cation having an iodine atom and an organic anion are useful because they allow for a high degree of freedom in selecting the radiation-sensitive cation and make it easy to adjust the sensitivity, etc., of the composition. Furthermore, when the radiation-sensitive onium cation has an iodine atom, the radiation-sensitive onium cation may be an iodonium cation or a sulfonium cation having an iodo group.

[0140] When the radiation-sensitive onium salt (C) contains iodine atoms, the number of iodine atoms in the radiation-sensitive onium salt (C) is not particularly limited. The number of iodine atoms per molecule of the iodine-containing radiation-sensitive onium salt (C) may be 1 or more, and preferably 2 or more. From the viewpoints of ease of synthesis and solubility in a developer, the number of iodine atoms per molecule of the radiation-sensitive onium salt (C) is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

[0141] <Other Components> The present composition may further contain components (hereinafter also referred to as "other components") other than the polymer (A), polymer (E), and radiation-sensitive onium salt (C). Examples of other components include the components shown below.

[0142] (Solvent) The solvent is preferably a solvent capable of dissolving or dispersing the components to be blended in the composition, and an organic solvent can be preferably used. Specific examples of the solvent include alcohols, ethers, ketones, amides, esters, and hydrocarbons.

[0143] Examples of alcohols include aliphatic monoalcohols having 1 to 18 carbon atoms, such as 4-methyl-2-pentanol and n-hexanol; alicyclic monoalcohols having 3 to 18 carbon atoms, such as cyclohexanol; polyhydric alcohols having 2 to 18 carbon atoms, such as 1,2-propylene glycol; and partial ethers of polyhydric alcohols having 3 to 19 carbon atoms, such as propylene glycol monomethyl ether. Examples of ethers include dialkyl ethers, such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ethers, such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ethers, such as diphenyl ether and anisole.

[0144] Examples of ketones include chain ketones such as acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, diethyl ketone, methyl isobutyl ketone, 2-heptanone, ethyl n-butyl ketone, methyl n-hexyl ketone, di-isobutyl ketone, and trimethylnonanone; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, acetophenone, and diacetone alcohol. Examples of amides include cyclic amides such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amides such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0145] Examples of esters include monocarboxylic acid esters such as n-butyl acetate, ethyl lactate, and methyl 2-hydroxyisobutyrate; polyhydric alcohol carboxylates such as propylene glycol diacetate; polyhydric alcohol partial ether carboxylates such as propylene glycol monomethyl ether acetate; polycarboxylic acid diesters such as diethyl oxalate; carbonates such as dimethyl carbonate and diethyl carbonate; and cyclic esters such as γ-butyrolactone. Examples of hydrocarbons include aliphatic hydrocarbons having 5 to 12 carbon atoms such as n-pentane and n-hexane; and aromatic hydrocarbons having 6 to 16 carbon atoms such as toluene and xylene.

[0146] Of these, the solvent preferably contains at least one selected from the group consisting of esters and ketones, and more preferably contains at least one selected from the group consisting of polyhydric alcohol partial ether carboxylates and cyclic ketones.

[0147] (Other Optional Components) The present composition may further contain other components other than the solvent (hereinafter also referred to as "other optional components"). Examples of the other optional components include surfactants, alicyclic skeleton-containing compounds (e.g., 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl deoxycholate, etc.), sensitizers, and uneven distribution promoters.

[0148] <Method for producing radiation-sensitive composition> The present composition can be produced, for example, by mixing the polymer (A) and, if necessary, other components such as a solvent in a desired ratio, and filtering the resulting mixture, preferably using a filter (for example, a filter with a pore size of about 0.2 μm). The solids concentration of the present composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. The solids concentration of the present composition is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 5% by mass or less. By setting the solids concentration of the present composition within the above range, good coatability can be achieved, and it is advantageous in that a good resist pattern shape can be obtained.

[0149] The composition thus obtained can be used as a positive pattern-forming composition for forming a pattern using an alkaline developer, or as a negative pattern-forming composition for forming a pattern using a developer containing an organic solvent.

[0150] <<Method of Forming Resist Pattern>> The method of forming a resist pattern according to the present disclosure includes a step of applying the present composition to one surface of a substrate (hereinafter also referred to as a "coating step"), a step of exposing the resist film obtained by the coating step (hereinafter also referred to as an "exposure step"), and a step of developing the resist film exposed by the exposure step (hereinafter also referred to as a "developing step"). Examples of patterns formed by the method of forming a resist pattern according to the present disclosure include a line-and-space pattern and a hole pattern. Because the method of forming a resist pattern according to the present disclosure uses the present composition to form a resist film, it is possible to form a resist pattern that has good sensitivity, good CDU, and good resolution. Each step will be described below.

[0151] [Coating Step] In the coating step, the present composition is applied to one side of a substrate to form a resist film on the substrate. Conventional substrates can be used as the substrate on which the resist film is formed, including, for example, silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as that disclosed in JP-A-59-93448, may be formed on the substrate. Examples of methods for applying the present composition include spin coating, casting coating, and roll coating. After coating, a soft bake (also referred to as SB or pre-bake (PB)) may be performed to volatilize the solvent in the coating. The SB temperature is preferably 60°C or higher, more preferably 80°C or higher. The SB temperature is preferably 140°C or lower, more preferably 120°C or lower. The SB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The SB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter. The average thickness of the resist film formed is preferably 10 to 1,000 nm, and more preferably 20 to 500 nm.

[0152] [Exposure Step] In the exposure step, the resist film obtained in the coating step is exposed. This exposure is carried out by irradiating the resist film with radiation through a photomask, and optionally through an immersion medium such as water. Examples of radiation include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, the radiation irradiated onto the resist film formed using the present composition is preferably far ultraviolet light, EUV, or electron beams, more preferably ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV, or electron beams, even more preferably ArF excimer laser light, EUV, or electron beams, even more preferably EUV or electron beams, and particularly preferably EUV.

[0153] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the exposed portions of the resist film by acid generated from a compound that generates acid upon exposure (such as a radiation-sensitive acid generator). This PEB can increase the difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is preferably 50°C or higher, more preferably 80°C or higher. The PEB temperature is preferably 180°C or lower, more preferably 130°C or lower. The PEB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PEB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter.

[0154] [Development Step] In the development step, the exposed resist film is developed. This allows a desired 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. The development method in the development step may be alkali development or organic solvent development.

[0155] In the case of alkaline development, examples of the developer used for development include an alkaline aqueous solution containing at least one alkaline compound dissolved therein, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, an aqueous TMAH solution is preferred, and a 2.38% by mass TMAH solution is more preferred. In the case of organic solvent development, examples of the developer include one or more organic solvents such as hydrocarbons, ethers, esters, ketones, and alcohols, and solvents containing the above organic solvents.

[0156] 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 developing by piling up the developer on the surface of the substrate by surface tension and leaving it to stand for a certain period of time (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).

[0157] <Polymer and Compound> The present disclosure provides a polymer comprising a first structural unit which is at least one selected from the group consisting of structural units represented by formula (1-1) and structural units represented by formula (1-2), a second structural unit represented by formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit). This polymer allows for the production of a radiation-sensitive composition which has high sensitivity, excellent CDU performance, and a wide process window.

[0158] The present disclosure also provides a compound represented by the following formula (1B-1) and a compound represented by the following formula (1B-2): The compound represented by the following formula (1B-1) and the compound represented by the following formula (1B-2) can be preferably used as at least a part of the monomers constituting a polymer used in forming a resist pattern. (In formula (1B-1) and formula (1B-2), R １Ａ is a monovalent organic group having 6 or more carbon atoms. ２Ａ Is -COOR １Ａ m3 is an integer of 1 to 3. m4 is an integer of 0 to 5, and m3+m4≦6. When m3 is 2 or more, multiple R １Ａ When m4 is 2 or more, a plurality of R ２Ａ are the same or different.)

[0159] In the above formula (1B-1) and formula (1B-2), R １Ａ , R ２Ａ , m3 and m4 are R in the above formula (1A-1) and formula (1A-2), respectively. １Ａ , R ２Ａ , m3 and m4.

[0160] The compound represented by the formula (1B-1) and the compound represented by the formula (1B-2) can be synthesized by appropriately combining standard methods in organic chemistry. As an example of a method for synthesizing the compound represented by the formula (1B-1), a method for synthesizing a compound represented by the formula (1B-1) can be performed by combining the carboxy group of acenaphthylenecarboxylic acid with the group R １Ａ As an example of a method for synthesizing the compound represented by the above formula (1B-2), a method for synthesizing a compound represented by the above formula (1B-3) is to react a carboxy group of an indenecarboxylic acid with a hydroxy group of an alcohol having a group R １Ａ However, the synthesis methods of the compound represented by formula (1B-1) and the compound represented by formula (1B-2) are not limited to those described above.

[0161] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" are by mass unless otherwise specified.

[0162] The methods for measuring the physical properties of the polymer are as follows: [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 (two "G2000HXL", one "G3000HXL", and one "G4000HXL") under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, and column temperature: 40°C, with monodisperse polystyrene as the standard.

[0163] <Synthesis of Compounds> [Synthesis Example 1-1] (Synthesis of Monomer (M-20)) According to the following scheme, a monomer (M-20) that provides a structural unit represented by the above formula (1-1) was synthesized.

[0164] The compound represented by the above formula (PM-20) (100 mmol), N,N-dimethylaminopyridine (10 mmol), t-butyl alcohol (100 mL), and tetrahydrofuran (100 mL) were added to a reaction vessel and stirred at room temperature. Next, a solution of N,N'-dicyclohexylcarbodiimide (110 mmol) in tetrahydrofuran (THF) (100 mL) was added dropwise over 1 hour. After stirring at room temperature, methylene chloride was added and the mixture was filtered, and the solvent in the filtrate was distilled off. The mixture was purified by silica gel column chromatography to obtain a monomer (M-20).

[0165] [Synthesis Examples 1-2 to 1-14] (Synthesis of Monomers (M-21) to (M-33)) Compounds represented by the following formulas (M-21) to (M-33) (monomers (M-21) to (M-33)) were synthesized in the same manner as in Synthesis Example 1-1, except that the raw materials were appropriately changed.

[0166] <Synthesis of Polymer [A]> Polymers (A-1) to (A-37) and (AX-1) to (AX-3) were synthesized as the polymer [A] according to the following method. Compounds represented by the following formulas (M-1) to (M-35) (hereinafter also referred to as "monomers (M-1) to (M-35)") were used in the synthesis of the polymer [A]. In the following synthesis examples, unless otherwise specified, "parts by mass" means the value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means the value when the total number of moles of the monomers used is taken as 100 mol %.

[0167]

[0168]

[0169] Synthesis Examples 2-1 to 2-40 (Synthesis of Polymers (A-1) to (A-37) and (AX-1) to (AX-3)) Each monomer was combined and copolymerized in tetrahydrofuran (THF) solvent. After the reaction was completed, the polymer was isolated and dried to obtain polymers (A-1) to (A-37) and (AX-1) to (AX-3) having the compositions shown in Tables 1 and 2 below. The amount of each monomer used, Mw, and Mw / Mn of the obtained polymers are also shown in Tables 1 and 2.

[0170]

[0171]

[0172] <Synthesis of [E] Additive (High Fluorine Content Polymer)> Monomers (M-36), (M-37), and (F-1) were combined according to the composition 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. Thereafter, the solvent was replaced with propylene glycol monomethyl ether acetate to obtain high fluorine content polymers (E-1) and (E-2) having the compositions shown in Table 3 below. The amount of each monomer used, Mw, and Mw / Mn of the resulting polymers are also shown in Table 3.

[0173]

[0174] <Preparation of Radiation-Sensitive Composition> The acid generator [B], acid diffusion controller [C], and solvent [D] 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 when the mass of the polymer [A] used in the preparation of the radiation-sensitive composition is taken as 100 parts by mass. "mol %" means a value when the number of moles of the acid generator [B] used in the preparation of the radiation-sensitive composition is taken as 100 mol %.

[0175] [B] Acid Generator Compounds represented by the following formulae (B-1) to (B-7) were used as acid generators.

[0176] [C] Acid Diffusion Controller Compounds represented by the following formulae (C-1) to (C-6) were used as acid diffusion controllers.

[0177] [D] Solvent The following organic solvents were used as the [D] solvent: (D-1): Propylene glycol monomethyl ether acetate (D-2): Propylene glycol monomethyl ether

[0178] [Example 1] Preparation of Radiation-Sensitive Composition (R-1) 100 parts by mass of [A] polymer (A-1), 60 parts by mass of [B] acid generator (B-1), [C] acid diffusion controller (C-1) in an amount of 70 mol% relative to (B-1), [E] additive (high fluorine content polymer), 5 parts by mass of [D] additive (D-1), 1,500 parts by mass of [D] solvent (D-2), and 5,500 parts by mass of [D-2] were mixed. The resulting mixture was filtered through a filter with a pore size of 0.2 μm to prepare radiation-sensitive composition (R-1).

[0179] [Examples 2 to 57 and Comparative Examples 1 to 4] Preparation of Radiation-Sensitive Compositions (R-2) to (R-57) and (RX-1) to (RX-4) Radiation-sensitive compositions (R-2) to (R-57) and (RX-1) to (RX-4) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 4 and 5 were used. In (R-28) to (R-31), (R-48), (R-49), (R-57), and (RX-3), (C-1) as the acid diffusion controller [C] was the total amount of (B-1) and the (M-34) component in (A-28) for (R-28) and (R-30); the total amount of (B-1) and the (M-35) component in (A-29) for (R-29) and (R-31); For (R-8), 70 mol % was blended relative to the total amount of the (M-35) component in (AX-3); for (R-49), 70 mol % was blended relative to the total amount of the (M-37) component in (B-1) and (E-2); for (R-57), 70 mol % was blended relative to the total amount of the (M-34) component in (B-1) and (A-37); and for (RX-3), 70 mol % was blended relative to the total amount of the (M-35) component in (B-1) and (AX-3).

[0180]

[0181]

[0182] <Evaluation> Using the radiation-sensitive compositions prepared above, sensitivity, CDU performance, overexposure CDU performance, and underexposure CDU performance were evaluated according to the following methods. The evaluation results are shown in Tables 6 and 7.

[0183] [Sensitivity] Each of the radiation-sensitive compositions shown in Tables 4 and 5 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, on-wafer dimension 50 nm pitch, +20% bias hole pattern mask)). 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).

[0184] [CDU Performance] 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). The smaller the CDU value, the smaller the long-period hole diameter variation (i.e., diameter variation between different holes), indicating better performance. CDU performance was evaluated as "A" (very good) when the CDU value was less than 3.3 nm, "B" (good) when it was 3.3 nm or greater but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or greater.

[0185] [Over-exposure CDU Performance] A 27-nm contact hole pattern was formed using the same procedure as in the [Sensitivity] section above, except that the EUV exposure dose was approximately 1 to 10 mJ higher than 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 calculated 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, indicating better performance. Over-exposure CDU performance was evaluated as "A" (very good) when the over-exposure CDU value was less than 3.3 nm, "B" (good) when it was 3.3 nm or greater but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or greater.

[0186] [Under-exposure CDU Performance] A 23 nm contact hole pattern was formed using the same procedure as in the [Sensitivity] section above, except that the EUV exposure dose was approximately 1 to 10 mJ less 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 calculated and used as the under-exposure CDU (nm). The smaller the under-exposure CDU value, the smaller the hole diameter variation over a long period, indicating better performance. Under-exposure CDU performance was evaluated as "A" (very good) when the under-exposure CDU value was less than 3.3 nm, "B" (good) when it was 3.3 nm or greater but less than 3.6 nm, and "C" (poor) when it was 3.6 nm or greater.

[0187]

[0188]

[0189] As is clear from the results in Tables 6 and 7, the radiation-sensitive compositions of Examples 1 to 57 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 4, and were favorable.

[0190] The radiation-sensitive composition and the method for forming a resist pattern according to the present disclosure can improve sensitivity, CDU performance, overexposure CDU performance, and underexposure CDU performance, thereby widening the process window, and therefore can be suitably used for forming 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 polymer (A) including a first structural unit which is at least one selected from the group consisting of structural units represented by the following formula (1-1) and structural units represented by the following formula (1-2), a second structural unit represented by the following formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit), wherein the composition satisfies one or more of the following first, second, and third requirements: first requirement: the polymer (A) further includes a fourth structural unit derived from a radiation-sensitive onium salt; second requirement: the composition further includes a polymer (E1) which is a polymer different from the polymer (A) and includes a structural unit (b1) derived from a radiation-sensitive onium salt; and third requirement: the composition further includes a non-polymeric radiation-sensitive onium salt (C), wherein at least one selected from the group consisting of the polymer (A), the structural unit (b1) in the polymer (E1), and the radiation-sensitive onium salt (C) contains an iodine atom. (In formula (1-1) and formula (1-2), R １ is a hydrogen atom or a monovalent organic group. ２ Is -COOR １ m1 is an integer of 1 to 3. m2 is an integer of 0 to 5, and m1+m2≦6. When m1 is 2 or more, a plurality of R １ are the same or different. When m2 is 2 or more, a plurality of R ２ are the same or different. In formula (2), R ３ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ represents a single bond, —COO—, or —CONH—. １ is an aromatic ring group. ４ is a substituent that is a group other than a hydroxyl group and does not have an acid-dissociable group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.) 2. The radiation-sensitive composition according to claim 1, wherein the total amount of the structural units having an acid-dissociable group among the first structural units and the third structural units in the polymer (A) is less than 50 mol % based on the total amount of structural units in the polymer (A).

3. The radiation-sensitive composition according to claim 1, which satisfies the third requirement.

4. The radiation-sensitive composition according to claim 3, wherein the radiation-sensitive onium salt (C) includes a compound having an iodine atom.

5. The radiation-sensitive composition according to claim 4, wherein the radiation-sensitive onium salt (C) comprises an onium salt composed of a radiation-sensitive cation having an iodine atom and an organic anion.

6. The radiation-sensitive composition according to claim 1, wherein at least one selected from the group consisting of the first structural unit and the third structural unit in the polymer (A) has an iodine atom.

7. R in the above formula (1-1) and formula (1-2) １ The radiation-sensitive composition according to claim 1 , wherein the number of carbon atoms is 6 or more.

8. R in the above formula (1-1) and formula (1-2) １ The radiation-sensitive composition according to claim 7 , wherein has a cyclic structure.

9. A method for forming a resist pattern, comprising: forming a resist film on a substrate using the radiation-sensitive composition according to any one of claims 1 to 8; exposing the resist film; and developing the exposed resist film.

10. The method for forming a resist pattern according to claim 9, wherein the resist film is exposed using extreme ultraviolet light.

11. A polymer comprising a first structural unit which is at least one type selected from the group consisting of structural units represented by the following formula (1-1) and structural units represented by the following formula (1-2), a second structural unit represented by the following formula (2), and a third structural unit having an acid-dissociable group (excluding the first structural unit and the second structural unit). (In formula (1-1) and formula (1-2), R １ is a hydrogen atom or a monovalent organic group. ２ Is -COOR １ m1 is an integer of 1 to 3. m2 is an integer of 0 to 5, and m1+m2≦6. When m1 is 2 or more, a plurality of R １ are the same or different. When m2 is 2 or more, a plurality of R ２ are the same or different. In formula (2), R ３ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ represents a single bond, —COO—, or —CONH—. １ is an aromatic ring group. ４ is a substituent that is a group other than a hydroxyl group and does not have an acid-dissociable group. n1 is an integer of 1 or more. n2 is an integer of 0 or more. When n2 is 2 or more, a plurality of R ４ are the same or different.) 12. A compound represented by the following formula (1B-1) or formula (1B-2): (In formula (1B-1) and formula (1B-2), R １Ａ is a monovalent organic group having 6 or more carbon atoms. ２Ａ Is -COOR １Ａ m3 is an integer of 1 to 3. m4 is an integer of 0 to 5, and m3+m4≦6. When m3 is 2 or more, multiple R １Ａ are the same or different. When m4 is 2 or more, multiple R ２Ａ are the same or different.) 13. The above R １Ａ The compound of claim 12, wherein has a cyclic structure.

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