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

Abstract

This radiation-sensitive composition contains a polymer which has a structural unit (I) containing an aromatic ring having a substituent and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and in which the solubility in a developing solution changes due to an action of an acid.

Description

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

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

[0002] Radiation-sensitive compositions used in microfabrication by lithography generate an acid in exposed areas when irradiated with radiation such as far ultraviolet rays such as ArF excimer laser light (wavelength 193 nm) and KrF excimer laser light (wavelength 248 nm), electromagnetic waves such as extreme ultraviolet rays (EUV, wavelength 13.5 nm), or charged particle rays such as electron beams, and a chemical reaction initiated by this acid causes a difference in the dissolution rate in a developer between exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The radiation-sensitive composition is required to have good sensitivity to radiation such as extreme ultraviolet rays and electron beams, as well as excellent CDU (Critical Dimension Uniformity) and suppressed occurrence of development defects.

[0004] In response to these requirements, the types and molecular structures of polymers, acid generators, and other components used in radiation-sensitive compositions have been investigated, and combinations thereof have also been investigated in detail (see JP-A-2010-134279, JP-A-2014-224984, JP-A-2016-047815, and JP-A-2021-009357).

[0005] JP 2010-134279 A JP 2014-224984 A JP 2016-047815 A JP 2021-009357 A

[0006] As resist patterns become finer, the level of performance required is becoming higher and higher, and there is a demand for radiation-sensitive compositions that satisfy these requirements.

[0007] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to provide a radiation-sensitive composition and a method for forming a resist pattern that are excellent in sensitivity and CDU and suppress the occurrence of development defects. Another object of the present invention is to provide a polymer that is suitable as a component of the radiation-sensitive composition. A still further object of the present invention is to provide a monomer that is suitable for synthesizing the polymer.

[0008] The invention made to solve the above-mentioned problems provides a radiation-sensitive composition containing a polymer that has a structural unit (I) including a substituted aromatic ring and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and whose solubility in a developer changes upon the action of an acid.

[0009] Another invention made to solve the above-mentioned problems is a method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition described above directly or indirectly to a substrate; exposing the resist film formed by the application; and developing the exposed resist film.

[0010] Yet another invention made to solve the above problems is a polymer having a structural unit represented by the following formula (1a) or (1b): (In formula (1a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａis a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different. In formula (1b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different.)

[0011] Yet another invention made to solve the above problems is a monomer represented by the following formula (2a) or (2b). (In formula (2a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different.２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different. In formula (2b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different.)

[0012] The radiation-sensitive composition of the present invention is excellent in sensitivity and CDU, and the occurrence of development defects is suppressed. According to the method for forming a resist pattern of the present invention, a resist pattern can be formed that is excellent in sensitivity and CDU, and the occurrence of development defects is suppressed. The polymer of the present invention is suitable as a base resin contained in the radiation-sensitive composition. The monomer of the present invention is suitable as a monomer for synthesizing the polymer contained in the radiation-sensitive composition. Therefore, these can be suitably used in the processing of semiconductor devices, which are expected to become even more miniaturized in the future.

[0013] The radiation-sensitive composition, method of forming a resist pattern, polymer and monomer of the present invention will be described in detail below.

[0014] The upper and lower limits in this specification can be any combination of the disclosed numerical values. Furthermore, when a numerical range is indicated using the symbol "to", it means that the numerical range includes the upper and lower limit numerical values. For example, "1 to 20 carbon atoms" means "1 to 20 carbon atoms inclusive."

[0015] <Radiation-Sensitive Composition> The radiation-sensitive composition contains a polymer (hereinafter also referred to as “polymer [A]”) that has a structural unit (I) including a substituted aromatic ring and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and whose solubility in a developer changes upon the action of an acid.

[0016] The polymer [A] includes the following two embodiments: Polymer [A1]: A polymer having a structural unit (Ia) including an aromatic ring having, as a substituent, at least one group selected from the group consisting of a phenolic hydroxyl group, a phenolic hydroxyl group protected by a protecting group, and an iodo group, and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and whose solubility in a developer changes upon the action of an acid; Polymer [A2]: A polymer having a structural unit (Ib) including a structure in which a lactone structure is bonded to a substituted aromatic ring via an oxygen atom or a sulfur atom, and whose solubility in a developer changes upon the action of an acid.

[0017] In this specification, a radiation-sensitive composition containing the polymer [A1] may be referred to as "composition (1)," and a radiation-sensitive composition containing the polymer [A2] may be referred to as "composition (2)."

[0018] The radiation-sensitive composition having the above-described structure exhibits the effects of being excellent in sensitivity and CDU and suppressing the occurrence of development defects. The reason for this is not entirely clear, but is presumed to be, for example, as follows.

[0019] When the radiation-sensitive composition contains the polymer [A1], it is believed that a good balance between sensitivity, CDU, and suppression of development defects can be achieved by containing, in the same structural unit, a phenolic hydroxyl group and a phenolic hydroxyl group protected by a protecting group, which serve as a proton source and improve acid generation efficiency, an iodine group, which improves radiation absorption efficiency, and a lactone structure or the like that reacts with an alkaline developer to hydrophilize the resist film surface.

[0020] When the radiation-sensitive composition contains the polymer [A2], the lactone structure that reacts with an alkaline developer to hydrophilize the surface of the resist film is bonded to an aromatic ring via a short linker such as an oxygen atom or a sulfur atom, which is believed to enable the lactone structure to be introduced without impairing the rigidity of the resist film formed therefrom, thereby suppressing acid diffusion. Furthermore, the aromatic ring has a substituent other than the lactone structure, which is believed to enable functional groups that impart various functionality to be arranged at a high density. These effects combined are believed to enable the radiation-sensitive composition to achieve a good balance between sensitivity, CDU, and suppression of development defects.

[0021] The radiation-sensitive composition typically contains an organic solvent (hereinafter also referred to as "organic solvent [D]"). The radiation-sensitive composition typically contains a radiation-sensitive acid generator. For example, when the polymer [A] has a structural unit containing a group that generates an acid upon the action of radiation, the radiation-sensitive acid generator may be the polymer [A] itself. Furthermore, as a component other than the polymer [A], a radiation-sensitive acid generator (hereinafter also referred to as "acid generator [B]") may be used. The radiation-sensitive composition may also contain an acid diffusion controller. For example, when the polymer [A] has a structural unit containing a group that generates a carboxylic acid upon the action of radiation, the acid diffusion controller may be the polymer [A] itself. Furthermore, as a component other than the polymer [A], an acid diffusion controller (hereinafter also referred to as "acid diffusion controller [C]") may be used. The radiation-sensitive composition may also contain a polymer (hereinafter also referred to as "polymer [F]") having a higher fluorine atom content than the polymer [A]. The radiation-sensitive composition may contain other optional components as long as the effects of the present invention are not impaired.

[0022] The radiation-sensitive composition can be prepared, for example, by mixing (A) the polymer, and, if necessary, (B) the acid generator, (C) the acid diffusion controller, (D) the organic solvent, and (F) the polymer and other optional components in a predetermined ratio, and filtering the resulting mixture through a membrane filter having a pore size of 0.2 μm or less.

[0023] Each component contained in the radiation-sensitive composition will be described below.

[0024] <Polymer [A]> The polymer [A] is a polymer that has a structural unit (I) that includes a substituted aromatic ring and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and whose solubility in a developer changes due to the action of an acid.

[0025] The radiation-sensitive composition may contain one or more types of polymer (A).

[0026] The polymer (A) usually has a structural unit (II) containing an acid-dissociable group. The polymer (A) preferably has a structural unit (III) other than the structural unit (I) that contains a phenolic hydroxyl group.

[0027] The polymer [A] may further have other structural units (hereinafter simply referred to as "other structural units") in addition to the structural units (I) to (III). The polymer [A] may have one or more types of each structural unit.

[0028] The other structural units are structural units other than the above structural units (I) to (III), such as the structural unit (IV) containing a group that generates an acid when exposed to radiation.

[0029] In this specification, the term "structural unit" refers to one of the repeating units obtained by polymerizing a monomer, and is composed of a portion that constitutes a main chain and a side chain. The term "main chain" refers to the longest atomic chain that constitutes a polymer. The term "side chain" refers to an atomic chain other than the main chain that constitutes a polymer.

[0030] The lower limit of the content of the polymer (A) in the radiation-sensitive composition is preferably 50% by mass, more preferably 70% by mass, and even more preferably 80% by mass, based on all components other than the organic solvent (D) contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99% by mass, more preferably 95% by mass.

[0031] The lower limit of the weight average molecular weight (Mw) of the polymer [A], as measured by gel permeation chromatography (GPC) in terms of polystyrene, is preferably 1,000, more preferably 2,000, even more preferably 3,000, and still more preferably 4,000. The upper limit of the Mw is preferably 30,000, more preferably 20,000, and even more preferably 10,000, with 8,000 being preferred and 7,000 being preferred in some cases. By setting the Mw of the polymer [A] within the above range, the coatability of the radiation-sensitive composition can be improved. The Mw of the polymer [A] can be adjusted, for example, by adjusting the type and amount of polymerization initiator used in the synthesis of the polymer [A].

[0032] The upper limit of the ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer (A) as determined by GPC (hereinafter also referred to as "Mw / Mn") is preferably 2.5, more preferably 2.0, and even more preferably 1.9. The lower limit of the ratio is usually 1.0, preferably 1.1, and more preferably 1.2.

[0033] [Method for measuring Mw and Mn] The Mw and Mn of the polymer in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions: GPC columns: two "G2000HXL" columns, one "G3000HXL" column, and one "G4000HXL" column, all manufactured by Tosoh Corporation; column temperature: 40°C; elution solvent: tetrahydrofuran; flow rate: 1.0 mL / min; sample concentration: 1.0 mass%; sample injection amount: 100 μL; detector: differential refractometer; standard material: monodisperse polystyrene.

[0034] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0035] Each structural unit contained in the polymer (A) will be described below.

[0036] [Structural Unit (I)] The structural unit (I) is a structural unit containing a substituted aromatic ring and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. The "substituted aromatic ring" will be described later in the section [Structural Unit (Ib)]. The "lactone structure, cyclic carbonate structure, sultone structure, or a combination thereof" will be described later in the section [Structural Unit (Ia)].

[0037] [Structural Unit (Ia)] The structural unit (Ia) is a structural unit containing at least one group selected from the group consisting of a phenolic hydroxyl group, a phenolic hydroxyl group protected by a protecting group, and an iodo group (hereinafter also referred to as a "group (c)," and a phenolic hydroxyl group and a phenolic hydroxyl group protected by a protecting group are also collectively referred to as "phenolic hydroxyl groups (a)"), and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof (hereinafter also referred to as a "lactone structure (b)").

[0038] The term "phenolic hydroxyl group" refers not only to a hydroxy group directly bonded to a benzene ring, but also to any hydroxy group directly bonded to an aromatic ring. The structural unit (Ia) preferably contains a substituted or unsubstituted aromatic ring to which the group (c) is bonded. The term "unsubstituted aromatic ring to which the group (c) is bonded" refers to an aromatic ring that does not have any substituents other than the group (c).

[0039] The number of groups (c) in the structural unit (Ia) is preferably 1 to 3, and more preferably 1 or 2.

[0040] The number of phenolic hydroxyl groups (a) in the structural unit (Ia) is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

[0041] The term "phenolic hydroxyl group protected by a protecting group" refers to a group in which the hydrogen atom of a phenolic hydroxyl group is substituted with a protecting group, and which gives a phenolic hydroxyl group when deprotected by hydrolysis or the like.

[0042] The protecting group is not particularly limited as long as it is a group that can protect a phenolic hydroxyl group, and examples thereof include *-R, *-COOR (R is a monovalent hydrocarbon group having 1 to 10 carbon atoms), and *-R'-O-R (R' is a divalent hydrocarbon group having 1 to 10 carbon atoms; R is a monovalent hydrocarbon group having 1 to 10 carbon atoms). The protecting group is preferably a tert-butyl group or a tert-butoxycarbonyl group.

[0043] When the phenolic hydroxyl group (a) is a phenolic hydroxyl group protected with a protecting group, the sensitivity and CDU of the radiation-sensitive composition tend to be further improved.

[0044] The number of iodo groups in the structural unit (Ia) is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

[0045] The structural unit (Ia) may have the group (c) only as a phenolic hydroxyl group (a), only as an iodo group, or as a phenolic hydroxyl group (a) and an iodo group. By having both the phenolic hydroxyl group (a) and an iodo group, it is possible to simultaneously achieve a good balance between the three factors of sensitivity, CDU, and suppression of development defects.

[0046] The number of lactone structures (b) in the structural unit (Ia) is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

[0047] A "lactone structure" refers to a structure containing one ring (lactone ring) containing a bond represented by -O-C(O)-. The lactone ring is counted as the first ring, and when there is only a lactone ring, it is called a monocyclic lactone structure, and when there is further ring structure, it is called a polycyclic lactone structure regardless of the structure.

[0048] Examples of the lactone structure include monocyclic lactone structures such as a propiolactone structure, a butyrolactone structure, a valerolactone structure, and a caprolactone structure; and polycyclic lactone structures such as a cyclopentanelactone structure, a cyclohexanelactone structure, a norbornanelactone structure, a benzobutyrolactone structure, and a benzovalerolactone structure.

[0049] When the lactone structure (b) is a lactone structure, the occurrence of development defects in the radiation-sensitive composition tends to be further suppressed.

[0050] When the lactone structure is a monocyclic lactone structure, the CDU of the radiation-sensitive composition tends to be improved, and when the lactone structure is a polycyclic structure, the sensitivity of the radiation-sensitive composition tends to be further improved.

[0051] The term "cyclic carbonate structure" refers to a structure containing one ring (cyclic carbonate ring) containing a bond represented by -O-C(O)-O-. The cyclic carbonate ring is counted as the first ring, and when there is only a cyclic carbonate ring, it is called a monocyclic carbonate structure, and when there is further other ring structures, it is called a polycyclic carbonate structure regardless of the structures.

[0052] Examples of the cyclic carbonate structure include monocyclic carbonate structures such as an ethylene carbonate structure, a trimethylene carbonate structure, and a tetramethylene carbonate structure; and polycyclic carbonate structures such as a cyclopentylene carbonate structure, a cyclohexylene carbonate structure, a norbornylene carbonate structure, a phenylene carbonate structure, and a naphthylene carbonate structure.

[0053] When the lactone structure (b) is a cyclic carbonate structure, the sensitivity and CDU of the radiation-sensitive composition tend to be further improved.

[0054] The "sultone structure" is defined as -O-S(O) ２ The term "sultone structure" refers to a structure having one ring (sultone ring) containing a bond represented by the symbol "-." The sultone ring is counted as the first ring, and when there is only a sultone ring, it is called a monocyclic sultone structure. When there is another ring structure, it is called a polycyclic sultone structure regardless of the structure.

[0055] Examples of the sultone structure include monocyclic sultone structures such as a propane sultone structure and a butane sultone structure; and polycyclic sultone structures such as a norbornane sultone structure.

[0056] When the lactone structure (b) is a sultone structure, the sensitivity and CDU of the radiation-sensitive composition tend to be further improved.

[0057] The lactone structure (b) may have a substituent, such as an iodo group, a halogeno group such as a fluoro group, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group (a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, an amino group, a monoalkylamino group, or a dialkylamino group.

[0058] When the lactone structure (b) has a fluorinated alkyl group as a substituent, the sensitivity and CDU of the radiation-sensitive composition tend to be further improved, and the occurrence of development defects tend to be further suppressed. The fluorinated alkyl group is preferably a perfluoroalkyl group, and more preferably a trifluoromethyl group.

[0059] The lactone structure (b) is preferably bonded directly or via a linking group to the aromatic ring to which the group (c) is bonded. In other words, the structural unit (Ia) is preferably a structural unit containing a structure in which the group (c) is directly bonded to the aromatic ring and the lactone structure (b) is bonded directly or via a linking group.

[0060] In the aromatic ring to which the phenolic hydroxyl group (a) as the group (c) is bonded, the lactone structure (b) is preferably bonded directly or via a linking group to a carbon atom adjacent to the carbon atom to which the phenolic hydroxyl group (a) is bonded, which tends to further suppress the occurrence of development defects in the radiation-sensitive composition.

[0061] The term "aromatic ring" includes "aromatic hydrocarbon ring" and "aromatic heterocycle." Among aromatic rings, polycyclic rings including aromatic hydrocarbon rings and aromatic heterocycles are considered to be "aromatic heterocycles."

[0062] The number of ring members in the aromatic ring may be an aromatic hydrocarbon ring having 6 to 30 ring members or an aromatic heterocyclic ring having 5 to 30 ring members. The term "number of ring members" refers to the number of atoms constituting the ring structure, and in the case of a polycyclic ring, refers to the number of atoms constituting the polycyclic ring.

[0063] Examples of the aromatic hydrocarbon ring include a benzene ring; condensed polycyclic aromatic hydrocarbon rings such as a naphthalene ring, an anthracene ring, a fluorene ring, a biphenylene ring, a phenanthrene ring, and a pyrene ring; ring-assembly aromatic hydrocarbon rings such as a biphenyl ring, a terphenyl ring, a binaphthalene ring, and a phenylnaphthalene ring; and a 9,10-ethanoanthracene ring.

[0064] Examples of the aromatic heterocycle include oxygen atom-containing heterocycles such as a furan ring, a pyran ring, a benzofuran ring, and a benzopyran ring; nitrogen atom-containing heterocycles such as a pyridine ring, a pyrimidine ring, a pyrrole ring, and an indole ring; and sulfur atom-containing heterocycles such as a thiophene ring and a benzothiophene ring.

[0065] The aromatic ring is preferably an aromatic hydrocarbon ring, more preferably a benzene ring or a naphthalene ring, and even more preferably a benzene ring.

[0066] The aromatic ring may have a substituent, such as a halogeno group other than an iodo group (e.g., a fluoro group or a bromo group), a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group (a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, an acyloxy group, an amino group, a monoalkylamino group, or a dialkylamino group.

[0067] The aromatic ring preferably does not have the above-mentioned substituent.

[0068] The structural unit (Ia) is preferably a structural unit represented by the following formula (1a).

[0069]

[0070] In the above formula (1a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａis a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different from each other.

[0071] R １ is preferably a hydrogen atom or a methyl group.

[0072] L １ａ is preferably a single bond, —COO— or —CONH—. １ａ When is —CONH—, the sensitivity and CDU of the radiation-sensitive composition can be further improved, and the occurrence of development defects can be further suppressed.

[0073] Ar １ａ The aromatic ring giving the formula (I) is explained above as "the aromatic ring to which the group (c) is bonded."

[0074] R ２ａ may be a hydrogen atom or a protecting group. ２ａ When is a protecting group, the sensitivity and CDU of the radiation-sensitive composition tend to be further improved.

[0075] n １ａ is preferably 0 to 2, and more preferably 0 or 1. ２ａ is preferably 0 to 2, and more preferably 0 or 1. １ａ +n ２ａ As the number, 1 to 3 is preferred, and 1 or 2 is more preferred.

[0076] The term "linking group" refers to a group that links two or more structures.

[0077] L ２ａ Examples of the divalent linking group represented by ２ａis not particularly limited as long as it is a group that connects two structures to which each of the groups is bonded, and examples thereof include a carbonyl group, an ether group, a carbonyloxy group, a sulfide group, a sulfonyl group, an alkanediyl group having 1 to 10 carbon atoms, or a group combining these.

[0078] L ２ａ is preferably a divalent linking group, more preferably —COO—.

[0079] R ３ａ The lactone structure, cyclic carbonate structure and sultone structure giving the above formula are described as "lactone structure (b)" above.

[0080] R ３ａ Examples of the group in which one hydrogen atom has been removed from a lactone structure include groups represented by the following formulas.

[0081]

[0082] In the above formula, * represents L in formula (1a). ２ａ This is the binding site for

[0083] R ３ａ Examples of the group in which one hydrogen atom has been removed from a cyclic carbonate structure include groups represented by the following formulas.

[0084]

[0085] In the above formula, * represents L in formula (1a). ２ａ This is the binding site for

[0086] R ３ａ Examples of the group in which one hydrogen atom has been removed from a sultone structure include groups represented by the following formulas.

[0087]

[0088] In the above formula, * represents L in formula (1a). ２ａ This is the binding site for

[0089] m ａ As the number, 1 or 2 is preferred, and 1 is more preferred.

[0090] The lower limit of the content of the structural unit (Ia) in the polymer [A1] is preferably 1 mol%, more preferably 5 mol%, even more preferably 10 mol%, and in some cases even more preferably 15 mol%, based on the total structural units constituting the polymer [A1]. The upper limit of the content is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. When the content is 15 mol% or more, the sensitivity tends to be further improved.

[0091] [Structural Unit (Ib)] The structural unit (Ib) is a structural unit containing a structure (hereinafter also referred to as "structure (x)") in which a lactone structure (hereinafter also referred to as "lactone structure (q)") is bonded via an oxygen atom or a sulfur atom to an aromatic ring (hereinafter also referred to as "aromatic ring (p)") having a substituent (hereinafter also referred to as "substituent (b)").

[0092] Examples of the aromatic ring that provides the aromatic ring (p) include the same aromatic rings as those to which the above-mentioned group (c) is bonded.

[0093] The aromatic ring (p) is preferably an aromatic hydrocarbon ring, more preferably a benzene ring or a naphthalene ring, and even more preferably a benzene ring.

[0094] Examples of lactone structures that give the lactone structure (q) include the same lactone structures that give the lactone structure (b) described above.

[0095] The lactone structure (q) is preferably a monocyclic lactone structure, more preferably a butyrolactone structure or a valerolactone structure. In the case of a monocyclic lactone structure, the hydrophilicity of the polymer is more easily ensured and the occurrence of development defects tends to be more effectively suppressed than in the case of a polycyclic lactone structure.

[0096] The lactone structure (q) may have a substituent, and examples of the substituent include the same substituents as those of the lactone structure (b).

[0097] The lactone structure (q) is bonded to the aromatic ring (p) via an oxygen atom or a sulfur atom (hereinafter also referred to as a "linker (c)"). By bonding the lactone structure (q) to the aromatic ring (p) via the short linker (c), the rigidity of the resist film is not impaired, and the lactone structure can be introduced without decreasing the Tg of the polymer, which is thought to suppress acid diffusion.

[0098] The number of lactone structures (a) bonded to the aromatic ring (p) via the linker (c) is one or more, preferably one to three, and more preferably one or two.

[0099] In this specification, when the number of lactone structures (q) bonded to an aromatic ring (p) via a linker (c) is two or more, the second and subsequent structures are treated as substituents (b) described below. A specific example will be used to explain this. For example, the structure represented by the following formula (ex-1) has two butyrolactone structures bonded to a benzene ring via an oxygen atom. In other words, the structure represented by the following formula (ex-1) has two oxy-butyrolactone groups bonded to a benzene ring. In this specification, the first of these structures is treated as a lactone structure (q) bonded to the aromatic ring (p) via a linker (c), and the second is treated as a substituent (b).

[0100]

[0101] The lactone structure (q) is preferably bonded via a linker (c) to a carbon atom in the aromatic ring (p) that is adjacent to the carbon atom to which the substituent (b) is bonded.

[0102] The substituent (b) is not particularly limited, and may be a monovalent group capable of substituting a hydrogen atom bonded to a carbon atom constituting the aromatic ring (p). It is believed that the aromatic ring (p) to which the lactone structure (q) is bonded via the linker (c) further has a substituent (b), thereby enabling functional groups imparting various functionalities to be arranged at a high density.

[0103] Examples of the substituent (b) include a halogeno group such as an iodo group (-I) or a fluoro group (-F), a hydroxy group (-OH), a carboxy group (-COOH), a cyano group (-CN), a nitro group (-NO２ ), alkyl group (hereinafter referred to as "-R"), fluorinated alkyl group (a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom), alkoxy group (-OR), alkoxycarbonyl group (-CO-OR), alkoxycarbonyloxy group (-O-CO-OR), acyl group (-COR), acyloxy group (-O-COR), amino group (-NH ２ , -NHR, -NRR), amide group (-CO-NH ２ , —CO—NHR, —CO—NRR), aminoacyl group (—NH—COR), alkylsulfonyl group (—SO ２ —R), a group containing an acid-dissociable group, a group that generates an acid when acted upon by radiation, and a group that combines a linker (c) and a lactone structure (q).

[0104] Examples of the alkyl group include alkyl groups having 1 to 10 carbon atoms, and specific examples include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group.

[0105] Examples of fluorinated alkyl groups include groups in which at least one hydrogen atom of an alkyl group having 1 to 10 carbon atoms has been substituted with a fluorine atom, and specific examples include a trifluoromethyl group.

[0106] The alkoxy group includes, for example, an alkoxy group having 1 to 10 carbon atoms, and specific examples thereof include a methoxy group, an ethoxy group, and a propoxy group.

[0107] The alkoxycarbonyl group includes, for example, an alkoxycarbonyl group having 1 to 10 carbon atoms, and specifically includes a methoxycarbonyl group.

[0108] The amide group may be any of a primary amide group, a secondary amide group, and a tertiary amide group, but a secondary amide group is preferred. A specific example of the secondary amide group is a methyl amide group.

[0109] The term "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group and dissociates by the action of an acid to give a carboxy group. Examples of the acid-dissociable group include the groups described later in the section on [Structural Unit (II)].

[0110] Examples of the group that generates an acid when acted upon by radiation include the groups described below in the section on [Structural Unit (IV)].

[0111] In addition, when the substituent (b) is a group containing an acid-dissociable group or a group that generates an acid when acted upon by radiation, the structural unit (Ib) can be said to formally correspond to a "structural unit (II) containing an acid-dissociable group" or a "structural unit (IV) containing a group that generates an acid when acted upon by radiation" according to the classification in this specification. However, even in such cases, in this specification, the structural unit containing the structure (x) is classified as a "structural unit (Ib)."

[0112] Examples of the group combining the linker (c) and the lactone structure (a) include a group in which the above-mentioned linker (c) is bonded to the above-mentioned lactone structure (q).

[0113] The substituent (b) may be an iodo group (-I), a fluoro group (-F), a hydroxy group (-OH), a cyano group (-CN), a nitro group (-NO ２ ), alkyl group (-R), fluorinated alkyl group, alkoxy group (-OR), alkoxycarbonyl group (-CO-OR), amide group (-CO-NH ２ , —CO—NHR, —CO—NRR), an aminoacyl group (—NH—COR), a group containing an acid-dissociable group, a group that generates an acid when acted upon by radiation, and a group combining a linker (c) and a lactone structure (a) are preferred.

[0114] The substituent (b) may impart various functionalities to the polymer. For example, a group that generates an acid when exposed to radiation, such as an iodo group or a fluoro group, is expected to increase the amount of acid generated; a cyano group, an alkoxy group, a nitro group, or a group combining a linker (c) with a lactone structure (a) is expected to improve hydrophilicity; a hydroxy group, an alkoxycarbonyl group, an amide group, an aminoacyl group, or the like is expected to improve hydrophilicity or increase Tg; or a group containing an acid-dissociable group is expected to improve contrast, etc.

[0115] The structural unit (Ib) is preferably a structural unit represented by the following formula (1b): １ｂ (R ２ｂ ) ｎｂ (X-R ３ｂ ) ｍｂ The structure represented by the following formula corresponds to the above structure (x).

[0116]

[0117] In the above formula (1b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different from each other.

[0118] R １ｂ is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.

[0119] L １ｂ is preferably a single bond or —COO—, which tends to further improve the sensitivity of the radiation-sensitive composition.

[0120] Ar １ｂ The aromatic ring that provides the aromatic ring (p) is described above as "the aromatic ring that provides the aromatic ring (p)."

[0121] R ２ｂ The substituent represented by R is explained above as "substituent (b)".２ｂ The substituent represented by the formula (I) does not include a group obtained by combining the linker (c) and the lactone structure (q) among the above-mentioned substituents (b).

[0122] X is explained as the "linker (c)" above.

[0123] R ３ｂ The lactone structure giving the formula (I) is described above as "lactone structure (q)."

[0124] m ｂ As the number, 1 or 2 is preferred.

[0125] n ｂ is preferably 0 to 2. ｂ If m is 0, ｂ is 2 or more.

[0126] n ｂ +m ｂ As the number, 2 or 3 is preferred.

[0127] The lower limit of the content of the structural unit (Ib) in the polymer [A2] is preferably 0.5 mol %, more preferably 1 mol %, even more preferably 2 mol %, and still more preferably 5 mol %, based on the total structural units constituting the polymer [A2]. The upper limit of the content is preferably 30 mol %, more preferably 20 mol %, and still more preferably 15 mol %.

[0128] [Structural Unit (II)] The structural unit (II) is a structural unit containing an acid-dissociable group. Since the structural unit (II) contains an acid-dissociable group, the polymer [A] exhibits a property in which its solubility in a developer changes under the action of acid. The acid-dissociable group dissociates under the action of acid generated from a radiation-sensitive acid generator under the action of radiation, resulting in a difference in the solubility of the polymer [A] in a developer between an exposed area and a non-exposed area, thereby enabling the formation of a resist pattern.

[0129] The acid-dissociable group is a group that substitutes a hydrogen atom of the carboxy group in the structural unit (II). In other words, in the structural unit (II), the acid-dissociable group is bonded to the etheric oxygen atom of the carbonyloxy group.

[0130] Examples of the acid-dissociable group include groups represented by the following formulae (a-1) and (a-2) (hereinafter also referred to as "acid-dissociable groups (a-1) and (a-2)").

[0131]

[0132] In the above formulas (a-1) and (a-2), * indicates the bonding site of the carbonyloxy group with the etheric oxygen atom.

[0133] In the above formula (a-1), R Ｘ R is a substituted or unsubstituted monovalent chain hydrocarbon group having 1 to 20 carbon atoms, or a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic ring having 5 to 20 ring members. Ｙ and R Ｚ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or these groups are combined with each other to form a saturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are attached.

[0134] In the above formula (a-2), R Ａ and R Ｂ are each independently a monovalent hydrocarbon group having 1 to 20 carbon atoms, or R Ａ and R Ｂ are combined with each other to form an unsaturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are attached. Ｂ has a carbon atom forming a carbon-carbon double bond at the α-position of the carbon atom bonded to *.

[0135] The term "hydrocarbon group" includes "aliphatic hydrocarbon groups" and "aromatic hydrocarbon groups." The term "aliphatic hydrocarbon group" includes "chain hydrocarbon groups" and "alicyclic hydrocarbon groups." From another perspective, the term "aliphatic hydrocarbon group" includes "saturated hydrocarbon groups" and "unsaturated hydrocarbon groups." The term "chain hydrocarbon group" refers to a hydrocarbon group that does not contain a ring structure and is composed only of a chain structure, and includes both straight-chain hydrocarbon groups and branched-chain hydrocarbon groups. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic ring as a ring structure and does not contain an aromatic ring, and includes both monocyclic alicyclic hydrocarbon groups and polycyclic alicyclic hydrocarbon groups. However, it does not have to be composed only of an alicyclic ring, and may contain a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring as a ring structure. However, it does not have to be composed only of an aromatic ring, and may contain a chain structure or an alicyclic ring as part of it.

[0136] R Ｘ Examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms that gives the formula (I) include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group; alkenyl groups such as an ethenyl group, a propenyl group, a butenyl group, and a 2-methylprop-1-en-1-yl group; and alkynyl groups such as an ethynyl group, a propynyl group, and a butynyl group.

[0137] R Ｘ Examples of aromatic rings having 5 to 20 ring members that give the formula include aromatic hydrocarbon rings having 6 to 20 ring members and aromatic heterocyclic rings having 5 to 20 ring members.

[0138] Examples of the aromatic hydrocarbon ring having 6 to 20 ring members and the aromatic heterocyclic ring having 5 to 20 ring members include those exemplified above as "aromatic ring to which group (c) is bonded."

[0139] R Ｘ Examples of the substituent that the group represented by the formula (I) may have include a halogeno group such as a fluoro group or an iodo group, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, and an acyloxy group.

[0140] R Ｙ , RＺ , R Ａ , or R Ｂ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives 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.

[0141] 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, sec-butyl, isobutyl, and tert-butyl; alkenyl groups such as ethenyl, propenyl, butenyl, and 2-methylprop-1-en-1-yl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0142] Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include monocyclic alicyclic saturated hydrocarbon groups such as a cyclopentyl group and a cyclohexyl group; polycyclic alicyclic saturated hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group and a tetracyclododecyl group; monocyclic alicyclic unsaturated hydrocarbon groups such as a cyclopentenyl group and a cyclohexenyl group; and polycyclic alicyclic unsaturated hydrocarbon groups such as a norbornenyl group, a tricyclodecenyl group and a tetracyclododecenyl group.

[0143] Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, naphthylmethyl, and anthrylmethyl.

[0144] R Ｙ and R Ｚ Among the saturated alicyclic rings having 3 to 20 ring members formed by combining these rings together with the carbon atoms to which they are bonded, examples of the aliphatic hydrocarbon ring include monocyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring; and polycyclic rings such as a norbornane ring, an adamantane ring, a tricyclodecane ring, and a tetracyclododecane ring.

[0145] R Ｙ and R ＺAmong saturated alicyclic rings having 3 to 20 ring members formed by combining these rings together with the carbon atoms to which they are bonded, examples of the aliphatic heterocyclic ring include oxygen atom-containing heterocyclic rings such as tetrahydropyran ring.

[0146] R Ａ and R Ｂ Examples of the unsaturated alicyclic ring having 3 to 20 ring members formed by combining these together with the carbon atoms to which they are bonded include monocyclic unsaturated alicyclic rings such as a cyclobutene structure, a cyclopentene structure, and a cyclohexene structure, and polycyclic unsaturated alicyclic rings such as a norbornene structure.

[0147] R Ｙ and R Ｚ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, R Ｙ and R Ｚ As R, a chain hydrocarbon group is preferable, an alkyl group is preferable, and a methyl group is more preferable. Ｘ As the alkyl group, an alkyl group or a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 20 ring members is more preferred, and a methyl group, a phenyl group or an iodophenyl group is even more preferred.

[0148] R Ｙ and R Ｚ When R are combined with each other to form a saturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are bonded, the saturated alicyclic ring is preferably a cyclopentane ring or a tetrahydropyran ring. Ｘ As the alkyl group, an alkyl group or a group in which one hydrogen atom has been removed from a substituted or unsubstituted benzene ring is preferred, and a methyl group, an ethyl group, a phenyl group or an iodophenyl group is more preferred.

[0149] R Ａ and R Ｂ When these are combined with each other to form an unsaturated alicyclic ring having 3 to 20 ring members together with the carbon atoms to which they are bonded, the unsaturated alicyclic ring is preferably a monocyclic unsaturated alicyclic ring, more preferably a cyclohexene ring.

[0150] Examples of the acid-dissociable group (a-1) include groups represented by the following formulae (a-1-1) to (a-1-16): Examples of the acid-dissociable group (a-2) include groups represented by the following formulae (a-2-1) to (a-2-2):

[0151]

[0152] Examples of the structural unit (II) include a structural unit represented by the following formula (II).

[0153]

[0154] In the above formula (II), R Ｈ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｈ is a single bond, *-COO- or *-CONH-. * is R Ｈ１ indicates the bonding site with the carbon atom to which R is attached. Ｈ２ R is a single bond, a divalent chain hydrocarbon group having 1 to 10 carbon atoms, or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring having 6 to 20 ring members. Ｈ３ is the acid-dissociable group.

[0155] R Ｈ１ From the viewpoint of copolymerizability of the monomer that gives the structural unit (II), a hydrogen atom or a methyl group is preferred.

[0156] L Ｈ is preferably a single bond or *-COO-.

[0157] R Ｈ２ Examples of the divalent chain hydrocarbon group having 1 to 10 carbon atoms that gives the formula Ｘ Among the examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms that gives the formula (I), a group in which one hydrogen atom has been removed from a group having 1 to 10 carbon atoms can be mentioned. Ｈ２ The divalent chain hydrocarbon group giving the formula (I) is preferably a methanediyl group.

[0158] R Ｈ２Examples of aromatic hydrocarbon rings having 6 to 20 ring members that give the formula include those exemplified as aromatic hydrocarbon rings having 6 to 20 ring members among the above-mentioned "aromatic rings to which group (c) is bonded." R Ｈ２ As the aromatic hydrocarbon ring which gives the following formula, a benzene ring is preferred.

[0159] R Ｈ２ Examples of the substituent that the aromatic hydrocarbon ring that gives the following formula may have include those exemplified as the substituent that the lactone structure (b) may have.

[0160] The lower limit of the content of the structural unit (II) in the polymer [A] is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, still more preferably 40 mol%, and sometimes 45 mol%, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, even more preferably 70 mol%, and sometimes 65 mol%, and sometimes 60 mol% or 50 mol% is preferred.

[0161] [Structural Unit (III)] The structural unit (III) is a structural unit containing a phenolic hydroxyl group other than the structural unit (Ia). The structural unit (III) is a structural unit containing a phenolic hydroxyl group that does not fall under the category of the structural unit (Ia).

[0162] In the case of KrF exposure, EUV exposure, or electron beam exposure, the polymer (A) having the structural unit (III) can further increase the sensitivity of the radiation-sensitive composition, and therefore the radiation-sensitive composition can be suitably used as a radiation-sensitive composition for KrF exposure, EUV exposure, or electron beam exposure.

[0163] Examples of the structural unit (III) include a structural unit represented by the following formula (III).

[0164]

[0165] In the above formula (III), R Ｐ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. Ｐis a single bond, *-COO-, -O-, or *-CONH-. * is R Ｐ indicates the bonding site with the carbon atom to which Ar is bonded. Ｐ represents a group in which (p+1) hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring, where p is an integer of 1 to 3.

[0166] R Ｐ From the viewpoint of copolymerizability of the monomer that gives the structural unit (III), a hydrogen atom or a methyl group is preferred.

[0167] L Ｐ is preferably a single bond.

[0168] Ar Ｐ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 20 ring members.

[0169] Ar Ｐ Examples of the aromatic hydrocarbon ring that gives the above formula (I) include the aromatic hydrocarbon rings having 6 to 20 ring members among the above-mentioned examples of the "aromatic ring to which the phenolic hydroxyl group (a) is bonded."

[0170] Ar Ｐ Examples of the substituent that the aromatic hydrocarbon ring that gives the following may have include those exemplified as the substituent that the lactone structure (b) may have.

[0171] As p, 1 or 2 is preferred.

[0172] Examples of the structural unit (III) include structural units represented by the following formulae (III-1) to (III-20).

[0173]

[0174] In the above formulas (III-1) to (III-20), R Ｐ has the same meaning as the above formula (III).

[0175] When the polymer [A] has the structural unit (III), the lower limit of the content of the structural unit (III) in the polymer [A] is preferably 5 mol%, more preferably 10 mol%, and even more preferably 20 mol%, and sometimes 30 mol%, sometimes 40 mol%, and sometimes 45 mol% relative to all structural units constituting the polymer [A]. The upper limit of the content is preferably 80 mol%, more preferably 70 mol%, even more preferably 60 mol%, and even more preferably 50 mol%.

[0176] [Structural Unit (IV)] The structural unit (IV) is a structural unit containing a group that generates an acid when exposed to radiation. Examples of the acid generated from the group that generates an acid when exposed to radiation include sulfonic acid and carboxylic acid. Examples of the radiation include those exemplified as radiation in the section <Method of Forming a Resist Pattern> described below.

[0177] Examples of the group that generates an acid when acted upon by radiation include a group containing an anion and a radiation-sensitive onium cation. Such groups are classified into a structure in which an anion is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 1") and a structure in which a radiation-sensitive onium cation is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 2"). The group that generates an acid when acted upon by radiation may be Structure 1 or Structure 2.

[0178] Examples of the group that generates an acid when acted upon by radiation include a group represented by the following formula (y) (hereinafter also referred to as "group (y)").

[0179]

[0180] In the above formula (y), R ａ１ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure having five or more ring members. ａ１ is 0 or 1. ａ１ is a single bond or a divalent linking group. ａ２ and R ａ３ are each independently a hydrogen atom, a fluoro group, or a substituted or unsubstituted hydrocarbon group. ａ２ is an integer from 0 to 10.ａ４ and R ａ５ are each independently a fluoro group or a fluorinated hydrocarbon group. ａ３ is an integer from 0 to 10. － is a sulfonate anion or a carboxylate anion. ＋ is a monovalent radiation-sensitive onium cation. * indicates a binding site.

[0181] The "ring structure" includes an "alicyclic ring" and an "aromatic ring".

[0182] R ａ１ Examples of the ring structure having 5 or more ring members that gives the formula (I) include an aliphatic hydrocarbon ring having 5 or more ring members, an aliphatic heterocycle having 5 or more ring members, an aromatic hydrocarbon ring having 6 or more ring members, and an aromatic heterocycle having 5 or more ring members.

[0183] Examples of aliphatic hydrocarbon rings having 5 or more ring members include monocyclic saturated alicyclic rings such as a cyclopentane ring, cyclohexane ring, cycloheptane ring, cyclooctane ring, cyclononane ring, cyclodecane ring, and cyclododecane ring; monocyclic unsaturated alicyclic rings such as a cyclopentene ring, cyclohexene ring, cycloheptene ring, cyclooctene ring, and cyclodecene ring; polycyclic saturated alicyclic rings such as a norbornane ring, adamantane ring, tricyclodecane ring, tetracyclododecane ring, and steroid structure; and polycyclic unsaturated alicyclic rings such as a norbornene ring and tricyclodecene ring. The term "steroid structure" refers to a structure having a basic skeleton (sterane skeleton) in which three 6-membered rings and one 5-membered ring are fused.

[0184] Examples of the aliphatic heterocyclic ring having 5 or more ring members include lactone rings such as a hexanolactone ring and a norbornanelactone ring; sultone rings such as a hexanosultone ring and a norbornanesultone ring; dioxolane ring, oxacycloheptane ring, oxanorbornane ring, 3,5-dioxatricyclo[5.2.1.0 ２，６ ] Examples of heterocycles include an oxygen atom-containing heterocycle such as a decane ring; a nitrogen atom-containing heterocycle such as an azacyclohexane ring or a diazabicyclooctane ring; and a sulfur atom-containing heterocycle such as a thiacyclohexane ring or a thianorbornane ring.

[0185] Examples of the aromatic hydrocarbon ring having 6 or more ring members and the aromatic heterocyclic ring having 5 or more ring members include those exemplified above as "aromatic rings providing the aromatic ring (p)".

[0186] The lower limit of the number of ring members in the ring structure is preferably 6, more preferably 8, still more preferably 9, and particularly preferably 10. The upper limit of the number of ring members is preferably 25.

[0187] The ring structure is preferably an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring, and more preferably a polycyclic saturated alicyclic ring or a benzene ring.

[0188] In the ring structure, some or all of the hydrogen atoms bonded to the atoms constituting the ring structure may be substituted with a substituent, such as those exemplified as the substituents that the lactone structure (a) may have.

[0189] L ａ１ Examples of the divalent linking group represented by ａ１ is not particularly limited as long as it is a group that connects two structures to which each of the groups is bonded, and examples thereof include a carbonyl group, an ether group, a carbonyloxy group, a sulfide group, a sulfonyl group, an alkanediyl group having 1 to 10 carbon atoms, or a group combining these.

[0190] n ａ１ is preferably 0 or 1.

[0191] R ａ２ and R ａ３ Examples of the hydrocarbon group that gives Ｙ , R Ｚ , R Ａ , or R Ｂ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives the following formula are given below.

[0192] R ａ２ and R ａ３ Examples of the substituent that the hydrocarbon group that gives the following formula may have include those exemplified as the substituent that the lactone structure (a) may have.

[0193] R ａ２ and R ａ３ is preferably a hydrogen atom.

[0194] n ａ２ is preferably 0 to 5, and more preferably 0 or 1.

[0195] The term "fluorinated hydrocarbon group" refers to a hydrocarbon group in which at least one hydrogen atom has been substituted with a fluorine atom.

[0196] Examples of the hydrocarbon group that gives the fluorinated hydrocarbon group include the above-mentioned R ａ２ and R ａ３ Examples of hydrocarbon groups that give the following formula include those given above.

[0197] The fluorinated hydrocarbon group is preferably a fluorinated alkyl group, more preferably a perfluoroalkyl group, and even more preferably a trifluoromethyl group.

[0198] n ａ３ is preferably 0 to 5, and more preferably 0 to 2.

[0199] A － As the anion, sulfonate anion (-SO ３ － ), or a carboxylate anion (—COO － ) may also be used. － is a sulfonate anion, the polymer [P] functions as a radiation-sensitive acid generator. － When A is a carboxylate anion, the polymer [P] functions as an acid diffusion controller. － is a carboxylate anion, the polymer [P] generates a carboxylic acid under the action of radiation, and therefore can be broadly called a "radiation-sensitive acid generator." However, the carboxylic acid generated from the structural unit (IV) under the action of radiation does not dissociate the acid-dissociable group under conditions in which an acid generated from the acid generator [A] or the like dissociates the acid-dissociable group, and therefore the "radiation-sensitive acid generator" is clearly distinguished from the "acid diffusion controller."

[0200] In addition, the polymer [P] is － Structural units (IV) and A －and a structural unit (IV) in which each of the structural units (IV) is a carboxylate anion, the polymer (P) not only functions as a base resin but also as a radiation-sensitive acid generator and an acid diffusion controller in the radiation-sensitive composition.

[0201] Examples of the group (y) include groups represented by the following formulae (y-1) to (y-4).

[0202]

[0203] In the above formulas (y-1) to (y-4), * indicates a bonding site.

[0204] M ＋ Examples of the monovalent onium cation represented by the formula (I) include those known as radiation-sensitive onium cations in onium salts used as radiation-sensitive acid generators or acid diffusion controllers contained in radiation-sensitive compositions. For example, sulfonium cations (S ＋ ), iodonium cation (I ＋ ) are listed.

[0205] Examples of the monovalent radiation-sensitive onium cation include monovalent cations represented by the following formulas (r-a) to (r-c) (hereinafter also referred to as "cations (r-a) to (r-c)").

[0206]

[0207] In the above formula (r-a), b1 is an integer of 0 to 4. When b1 is 1, R Ｂ１ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ１ 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 halogeno group, or a plurality of R Ｂ１ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are attached. b2 is an integer of 0 to 4. When b2 is 1, R Ｂ２ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ２are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogeno group, or a plurality of R Ｂ２ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are attached. Ｂ３ and R Ｂ４ are each independently a hydrogen atom, a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group, or R Ｂ３ and R Ｂ４ are combined with each other to form a polycyclic sulfur atom-containing aromatic heterocycle together with the sulfur atom to which they are bonded. b3 is an integer of 0 to 11. When b3 is 1, R Ｂ５ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ５ 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 halogeno group, or a plurality of R Ｂ５ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are attached. ｂ１ is an integer from 0 to 3.

[0208] In the above formula (r-b), b4 is an integer of 0 to 9. When b4 is 1, R Ｂ６ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ６ 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 halogeno group, or a plurality of R Ｂ６ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are bonded. b5 is an integer of 0 to 10. When b5 is 1, R Ｂ７ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ７ 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 halogeno group, or a plurality of R Ｂ７ are combined with each other to form a ring structure having 3 to 20 ring members together with the carbon atoms or carbon chains to which they are attached.ｂ３ is an integer from 0 to 3. Ｂ８ is a single bond or a divalent linking group. ｂ２ is an integer from 0 to 2.

[0209] In the above formula (rc), b6 is an integer of 0 to 5. When b6 is 1, R Ｂ９ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ９ 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 halogeno group, or a plurality of R Ｂ９ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are bonded. b7 is an integer of 0 to 5. When b7 is 1, R Ｂ１０ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ１０ 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 halogeno group, or a plurality of R Ｂ１０ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are attached.

[0210] "Organic group" refers to a group containing at least one carbon atom.

[0211] R Ｂ１ , R Ｂ２ , R Ｂ３ , R Ｂ４ , R Ｂ５ , R Ｂ６ , R Ｂ７ , R Ｂ９ or R Ｂ１０ Examples of the monovalent organic group having 1 to 20 carbon atoms and represented by the formula (I) include a monovalent hydrocarbon group having 1 to 20 carbon atoms, a group containing a divalent heteroatom-containing group between the carbon-carbon bonds of this hydrocarbon group (hereinafter also referred to as "group (β1)"), a group in which some or all of the hydrogen atoms in the hydrocarbon group or the group (β1) have been substituted with a monovalent heteroatom-containing group (hereinafter also referred to as "group (β2)"), and a group in which the hydrocarbon group, the group (β1) or the group (β2) is combined with a divalent heteroatom-containing group (hereinafter also referred to as "group (β3)").

[0212] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include the above-mentioned R Ｙ , R Ｚ , R Ａ , or R Ｂ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives the following formula are given below.

[0213] Examples of heteroatoms constituting the monovalent or divalent heteroatom-containing group include oxygen atoms, nitrogen atoms, sulfur atoms, phosphorus atoms, silicon atoms, and halogen atoms.

[0214] Examples of the monovalent heteroatom-containing group include a halogeno group, a hydroxy group, a carboxy group, a cyano group, an amino group, a sulfanyl group (-SH), and an oxo group (=O).

[0215] Examples of divalent heteroatom-containing groups include -O-, -CO-, -S-, -CS-, -NR'-, and groups combining two or more of these (for example, -COO-, -CONR'-, etc.). R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by R' include those having 1 to 10 carbon atoms among the groups exemplified above as the "monovalent hydrocarbon group having 1 to 20 carbon atoms".

[0216] R Ｂ８ Examples of the divalent organic group represented by the formula (I) include those in which one hydrogen atom has been removed from the above monovalent organic group.

[0217] R Ｂ１ , R Ｂ２ , R Ｂ５ , R Ｂ６ , R Ｂ９ and R Ｂ１０ As the group, a perfluoroalkyl group, a fluoro group, an iodo group, a hydroxy group, an alkoxy group or a carboxy group is preferred, and a trifluoromethyl group, a fluoro group or an iodo group is more preferred.

[0218] R Ｂ３ and R Ｂ４ is preferably a hydrogen atom or a single bond formed by combining these, and is preferably a hydrogen atom.

[0219] b1 and b2 are preferably 0 to 2, more preferably 0 or 1, and even more preferably 0. b3 is preferably 0 to 4, more preferably 0 to 2, and even more preferably 0 or 1. n ｂ１ is preferably 0 or 1.

[0220] The radiation-sensitive onium cation is preferably the cation (ra) or the cation (rc).

[0221] Examples of the cation (ra) include cations represented by the following formulae (ra-1) to (ra-17).

[0222]

[0223] Examples of the cation (r-c) include cations represented by the following formulae (r-c-1) to (r-c-4).

[0224]

[0225] When the polymer [A] has the structural unit (IV), the lower limit of the content of the structural unit (IV) in the polymer [A] is preferably 1 mol %, more preferably 5 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 20 mol %, more preferably 10 mol %.

[0226] <[B] Acid Generator> The acid generator [B] is a substance that generates an acid when exposed to radiation. Examples of radiation include those exemplified as radiation in the section <Method of Forming a Resist Pattern> described below. The acid generated by the radiation dissociates acid-dissociable groups and the like to generate carboxyl groups, which results in a difference in the solubility of the resist film in a developer between exposed and unexposed areas, thereby forming a resist pattern.

[0227] Examples of the acid generated from the acid generator (B) include sulfonic acids, carboxylic acids, and imide acids.

[0228] The acid generator (B) is not particularly limited as long as it is usable as a radiation-sensitive acid generator contained in the radiation-sensitive composition, and examples thereof include an onium salt compound, an N-sulfonyloxyimide compound, a sulfonimide compound, a halogen-containing compound, and a diazoketone compound.

[0229] Examples of the onium salt compound include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts.

[0230] Specific examples of the acid generator (B) include the compounds described in paragraphs

[0080] to

[0113] of JP-A No. 2009-134088.

[0231] The acid generator (B) is preferably an onium salt compound, and more preferably an onium salt compound comprising a radiation-sensitive onium cation and an organic acid anion.

[0232] The radiation-sensitive onium cation in the acid generator (B) is not particularly limited as long as it is usable as a radiation-sensitive onium cation in a radiation-sensitive acid generator, and examples thereof include the radiation-sensitive onium cations described above in the section <Polymer (A)>.

[0233] The organic acid anion in the acid generator (B) is not particularly limited as long as it is usable as an anion in a radiation-sensitive acid generator, and examples thereof include a sulfonate anion.

[0234] As the acid generator (B), a compound in which the above-mentioned radiation-sensitive onium cation and the above-mentioned anion are appropriately combined can be used.

[0235] The lower limit of the content of the acid generator (B) in the radiation-sensitive composition is preferably 10 parts by mass and more preferably 20 parts by mass, relative to 100 parts by mass of the polymer (A), and the upper limit of the content is preferably 60 parts by mass and more preferably 50 parts by mass.

[0236] <Acid Diffusion Controller (C)> The acid diffusion controller (C) controls the diffusion phenomenon in the resist film of the acid generated from the acid generator (B) or the like upon exposure, thereby suppressing undesirable chemical reactions in unexposed areas. The radiation-sensitive composition may contain one or more acid diffusion controllers (C).

[0237] Examples of the acid diffusion controller (C) include nitrogen atom-containing compounds and compounds having a radiation-sensitive onium cation and an organic acid anion (hereinafter also referred to as "photodegradable bases").

[0238] Examples of the nitrogen atom-containing compound include amine compounds such as tripentylamine and trioctylamine; amide group-containing compounds such as formamide and N,N-dimethylacetamide; urea compounds such as urea and 1,1-dimethylurea; and nitrogen-containing heterocyclic compounds such as pyridine, N-(undecylcarbonyloxyethyl)morpholine, and N-t-pentyloxycarbonyl-4-hydroxypiperidine.

[0239] The photodegradable base generates a weak acid in the exposed area to increase the solubility or insolubility of the polymer (A) in a developer, thereby suppressing the surface roughness of the exposed area after development. On the other hand, in the unexposed area, the anion exerts a high acid-scavenging function and functions as a quencher, capturing acid diffusing from the exposed area.

[0240] Examples of the radiation-sensitive onium cation in the photodegradable base include the radiation-sensitive onium cations described above in the section <Polymer (A)>.

[0241] The organic acid anion in the photodegradable base is not particularly limited as long as it is usable as an organic acid anion in a photodegradable base, and examples thereof include carboxylate anions.

[0242] As the photodegradable base, a compound in which the above-mentioned radiation-sensitive onium cation and the above-mentioned anion are appropriately combined can be used.

[0243] When the radiation-sensitive composition contains the acid diffusion controller (C), the lower limit of the content of the acid diffusion controller (C) in the radiation-sensitive composition is preferably 5 mol %, more preferably 10 mol %, and even more preferably 15 mol %, relative to 100 mol % of the radiation-sensitive acid generator (or the total amount of the radiation-sensitive acid generators, if multiple radiation-sensitive acid generators are present). The upper limit of the content is preferably 100 mol %, more preferably 70 mol %, and even more preferably 60 mol %.

[0244] <[D] Organic Solvent> The radiation-sensitive composition usually contains an organic solvent [D]. The organic solvent [D] is not particularly limited as long as it is a solvent that can dissolve or disperse at least the polymer [A], the acid generator [B], the acid diffusion controller [C], and other optional components that may be contained as needed.

[0245] Examples of the organic solvent (D) include alcohol solvents, ether solvents, ketone solvents, amide solvents, ester solvents, and hydrocarbon solvents. The radiation-sensitive composition may contain one or more organic solvents (D).

[0246] Examples of alcohol-based solvents include aliphatic monoalcohol-based solvents such as 4-methyl-2-pentanol, n-hexanol, diacetone alcohol, and methyl 2-hydroxyisobutyrate; alicyclic monoalcohol-based solvents such as cyclohexanol; polyhydric alcohol-based solvents such as 1,2-propylene glycol; and polyhydric alcohol partial ether-based solvents such as propylene glycol monomethyl ether.

[0247] Examples of ether solvents include dialkyl ether solvents such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ether solvents such as diphenyl ether and anisole.

[0248] Examples of ketone solvents include chain ketone solvents 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 ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, and acetophenone.

[0249] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; and chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0250] Examples of ester-based solvents include monocarboxylic acid ester-based solvents such as n-butyl acetate and ethyl lactate; lactone-based solvents such as γ-butyrolactone and valerolactone; polyhydric alcohol carboxylate-based solvents such as propylene glycol acetate; polyhydric alcohol partial ether carboxylate-based solvents such as propylene glycol monomethyl ether acetate; polycarboxylic acid diester-based solvents such as diethyl oxalate; and carbonate-based solvents such as dimethyl carbonate and diethyl carbonate.

[0251] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-pentane and n-hexane; and aromatic hydrocarbon solvents such as toluene and xylene.

[0252] The organic solvent (D) is preferably an alcohol solvent, an ester solvent, or a combination thereof, more preferably an aliphatic monoalcohol solvent, a polyhydric alcohol partial ether solvent, a polyhydric alcohol partial ether carboxylate solvent, or a combination thereof, and even more preferably diacetone alcohol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or a combination thereof.

[0253] When the radiation-sensitive composition contains the organic solvent (D), the lower limit of the content of the organic solvent (D) is preferably 50 mass %, more preferably 60 mass %, still more preferably 70 mass %, and particularly preferably 80 mass %, based on all components contained in the radiation-sensitive composition, and the upper limit of the content is preferably 99.9 mass %, preferably 99.5 mass %, and more preferably 99.0 mass %.

[0254] <Polymer [F]> The polymer [F] is a polymer different from the polymer [A] and has a higher fluorine atom content than the polymer [A]. Typically, polymers that are more hydrophobic than the base polymer tend to be unevenly distributed in the surface layer of the resist film. The polymer [F] has a higher fluorine atom content than the polymer [A], and due to this hydrophobicity-induced property, the polymer [F] tends to be unevenly distributed in the surface layer of the resist film. As a result, when the radiation-sensitive composition contains the polymer [F], it is expected that the cross-sectional shape of the formed resist pattern will be excellent.

[0255] The form of fluorine atoms contained in the polymer [F] is not particularly limited, and the fluorine atoms may be bonded to either the main chain or the side chain of the polymer [F]. As the form of fluorine atoms contained in the polymer [F], it is preferable that the polymer [F] has a structural unit containing a fluorine atom (hereinafter also referred to as a "structural unit (f)").

[0256] The polymer [F] may further have a structural unit other than the structural unit (f). Examples of the structural unit other than the structural unit (f) include the structural unit (II) containing an acid-dissociable group described above in the section <Polymer [A]>. The polymer [F] may have one or more types of each structural unit.

[0257] When the radiation-sensitive composition contains the polymer [F], the lower limit of the amount of the polymer [F] relative to 100 parts by mass of the polymer [A] is preferably 0.1 parts by mass and more preferably 0.5 parts by mass, and the upper limit of the amount is preferably 20 parts by mass and more preferably 10 parts by mass.

[0258] <Other Optional Components> Examples of other optional components include surfactants, etc. The radiation-sensitive composition may contain one or more other optional components.

[0259] <Method of Forming a Resist Pattern> The method of forming a resist pattern includes a step of applying a radiation-sensitive composition directly or indirectly to a substrate (hereinafter also referred to as a "coating step"), a step of exposing the resist film formed in the coating step (hereinafter also referred to as an "exposure step"), and a step of developing the exposed resist film (hereinafter also referred to as a "developing step").

[0260] In the coating step, the radiation-sensitive composition is the radiation-sensitive composition described above. Therefore, according to the method for forming a resist pattern, a resist pattern having excellent sensitivity and CDU and suppressing the occurrence of development defects can be formed.

[0261] Each step of the resist pattern forming method will be described below.

[0262] [Coating Step] In this step, the radiation-sensitive composition is coated directly or indirectly onto a substrate, thereby forming a resist film directly or indirectly on the substrate.

[0263] In this step, the radiation-sensitive composition described above is used as the radiation-sensitive composition.

[0264] Substrates include, for example, silicon wafers, silicon dioxide, and aluminum coated wafers.

[0265] Examples of coating methods include spin coating, casting coating, and roll coating. After coating, if necessary, pre-baking (hereinafter also referred to as "PB") may be performed to volatilize the solvent in the coating film. The PB temperature and PB time are not particularly limited, and are, for example, performed at a temperature of 60°C to 150°C for 5 seconds to 300 seconds. The average thickness of the formed resist film is not particularly limited, and is, for example, 10 nm to 1,000 nm.

[0266] [Exposure Step] In this step, the resist film formed in the coating step is exposed to radiation. This exposure is carried out by irradiating the resist film through a photomask (or, in some cases, through an immersion medium such as water). The radiation can be appropriately selected depending on the line width, diameter, etc. of the desired pattern, and examples thereof include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays. Among these, far ultraviolet light, EUV, or electron beams are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV (wavelength 13.5 nm), or electron beams being more preferred, with KrF excimer laser light, EUV, or electron beams being even more preferred, and EUV or electron beams being particularly preferred.

[0267] After the exposure, it is preferable to perform post-exposure baking (hereinafter also referred to as "PEB"). This PEB can increase the difference in solubility in a developer between the exposed and unexposed areas. The PEB temperature and PEB time are not particularly limited, and can be performed, for example, at a temperature of 50°C to 180°C for 5 to 600 seconds.

[0268] [Development Step] In this step, the exposed resist film is developed. This allows a predetermined resist pattern to be formed. The development method in the development step may be alkali development or organic solvent development.

[0269] In the case of alkaline development, examples of the developer used for development include alkaline aqueous solutions 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 (hereinafter also referred to as "TMAH"), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, aqueous TMAH solutions are preferred, and 2.38% by mass aqueous TMAH solutions are more preferred.

[0270] In the case of organic solvent development, examples of the developer include the organic solvents exemplified above as the organic solvent (D) of the radiation-sensitive composition.

[0271] <Polymer> The polymer has a structural unit represented by the following formula (1a) or (1b): The polymer can be suitably used as a base resin for a radiation-sensitive composition.

[0272]

[0273] In the above formula (1a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａis a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different from each other.

[0274] In the above formula (1b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different from each other.

[0275] The polymer is described above in the section <Polymer (A)>.

[0276] <Monomer> The monomer is a monomer represented by the following formula (2a) or (2b): This monomer can be suitably used as a monomer for synthesizing a base resin of a radiation-sensitive composition.

[0277]

[0278] In the above formula (2a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａis a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different from each other.

[0279] In the above formula (2b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different from each other.

[0280] In the above formula (2a), R １ａ , L １ａ , Ar １ａ , n １ａ , n ２ａ , m ａ , R ２ａ , L ２ａ and R ３ａ represents R in formula (1a) in the above section <Polymer (A)>. １ａ , L １ａ , Ar １ａ , n １ａ , n ２ａ , m ａ , R ２ａ , L ２ａ and R ３ａ is synonymous with.

[0281] In the above formula (2b), R １ｂ , L １ｂ , Ar １ｂ , R ２ｂ , X, R ３ｂ , n ｂ and m ｂ represents R in formula (1b) in the above section <Polymer (A)>. １ｂ , L １ｂ , Ar １ｂ , R ２ｂ , X, R ３ｂ , n ｂ and m ｂ is synonymous with.

[0282] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0283] Example a This Example a is an example relating to composition (1).

[0284] <Synthesis of [Ma] Monomer> Compounds represented by formulas (Ma-1) to (Ma-16) described below (hereinafter also referred to as "monomers (Ma-1) to (Ma-16)") were synthesized according to the following method.

[0285] [Synthesis Example 1a-1] Synthesis of Monomer (Ma-1) Monomer (Ma-1) was synthesized according to the following synthesis scheme.

[0286]

[0287] A reaction vessel was charged with 183 mmol of 2-hydroxy-5-vinylbenzenecarboxylic acid, 183 mmol of α-hydroxy-γ-butyrolactone, 201 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI·HCl), 274 mmol of dimethylaminopyridine (DMAP), and 400 g of tetrahydrofuran (THF), and the mixture was stirred at 25°C for 5 hours. A saturated aqueous ammonium chloride solution was added, and then extraction was performed using ethyl acetate. The resulting organic layer was washed with water and dried over sodium sulfate. The solvent was then distilled off, and the mixture was purified by column chromatography to obtain monomer (Ma-1) in good yield.

[0288] [Synthesis Examples 1a-2 to 1a-11] Monomers (Ma-2) to (Ma-11) were synthesized in the same manner as in Synthesis Example 1a-1, except that the raw materials and precursors for synthesis of monomers (Ma-2) to (Ma-11) were appropriately changed.

[0289]

[0290] [Synthesis Example 1a-12] Synthesis of Monomer (Ma-12) Monomer (Ma-12) was synthesized according to the following synthesis scheme.

[0291]

[0292] A reaction vessel was charged with 196 mmol of 5-amino-2-hydroxybenzoic acid and triethylamine (Et ３ 294 mmol of methacrylic anhydride (N) and 400 g of tetrahydrofuran (THF) were added and stirred at 0°C for 1 hour. Then, 215.0 mmol of methacrylic anhydride was slowly added dropwise, and the mixture was stirred at 25°C for 5 hours. The reaction solution was cooled to 20°C or below, and a saturated aqueous ammonium chloride solution was added to terminate the reaction. Thereafter, extraction was carried out using ethyl acetate. The obtained organic layer was washed with water and dried over sodium sulfate. Thereafter, the solvent was distilled off, and the mixture was purified by column chromatography to obtain a compound represented by the above formula (Ma-12-a) (hereinafter also referred to as "compound (Ma-12-a)") in good yield.

[0293] To 136 mmol of compound (Ma-12-a), 136 mmol of α-hydroxy-γ-butyrolactone, 149 mmol of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI.HCl), 203 mmol of dimethylaminopyridine (DMAP), and 300 g of tetrahydrofuran (THF) were added, and the mixture was stirred at 25°C for 5 hours. A saturated aqueous ammonium chloride solution was added, and then extraction was performed using ethyl acetate. The obtained organic layer was washed with water and dried over sodium sulfate. Thereafter, the solvent was distilled off, and the mixture was purified by column chromatography to obtain monomer (Ma-12) in good yield.

[0294] [Synthesis Examples 1a-13 to 1a-16] Monomers (Ma-13) to (Ma-16) were synthesized in the same manner as in Synthesis Example 1a-12, except that the raw materials and precursors for synthesis of monomers (Ma-13) to (Ma-16) were appropriately changed.

[0295]

[0296] <Synthesis of Polymer [A1]> Polymers (A1-1) to (A1-32) were synthesized according to the following method. For the synthesis of Polymer [A1], monomers (Ma-1) to (Ma-16) and compounds represented by the following formulae (Ma-17) to (Ma-31) (hereinafter also referred to as "monomers (Ma-17) to (Ma-31)") were used. The Mw and Mw / Mn of the obtained Polymer [A] were confirmed by GPC as described above in the section [Method for measuring Mw and Mn].

[0297]

[0298] [Synthesis Example 2a-1] Synthesis of Polymer (A1-1) Monomer (Ma-1), monomer (Ma-17), and monomer (Ma-28) were dissolved in propylene glycol monomethyl ether (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer obtained was 20 / 60 / 20. Next, 2,2'-azobis(methyl isobutyrate) was added as an initiator in an amount of 10 mol% relative to the total amount of monomers to prepare a monomer solution. Meanwhile, propylene glycol monomethyl ether (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for an additional 3 hours, allowing the polymerization reaction to proceed for a total of 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. The cooled polymerization solution was added to hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, then filtered and dissolved in propylene glycol monomethyl ether (300 parts by mass). The solution was added dropwise to 500 parts by mass of water to coagulate the resin, and the resulting solid was filtered. The resulting solution was dried at 50°C for 12 hours to obtain a white powdery polymer (A1-1). The Mw of the resulting polymer (A1-1) was 5,100, and the Mw / Mn was 1.6.

[0299] [Synthesis Examples 2a-2 to 2a-32] Synthesis of polymers (A1-2) to (A1-32) Polymers (A1-2) to (A1-32) were synthesized in the same manner as in Synthesis Example 2a-1, except that the types and ratios of the monomers were changed as shown in Table 1. The Mw and Mw / Mn of each of the resulting polymers are shown in Table 1.

[0300] In Table 1 below, "-" indicates that the corresponding monomer was not used. Furthermore, although monomer (Ma-26) does not correspond to a monomer that provides structural unit (Ia), it is listed in the column "Monomer that provides structural unit (Ia)" for comparison.

[0301]

[0302] <Synthesis of Polymer [F]> Polymers (Fa-1) to (Fa-2) were synthesized according to the following method. For the synthesis of Polymer [F], monomers (Ma-17) to (Ma-18) and compounds represented by the following formulae (Ma-32) to (Ma-33) (hereinafter also referred to as "Monomers (Ma-32) to (Ma-33)") were used. The Mw and Mw / Mn of the obtained Polymer [F] were confirmed by GPC as described above in the section [Method for measuring Mw and Mn].

[0303]

[0304] [Synthesis Example 3a-1] Synthesis of Polymer (Fa-1) Monomer (Ma-17) and monomer (Ma-32) were dissolved in 2-butanone (200 parts by mass) so that the molar ratio in the final polymer obtained was 30 / 70. Azobisisobutyronitrile (5 mol% relative to the total monomers) was added thereto as an initiator to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel, and the vessel was purged with nitrogen for 30 minutes. The temperature inside the reaction vessel was brought to 80°C, and the monomer solution was added dropwise over 3 hours with stirring. After the dropwise addition was completed, the mixture was stirred at 80°C for an additional 3 hours. After the polymerization reaction was completed, the polymerization solution was cooled to below 30°C with water, and the solvent was then replaced with acetonitrile (400 parts by mass). Subsequently, hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was collected, and this process was repeated three times. By replacing the solvent with propylene glycol monomethyl ether acetate, a solution of polymer (F-1) was obtained in good yield. The Mw of the obtained polymer (Fa-1) was 5,200, and the Mw / Mn was 1.7.

[0305] [Synthesis Example 3a-2] Synthesis of Polymer (Fa-2) Polymer (Fa-2) was synthesized in the same manner as in Synthesis Example 3a-1, except that the types and ratios of the monomers were changed as shown in Table 2. The Mw and Mw / Mn of each of the obtained polymers are shown in Table 2.

[0306]

[0307] <Preparation of Radiation-Sensitive Composition> The acid generator [B], the acid diffusion controller [C], and the organic 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 is taken as 100 parts by mass.

[0308] [[B] Acid Generator] As the acid generator [B], compounds represented by the following formulas (B-1) to (B-8) (hereinafter also referred to as "acid generators (B-1) to (B-8)") were used.

[0309]

[0310] [[C] Acid Diffusion Controller] As the acid diffusion controller [C], compounds represented by the following formulas (C-1) to (C-6) (hereinafter also referred to as "acid diffusion controllers (C-1) to (C-6)") were used.

[0311]

[0312] [[D] Organic Solvent] The following organic solvents were used as the organic solvent [D]: (D-1): Propylene glycol monomethyl ether acetate (D-2): Propylene glycol monomethyl ether (D-3): Diacetone alcohol

[0313] [Example 1a] Preparation of radiation-sensitive composition (Ra-1) 100 parts by mass of polymer (A1-1), 45 parts by mass of acid generator (B-1), 50 mol% of acid diffusion controller (C-1) based on acid generator (B-1), 3 parts by mass (solid content) of polymer (F-1), 5,500 parts by mass of organic solvent (D-1), and 1,500 parts by mass of organic solvent (D-2) were mixed. The resulting mixture was filtered through a membrane filter with a pore size of 0.2 μm to prepare radiation-sensitive composition (Ra-1).

[0314] [Examples 2a to 41a and Comparative Examples 1a to 2a] Preparation of radiation-sensitive compositions (Ra-2) to (Ra-44) and (CRa-1) to (CRa-3) Radiation-sensitive compositions (Ra-2) to (Ra-44) and (CRa-1) to (CRa-3) were prepared in the same manner as in Example 1a, except that the types and blending amounts of each component shown in Table 3 below were used.

[0315] In Table 3 below, "-" indicates that the corresponding component was not used. The content of the acid diffusion controller (C) refers to the molar ratio relative to the radiation-sensitive acid generator.

[0316]

[0317] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (manufactured by Brewer Science)) was formed using a spin coater (Tokyo Electron Limited's "CLEAN TRACK ACT12"). After PB at 100°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 30-nm-thick resist film. Next, this resist film was irradiated with EUV using an EUV exposure machine (ASML's "NXE3300", NA = 0.33, illumination conditions: Conventional s = 0.89). The resist film was subjected to PEB at 100°C for 60 seconds. The wafer was then developed using a 2.38% by mass aqueous TMAH solution at 23°C for 30 seconds to form a positive-tone 50-nm-pitch, 25-nm-thick contact hole pattern.

[0318] <Evaluation> The sensitivity, CDU and number of development defects were evaluated according to the following methods. The results are shown in Table 4 below.

[0319] [Sensitivity] The exposure dose at which the resist pattern was formed in the above section <Formation of Resist Pattern> was taken as the optimum exposure dose, and this value was used to determine the sensitivity (unit: mJ / cm ２ The smaller the sensitivity value, the better the result. The sensitivity was 40 mJ / cm ２ If it is less than 40 mJ / cm, it is rated as "A" (very good). ２ More than 42mJ / cm ２ The following cases are rated as "B" (good) and 42 mJ / cm ２ If it was over 100%, it was rated as "C" (poor).

[0320] [CDU] The resist pattern formed in the above section <Formation of Resist Pattern> was observed from above the pattern using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-4100"). A total of 600 points of hole diameter variation were measured, and a 3 sigma value was calculated from the distribution of the measured values. The calculated 3 sigma value was taken as CDU (unit: nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating a better result. CDU was evaluated as "A" (very good) when it was less than 2.8 nm, "B" (good) when it was 2.8 nm or more but 3.0 nm or less, and "C" (poor) when it exceeded 3.0 nm.

[0321] [Number of Development Defects] The number of defects (pieces) for the resist patterns formed in the above section <Formation of Resist Pattern> was measured using a defect inspection device (KLA-Tencor's "KLA2810"). The measured defects were then classified into those determined to be derived from the resist film and foreign matter derived from the external environment. The number of development defects was evaluated as "A" (very good) when the number of defects determined to be derived from the resist film was less than 30, as "B" (good) when the number was 30 to 50, and as "C" (poor) when the number was more than 50.

[0322]

[0323] Example b This Example b is an example relating to composition (2).

[0324] <Synthesis of [Mb] Monomer> Compounds represented by the following formulas (Mb-23) to (Mb-49) (hereinafter also referred to as "monomers (Mb-23) to (Mb-49)") were synthesized according to the following method.

[0325]

[0326] [Synthesis Example 1b-1] Synthesis of Monomer (Mb-23) Monomer (Mb-23) was synthesized according to the following synthesis scheme.

[0327]

[0328] 120 mmol of 2,6-diiodo-4-vinylphenol, 132 mmol of potassium carbonate, 12 mmol of potassium iodide, and 60 g of dimethylformamide (DMF) were added to a reaction vessel and stirred for 30 minutes. 132 mmol of α-bromo-γ-butyrolactone dissolved in 30 g of DMF was added and stirred at 50°C for 5 hours. The mixture was cooled to 0°C using an ice bath, water was added, and then extraction was performed using ethyl acetate. The resulting organic layer was dried over sodium sulfate. The solvent was then distilled off, and the resulting mixture was purified by silica gel column chromatography to obtain monomer (Mb-23).

[0329] [Synthesis Examples 1b-2 to 1b-25] Synthesis of Monomers (Mb-24) to (Mb-47) Monomers (Mb-24) to (Mb-47) were synthesized in the same manner as in Synthesis Example 1b-1, except that the substrate, reaction solvent, and reaction temperature were appropriately selected.

[0330] [Synthesis Example 1b-26] Synthesis of Monomer (Mb-48) Monomer (Mb-48) was synthesized according to the following synthesis scheme.

[0331]

[0332] Compound (2b-a) was obtained in the same manner as in Synthesis Example 1-1, except that the substrate was appropriately selected. Then, 30 mmol of compound (2b-a), 30 mmol of compound (2b-b), 50 g of water, and 50 g of dichloromethane were added to a reaction vessel and stirred for 2 hours. Extraction was performed using dichloromethane, and the resulting organic layer was dried over sodium sulfate. The solvent was then distilled off, and the resulting mixture was purified by silica gel column chromatography to obtain monomer (Mb-48).

[0333] [Synthesis Example 1b-27] Synthesis of Monomer (Mb-49) Monomer (Mb-49) was synthesized according to the following synthesis scheme.

[0334]

[0335] 50 mmol of monomer (Mb-44) and 100 g of dichloromethane were added to a reaction vessel and cooled to 0° C. 250 mmol of trifluoroacetic acid was added, and the mixture was stirred at 0° C. for 2 hours. Water was added, and the organic layer was washed with water. The obtained organic layer was dried over sodium sulfate, and then the solvent was distilled off. The residue was purified by silica gel column chromatography to obtain compound (3b-a).

[0336] 35 mmol of compound (3b-a), 35 mmol of compound (2b-b), 39 mmol of sodium bicarbonate, 60 g of water, and 60 g of dichloromethane were added to a reaction vessel and stirred for 2 hours. Extraction was performed using dichloromethane, and the resulting organic layer was dried over sodium sulfate. The solvent was then distilled off, and the residue was purified by silica gel column chromatography to obtain monomer (Mb-49).

[0337] <Synthesis of Polymer [A2]> [Synthesis Examples 2b-1 to 2b-53] Synthesis of Polymers (A2-1) to (A2-53) The monomers shown in Table 1 below were combined and copolymerized in a solvent of propylene glycol monomethyl ether (200 parts by mass relative to the total amount of monomers). The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane (100 parts by mass relative to the polymerization solution), filtered off, and dissolved in propylene glycol monomethyl ether (300 parts by mass). The resin was coagulated by dropping the mixture into 500 parts by mass of water, and the resulting solid was filtered off. The mixture was dried at 50°C for 12 hours to obtain Polymers (A2-1) to (A2-53) in the form of white powder. The composition of the obtained Polymer [A2] was determined using a nuclear magnetic resonance spectrometer (JEOL Ltd., "JNM-Delta400"). １ The Mw and dispersity (Mw / Mn) were confirmed by H-NMR, and by GPC as described in the above section [Method for measuring Mw and Mn].

[0338] Polymer [A2] was synthesized using monomers (Mb-23) to (Mb-49) and compounds represented by the following formulas (Mb-1) to (Mb-22) (hereinafter also referred to as "monomers (Mb-1) to (Mb-22)").

[0339]

[0340] In Table 5 below, "-" indicates that the corresponding monomer was not used. Furthermore, although monomer (Mb-43) does not correspond to a monomer that provides structural unit (Ib), it is listed in the column "Monomer that provides structural unit (Ib)" for comparison.

[0341]

[0342] <Synthesis of Polymer [F]> [Synthesis Example 3b-1] Synthesis of Polymer (Fb-1) Polymer (Fb-1) was obtained in the same manner as in Synthesis Examples 2b-1 to 2b-53, except that the monomers of the compositions shown in Table 6 below were combined. Compounds represented by the following formulae (FM-1) to (FM-3) (hereinafter also referred to as "monomers (FM-1) to (FM-3)") were used to synthesize Polymer [F]. The Mw and Mw / Mn of the obtained Polymer [F] were confirmed by GPC as described in the above section [Method for measuring Mw and Mn].

[0343]

[0344]

[0345] <Preparation of Radiation-Sensitive Composition> The radiation-sensitive composition was prepared using the acid generators (B-1) to (B-8), acid diffusion controllers (C-1) to (C-6), and organic solvents (D-1) to (D-3) used in Example a. In the following examples and comparative examples, unless otherwise specified, "parts by mass" refers to a value when the mass of the polymer [P] used is taken as 100 parts by mass.

[0346] [Example 1b] Preparation of radiation-sensitive composition (Rb-1) 100 parts by mass of polymer (A2-1), 30 parts by mass of acid generator (B-1), 50 mol% of acid diffusion controller (C-1) based on acid generator (B-1), 2,000 parts by mass of organic solvent (D-1), and 4,800 parts by mass of organic solvent (D-2) were mixed. The resulting mixture was filtered through a membrane filter with a pore size of 0.2 μm to prepare radiation-sensitive composition (Rb-1).

[0347] [Examples 2b to 66b and Comparative Example 1b] Preparation of radiation-sensitive compositions (Rb-2) to (Rb-66) and (CRb-1) Radiation-sensitive compositions (Rb-2) to (Rb-66) and (CRb-1) were prepared in the same manner as in Example 1b, except that the types and blending amounts of each component shown in Table 7 below were used.

[0348] In Table 7 below, "-" indicates that the corresponding component was not used. In Table 7 below, the content ratio of the acid diffusion controller (B) means the molar ratio relative to the radiation-sensitive acid generator (or the total of the radiation-sensitive acid generators, if multiple radiation-sensitive acid generators are present).

[0349]

[0350] <Formation of Resist Pattern> A positive contact hole pattern with a 50 nm pitch and a 25 nm diameter was formed in the same manner as in <Formation of Resist Pattern> in the above-mentioned <Example a>.

[0351] <Evaluation> The sensitivity, CDU and number of development defects were evaluated according to the following methods. The results are shown in Table 8 below.

[0352] [Sensitivity] The exposure dose at which the resist pattern was formed in the above section <Formation of Resist Pattern> was taken as the optimum exposure dose, and this value was used to determine the sensitivity (unit: mJ / cm ２ The smaller the sensitivity value, the better the result. The sensitivity was 38 mJ / cm ２ If it is less than 38 mJ / cm, it is rated as "A" (very good). ２ More than 40mJ / cm ２ In the following cases, it is rated as "B" (good) and 40 mJ / cm ２ If it was over 100%, it was rated as "C" (poor).

[0353] [CDU] The resist pattern formed in the above section <Formation of Resist Pattern> was observed from above the pattern using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-4100"). A total of 600 points of hole diameter variation were measured, and a 3 sigma value was calculated from the distribution of the measured values. The calculated 3 sigma value was taken as CDU (unit: nm). The smaller the CDU value, the smaller the variation in hole diameter over a long period, indicating a better result. CDU was evaluated as "A" (very good) when it was less than 2.8 nm, "B" (good) when it was 2.8 nm or more but 3.0 nm or less, and "C" (poor) when it exceeded 3.0 nm.

[0354] [Number of Development Defects] The number of defects (pieces) for the resist patterns formed in the above section <Formation of Resist Pattern> was measured using a defect inspection device (KLA-Tencor's "KLA2810"). The measured defects were then classified into those determined to be derived from the resist film and foreign matter derived from the external environment. The number of development defects was evaluated as "A" (very good) when the number of defects determined to be derived from the resist film was less than 25, as "B" (good) when it was 25 to 50, and as "C" (poor) when it was more than 50.

[0355]

Claims

1. A radiation-sensitive composition containing a polymer having a structural unit (I) including a substituted aromatic ring and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and whose solubility in a developer changes upon the action of an acid.

2. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) is a structural unit (Ia) containing an aromatic ring having, as a substituent, at least one group selected from the group consisting of a phenolic hydroxyl group, a phenolic hydroxyl group protected by a protecting group, and an iodo group, and a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof.

3. The radiation-sensitive composition according to claim 2, wherein the structural unit (Ia) is represented by the following formula (1a): (In formula (1a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different.) 4. L １ａ 4. The radiation-sensitive composition according to claim 3, wherein is -CONH-.

5. n １ａ is 1 or more, and n ２ａ 4. The radiation-sensitive composition according to claim 3, wherein:

6. R ２ａ 4. The radiation-sensitive composition according to claim 3, wherein is a protecting group.

7. R ３ａ 4. The radiation-sensitive composition according to claim 3, wherein is a group in which one hydrogen atom has been removed from a lactone structure.

8. The radiation-sensitive composition according to claim 7, wherein the lactone structure is a monocyclic lactone structure.

9. The radiation-sensitive composition according to claim 7, wherein the lactone structure is a polycyclic lactone structure.

10. The radiation-sensitive composition according to claim 7, wherein said lactone structure contains a fluorinated alkyl group.

11. R ３ａ 4. The radiation-sensitive composition according to claim 3, wherein is a group in which one hydrogen atom has been removed from a cyclic carbonate structure.

12. R ３ａ 4. The radiation-sensitive composition according to claim 3, wherein is a group in which one hydrogen atom has been removed from a sultone structure.

13. The radiation-sensitive composition according to claim 2, wherein at least one of said polymer and said non-polymer component has an iodine group.

14. The radiation-sensitive composition according to claim 1, wherein the structural unit (I) is a structural unit (Ib) containing a structure in which a lactone structure is bonded to a substituted aromatic ring via an oxygen atom or a sulfur atom.

15. The above substituents are halogeno groups, hydroxy groups (-OH), carboxy groups (-COOH), cyano groups (-CN), nitro groups (-NO ２ ), alkyl group (-R), fluorinated alkyl group, alkoxy group (-OR), alkoxycarbonyl group (-CO-OR), alkoxycarbonyloxy group (-O-CO-OR), acyl group (-COR), acyloxy group (-O-COR), amino group (-NH ２ , -NHR, -NRR), amide group (-CO-NH ２ , —CO—NHR, —CO—NRR), aminoacyl group (—NH—COR), alkylsulfonyl group (—SO ２ 15. The radiation-sensitive composition according to claim 14, wherein the alkyl group is at least one selected from the group consisting of a group containing an acid-dissociable group, a group that generates an acid under the action of radiation, and a group in which an oxygen atom or a sulfur atom is combined with a lactone structure.

16. The radiation-sensitive composition according to claim 14, wherein the structural unit (Ib) is represented by the following formula (1b): (In formula (1b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different.) 17. R ２ｂ However, halogeno groups, hydroxy groups (-OH), carboxy groups (-COOH), cyano groups (-CN), nitro groups (-NO ２ ), alkyl group (-R), fluorinated alkyl group, alkoxy group (-OR), alkoxycarbonyl group (-CO-OR), alkoxycarbonyloxy group (-O-CO-OR), acyl group (-COR), acyloxy group (-O-COR), amino group (-NH ２ , -NHR, -NRR), amide group (-CO-NH ２ , —CO—NHR, —CO—NRR), aminoacyl group (—NH—COR), alkylsulfonyl group (—SO ２ 17. The radiation-sensitive composition according to claim 16, wherein the alkyl group is at least one selected from the group consisting of a group containing an acid-dissociable group, a group that generates an acid under the action of radiation, and a group in which an oxygen atom or a sulfur atom is combined with a lactone structure.

18. A method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 17 directly or indirectly to a substrate; exposing a resist film formed by said application; and developing the exposed resist film.

19. A polymer having a structural unit represented by the following formula (1a) or (1b): (In formula (1a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different. In formula (1b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different.) 20. A monomer represented by the following formula (2a) or (2b): (In formula (2a), R １ａ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ａ is a single bond, —COO—, —CONH— or —O—. １ａ is a substituted or unsubstituted aromatic ring (n １ａ +n ２ａ +m ａ +1) hydrogen atoms are removed. ２ａ is a hydrogen atom or a protecting group. １ａ is an integer from 0 to 3. １ａ If there are two or more R ２ａ are the same or different. ２ａ is an integer from 0 to 3. １ａ +n ２ａ is 1 or more. ２ａ is a single bond or a divalent linking group. ３ａ is a group in which one hydrogen atom has been removed from a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. ａ is an integer from 1 to 3. ａ If there are two or more L ２ａ are the same or different, and multiple R ３ａ are the same or different. In formula (2b), R １ｂ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. １ｂ is a single bond, —COO— or —CONH—. １ｂ is the aromatic ring from (n ｂ +m ｂ +1) hydrogen atoms are removed. ２ｂ is a substituent. X is —O— or —S—. R ３ｂ is a group in which one hydrogen atom has been removed from a lactone structure. ｂ is 1 to 3. ｂ is 0 to 3. ｂ +m ｂ is 2 or more. ｂ When there are two or more, the plurality of Xs are the same or different, and the plurality of R ３ｂ are the same or different. ｂ If there are two or more R ２ｂ are the same or different.)

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