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

Abstract

Disclosed is a radiation-sensitive composition that contains a polymer which has a structural unit (ma) derived from a (meth)acrylic acid-based monomer having a group (x) that is other than a hydrogen atom, a fluoro group, a methyl group, and a trifluoromethyl group at the α-position, and which satisfies any one of requirements (i) to (iii), wherein at least one of the polymer and a component other than the polymer has an iodine group (provided that the component other than the polymer has an iodine group in cases where the polymer satisfies requirement (i)).

Description

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

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

[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 to leave little development residue and to have excellent rectangular cross-sectional shape.

[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 exhibit an excellent balance between sensitivity, development residue, and rectangularity of the cross-sectional shape. Another object of the present invention is to provide a polymer that is suitable as a component of the radiation-sensitive composition. Yet another 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 problems is a radiation-sensitive composition containing a polymer (hereinafter also referred to as "polymer [A]") having a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and satisfying any of the following requirements (i) to (iii), wherein at least one of the polymer and a component other than the polymer has an iodine group (provided that when the polymer satisfies the following requirement (i), the component other than the polymer has an iodine group): (i) The group (x) is a group (y) that generates an acid when acted upon by radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (provided that a methyl group, a trifluoromethyl group, and the group (y) are excluded), and the structural unit (ma) further has the group (y) in addition to the group (x). (iii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[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-mentioned problems is a polymer having a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and an iodine group, and satisfying any of the following requirements (i') to (iii): (i') The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the structural unit (ma) further has the group (y) in addition to the group (x). (iii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[0011] Still another invention made to solve the above problems is a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, which has an iodine group, and satisfies either of the following requirements (i') or (ii): (i') The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the compound further has the group (y) in addition to the group (x).

[0012] The radiation-sensitive composition of the present invention has an excellent balance between sensitivity, development residue, and rectangular cross-sectional shape. According to the method for forming a resist pattern of the present invention, a resist pattern having an excellent balance between sensitivity, development residue, and rectangular cross-sectional shape can be formed. The polymer of the present invention is suitable as a polymer contained in a radiation-sensitive composition. Therefore, these can be suitably used in processing processes for 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 compound of the present invention will be described in detail below.

[0014] Unless otherwise specified, the description of the upper and lower limits of a numerical range in this specification may be "less than or equal to" or "less than," and the lower limit may be "greater than or equal to" or "greater than." The upper and lower limits may be any combination of the disclosed numerical values. 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 (polymer [A]) that has a structural unit (ma) derived from a (meth)acrylic acid monomer having, at the α-position, a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group, and that satisfies any of the following requirements (i) to (iii), wherein at least one of the polymer and a component other than the polymer has an iodine group (provided that, when the polymer satisfies the following requirement (i), the component other than the polymer has an iodine group) (hereinafter, also referred to as "requirement (iv)"). Requirement (i): The group (x) is a group (y) that generates an acid when acted upon by radiation. Requirement (ii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (provided that a methyl group, a trifluoromethyl group, and the group (y) are excluded), and the structural unit (ma) further has the group (y) in addition to the group (x). Requirement (iii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[0016] The radiation-sensitive composition has the above-described structure, and thus has an excellent balance of sensitivity, development residue, and rectangularity of the cross-sectional shape. In other words, the radiation-sensitive composition has excellent sensitivity, little development residue, and excellent rectangularity of the cross-sectional shape. The reason for this is not necessarily clear, but is presumed to be, for example, as follows. It is thought that the polymer [A] containing the structural unit (ma) forms a coating film with a uniform distribution, resulting in little development residue and excellent rectangularity of the cross-sectional shape. Furthermore, it is thought that the presence of an iodine group in any of the components contained in the radiation-sensitive composition improves the efficiency of radiation absorption, thereby improving sensitivity. It is thought that the radiation-sensitive composition has the above-described structure, and the above-described effects combined enable a good balance of the three factors of sensitivity, development residue, and rectangularity of the cross-sectional shape.

[0017] The radiation-sensitive composition usually contains an organic solvent (hereinafter also referred to as "organic solvent [D]"). The radiation-sensitive composition may contain a radiation-sensitive acid generator (hereinafter also referred to as "acid generator [B]"). The radiation-sensitive composition may contain an acid diffusion controller (hereinafter also referred to as "acid diffusion controller [C]"). The radiation-sensitive composition may contain other optional components as long as the effects of the present invention are not impaired.

[0018] The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A), and, if necessary, the acid generator (B), the acid diffusion controller (C), the organic solvent (D), 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.

[0019] [Requirement (iv)] Requirement (iv) is that the polymer [A] and a component other than the polymer [A] (i.e., a component contained in the radiation-sensitive composition) have an iodine group (however, when the polymer satisfies the following requirement (i), the component other than the polymer has an iodine group). This means that it is sufficient for any component contained in the radiation-sensitive composition to contain an iodine group. However, when the polymer "A" satisfies the later-described requirement (i), it is necessary for a component other than the polymer [A] to contain an iodine group. In this case, the polymer [A] may or may not contain an iodine group.

[0020] The components other than the polymer [A] are not particularly limited as long as they are components contained in the radiation-sensitive composition. The component other than the polymer [A] is preferably an acid generator [B] or an acid diffusion controller [C]. In other words, it is preferable that an iodine group is contained in either the polymer [A], the acid generator [B], or the acid diffusion controller [C]. When the polymer "A" satisfies the requirement (i) described below, it is preferable that an iodine group is contained in either the acid generator [B] or the acid diffusion controller [C].

[0021] The number of iodo groups may be 1 or more, and the sensitivity of the radiation-sensitive composition tends to be further improved when the number is 2 or more. In this specification, the number of iodo groups means the number of iodo groups in one structural unit when the polymer (A) has an iodo group, and means the number of iodo groups in one molecule when the acid generator (B) or the acid diffusion controller (C) has an iodo group.

[0022] Preferred embodiments from the viewpoint of development residue are described below. When the polymer [A] has an iodine group and the anion moiety of the acid generator [B] or the acid diffusion controller [C] has an iodine group, development residue tends to be reduced, which is preferred. When the polymer [A] does not have an iodine group and the anion moiety of the acid generator [B] or the acid diffusion controller [C] has an iodine group, development residue tends to be reduced even more, which is more preferred. When only the polymer [A] has an iodine group, development residue tends to be reduced even more, which is even more preferred. When only the cation moiety of the acid generator [B] or the acid diffusion controller [C] has an iodine group, development residue tends to be reduced even more, which is particularly preferred.

[0023] A preferred embodiment will be described from the viewpoint of the rectangularity of the cross-sectional shape. When the polymer [A] does not have an iodine group and the anion moiety of the acid generator [B] or the acid diffusion controller [C] has an iodine group, the rectangularity of the cross-sectional shape tends to be better, which is preferred. When only the cation moiety of the acid generator [B] or the acid diffusion controller [C] has an iodine group, the rectangularity of the cross-sectional shape tends to be even better, which is more preferred. When only the polymer [A] has an iodine group, the rectangularity of the cross-sectional shape tends to be even better, which is even more preferred. When the polymer [A] has an iodine group and the acid generator [B] or the acid diffusion controller [C] has an iodine group, the rectangularity of the cross-sectional shape tends to be even better, which is particularly preferred.

[0024] From the viewpoint of further improving the radiation absorption efficiency, the iodo group is preferably bonded to an aromatic ring. In other words, it is preferable that any component contained in the radiation-sensitive composition has an aromatic ring in which at least one hydrogen atom is substituted with an iodo group. The term "aromatic ring" includes an "aromatic hydrocarbon ring" and an "aromatic heterocycle." Among aromatic rings, polycyclic rings including an aromatic hydrocarbon ring and an aromatic heterocycle are considered to be "aromatic heterocycles."

[0025] The number of ring members in the aromatic ring is not particularly limited and is, for example, 5 to 30, preferably 5 to 20, and more preferably 6 to 20. "Number of ring members" refers to the number of atoms constituting the ring structure, and in the case of a polycycle, it refers to the number of atoms constituting the polycycle. "Polycycle" includes not only fused polycycles in which two rings share two common atoms, but also ring assembly polycycles in which two rings do not share a common atom and are connected by a single bond.

[0026] Examples of the aromatic ring include an aromatic hydrocarbon ring having 6 to 30 ring members and an aromatic heterocyclic ring having 5 to 30 ring members.

[0027] 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.

[0028] 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.

[0029] The aromatic ring may have a substituent other than the iodo group, such as 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 fluoro group), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group.

[0030] Each component contained in the radiation-sensitive composition will be described below.

[0031] <Polymer [A]> The polymer [A] is a polymer that has a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and satisfies any of the following requirements (i) to (iii): Requirement (i): The group (x) is a group (y) that generates an acid when acted on by radiation; Requirement (ii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the structural unit (ma) further has the group (y) in addition to the group (x); Requirement (iii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[0032] The radiation-sensitive composition may contain one or more types of polymer (A).

[0033] The polymer [A] preferably has a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (II)"). The polymer [A] preferably has a structural unit containing a phenolic hydroxyl group (hereinafter also simply referred to as "structural unit (III)"). The polymer [A] may further have other structural units (hereinafter also simply referred to as "other structural units") other than the structural units (ma), (II), and (III). The polymer [A] can have one or more types of each structural unit.

[0034] The other structural units are structural units other than the above structural units (ma), (mb), (II), and (III). Examples of the other structural units include a structural unit containing an alcoholic hydroxyl group (hereinafter also referred to as "structural unit (IV)").

[0035] 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.

[0036] 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.

[0037] 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 5,000. The upper limit of the Mw is preferably 30,000, more preferably 20,000, and even more preferably 10,000. 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].

[0038] 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 1.8. The lower limit of the ratio is usually 1.0, preferably 1.1, more preferably 1.2, and even more preferably 1.3.

[0039] [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", one "G3000HXL", and one "G4000HXL" 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

[0040] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0041] Each structural unit contained in the polymer (A) will be described below.

[0042] [Structural unit (ma)] The structural unit (ma) is a structural unit derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position. "(Meth)acrylic acid" includes acrylic acid and methacrylic acid. "(Meth)acrylic acid monomer" includes "(meth)acrylic acid ester monomer" and "(meth)acrylamide ester monomer." "Having a group (x) at the α-position" means that the group (x) is bonded to the carbon atom to which -COO- or -CONH- is bonded in the (meth)acrylic acid monomer.

[0043] The lower limit of the content of the structural unit (ma) in the polymer [A] is preferably 0.5 mol %, more preferably 1 mol %, still more preferably 2 mol %, and particularly preferably 5 mol %, based on the total structural units constituting the polymer [A]. The upper limit of the content is preferably 30 mol %, more preferably 20 mol %, and still more preferably 15 mol %.

[0044] (Requirement (i)) Requirement (i) is that the group (x) is a group (y) 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.

[0045] Examples of the acid that the group (y) generates by the action of radiation include sulfonic acid and carboxylic acid.

[0046] Examples of the group (y) include a structure containing an anion and a radiation-sensitive onium cation. Such structures 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"). As the group (y), Structure 1 is preferred.

[0047] The group (y) is classified according to the type of acid generated by the action of radiation, for example, into a group that generates a sulfonic acid by the action of radiation (hereinafter also referred to as a "group (ya)") and a group that generates a carboxylic acid by the action of radiation (hereinafter also referred to as a "group (yb)").

[0048] The polymer [A] acts as a radiation-sensitive acid generator or an acid diffusion controller in the radiation-sensitive composition depending on the type of group (y). When the structural unit (ma) has a group (ya), the polymer [A] acts as a radiation-sensitive acid generator in the radiation-sensitive composition. When the structural unit (ma) has a group (yb), the polymer [A] acts as an acid diffusion controller in the radiation-sensitive composition. When the structural unit (ma) has a group (ya) and a group (yb), or when the polymer [A] has a structural unit (ma) having a group (ya) and a structural unit (ma) having a group (yb), the polymer [A] acts as both a radiation-sensitive acid generator and an acid diffusion controller in the radiation-sensitive composition.

[0049] When the structural unit (ma) has a group (yb) (i.e., when it has a group that generates a carboxylic acid upon the action of radiation), the polymer [A] can also be broadly referred to as a "radiation-sensitive acid generator." However, the carboxylic acid generated from the group (yb) upon the action of radiation does not dissociate the acid-dissociable group under conditions in which the acid generated from the acid generator [B] or the like dissociates the acid-dissociable group, and therefore the "radiation-sensitive acid generator" is clearly distinguished from the "acid diffusion controller."

[0050] Examples of the group (ya) include groups represented by the following formula (ya):

[0051]

[0052] In the above formula (ya), 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 and L ａ２ are each independently a single bond or a divalent linking group. ａ２ and R ａ３are 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. ａ１ +n ａ２ +n ａ３ is 1 or more. ＋ is a monovalent radiation-sensitive onium cation. * is a bonding site with the α-position of the (meth)acrylic acid monomer.

[0053] Examples of the group (yb) include groups represented by the following formula (yb).

[0054]

[0055] In the above formula (yb), R ｂ１ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure having five or more ring members. ｂ１ is 0 or 1. ｂ１ and L ｂ２ are each independently a single bond or a divalent linking group. ｂ２ and R ｂ３ are each independently a hydrogen atom, a fluoro group, or a substituted or unsubstituted hydrocarbon group. ｂ２ is an integer from 0 to 10. ｂ４ and R ｂ５ are each independently a fluoro group or a fluorinated hydrocarbon group. ｂ３ is an integer from 0 to 10. ｂ１ +n ｂ２ +n ｂ３ is 1 or more. ＋ is a monovalent radiation-sensitive onium cation. * is a bonding site with the α-position of the (meth)acrylic acid monomer.

[0056] R ａ１ and R ｂ１ 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.

[0057] The "number of ring members" refers to the number of atoms constituting the ring structure, and in the case of a polycyclic ring, it refers to the number of atoms constituting the polycyclic ring. "Polycyclic rings" include not only spiro-type polycyclic rings in which two rings share one shared atom and fused-type polycyclic rings in which two rings share two shared atoms, but also ring assembly-type polycyclic rings in which two rings do not share an atom and are connected by a single bond.

[0058] "Ring structure" includes "alicyclic ring" and "aromatic ring". "Alicyclic ring" includes "aliphatic hydrocarbon ring" and "aliphatic heterocyclic ring". Among alicyclic rings, polycyclic rings containing an aliphatic hydrocarbon ring and an aliphatic heterocyclic ring are considered to be "aliphatic heterocyclic ring". "Aromatic ring" includes "aromatic hydrocarbon ring" and "aromatic heterocyclic ring". Among aromatic rings, polycyclic rings containing an aromatic hydrocarbon ring and an aromatic heterocyclic ring are considered to be "aromatic heterocyclic ring".

[0059] 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.

[0060] Examples of the aliphatic heterocycle 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; oxygen atom-containing heterocycles such as a dioxolane ring, an oxacycloheptane ring and an oxanorbornane ring; nitrogen atom-containing heterocycles such as an azacyclohexane ring and a diazabicyclooctane ring; and sulfur atom-containing heterocycles such as a thiacyclohexane ring and a thianorbornane ring.

[0061] Examples of aromatic hydrocarbon rings having 6 or more ring members 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; a 9,10-ethanoanthracene ring; and a triptycene ring.

[0062] Examples of aromatic heterocycles having 5 or more ring members 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, and an indole ring; and sulfur atom-containing heterocycles such as a thiophene ring.

[0063] The ring structure is preferably an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring, and more preferably a polycyclic saturated alicyclic ring, a benzene ring, or a condensed polycyclic aromatic hydrocarbon ring.

[0064] 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.

[0065] 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 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 alkyl group, a fluorinated alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group.

[0066] The term "linking group" refers to a group that links two or more structures. The linking group remains in the structure of a compound or polymer due to reasons such as the synthetic materials or synthetic methods, and does not affect the effects of the present invention, or has an extremely small effect on the effects of the present invention. However, this does not mean that all structures other than the linking group contribute to the exertion of the effects of the present invention.

[0067] L ａ１ , L ａ２ , L ｂ１ and L ｂ２ Examples of the divalent linking group represented byａ１ , L ａ２ , L ｂ１ and L ｂ２ 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.

[0068] n ａ１ and n ｂ１ As the number, 1 is preferred.

[0069] 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.

[0070] R ａ２ , R ａ３ , R ｂ２ and R ｂ３ Examples of the hydrocarbon group 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] R ａ２ , R ａ３ , R ｂ２ and R ｂ３ Examples of substituents that may be possessed by the hydrocarbon group that gives the formula include R ａ１ and R ｂ１ Examples of the substituent that may be possessed by a ring structure having 5 or more ring members that gives the following formula are given below.

[0075] R ａ２ and R ａ３ is preferably a hydrogen atom.

[0076] R ｂ２ and R ｂ３ is preferably a hydrogen atom or a substituted or unsubstituted hydrocarbon group, more preferably a hydrogen atom or a substituted or unsubstituted aromatic hydrocarbon group, and even more preferably a hydrogen atom or an iodophenyl group.

[0077] n ａ２ and nｂ２ is preferably 0 to 5, and more preferably 0 to 2.

[0078] The term "fluorinated hydrocarbon group" refers to a hydrocarbon group in which at least one hydrogen atom has been substituted with a fluoro group.

[0079] Examples of the hydrocarbon group that gives the fluorinated hydrocarbon group include the above-mentioned R ａ２ , R ａ３ , R ｂ２ and R ｂ３ Examples of hydrocarbon groups that give the following formula include those given above.

[0080] The fluorinated hydrocarbon group is preferably a fluorinated alkyl group, more preferably a perfluoroalkyl group, and even more preferably a trifluoromethyl group.

[0081] n ａ３ and n ｂ３ is preferably 0 to 5, and more preferably 0 to 2.

[0082] As the group (ya), groups represented by the following formulae (ya-1) to (ya-10) are preferred.

[0083]

[0084] In the above formulas (ya-1) to (ya-10), * has the same meaning as in the above formula (ya).

[0085] The group (yb) is preferably a group represented by the following formulae (yb-1) to (yb-7).

[0086]

[0087] In the above formulas (yb-1) to (yb-7), * has the same meaning as in the above formula (yb).

[0088] 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.

[0089] 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)").

[0090]

[0091] 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. Ｂ２ 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 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. ｂ１is an integer from 0 to 3.

[0092] 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.

[0093] 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 Ｂ１０are 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.

[0094] "Organic group" refers to a group containing at least one carbon atom.

[0095] 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)").

[0096] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include the above-mentioned R ａ２ , R ａ３ , R ｂ２ and R ｂ３ Examples of hydrocarbon groups that give the following formula include those given above.

[0097] 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.

[0098] 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).

[0099] 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".

[0100] 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.

[0101] 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.

[0102] R Ｂ３ and R Ｂ４ is preferably a hydrogen atom or a single bond formed by combining these, and is preferably a hydrogen atom.

[0103] 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.

[0104] The radiation-sensitive onium cation is preferably the cation (ra) or the cation (rc).

[0105] Examples of the cation (ra) include cations represented by the following formulae (ra-1) to (ra-18).

[0106]

[0107] Examples of the cation (rc) include cations represented by the following formulae (rc-1) to (rc-5).

[0108]

[0109] An example of the structural unit (ma) that satisfies the requirement (i) is the structural unit (ma-1) represented by the following formula (ma-1).

[0110]

[0111] In the above formula (ma-1), R １ is the above group (y). １ is *-COO- or *-CONH-. * is R １ indicates the bonding site with the carbon atom to which R is attached. ２ is a monovalent organic group.

[0112] R １ The group (y) which gives the formula is described above.

[0113] R ２ Examples of the monovalent organic group that gives the formula include the above-mentioned 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 following formula are given below.

[0114] R ２ The monovalent organic group giving the formula (I) is preferably a substituted or unsubstituted hydrocarbon group.

[0115] Specific examples of the structure of the monomer that provides the structural unit (ma-1) include the monomers (Z-101) to (Z-109) (suitably combined with the cations (cat-1) to (cat-8)) in the examples described later.

[0116] (Requirement (ii)) Requirement (ii) is that the group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the structural unit (ma) further has the group (y) in addition to the group (x).

[0117] Examples of the monovalent organic group having 1 to 30 carbon atoms that provides the group (x) include the above-mentioned 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 following formula are given below.

[0118] The monovalent organic group having 1 to 30 carbon atoms that provides the group (x) is preferably a group (x1) containing an acid-dissociable group or a group (x2) containing a polar group.

[0119] Examples of the acid-dissociable group contained in the group (x1) include the acid-dissociable groups described later in the section on [Structural Unit (II)].

[0120] Examples of the polar group contained in the group (x2) include a group containing a lactone ring structure or a cyclic carbonate structure, a group that gives a hydroxy group upon hydrolysis, a fluorinated alcohol group, a ketone group, and an alkoxy group.

[0121] In an embodiment in which the structural unit (ma) further has a group (y) in addition to the group (x), the group (y) is preferably bonded to —COO— or —CONH—.

[0122] An example of the structural unit (ma) that satisfies the requirement (ii) is the structural unit (ma-2) represented by the following formula (ma-2).

[0123]

[0124] In the above formula (ma-2), R ３ is a monovalent organic group having 1 to 30 carbon atoms (excluding methyl, trifluoromethyl and the above group (y)). ２ is *-COO- or *-CONH-. * is R３ indicates the bonding site with the carbon atom to which R is attached. ４ is the above group (y).

[0125] R ３ and R ４ The group (y) which gives the formula is described above.

[0126] Specific examples of the structure of the monomer that provides the structural unit (ma-2) include the monomers (Z-201) to (Z-209) (suitably combined with the cations (cat-1) to (cat-8)) in the examples described later.

[0127] (Requirement (iii)) Requirement (iii) is that the group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[0128] The monovalent organic group having 1 to 30 carbon atoms that provides the group (x) is as explained above in the section (requirement (ii)).

[0129] The structural unit (mb) of the polymer (A) is a structural unit other than the structural unit (ma) and includes a group (y). The group (y) is described above in the section (Requirement (i)).

[0130] An example of the structural unit (ma) that satisfies the requirement (iii) is the structural unit (ma-3) represented by the following formula (ma-3).

[0131]

[0132] In the above formula (ma-3), R ５ is a monovalent organic group having 1 to 30 carbon atoms (excluding methyl, trifluoromethyl and the above group (y)). ３ is *-COO- or *-CONH-. * is R ５ indicates the bonding site with the carbon atom to which R is attached. ６ is a monovalent organic group.

[0133] R ５The monovalent organic group having 1 to 30 carbon atoms which gives the formula (I) is described above.

[0134] R ６ Examples of the monovalent organic group that gives the formula include the above-mentioned 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 following formula are given below.

[0135] R ６ The monovalent organic group that provides the formula (I) is preferably a group containing an acid-dissociable group. Examples of the acid-dissociable group include the acid-dissociable groups described in the section below on [Structural Unit (II)].

[0136] Specific examples of the structure of the monomer that provides the structural unit (ma-3) include the monomers (Z-301) to (Z-311) (suitably combined with cations (cat-1) to (cat-8)) in the examples described below.

[0137] An example of the structural unit (mb) that satisfies the requirement (iii) is the structural unit (mb) represented by the following formula (mb):

[0138]

[0139] In the above formula (mb), R ７ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. ８ is a single bond or a substituted or unsubstituted aromatic hydrocarbon ring from which two hydrogen atoms have been removed. ４ is *-COO- or *-CONH-. ４ indicates the bonding site with the carbon atom to which R is attached. ｙ is the above group (y).

[0140] R ７ is preferably a hydrogen atom or a methyl group.

[0141] R ８ Examples of aromatic hydrocarbon rings that give ａ１ and Rｂ１ Among the ring structures having 5 or more ring members that give the formula R, examples of aromatic hydrocarbon rings having 6 or more ring members include those exemplified above. ８ The aromatic hydrocarbon ring that provides the following is preferably a benzene ring.

[0142] Specific examples of the structure of the monomer that provides the structural unit (mb) include monomers (Z-501) to (Z-506) (suitably combined with cations (cat-1) to (cat-8)) in the examples described later.

[0143] When the polymer [A] has the structural unit (mb), the lower limit of the content of the structural unit (mb) in the polymer [A] is preferably 0.5 mol %, more preferably 1 mol %, still more preferably 2 mol %, and particularly preferably 5 mol %, based on the total structural units constituting the polymer [A]. The upper limit of the content is preferably 30 mol %, more preferably 20 mol %, and still more preferably 15 mol %.

[0144] [Structural Unit (II)] The structural unit (II) is a structural unit containing an acid-dissociable group. The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group and dissociates under the action of an acid to give a carboxy group. More specifically, the structural unit (II) is a structural unit containing a partial structure in which a hydrogen atom in a carboxy group is substituted with an acid-dissociable group.

[0145] The polymer (A) contains an acid-dissociable group, and thereby exhibits a property in which its solubility in a developer changes under the action of an acid. The acid-dissociable group is dissociated by the action of an acid generated from the acid generator (B) or the like under the action of radiation, and a difference in the solubility of the polymer (A) in a developer occurs between the exposed and unexposed areas, thereby forming a resist pattern.

[0146] 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.

[0147] 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)").

[0148]

[0149] In the above formulas (a-1) and (a-2), * indicates the bonding site with the etheric oxygen atom of the carboxy group.

[0150] In the above formula (a-1), R Ｘ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms. 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.

[0151] In the above formula (a-2), R Ａ is a hydrogen atom. Ｂ and R Ｃ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. Ｄ is R Ａ , R Ｂ and R Ｃ are divalent hydrocarbon groups having 1 to 20 carbon atoms which, together with the three carbon atoms to which they are bonded, constitute an unsaturated alicyclic ring having 4 to 20 ring members.

[0152] R Ｘ , R Ｙ , R Ｚ , R Ｂ , or R Ｃ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives the formula ａ２ , R ａ３ , R ｂ２ and R ｂ３ Examples of hydrocarbon groups that give the following formula include those given above.

[0153] R Ｘ Examples of the substituent that the hydrocarbon group represented by the formula (I) may have include R ａ１ and R ｂ１ Examples of the substituent that may be possessed by a ring structure having 5 or more ring members that gives the following formula are given below.

[0154] R Ｙ and R Ｚ Examples of the saturated alicyclic ring having 3 to 20 ring members formed by combining these together with the carbon atoms to which they are bonded include monocyclic saturated alicyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring; and polycyclic saturated alicyclic rings such as a norbornane ring, an adamantane ring, a tricyclodecane ring, and a tetracyclododecane ring.

[0155] R Ｄ Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include groups in which one hydrogen atom has been removed from the above-mentioned examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0156] R Ｄ And, R Ａ , R Ｂ and R Ｃ and three carbon atoms to which each of the carbon atoms is bonded, include, for example, monocyclic unsaturated alicyclic structures such as a cyclobutene structure, a cyclopentene structure, and a cyclohexene structure, and polycyclic unsaturated alicyclic structures such as a norbornene structure.

[0157] 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, a substituted or unsubstituted chain hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group is preferable, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group is more preferable, and a methyl group or an iodophenyl group is even more preferable.

[0158] 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, a cyclohexane ring, or an adamantane ring. Ｘis preferably a substituted or unsubstituted chain hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group, more preferably a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and further preferably a methyl group, an ethyl group, a tert-butyl group, a phenyl group or an iodophenyl group.

[0159] R Ｂ is preferably a hydrogen atom.

[0160] R Ｃ As the alkyl group, a chain hydrocarbon group is preferable, an alkyl group is more preferable, and a methyl group is even more preferable.

[0161] R Ｄ And, R Ａ , R Ｂ and R Ｃ The unsaturated alicyclic ring having 4 to 20 ring members constituted by each of the carbon atoms to which each of the carbon atoms is bonded is preferably a monocyclic unsaturated alicyclic ring, more preferably a cyclohexene ring.

[0162] Examples of the acid-dissociable group (a-1) include groups represented by the following formulae (a-1-1) to (a-1-7): Examples of the acid-dissociable group (a-2) include groups represented by the following formula (a-2-1):

[0163]

[0164] In the above formulas (a-1-1) to (a-1-7) and (a-2-1), * has the same meaning as in the above formulas (a-1) and (a-2).

[0165] Examples of the structural unit (II) include a structural unit represented by the following formula (II).

[0166]

[0167] In the above formula (II), R Ｈ１ is a hydrogen atom, a fluoro group, 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 is a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring.Ｈ３ is the acid-dissociable group.

[0168] 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.

[0169] L Ｈ is preferably a single bond.

[0170] R Ｈ２ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 30 ring members, more preferably 6 to 20 ring members.

[0171] R Ｈ２ The aromatic hydrocarbon ring that gives ａ１ and R ｂ１ Among the ring structures having 5 or more ring members that give the formula R, examples of aromatic hydrocarbon rings having 6 or more ring members include those exemplified above. Ｈ２ The aromatic hydrocarbon ring that provides the following is preferably a benzene ring.

[0172] R Ｈ２ Examples of the substituents that the aromatic hydrocarbon ring may have include the above-mentioned R ａ１ and R ｂ１ Examples of the substituent that may be possessed by a ring structure having 5 or more ring members that gives the following formula are given below.

[0173] R Ｈ２ may be a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring.

[0174] Specific examples of the structure of the monomer that provides the structural unit (II) include the monomers (M-4) to (M-13) in the examples described below.

[0175] The lower limit of the content of the structural unit (II) in the polymer [A] is preferably 20 mol%, more preferably 30 mol%, even more preferably 40 mol%, and particularly preferably 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%, and even more preferably 70 mol%.

[0176] [Structural Unit (III)] The structural unit (III) is a structural unit containing a phenolic hydroxyl group. The term "phenolic hydroxyl group" refers not only to a hydroxyl group directly bonded to a benzene ring, but also to any hydroxyl group directly bonded to an aromatic ring.

[0177] In the case of KrF exposure, EUV exposure, or electron beam exposure, the sensitivity of the radiation-sensitive composition can be further increased when the polymer [A] contains the structural unit (III). Therefore, when the polymer [A] contains the structural unit (III), the radiation-sensitive composition can be suitably used as a radiation-sensitive composition for KrF exposure, EUV exposure, or electron beam exposure.

[0178] Examples of the structural unit (III) include a structural unit represented by the following formula (III).

[0179]

[0180] In the above formula (III), R Ｐ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. Ｐ is 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.

[0181] 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.

[0182] L Ｐ is preferably a single bond or *-COO-.

[0183] Ar Ｐ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 30 ring members, more preferably 6 to 20 ring members.

[0184] Ar Ｐ Examples of the aromatic hydrocarbon ring that gives ａ１ and R ｂ１Among the ring structures having 5 or more ring members that give the formula (I), examples of aromatic hydrocarbon rings having 6 or more ring members include those exemplified as Ar Ｐ The aromatic hydrocarbon ring that gives the following formula is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring.

[0185] Ar Ｐ Examples of the substituents that the aromatic hydrocarbon ring may have include the above-mentioned R ａ１ and R ｂ１ Examples of the substituent that may be possessed by a ring structure having 5 or more ring members that gives the following formula are given below.

[0186] As p, 1 or 2 is preferred.

[0187] Examples of the structural unit (III) include structural units represented by the following formulae (III-1) to (III-18).

[0188]

[0189] In the above formulas (III-1) to (III-18), R Ｐ has the same meaning as the above formula (III).

[0190] Specific examples of the structure of the monomer that provides the structural unit (III) include the monomers (M-1) to (M-3) in the examples described below.

[0191] 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 20 mol %, more preferably 30 mol %, based on all structural units constituting the polymer [A].The upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0192] [Structural Unit (IV)] The structural unit (IV) is a structural unit containing an alcoholic hydroxyl group. When the polymer (A) further includes the structural unit (IV), the solubility in a developer can be more appropriately adjusted.

[0193] Examples of the structural unit (IV) include structural units represented by the following formula:

[0194]

[0195] In the above formula, R Ｌ２ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0196] A specific example of the structure of the monomer that provides the structural unit (IV) is the monomer (M-14) in the examples described below.

[0197] When the polymer [A] has the structural unit (IV), the lower limit of the content of the structural unit (IV) 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 30 mol %, more preferably 20 mol %.

[0198] <[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.

[0199] Examples of the acid generated from the acid generator (B) include sulfonic acid, carboxylic acid, and imide acid.

[0200] 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.

[0201] Examples of the onium salt compound include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts.

[0202] Specific examples of the acid generator (B) include the compounds described in paragraphs

[0080] to

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

[0203] 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.

[0204] 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)>.

[0205] 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.

[0206] 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.

[0207] Specific examples of the structure of the acid generator [B] include the acid generators (B-1) to (B-7) in the examples described later.

[0208] The lower limit of the content of the acid generator (B) in the radiation-sensitive composition is preferably 1 part by mass, more preferably 5 parts by mass, and even more preferably 10 parts by mass, relative to 100 parts by mass of the polymer (A).The upper limit of the content is preferably 50 parts by mass, more preferably 40 parts by mass, and even more preferably 30 parts by mass.

[0209] <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).

[0210] 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").

[0211] 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.

[0212] 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.

[0213] Examples of the radiation-sensitive onium cation in the photodegradable base include the radiation-sensitive onium cations described above in the section <Polymer (A)>.

[0214] 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.

[0215] 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.

[0216] Specific examples of the structure of the acid diffusion controller [C] include the acid diffusion controllers (C-1) to (C-6) in the examples described later.

[0217] 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 component (or the total of the components if there are multiple components) having a radiation-sensitive acid-generating structure, and the upper limit of the content is preferably 100 mol %, more preferably 60 mol %, and even more preferably 50 mol %.

[0218] <[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.

[0219] 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).

[0220] 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.

[0221] 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.

[0222] 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.

[0223] 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.

[0224] 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.

[0225] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-pentane and n-hexane; and aromatic hydrocarbon solvents such as toluene and xylene.

[0226] 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 methyl 2-hydroxyisobutyrate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or a combination thereof.

[0227] 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 %.

[0228] <Other Optional Components> Examples of other optional components include surfactants, etc. The radiation-sensitive composition may contain one or more other optional components.

[0229] <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").

[0230] 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 an excellent balance of sensitivity, development residue, and rectangular cross-sectional shape can be formed.

[0231] Each step of the resist pattern forming method will be described below.

[0232] [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.

[0233] In this step, the radiation-sensitive composition described above is used as the radiation-sensitive composition.

[0234] Substrates include, for example, silicon wafers, silicon dioxide, and aluminum coated wafers.

[0235] 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.

[0236] [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.

[0237] 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.

[0238] [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.

[0239] 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.

[0240] 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.

[0241] <Polymer> The polymer has a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and an iodine group, and satisfies any of the following requirements (i') to (iii): Requirement (i'): The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; Requirement (ii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the structural unit (ma) further has the group (y) in addition to the group (x). Requirement (iii): The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

[0242] In other words, the polymer corresponds to a polymer having an iodine group among the above-mentioned polymers [A]. The polymer is described above as the polymer [A] in the radiation-sensitive composition. A radiation-sensitive composition containing the polymer exhibits an excellent balance of sensitivity, development residue, and rectangularity of the cross-sectional shape. Therefore, the polymer can be suitably used as a component of a radiation-sensitive composition.

[0243] The polymer may have an iodine group in the main chain or in a side chain. The polymer preferably has an iodine group in the side chain, and more preferably, the structural unit of the polymer contains an iodine group. The iodine group may be contained in any of the structural units (ma), (mb), (II), (III), and (IV) described above.

[0244] Specific examples of the polymer structure include polymers (Aa-20) to (Aa-35), (Aa-39) to (Aa-44), (Ab-1) to (Ab-4), and (Ab-6) to (Ab-9) in the Examples described below. Although all of these polymers have an iodine group on the anion side, polymers that do not have an iodine group on the anion side but have an iodine group on the cation side also fall under the category of polymers of the present invention.

[0245] <Compound> The compound is a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, has an iodine group, and satisfies either of the following requirements (i') or (ii): (i') The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and further has the group (y) in addition to the group (x).

[0246] In other words, the compound corresponds to a compound having an iodine group among monomers that provide a structural unit (ma) that satisfies the requirement (i') or (ii) of the polymer [A] described above. The compound is described as a monomer that provides a structural unit (ma) that satisfies the requirement (i) or (ii) of the polymer [A] in the radiation-sensitive composition described above. The compound can be suitably used as a compound for synthesizing the polymer [A] in the radiation-sensitive composition.

[0247] Specific structures of the monomers include, for example, monomers (Z-106) to (Z-109) (each of which is M ＋ is a cation (cat-1), monomer (Z-102) (M ＋ is a cation (cat-1), monomers (Z-206) to (Z-209) (all M ＋ is a cation (cat-1). Although all of these monomers have an iodine group on the anion side, monomers that do not have an iodine group on the anion side but have an iodine group on the cation side also fall under the category of compounds of the present invention.

[0248] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0249] <Synthesis of Polymer [A]> Polymers (Aa-1) to (Aa-46) and (Ab-1) to (Ab-12) were synthesized according to the following method. For the synthesis of Polymer [A], compounds represented by the following formulae (Z-101) to (Z-109), (Z-101) to (Z-209), (Z-301) to (Z-311), (Z-501) to (Z-506), and (M-1) to (M-14) (hereinafter also referred to as "monomers (Z-101) to (Z-109), (Z-101) to (Z-209), (Z-301) to (Z-311), (Z-501) to (Z-506), and (M-1) to (M-14)") were used. The Mw and Mw / Mn of the resulting polymer were confirmed by GPC as described above in the section [Method for measuring Mw and Mn].

[0250] In the following synthesis examples, "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0251]

[0252]

[0253]

[0254]

[0255] In the above formulas (Z-101) to (Z-109), (Z-101) to (Z-209) and (Z-501) to (Z-506), M ＋ represents radiation-sensitive onium cations represented by the following formulae (cat-1) to (cat-8) (hereinafter also referred to as "cations (cat-1) to (cat-8)"), and specific combinations are shown in Table 1 below.

[0256]

[0257]

[0258] Synthesis Examples 1 to 58 Synthesis of Polymers (Aa-1) to (Aa-46) and (Ab-1) to (Ab-12) Monomers were combined in the compositions shown in Table 1 below and copolymerization reaction was carried out in methyl ethyl ketone. The obtained polymerization solution was added dropwise to hexane, and the precipitated polymer was separated by filtration. The obtained polymer was washed with hexane and dried to obtain polymers (Aa-1) to (Aa-46) and (Ab-1) to (Ab-12).

[0259] The types and amounts (unit: mol %) of monomers that provide each structural unit of the polymers obtained in Synthesis Examples 1 to 58, as well as Mw and Mw / Mn, are shown in Table 1. In Table 1, "-" indicates that the corresponding monomer was not used.

[0260] In Table 1 below, for example, polymer (Aa-1) is M ＋ is a cation (cat-1), the structural units derived from the monomer (Z-101) account for 10 mol %, the structural units derived from the monomer (M-9) account for 30 mol %, the structural units derived from the monomer (M-12) account for 20 mol %, and the structural units derived from the monomer (M-1) account for 40 mol %.

[0261]

[0262] <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.

[0263] [[B] Acid Generator] As the acid generator [B], compounds represented by the following formulas (B-1) to (B-7) (hereinafter also referred to as "acid generators (B-1) to (B-7)") were used.

[0264]

[0265] [[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.

[0266]

[0267] [[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): Methyl 2-hydroxyisobutyrate

[0268] Examples 1 to 75 and Comparative Examples 1 to 9 Preparation of Radiation-Sensitive Compositions (R-1) to (R-75) and (CR-1) to (CR-9) The components shown in Tables 2 and 3 below were blended and mixed in the amounts shown, and then the mixture was passed through a 0.20 μm filter to prepare radiation-sensitive compositions (R-1) to (R-75) and (CR-1) to (CR-9).

[0269] <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 50-nm-thick underlayer film (AL412 (manufactured by Brewer Science)) had been formed, using a spin coater (Tokyo Electron Limited's "CLEAN TRACK ACT12"). After PB at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a 50-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, mask: imecDEFECT32FFR02). The resist film was subjected to PEB at 90°C for 60 seconds. The resist was then developed with a 2.38% by mass aqueous solution of TMAH at 23° C. for 30 seconds to form a positive 34 nm line and space pattern.

[0270] <Evaluation> The sensitivity, development residue, and rectangularity of the cross-sectional shape were evaluated according to the following methods. The results are shown in Tables 2 and 3 below.

[0271] [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 sensitivity was 25 mJ / cm ２ The following cases are rated as "A" (good), d, and 30 mJ / cm ２ If it was over 100%, it was rated as "C" (poor).

[0272] [Development Residue] A wafer having a resist film formed thereon was prepared by carrying out the same operations as those described in the above section <Formation of Resist Pattern> up to the step of forming a 50 nm thick resist film. Using the above EUV exposure machine, the entire surface of the resist film was irradiated with EUV at an optimal exposure dose, followed by PEB at 90°C for 60 seconds. Next, development was carried out using a 2.38 mass% aqueous TMAH solution at 23°C for 30 seconds to prepare a wafer for evaluation of development residue. This wafer was observed using a defect inspection device (AMAT's "COMPLUS"), and the number of residual defects was counted using a defect review SEM (Hitachi High-Technologies Corporation's "RS5500"). The number of residual defects was evaluated based on the following index: A (very good): 5 or less B (good): 6 to 10 C (fair): 11 to 20 D (poor): 21 or more

[0273] [Rectangularity of Cross-Sectional Shape] The cross-sectional shape of the resist pattern formed in the above section <Formation of Resist Pattern> was observed, and the line width Lb at the height center of the resist pattern and the line width La at the top of the resist pattern were measured. The value of La / Lb was calculated, and this value was used as an index of the rectangularity of the cross-sectional shape. The closer the La / Lb value is to 1.00, the better the rectangularity of the cross-sectional shape is. The La / Lb value was evaluated based on the following index: A (Very Good): 0.95 or more and 1.05 or less B (Good): 0.90 or more and less than 0.95, or more than 1.05 and 1.10 or less C (Fairly Good): 0.85 or more and less than 0.90, or more than 1.10 and 1.15 or less D (Poor): Less than 0.85 or more than 1.15

[0274] [Overall Evaluation] The radiation-sensitive compositions were overall evaluated based on the results of three items: sensitivity, development residue, and rectangularity of the cross-sectional shape. Among the evaluation results for sensitivity, A was given "3 points," B "2 points," and C "1 point." Among the evaluation results for development residue and rectangularity of the cross-sectional shape, A was given "4 points," B "3 points," C "2 points," and D "1 point." The scores for the evaluation results for the three items were added together. A total score of 9 points or more was evaluated as "A" (good), 8 points as "B" (fairly good), and 7 points or less as "C" (poor). Radiation-sensitive compositions with an overall evaluation of "B" or higher were evaluated as having an excellent balance in the three items of sensitivity, development residue, and rectangularity of the cross-sectional shape.

[0275] In Table 2 below, "-" indicates that the corresponding component was not used. In Table 2 below, the numbers in parentheses in the columns "[A] Polymer," "[B] Acid Generator," and "[D] Organic Solvent" indicate parts by mass, and the number in parentheses in the column "[C] Acid Diffusion Controller" indicates a value when the number of moles of the component having a radiation-sensitive acid-generating structure (or the total number of moles, if multiple components are present) is taken as 100 mol %.

[0276]

[0277]

[0278] Tables 2 and 3 show that the radiation-sensitive compositions of the Examples all have a better balance of sensitivity, development residue, and rectangular cross-sectional shape than the radiation-sensitive compositions of the Comparative Examples.

Claims

1. A radiation-sensitive composition comprising a polymer having a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and satisfying any of the following requirements (i) to (iii), wherein at least one of the polymer and a component other than the polymer has an iodine group (provided that when the polymer satisfies the following requirement (i), the component other than the polymer has an iodine group). (i) The group (x) is a group (y) that generates an acid when exposed to radiation. (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (provided that a methyl group, a trifluoromethyl group, and the group (y) are excluded), and the structural unit (ma) further has the group (y) in addition to the group (x). (iii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

2. The radiation-sensitive composition according to claim 1, wherein the structural unit (ma) has an iodine group.

3. The radiation-sensitive composition according to claim 1, wherein at least one of said polymer and said non-polymer component has a ring structure in which at least one hydrogen atom is substituted with an iodo group.

4. The radiation-sensitive composition according to claim 1, wherein the group (x) is a group that generates a sulfonic acid or a carboxylic acid upon the action of radiation.

5. The radiation-sensitive composition according to claim 1, wherein the monovalent organic group having 1 to 30 carbon atoms is a group (x1) containing an acid-dissociable group or a group (x2) containing a polar group.

6. The radiation-sensitive composition according to claim 1, wherein the polymer satisfies the requirement (i) and the structural unit (ma) is represented by the following formula (ma-1): (In formula (ma-1), R １ is the above group (y). １ is *-COO- or *-CONH-. * is R １ indicates the bonding site with the carbon atom to which R is attached. ２ is a monovalent organic group.

7. The radiation-sensitive composition according to claim 1, wherein the polymer satisfies the requirement (ii) and the structural unit (ma) is represented by the following formula (ma-2): (In formula (ma-2), R ３ is a monovalent organic group having 1 to 30 carbon atoms (excluding methyl, trifluoromethyl and the above group (y)). ２ is *-COO- or *-CONH-. * is R ３ indicates the bonding site with the carbon atom to which R is attached. ４ is the above group (y).

8. The radiation-sensitive composition according to claim 1, wherein the polymer satisfies the requirement (iii) and the structural unit (ma) is represented by the following formula (ma-3): (In formula (ma-3), R ５ is a monovalent organic group having 1 to 30 carbon atoms (excluding methyl, trifluoromethyl and the above group (y)). ３ is *-COO- or *-CONH-. * is R ５ indicates the bonding site with the carbon atom to which R is attached. ６ is a monovalent organic group.

9. A method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 8 directly or indirectly to a substrate; exposing a resist film formed by the application; and developing the exposed resist film.

10. A polymer having a structural unit (ma) derived from a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, and an iodine group, and satisfying any of the following requirements (i') to (iii): (i') The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the structural unit (ma) further has the group (y) in addition to the group (x). (iii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and the polymer further has a structural unit (mb) containing the group (y) in addition to the structural unit (ma).

11. A compound that is a (meth)acrylic acid monomer having a group (x) other than a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group at the α-position, has an iodine group, and satisfies either of the following requirements (i') or (ii): (i') The group (x) is a group (y) that generates an acid when exposed to radiation, and the group (y) is a group that generates a carboxylic acid when exposed to radiation; (ii) The group (x) is a monovalent organic group having 1 to 30 carbon atoms (excluding a methyl group, a trifluoromethyl group, and the group (y)), and further contains the group (y) in addition to the group (x).

Images