Radiation-sensitive composition and method for forming resist pattern

Abstract

A radiation-sensitive composition comprising a polymer, the solubility of which in a developer is changed by the action of an acid, wherein the polymer and / or a component other than the polymer comprises, in an identical component or different components: a partial structure comprising an anion and a radiation-sensitive onium cation having an aromatic heterocycle; and an iodine group. The aromatic heterocycle is directly bonded to an atom having a number of bonds that is greater than its standard number of bonds by one.

Description

Radiation-sensitive composition and method for forming resist pattern

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

[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] A radiation-sensitive composition is required to have good sensitivity to radiation such as extreme ultraviolet rays and electron beams, as well as excellent LWR (Line Width Roughness), resolution, and the like.

[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 of forming a resist pattern that are excellent in sensitivity, LWR, and resolution.

[0008] The invention made to solve the above problems is a radiation-sensitive composition comprising a polymer whose solubility in a developer changes under the action of an acid, wherein the polymer and a component other than the polymer, whether identical or different, have a partial structure containing a radiation-sensitive onium cation and an anion containing an aromatic heterocycle, and an iodo group, and the aromatic heterocycle is directly bonded to an atom having a bonding number that is one greater than the standard bonding number.

[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] The radiation-sensitive composition of the present invention is excellent in sensitivity, LWR, and resolution. According to the method of forming a resist pattern of the present invention, a resist pattern having good sensitivity and excellent LWR and resolution can be formed. Therefore, these compositions can be suitably used in the processing of semiconductor devices, which are expected to become even more miniaturized in the future.

[0011] The radiation-sensitive composition and the method for forming a resist pattern of the present invention will be described in detail below.

[0012] 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."

[0013] <Radiation-Sensitive Composition> The radiation-sensitive composition contains a polymer (hereinafter also referred to as "polymer [A]") whose solubility in a developer changes under the action of an acid.

[0014] The radiation-sensitive composition contains the polymer [A] and satisfies the following requirements (i) and (ii): Requirement (i): The polymer [A] and a component other than the polymer [A] have, in the same or different components, a partial structure (hereinafter also referred to as a "partial structure (x)") containing a radiation-sensitive onium cation and anion containing an aromatic heterocycle (hereinafter also referred to as an "aromatic heterocycle (p)"), and an iodo group; Requirement (ii): The aromatic heterocycle (p) is directly bonded to an atom having a bond number that is one larger than the standard bond number.

[0015] The radiation-sensitive composition has the above-described structure, and is therefore excellent in sensitivity, LWR, and resolution. The reason for this is not entirely clear, but is presumed to be, for example, as follows: It is believed that the inclusion of an aromatic heterocycle (p) in the radiation-sensitive onium cation improves the radiation absorption efficiency and improves the solubility in a developer. Furthermore, it is believed that the presence of an iodo group in any of the components contained in the radiation-sensitive composition also improves the radiation absorption efficiency. The radiation-sensitive composition has the above-described structure, and these combined effects enable a good balance between sensitivity, CDU, and resolution, resulting in excellent sensitivity, LWR, and resolution.

[0016] 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.

[0017] 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.

[0018] [Requirement (i)] Requirement (i) is that the polymer [A] and a component other than the polymer [A] (i.e., a component contained in the radiation-sensitive composition) have the partial structure (x) and an iodo group in the same or different components. This means that the partial structure (x) and the iodo group may be contained in any of the components contained in the radiation-sensitive composition. The partial structure (x) and the iodo group may be contained in the same component or different components. Furthermore, the iodo group may be contained in the partial structure (x).

[0019] 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 the partial structure (x) and an iodo group, which may be the same or different, are contained in any one of the polymer [A], the acid generator [B], and the acid diffusion controller [C].

[0020] The partial structure (x) is a structure containing a radiation-sensitive onium cation containing an aromatic heterocycle (p) and an anion. When the partial structure (x) is contained in the polymer [A], the polymer [A] functions as a radiation-sensitive acid generator, an acid diffusion controller, or a combination thereof, depending on the type of anion. When the acid-generating structure (x) is contained in a compound that is not a polymer, the compound functions as a radiation-sensitive acid generator or an acid diffusion controller, depending on the type of anion. Details of the partial structure (x) will be described later in the section [Requirement (ii)].

[0021] The number of ring members in the aromatic heterocycle (p) is not particularly limited and is, for example, 5 to 30, preferably 5 to 20. The "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. The "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.

[0022] Examples of the aromatic heterocycle (p) 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. The aromatic heterocycle (p) is preferably a thiophene ring, a benzothiophene ring, a pyrrole ring, a furan ring, or a benzofuran ring.

[0023] The number of aromatic heterocycles (p) in the radiation-sensitive onium cation may be 1 or more. When the number is 2, the LWR and resolution of the radiation-sensitive composition tend to be further improved, and when the number is 3, the sensitivity of the radiation-sensitive composition tends to be further improved. When the number of aromatic heterocycles (p) is 2 or more, the aromatic heterocycles (p) may be the same or different.

[0024] When any of the components contained in the radiation-sensitive composition has an iodine group, the radiation-sensitive composition has excellent sensitivity, LWR, and resolution. When the polymer [A] has an iodine group, the radiation-sensitive composition tends to have even more excellent sensitivity and resolution. Furthermore, when the partial structure (x) has an iodine group, the radiation-sensitive composition tends to have even more excellent sensitivity, LWR, and resolution.

[0025] 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.

[0026] 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."

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Examples of the aromatic heterocycle include those exemplified above as the aromatic heterocycle (p).

[0031] The iodo group may be contained in the aromatic heterocycle (p), which tends to further improve the sensitivity and resolution of the radiation-sensitive composition.

[0032] 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 fluorine atom), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, or an acyloxy group.

[0033] [Requirement (ii)] Requirement (ii) is that the aromatic heterocycle (p) is directly bonded to an atom having a bond number that is one larger than the standard bond number.

[0034] The "reference bond number" is set as a reference valence for some elements among the bond numbers, for example, F, Cl, Br, and I are set as "1", O and S are set as "2", N is set as "3", and C and Si are set as "4". The atom is preferably a sulfur atom (S) or an iodine atom (I). When the atom is a sulfur atom (reference bond number: 2), the aromatic heterocycle (p) is directly bonded to the sulfur atom with a bond number of 3. When the atom is an iodine atom (reference bond number: 1), the aromatic heterocycle (p) is directly bonded to the iodine atom with a bond number of 2.

[0035] The partial structure (x) is a structure containing a radiation-sensitive onium cation and anion containing an aromatic heterocycle (p).

[0036] Examples of the radiation-sensitive onium cation include sulfonium cations and iodonium cations depending on the type of the atom.

[0037] The radiation-sensitive onium cation preferably has an iodine group, in which case the radiation-sensitive composition tends to have better sensitivity, LWR, and resolution.

[0038] The radiation-sensitive onium cation preferably has a fluoro group, a fluorinated alkyl group, or a cyano group, in which case the radiation-sensitive composition tends to have better sensitivity.

[0039] When the radiation-sensitive onium cation has both an iodo group and a fluoro group, a fluorinated alkyl group, or a cyano group, the radiation-sensitive composition tends to be more excellent in sensitivity, LWR, and resolution.

[0040] The radiation-sensitive onium cation is preferably a cation represented by the following formula (1):

[0041]

[0042] In the above formula (1), M ＋ is an atom having a bond number that is one greater than the reference bond number. １ is a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic heterocycle. n is an integer of 1 or more and x or less. x is M ＋When x-n is 1, R １ is a substituted or unsubstituted hydrocarbon group. When x-n is 2 or more, R １ are the same or different, substituted or unsubstituted hydrocarbon groups, or a plurality of R １ are combined and combined into M ＋ Together with

[0043] M ＋ The atom represented by Ar is explained as an atom having a bond number that is one larger than the reference bond number described above. １ The aromatic heterocycle giving the formula (I) is described above as the aromatic heterocycle (p).

[0044] 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.

[0045] R １ 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] R １ As the alkyl group, a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms is preferred, and a phenyl group is more preferred.

[0050] R １ When is a substituted hydrocarbon group, examples of the substituent include a halogeno group such as a fluoro group or an iodo group, a hydroxy group, a carboxy group, a cyano group, a nitro group, an alkyl group, a fluorinated alkyl group (a group in which at least one hydrogen atom of an alkyl group is substituted with a fluorine atom), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, and an acyloxy group.

[0051] Multiple R １ are combined and combined into M ＋ Examples of the heterocyclic ring that can be formed together with the above include sulfur atom-containing aliphatic heterocyclic rings such as a tetrahydrothiophene ring.

[0052] x is 2 or 3. n is preferably 1 to 3.

[0053] When x-n is 2 or more, R １ are preferably the same or different and are substituted or unsubstituted hydrocarbon groups.

[0054] Specific examples of the cation represented by the above formula (1) include cations represented by the following formulas (1-1) to (1-17).

[0055]

[0056] Examples of the anion include a sulfonate anion and a carboxylate anion. Specific examples of the anion when the partial structure (x) is contained in the polymer [A] include the anion in the monomer (M-14) or the monomer (M-16) in the Examples described later. Specific examples of the anion when the partial structure (x) is contained in a compound that is not a polymer include the anions in the acid generators (B-1) to (B-25) and the anions in the acid diffusion controllers (C-1) to (C-9) in the Examples described later.

[0057] Each component contained in the radiation-sensitive composition will be described below.

[0058] <Polymer (A)> The polymer (A) is a polymer whose solubility in a developer changes under the action of an acid. The radiation-sensitive composition may contain one or more types of polymer (A).

[0059] The polymer [A] preferably has a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (I)"). The polymer [A] preferably has a structural unit containing a phenolic hydroxyl group (hereinafter also simply referred to as "structural unit (II)"). The polymer [A] may further have other structural units (hereinafter also simply referred to as "other structural units") other than the structural unit (I) and the structural unit (II). The polymer [A] can have one or more types of each structural unit.

[0060] The other structural units are structural units other than the structural units (I) and (II) described above. Examples of the other structural units include a structural unit containing a group that generates an acid when acted on by radiation (hereinafter also referred to as "structural unit (III)"), a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, and a structural unit containing an alcoholic hydroxyl group.

[0061] 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.

[0062] 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.

[0063] 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].

[0064] 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.

[0065] [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

[0066] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0067] Hereinafter, each structural unit contained in the polymer [A] will be described. Note that the structural units contained in the polymer [A] may be considered to overlap and fall into two or more structural unit classifications. For example, the polymer [A] may include not only the structural unit (I) but also a structural unit considered to fall into a structural unit other than the structural unit (I). In this specification, such a structural unit will be treated as falling into the structural unit with the lower number in parentheses.

[0068] [Structural Unit (I)] The structural unit (I) 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 (I) is a structural unit containing a partial structure in which a hydrogen atom in a carboxy group is substituted with an acid-dissociable group.

[0069] 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 dissociates under the action of an acid generated from a component containing a radiation-sensitive acid-generating structure under the action of radiation, and this causes a difference in the solubility of the polymer (A) in a developer between an exposed area and a non-exposed area, thereby enabling the formation of a resist pattern.

[0070] The acid-dissociable group is a group that substitutes a hydrogen atom of the carboxy group in the structural unit (I). In other words, in the structural unit (I), the acid-dissociable group is bonded to the etheric oxygen atom of the carbonyloxy group.

[0071] 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)").

[0072]

[0073] In the above formulas (a-1) and (a-2), * indicates the bonding site with the etheric oxygen atom of the carboxy group.

[0074] 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.

[0075] 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.

[0076] 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 R １ Examples of hydrocarbon groups that give the following formula include those given above.

[0077] R Ｘ Examples of the substituent that the hydrocarbon group represented by the formula (I) may have include the above-mentioned R１ Examples of the substituent that may be possessed by the group include those exemplified above.

[0078] R Ｙ and R Ｚ Examples of the saturated alicyclic ring having 3 to 20 ring members formed by combining these rings 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.

[0079] 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 groups exemplified above as the monovalent hydrocarbon group having 1 to 20 carbon atoms.

[0080] 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.

[0081] 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, an 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.

[0082] 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 monocyclic saturated alicyclic ring, more preferably a cyclopentane ring or a cyclohexane ring.Ｘ As the alkyl group, a substituted or unsubstituted linear hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group is preferable, an unsubstituted alkyl group, an unsubstituted alkenyl group or an unsubstituted aryl group is more preferable, and a methyl group, an ethyl group, a tert-butyl group, an ethenyl group or a phenyl group is even more preferable.

[0083] R Ｂ is preferably a hydrogen atom.

[0084] 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.

[0085] 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.

[0086] 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):

[0087]

[0088] 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).

[0089] Examples of the structural unit (I) include a structural unit represented by the following formula (I).

[0090] In the above formula (I), R Ｈ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. Ｈ is a single bond, *-COO- or *-CONH-. * is R Ｈ１ indicates the bonding site with the carbon atom to which R is attached. Ｈ２ is a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring. Ｈ３is the acid-dissociable group.

[0091] R Ｈ１ From the viewpoint of copolymerizability of the monomer that gives the structural unit (I), a hydrogen atom or a methyl group is preferred.

[0092] L Ｈ is preferably a single bond.

[0093] R Ｈ２ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 30 ring members, more preferably 6 to 20 ring members.

[0094] R Ｈ２ Examples of the aromatic hydrocarbon ring that gives R include those exemplified above as the aromatic hydrocarbon ring. Ｈ２ The aromatic hydrocarbon ring that gives the following is preferably a benzene ring.

[0095] R Ｈ２ Examples of the substituent that the aromatic hydrocarbon ring that gives １ Examples of the substituent that may be possessed by the group include those exemplified above.

[0096] 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. Ｈ２ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic hydrocarbon ring, this is preferred because it tends to further improve the sensitivity and resolution of the radiation-sensitive composition.

[0097] The lower limit of the content of the structural unit (I) 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 85 mol%, and even more preferably 80 mol%.

[0098] [Structural Unit (II)] The structural unit (II) 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.

[0099] 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 (II). Therefore, when the polymer [A] contains the structural unit (II), the radiation-sensitive composition can be suitably used as a radiation-sensitive composition for KrF exposure, EUV exposure, or electron beam exposure.

[0100] Examples of the structural unit (II) include a structural unit represented by the following formula (II).

[0101]

[0102] In the above formula (II), R Ｐ is a hydrogen atom, a fluorine atom, 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.

[0103] R Ｐ From the viewpoint of copolymerizability of the monomer that gives the structural unit (II), a hydrogen atom or a methyl group is preferred.

[0104] L Ｐ is preferably a single bond or *-COO-.

[0105] Ar Ｐ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 30 ring members, more preferably 6 to 20 ring members.

[0106] Ar Ｐ Examples of aromatic hydrocarbon rings that give the formula include those exemplified above as aromatic hydrocarbon rings. Ｐ The aromatic hydrocarbon ring that gives the following formula is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring.

[0107] Ar Ｐ Examples of the substituent that the aromatic hydrocarbon ring that gives １Examples of the substituent that may be possessed by the group include those exemplified above.

[0108] p is preferably 1 or 2, and more preferably 1.

[0109] Examples of the structural unit (II) include structural units represented by the following formulae (II-1) to (II-18).

[0110]

[0111] In the above formulas (II-1) to (II-18), R Ｐ has the same meaning as in formula (II) above.

[0112] When the polymer [A] contains the structural unit (II), the lower limit of the content of the structural unit (II) in the polymer [A] is preferably 10 mol %, more preferably 20 mol %, based on all structural units constituting the polymer [A], and the upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0113] Examples of monomers that provide the structural unit (II) include monomers in which the hydrogen atom of a phenolic hydroxyl group (—OH) is substituted with an acetyl group, such as 4-acetoxystyrene and 3,5-diacetoxystyrene. In this case, for example, the above-mentioned monomers can be polymerized, and then the resulting polymerization product can be hydrolyzed in the presence of a base such as an amine, thereby synthesizing the polymer [A] having the structural unit (II).

[0114] [Structural Unit (III)] The structural unit (III) is a structural unit containing a structure that generates an acid when exposed to radiation. When the polymer (A) further contains the structural unit (III), the sensitivity of the radiation-sensitive composition tends to be further improved. Examples of the acid generated when exposed to radiation include sulfonic acid and carboxylic acid. Examples of the radiation include those exemplified as radiation in the section <Method of Forming a Resist Pattern> below.

[0115] Examples of the structure that generates an acid upon the action of radiation 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 structural unit (III), Structure 1 is preferred. In the case of Structure 1, the diffusion of the acid generated upon the action of radiation is more controlled, which tends to further improve the LWR.

[0116] The structure that generates an acid when acted upon by radiation may be the partial structure (x) described above, or may be a structure other than the partial structure (x).

[0117] The structural unit (III) is classified according to the type of acid generated by the action of radiation, for example, into a structural unit containing a structure that generates a sulfonic acid by the action of radiation (hereinafter also referred to as a "structural unit (IIIa)") and a structural unit containing a structure that generates a carboxylic acid by the action of radiation (hereinafter also referred to as a "structural unit (IIIb)").

[0118] When the polymer [A] has the structural unit (IIIa), the polymer [A] acts as a radiation-sensitive acid generator in the radiation-sensitive composition. When the polymer [A] has the structural unit (IIIb), the polymer [A] acts as an acid diffusion controller in the radiation-sensitive composition. When the polymer [A] has both the structural unit (IIIa) and the structural unit (IIIb), the polymer [A] acts as both a radiation-sensitive acid generator and an acid diffusion controller in the radiation-sensitive composition.

[0119] In particular, when the polymer (A) has both the structural unit (IIIa) containing the partial structure (x) and the structural unit (IIIb) containing the partial structure (x), the resolution tends to be further improved.

[0120] Since the structural unit (IIIb) generates an acid in response to the action of radiation, the polymer [A] having the structural unit (IIIb) can also be broadly referred to as a "radiation-sensitive acid generator." However, the acid generated from the structural unit (IIIb) in response to the action of radiation does not dissociate the acid-dissociable group under the conditions under which the acid generated from the structural unit (IIIa) dissociates the acid-dissociable group, and therefore the "radiation-sensitive acid generator" is clearly distinguished from the "acid diffusion controller."

[0121] Specific structures of monomers that provide the structural unit (IIIa) include, for example, monomers (M-14) and (M-16) in the Examples described later. Of these, monomer (M-14) corresponds to a monomer having the partial structure (x). Specific structures of monomers that provide the structural unit (IIIb) include, for example, monomers (M-16) and (M-17) in the Examples described later. Of these, monomer (M-16) corresponds to a monomer having the partial structure (x).

[0122] <[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 generates carboxyl groups, which results in a difference in the solubility of the resist film in a developer between exposed and unexposed areas, allowing the formation of a resist pattern.

[0123] Examples of the acid generated from the acid generator (B) include sulfonic acid, carboxylic acid, and imide acid.

[0124] 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.

[0125] Examples of the onium salt compound include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts.

[0126] Specific examples of the acid generator (B) include the compounds described in paragraphs

[0080] to

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

[0127] 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.

[0128] 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 a triphenylsulfonium cation, a diphenyliodonium cation, and the radiation-sensitive onium cations described above in the partial structure (x) (radiation-sensitive onium cations containing an aromatic heterocycle (p)).

[0129] 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.

[0130] Specific examples of the acid generator [B] include acid generators (B-1) to (B-25) and acid generators (CB-1) to (CB-5) in the examples described later. Of these, acid generators (B-1) to (B-25) correspond to those having the partial structure (x).

[0131] 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.

[0132] The lower limit of the content of the acid generator (B) in the radiation-sensitive resin 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.

[0133] <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).

[0134] 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").

[0135] 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.

[0136] 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 surface roughness in the exposed area after development. On the other hand, in the non-exposed area, the anion exerts a high acid-scavenging function, functioning as a quencher and capturing acid diffusing from the exposed area. That is, since the base functions as a quencher only in the non-exposed area, the contrast of the elimination reaction of the acid-dissociable group is improved, resulting in improved resolution. Since the photodegradable base generates acid upon exposure, it can also be called a radiation-sensitive acid generator in a broad sense. However, under conditions where the acid generated from the acid generator (B) upon exposure dissociates the acid-dissociable group, the photodegradable base does not dissociate the acid-dissociable group upon exposure, and therefore the two are clearly distinguished.

[0137] Examples of the radiation-sensitive onium cation in the photodecomposable base include the same as the radiation-sensitive onium cation in the acid generator (B).

[0138] 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.

[0139] Specific examples of the acid diffusion controller [C] include the acid diffusion controllers (C-1) to (C-9) and the acid diffusion controllers (CC-1) to (CC-4) in the examples described later. Of these, the acid diffusion controllers (C-1) to (C-9) correspond to those having the partial structure (x).

[0140] 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.

[0141] 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 20 mol %, relative to 100 mol % of the acid generator (B).The upper limit of the content is preferably 100 mol %, more preferably 60 mol %, and even more preferably 50 mol %.

[0142] <[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.

[0143] 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).

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-pentane and n-hexane; and aromatic hydrocarbon solvents such as toluene and xylene.

[0150] 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.

[0151] 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 %.

[0152] <Other Optional Components> Examples of other optional components include surfactants, etc. The radiation-sensitive composition may contain one or more other optional components.

[0153] <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").

[0154] 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 with excellent sensitivity, LWR, and resolution can be formed.

[0155] Each step of the resist pattern forming method will be described below.

[0156] [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.

[0157] In this step, the radiation-sensitive composition described above is used as the radiation-sensitive composition.

[0158] Substrates include, for example, silicon wafers, silicon dioxide, and aluminum coated wafers.

[0159] 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.

[0160] [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.

[0161] 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.

[0162] [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.

[0163] 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.

[0164] 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.

[0165] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0166] <Synthesis of Compounds> Compounds represented by the following formulae (B-1) to (B-25), (C-1) to (C-9), (M-14), and (M-16) (hereinafter also referred to as "acid generators (B-1) to (B-25), acid diffusion controllers (C-1) to (C-9), and monomers (M-14) and (M-16)") were synthesized according to the following method. The acid generators (B-1) to (B-25), acid diffusion controllers (C-1) to (C-9), and monomers (M-14) and (M-16) each have the acid-generating structure (x) described above.

[0167]

[0168]

[0169]

[0170] Synthesis Example 1-1 Synthesis of Acid Generator (B-1) Acid generator (B-1) was synthesized according to the following reaction scheme. In the following reaction scheme, OTf represents a trifluoromethanesulfonate anion (CF ３ SO ３－ )

[0171]

[0172] 20 mmol of diphenyl sulfoxide, 40 mmol of thiophene, and 40 ml of dehydrated dichloromethane were added to a reaction vessel and cooled to -20°C. 30 mmol of Eaton's Reagent was added dropwise, followed by stirring at room temperature for 10 hours. 20 mmol of trifluoromethanesulfonic acid was then added, and the mixture was stirred for an additional 5 hours. The reaction solution was added to 20 ml of ice water to quench the reaction, and the mixture was extracted twice with 20 ml of dichloromethane. The organic layer was washed twice with 20 ml of ultrapure water, dried over sodium sulfate, and filtered. The mixture was concentrated and purified by silica gel column chromatography to obtain a compound represented by the above formula (pB-1) (hereinafter also referred to as "compound (pB-1)").

[0173] 15 mmol of compound (pB-1) was dissolved in 20 ml of methanol and subjected to ion exchange chromatography using a twice-by-weight amount of "QAE-Sephadex (registered trademark) A-25." The resulting solution was concentrated, and 15 mmol of sodium 1,1,3,3,3-pentafluoro-2-((2,3,5-triiodobenzoyl)oxy)propane-1-sulfonate, 30 ml of dichloromethane, and 15 ml of ultrapure water were added, followed by stirring at room temperature for 5 hours. The organic layer was recovered and washed twice with 15 ml of ultrapure water. The resulting crude product was purified by silica gel column chromatography to obtain acid generator (B-1).

[0174] Synthesis Examples 1-2 to 1-36 Synthesis of Acid Generators (B-2) to (B-25), Acid Diffusion Controllers (C-1) to (C-9), and Monomers (M-14) and (M-16) Acid generators (B-2) to (B-25), acid diffusion controllers (C-1) to (C-9), and monomers (M-14) and (M-16) were obtained in the same manner as in Synthesis Example 1-1, except that the substrates were appropriately selected.

[0175] <Synthesis of Polymer [A]> Polymers (A-1) to (A-18) were synthesized according to the following method. Compounds represented by the following formulae (M-1) to (M-17) (hereinafter also referred to as "monomers (M-1) to (M-17)") were used to synthesize Polymer [A]. Monomers (M-14) and (M-16) were synthesized in Synthesis Examples 1-35 and 1-36, respectively. Polymers (A-13) to (A-18) are polymers having the acid-generating structure (x) described above. The Mw and Mw / Mn of the obtained polymers were confirmed by GPC as described in the above section [Method for measuring Mw and Mn].

[0176] In the following synthesis examples, unless otherwise specified, "parts by mass" means a value when the total mass of the monomers used is taken as 100 parts by mass, and "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0177]

[0178] Synthesis Examples 2-1 to 2-18 Synthesis of Polymers (A-1) to (A-18) Monomers were combined according to the compositions shown in Table 1 below, and copolymerization was carried out in tetrahydrofuran (THF). The resulting crystals were crystallized in methanol, and then repeatedly washed with hexane, isolated, and dried to obtain Polymers (A-1) to (A-18).

[0179] The types and amounts of monomers used that provide each structural unit of the polymers obtained in Synthesis Examples 2-1 to 2-18, as well as Mw and Mw / Mn, are shown in Table 1. In Table 1, "-" indicates that the corresponding monomer was not used.

[0180]

[0181] <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.

[0182] [[B] Acid Generator] As the acid generator [B], acid generators (B-1) to (B-25) and compounds represented by the following formulae (CB-1) to (CB-5) (hereinafter also referred to as "acid generators (CB-1) to (CB-5)") were used.

[0183]

[0184] [[C] Acid Diffusion Controller] As the acid diffusion controller [C], acid diffusion controllers (C-1) to (C-9) and compounds represented by the following formulas (CC-1) to (CC-4) (hereinafter also referred to as "acid diffusion controllers (CC-1) to (CC-4)") were used.

[0185]

[0186] [[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

[0187] Example 1 Preparation of Radiation-Sensitive Composition (R-1) A radiation-sensitive composition (R-1) was prepared by blending 100 parts by mass of [A] a polymer (A-1), 20 parts by mass of [B] an acid generator (B-1), [C] 25 mol % of (C-1) as an acid diffusion inhibitor relative to the acid generator (B-1), and 2,000 parts by mass of [D] an organic solvent (D-1) and 4,800 parts by mass of (D-2).

[0188] [Examples 2 to 51 and Comparative Examples 1 to 12] Preparation of Radiation-Sensitive Compositions (R-2) to (R-51) and (CR-1) to (CR-12) Radiation-sensitive compositions (R-2) to (R-51) and (CR-1) to (CR-12) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 2 below were used.

[0189] In Table 2 below, the content of the acid diffusion controller (C) refers to the value when the number of moles of the component having a radiation-sensitive acid-generating structure (the total number of moles when there are multiple components) is taken as 100 mol %.

[0190]

[0191] <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 100°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 100°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 32 nm line and space pattern.

[0192] <Evaluation> The sensitivity, LWR and resolution were evaluated according to the following methods. The results are shown in Table 3 below.

[0193] [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 optimum exposure dose was used as the sensitivity (mJ / cm ２ The smaller the value, the higher the sensitivity, and the better the evaluation.

[0194] [LWR] The resist pattern formed in the above section <Formation of Resist Pattern> was observed from above the pattern using a scanning electron microscope ("CG-4100" manufactured by Hitachi High-Tech Corporation). Line widths were measured at a total of 50 arbitrary points. A 3 sigma value was calculated from the distribution of the measured values, and the calculated 3 sigma value was taken as the LWR (unit: nm). The smaller the LWR value, the smaller the line wobble, and the better the evaluation can be.

[0195] [Resolution] In the above section <Formation of Resist Pattern>, the minimum width of a space pattern that can be resolved without bridge defects or residue defects was defined as the minimum CD (Critical Dimension) (unit: nm). The smaller the minimum CD value, the better the resolution can be evaluated.

[0196]

[0197] From Table 3, it can be seen that all of the radiation-sensitive compositions of the Examples were superior in sensitivity, LWR, and resolution compared to the radiation-sensitive compositions of the Comparative Examples.

Claims

1. A radiation-sensitive composition comprising a polymer whose solubility in a developer changes under the action of an acid, wherein the polymer and a component other than the polymer, whether identical or different, have a partial structure containing a radiation-sensitive onium cation and anion containing an aromatic heterocycle, and an iodo group, and wherein the aromatic heterocycle is directly bonded to an atom having a bond number that is one larger than the standard bond number.

2. The radiation-sensitive composition according to claim 1, wherein the atom is a sulfur atom or an iodine atom.

3. The radiation-sensitive composition according to claim 1, wherein said radiation-sensitive onium cation has an iodo group.

4. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive onium cation further has a fluoro group, a fluorinated alkyl group, or a cyano group.

5. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive onium cation has an iodo group and a fluoro group, a fluorinated alkyl group, or a cyano group.

6. The radiation-sensitive composition according to claim 1, wherein the radiation-sensitive onium cation is represented by the following formula (1): (In formula (1), M ＋ is an atom having a bond number that is one greater than the reference bond number. １ is a group in which one hydrogen atom has been removed from a substituted or unsubstituted aromatic heterocycle. n is an integer of 1 or more and x or less. x is M ＋ When x-n is 1, R １ is a substituted or unsubstituted hydrocarbon group. When x-n is 2 or more, R １ are the same or different, substituted or unsubstituted hydrocarbon groups, or a plurality of R １ are combined and combined into M ＋ Together with 7. The radiation-sensitive composition according to claim 1, further comprising a radiation-sensitive acid generator, said radiation-sensitive acid generator having the partial structure described above.

8. The radiation-sensitive composition according to claim 1, wherein said polymer has a structural unit containing said partial structure.

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.

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