Radiation-sensitive composition and method for forming resist pattern

Abstract

This radiation-sensitive composition contains a first polymer which has a structural unit (Ia) containing a phenolic hydroxyl group and which exhibits a change in solubility in a developer as a result of the action of an acid, and a second polymer which has a higher fluorine atom content than the first polymer. The second polymer has a structural unit (If) which contains a group that generates a sulfonic acid through the action of radiation, and a structural unit (IIf) which is a structural unit other than the structural unit (If) and which contains a fluorine atom.

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] The radiation-sensitive composition is required to have good sensitivity to radiation such as extreme ultraviolet rays and electron beams, as well as excellent line width roughness (LWR), few development defects, and excellent film thickness uniformity.

[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 have excellent sensitivity and LWR, few development defects, and excellent film thickness uniformity.

[0008] The invention made to solve the above-mentioned problems provides a radiation-sensitive composition comprising: a first polymer having a structural unit (Ia) containing a phenolic hydroxyl group, and whose solubility in a developer changes under the action of an acid; and a second polymer having a higher fluorine atom content than the first polymer, wherein the second polymer has a structural unit (If) containing a group that generates sulfonic acid under the action of radiation, and a structural unit (IIf) other than the structural unit (If) that contains a fluorine atom.

[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 to light, and developing the exposed resist film.

[0010] The radiation-sensitive composition of the present invention has excellent sensitivity and LWR, few development defects, and excellent film thickness uniformity. According to the method for forming a resist pattern of the present invention, a resist pattern having excellent sensitivity and LWR, few development defects, and excellent film thickness uniformity 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 method for forming a resist pattern of the present invention will be described in detail below.

[0012] The upper and lower limits of the numerical ranges in this specification can be any combination of the disclosed numerical values. Furthermore, when a numerical range is indicated using the symbol "to", it means that the numerical range includes the upper and lower limit numerical values. For example, "1 to 20 carbon atoms" means "1 to 20 carbon atoms inclusive."

[0013] <Radiation-Sensitive Composition> The radiation-sensitive composition comprises a first polymer (hereinafter also referred to as "polymer [A]") having a structural unit (Ia) containing a phenolic hydroxyl group and whose solubility in a developer changes under the action of an acid, and a second polymer (hereinafter also referred to as "polymer [F]") having a higher fluorine atom content than the first polymer, wherein the second polymer has a structural unit (If) containing a group that generates sulfonic acid under the action of radiation, and a structural unit (IIf) other than the structural unit (If) that contains a fluorine atom.

[0014] By having the above-mentioned configuration, the radiation-sensitive composition has excellent sensitivity and LWR, few development defects, and excellent film thickness uniformity. The reason for this is not necessarily clear, but it is presumed, for example, as follows. It is thought that the polymer [A] containing the structural unit (Ia) exhibits high sensitivity and excellent LWR performance during EUV resist pattern formation. It is thought that the polymer [F] containing the structural unit (If) or the structural unit (IIf) hydrophilizes the film surface and reduces the surface tension, resulting in reduced development defects and excellent film thickness uniformity. It is thought that the radiation-sensitive composition has the above-mentioned configuration, and the above-mentioned effects combine to achieve a good balance between sensitivity, LWR, few development defects, and film thickness uniformity.

[0015] 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.

[0016] The radiation-sensitive composition can be prepared, for example, by mixing the polymer (A) and the polymer (F), 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.

[0017] Each component contained in the radiation-sensitive composition will be described below.

[0018] <Polymer (A)> The polymer (A) has a structural unit (Ia) containing a phenolic hydroxyl group, and is a polymer whose solubility in a developer changes due to the action of an acid.

[0019] The radiation-sensitive composition may contain one or more types of polymer (A).

[0020] The polymer [A] preferably has a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (IIa)"). The polymer [A] may further have other structural units (hereinafter also simply referred to as "other structural units") other than the structural unit (Ia) and the structural unit (IIa). The polymer [A] may have one or more types of each structural unit.

[0021] The other structural units are structural units other than the structural units (Ia) and (IIa). Examples of the other structural units include a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof (hereinafter also referred to as "structural unit (IIIa)"), a structural unit containing a carboxy group (hereinafter also referred to as "structural unit (IVa)"), a structural unit containing an alcoholic hydroxyl group (hereinafter also referred to as "structural unit (Va)"), and a structural unit containing a group that generates an acid when exposed to radiation (hereinafter also referred to as "structural unit (VIa)").

[0022] 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.

[0023] 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.

[0024] 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, and even more preferably 2,500. The upper limit of the Mw is preferably 30,000, more preferably 20,000, and even more preferably 15,000. 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].

[0025] 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, and more preferably 1.2.

[0026] [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

[0027] The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0028] Each structural unit contained in the polymer (A) will be described below.

[0029] [Structural Unit (Ia)] The structural unit (Ia) 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.

[0030] In the case of KrF exposure, EUV exposure, or electron beam exposure, the polymer (A) having the structural unit (Ia) can further increase the sensitivity of the radiation-sensitive composition, and therefore the radiation-sensitive composition can be suitably used as a radiation-sensitive composition for KrF exposure, EUV exposure, or electron beam exposure.

[0031] Examples of the structural unit (Ia) include a structural unit represented by the following formula (Ia):

[0032]

[0033] In the above formula (Ia), 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.

[0034] R Ｐ From the viewpoint of copolymerizability of the monomer that gives the structural unit (Ia), a hydrogen atom or a methyl group is preferred.

[0035] L Ｐ is preferably a single bond or *-COO-.

[0036] Ar Ｐ The number of ring members in the aromatic hydrocarbon ring giving the formula (I) is preferably 6 to 30, and more preferably 6 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.

[0037] Ar ＰExamples of aromatic hydrocarbon rings that give the formula (I) 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. Ｐ The aromatic hydrocarbon ring that gives the following formula is preferably a benzene ring or a naphthalene ring, more preferably a benzene ring.

[0038] Ar Ｐ Examples of the substituent that may be possessed by the aromatic hydrocarbon ring that gives the formula (I) 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 fluoro group), an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group, and an acyloxy group.

[0039] As p, 1 or 2 is preferred.

[0040] Examples of the structural unit (Ia) include structural units represented by the following formulae (Ia-1) to (Ia-21).

[0041]

[0042] In the above formulas (Ia-1) to (Ia-21), R Ｐ has the same meaning as in formula (Ia) above.

[0043] Specific examples of the structure of the monomer that provides the structural unit (Ia) include the monomers (M-1) to (M-11) in the examples described below.

[0044] The lower limit of the content of the structural unit (Ia) in the polymer [A] is preferably 5 mol %, more preferably 10 mol %, and even more preferably 20 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0045] [Structural Unit (IIa)] The structural unit (IIa) 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 (IIa) is a structural unit containing a partial structure in which a hydrogen atom in a carboxy group is substituted with an acid-dissociable group.

[0046] 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.

[0047] The acid-dissociable group is a group that substitutes a hydrogen atom of the carboxy group in the structural unit (IIa). In other words, in the structural unit (IIa), the acid-dissociable group is bonded to the etheric oxygen atom of the carbonyloxy group.

[0048] 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)").

[0049]

[0050] In the above formulas (a-1) and (a-2), * indicates the bonding site with the etheric oxygen atom of the carboxy group.

[0051] 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.

[0052] 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, form an unsaturated aliphatic hydrocarbon ring having 4 to 20 ring members.

[0053] 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.

[0054] 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 (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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] R Ｘ Examples of the substituent that the hydrocarbon group represented by the formula (I) may have include the above-mentioned Ar Ｐ Examples of the substituent that the aromatic hydrocarbon ring that gives the following may have include those exemplified above.

[0059] The term "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 rings."

[0060] R Ｙ and R Ｚ Among the saturated alicyclic rings having 3 to 20 ring members formed by combining these rings together with the carbon atoms to which they are bonded, examples of the aliphatic hydrocarbon ring include monocyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, and a cyclohexane ring; and polycyclic rings such as a norbornane ring, an adamantane ring, a tricyclodecane ring, and a tetracyclododecane ring.

[0061] R Ｙ and R Ｚ Among saturated alicyclic rings having 3 to 20 ring members formed by combining these rings together with the carbon atoms to which they are bonded, examples of the aliphatic heterocyclic ring include oxygen atom-containing heterocyclic rings such as tetrahydrofuran ring.

[0062] R ＤExamples 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.

[0063] R Ｄ And, R Ａ , R Ｂ and R Ｃ and three carbon atoms to which each of the carbon atoms is bonded, include 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.

[0064] 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, a substituted or unsubstituted alkenyl group or a substituted or unsubstituted aryl group is more preferable, and a methyl group, an ethenyl group, a phenyl group or an iodophenyl group is even more preferable.

[0065] 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 a tetrahydrofuran ring. Ｘ is preferably a substituted or unsubstituted chain hydrocarbon group or a substituted or unsubstituted aromatic hydrocarbon group, more preferably a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted aryl group, and even more preferably a methyl group, a tert-butyl group, an ethenyl group, a phenyl group, a naphthyl group, or an iodophenyl group.

[0066] R Ｂ is preferably a hydrogen atom.

[0067] 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.

[0068] 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.

[0069] Examples of the acid-dissociable group (a-1) include groups represented by the following formulas (a-1-1) to (a-1-11): Examples of the acid-dissociable group (a-2) include groups represented by the following formula (a-2-1):

[0070]

[0071] In the above formulas (a-1-1) to (a-1-11) and (a-2-1), * has the same meaning as in the above formulas (a-1) and (a-2).

[0072] Examples of the structural unit (IIa) include a structural unit represented by the following formula (IIa).

[0073]

[0074] In the above formula (IIa), 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.

[0075] R Ｈ１ From the viewpoint of copolymerizability of the monomer that gives the structural unit (IIa), a hydrogen atom or a methyl group is preferred.

[0076] L Ｈ is preferably a single bond.

[0077] RＨ２ The aromatic hydrocarbon ring giving the formula (I) preferably has 6 to 30 ring members, more preferably 6 to 20 ring members.

[0078] R Ｈ２ The aromatic hydrocarbon ring that gives the formula (I) is the same as the above-mentioned Ar Ｐ Examples of aromatic hydrocarbon rings that give R Ｈ２ The aromatic hydrocarbon ring that gives the following is preferably a benzene ring.

[0079] R Ｈ２ Examples of the substituents that the aromatic hydrocarbon ring may have include the above-mentioned Ar Ｐ Examples of the substituent that the aromatic hydrocarbon ring that gives the following may have include those exemplified above.

[0080] 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.

[0081] Specific examples of the structure of the monomer that provides the structural unit (IIa) include the monomers (M-12) to (M-30) in the examples described below.

[0082] The lower limit of the content of the structural unit (IIa) in the polymer [A] is preferably 20 mol %, more preferably 30 mol %, and even more preferably 40 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0083] [Structural Unit (IIIa)] The structural unit (IIIa) is a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. When the polymer (A) further contains the structural unit (IIIa), adhesion to the substrate can be improved.

[0084] Examples of the structural unit (IIIa) include structural units represented by the following formula:

[0085]

[0086]

[0087]

[0088]

[0089] In the above formula, R Ｌ１ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0090] The structural unit (IIIa) is preferably a structural unit containing a lactone structure.

[0091] Specific examples of the structure of the monomer that provides the structural unit (IIIa) include the monomers (M-31), (M-32) and (M-37) in the examples described below.

[0092] When the polymer [A] has the structural unit (IIIa), the lower limit of the content of the structural unit (IIIa) is preferably 5 mol %, more preferably 10 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 35 mol %, more preferably 25 mol %.

[0093] [Structural Unit (IVa)] The structural unit (IVa) is a structural unit containing a carboxy group. When the polymer (A) further contains the structural unit (IVa), hydrogen bonding between the polymers can be formed to prevent diffusion of acid generated in exposed areas to unexposed areas.

[0094] Examples of the structural unit (IVa) include a structural unit represented by the following formula:

[0095]

[0096] In the above formula, R Ｌ３ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0097] Specific examples of the structure of the monomer that provides the structural unit (IVa) include the monomers (M-33) to (M-36) in the examples described below.

[0098] When the polymer [A] has the structural unit (IVa), the lower limit of the content of the structural unit (IVa) is preferably 5 mol %, more preferably 10 mol %, based on all structural units constituting the polymer [A]. The upper limit of the content is preferably 35 mol %, more preferably 25 mol %.

[0099] [Structural Unit (Va)] The structural unit (Va) is a structural unit containing an alcoholic hydroxyl group. When the polymer (A) further contains the structural unit (Va), the solubility in a developer can be more appropriately adjusted.

[0100] Examples of the structural unit (Va) include structural units represented by the following formula:

[0101]

[0102] In the above formula, R Ｌ２ is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group.

[0103] A specific example of the structure of the monomer that provides the structural unit (Va) is the monomer (M-38) in the examples described below.

[0104] When the polymer [A] contains the structural unit (Va), the lower limit of the content of the structural unit (Va) is preferably 1 mol %, more 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 %.

[0105] [Structural Unit (VIa)] The structural unit (VIa) is a structural unit containing a group that generates an acid when exposed to radiation. Examples of the acid that can be 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> described below.

[0106] Examples of the group that generates an acid when acted upon by radiation include a group containing an anion and a radiation-sensitive onium cation. Such groups are classified into a structure in which an anion is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 1") and a structure in which a radiation-sensitive onium cation is bonded to a side chain of a polymer (hereinafter also referred to as "Structure 2"). The group that generates an acid when acted upon by radiation may be Structure 1 or Structure 2.

[0107] The structural unit (VIa) 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 (VIa-1)") 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 (VIa-2)").

[0108] When the polymer [A] has the structural unit (VIa-1), the polymer [A] acts as a radiation-sensitive acid generator in the radiation-sensitive composition. When the polymer [A] has the structural unit (VIa-2), the polymer [A] acts as an acid diffusion controller in the radiation-sensitive composition. When the polymer [A] has both the structural unit (VIa-1) and the structural unit (VIa-2), the polymer [A] acts as both a radiation-sensitive acid generator and an acid diffusion controller in the radiation-sensitive composition.

[0109] Since the structural unit (VIa-2) generates a carboxylic acid under the action of radiation, the polymer [A] having the structural unit (VIa-2) can also be broadly referred to as a "radiation-sensitive acid generator." However, the acid generated from the structural unit (VIa-2) under the action of radiation does not dissociate the acid-dissociable group under the conditions under which the acid generated from the structural unit (VIa-1) dissociates the acid-dissociable group, and therefore the "radiation-sensitive acid generator" is clearly distinguished from the "acid diffusion controller."

[0110] Specific examples of the structure of the monomer that provides the structural unit (VIa) include the monomers (M-39) to (M-42) in the examples described below.

[0111] The structural unit (VIa-1) may also be the structural unit (If) contained in the polymer (F) described below.

[0112] When the polymer [A] has the structural unit (VIa), the lower limit of the content of the structural unit (VIa) 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 %.

[0113] <Polymer [F]> The polymer [F] is a polymer having a higher fluorine atom content than the polymer [A], and has a structural unit (If) containing a group that generates sulfonic acid when acted on by radiation, and a structural unit (IIf) other than the structural unit (If) that contains a fluorine atom.

[0114] The polymer [F] is a polymer different from the polymer [A]. Typically, a polymer that is more hydrophobic than the base polymer tends to be unevenly distributed on the surface layer of the resist film. The polymer [F] has a higher fluorine atom content than the polymer [A], and therefore tends to be unevenly distributed on the surface layer of the resist film due to its hydrophobic properties.

[0115] The lower limit of the fluorine atom content of the polymer [F] is preferably 1% by mass, more preferably 2% by mass, and even more preferably 3% by mass. The upper limit of the fluorine atom content is preferably 60% by mass, more preferably 50% by mass, and even more preferably 40% by mass. The fluorine atom content of the polymer is １３ The fluorine atom content of the polymer (F) can be adjusted by, for example, adjusting the content of the structural unit (IIf).

[0116] The radiation-sensitive composition may contain one or more types of polymer (F).

[0117] The polymer [F] may further have other structural units (hereinafter simply referred to as "other structural units") in addition to the structural unit (If) and the structural unit (IIf). The polymer [F] may have one or more types of each structural unit.

[0118] The other structural units are structural units other than the structural unit (If) and the structural unit (IIf). Examples of the other structural units include a structural unit containing a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IIIf)"), a structural unit containing an acid-dissociable group (hereinafter also referred to as "structural unit (IVf)"), a structural unit containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof (hereinafter also referred to as "structural unit (Vf)"), a structural unit containing a carboxyl group (hereinafter also referred to as "structural unit (VIf)"), and a structural unit containing an alcoholic hydroxyl group (hereinafter also referred to as "structural unit (VIIf)").

[0119] The lower limit of the content of the polymer [F] in the radiation-sensitive composition is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, relative to 100 parts by mass of the polymer [A]. The upper limit of the content is preferably 20 parts by mass, more preferably 10 parts by mass. When the content of the polymer [F] is 1 part by mass or more relative to 100 parts by mass of the polymer [A], sensitivity tends to be further improved, development defects tend to be further reduced, and film thickness uniformity tend to be further improved. When the content of the polymer [F] is 7 parts by mass or less relative to 100 parts by mass of the polymer [A], sensitivity tends to be further improved.

[0120] The lower limit of the Mw of the polymer [F] is preferably 1,000, more preferably 2,000, and even more preferably 3,000. The upper limit of the Mw is preferably 30,000. When the Mw of the polymer [F] is 7,500 or more, the LWR tends to be further improved. When the Mw of the polymer [F] is 25,000 or less, development defects tend to be further reduced. The Mw of the polymer [F] can be adjusted, for example, by adjusting the type and amount of polymerization initiator used in the synthesis of the polymer [F].

[0121] The upper limit of the Mw / M of the polymer (F) 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, and more preferably 1.2.

[0122] The polymer (F) can be synthesized, for example, by polymerizing monomers that provide the respective structural units by a known method.

[0123] Hereinafter, each structural unit contained in the polymer (F) will be described.

[0124] [Structural Unit (If)] The structural unit (If) is a structural unit containing a group that generates sulfonic acid when acted on by radiation. By including the structural unit (If), the polymer (F) acts as a radiation-sensitive acid generator in the radiation-sensitive composition.

[0125] Examples of the group that generates sulfonic acid upon the action of radiation include a group containing a sulfonate anion and a radiation-sensitive onium cation. Such groups are classified into a structure (Structure 1) in which a sulfonate anion is bonded to a side chain of a polymer, and a structure (Structure 2) in which a radiation-sensitive onium cation is bonded to a side chain of a polymer. As the group that generates sulfonic acid upon the action of radiation, Structure 1 is preferred. In the case of Structure 1, the diffusion of sulfonic acid generated upon exposure is more controlled, which tends to further improve LWR.

[0126] Examples of the radiation include those exemplified as radiation in the section <Method of forming a resist pattern> below.

[0127] When the group capable of generating a sulfonic acid upon the action of radiation corresponds to the above structure 1, examples of the structural unit (If) include structural units represented by the following formula (If).

[0128]

[0129] In the above formula (If), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a single bond or *-COO-. * is R １ indicates the bonding site with the carbon atom to which R is attached. ２ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure. １ is 0 or 1. ２ is a single bond or a divalent linking group. ２is an integer from 1 to 3. ２ If is 2, multiple R ２ are the same or different, and multiple L ２ are the same or different. ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ３ is an integer from 0 to 10. ３ If there are two or more R ３ are the same or different, and multiple R ４ are the same or different. ５ and R ６ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ４ is an integer from 1 to 10. ４ If there are two or more R ５ are the same or different, and multiple R ６ are the same or different. ＋ is a monovalent radiation-sensitive onium cation.

[0130] R １ As the alkyl group, a hydrogen atom or a methyl group is preferred from the viewpoint of copolymerizability of the monomer that gives the structural unit (If).

[0131] L １ When is a single bond, the LWR and film thickness uniformity tend to be further improved.

[0132] R ２ The number of ring members in the ring structure giving the formula (I) is preferably 5 to 30, and more preferably 6 to 30.

[0133] R ２ Examples of the ring structure that gives the above formula include an aliphatic hydrocarbon ring, an aliphatic heterocyclic ring, an aromatic hydrocarbon ring, and an aromatic heterocyclic ring.

[0134] Examples of the aliphatic hydrocarbon ring include monocyclic saturated alicyclic rings such as a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a cyclononane ring, a cyclodecane ring, and a cyclododecane ring; monocyclic unsaturated alicyclic rings such as a cyclopentene ring, a cyclohexene ring, a cycloheptene ring, a cyclooctene ring, and a cyclodecene ring; polycyclic saturated alicyclic rings such as a norbornane ring, an adamantane ring, a tricyclodecane ring, a tetracyclododecane ring, and a steroid structure; and polycyclic unsaturated alicyclic rings such as a norbornene ring and a tricyclodecene ring. The term "steroid structure" refers to a structure having a basic skeleton (sterane skeleton) in which three six-membered rings and one five-membered ring are fused.

[0135] Examples of the aliphatic heterocycle 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 an oxetane ring, a tetrahydrofuran ring, 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.

[0136] Examples of the aromatic hydrocarbon ring include the Ar Ｐ Examples of aromatic hydrocarbon rings which give the following rings include those given as examples.

[0137] 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, and an indole ring; and sulfur atom-containing heterocycles such as a thiophene ring.

[0138] R ２ The ring structure that provides the above is preferably an aromatic ring, more preferably an aromatic hydrocarbon ring, and even more preferably a benzene ring. When the ring structure is an aromatic ring, development defects tend to be reduced. When the ring structure is a benzene ring, sensitivity tends to be improved.

[0139] R ２Examples of the substituents that may be possessed by the ring structure that gives the formula include the above-mentioned Ar Ｐ Examples of the substituent that may be possessed by the group include those exemplified above.

[0140] n １ is preferably 1. In this case, the sensitivity tends to be further improved.

[0141] L ２ is preferably a divalent linking group.

[0142] The term "linking group" refers to a group that links two or more structures.

[0143] Examples of the divalent linking group include L ２ is not particularly limited as long as it is a group that connects two structures to which the groups are bonded, and examples thereof include a carbonyl group, an ether group, a carbonyloxy group, an ester group, an amide group, a sulfide group, a sulfonyl group, an alkanediyl group having 1 to 10 carbon atoms, or a group combining these.

[0144] L ２ is a carbonyl group, an ether group, a carbonyloxy group, an ester group, an amide group, an alkanediyl group having 1 to 10 carbon atoms, or a combination thereof, and R ２ When the ring structure that gives the formula is a benzene ring, the sensitivity tends to be further improved.

[0145] L ２ When is a group containing an amide group, the sensitivity, LWR, fewer development defects, and film thickness uniformity tend to be further improved.

[0146] n ２ is preferably 1. ２ When the ratio is 1, the sensitivity and the number of development defects tend to be more improved than when the ratio is 2 or more.

[0147] R ３ and R ４ Examples of the alkyl group having 1 to 10 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, and a propyl group.

[0148] R ３ , R ４ , R ５ or R ６Examples of the fluorinated alkyl group having 1 to 10 carbon atoms represented by the formula (I) include perfluoroalkyl groups such as trifluoromethyl groups.

[0149] R ３ and R ４ is preferably a hydrogen atom.

[0150] R ５ and R ６ As the group, a fluoro group or a perfluoroalkyl group is preferred, and a fluoro group or a trifluoromethyl group is more preferred.

[0151] n ３ is preferably 0 to 5, more preferably 0 to 2, and even more preferably 0 or 1.

[0152] n ４ As the number, 1 to 5 is preferred, 1 to 3 is more preferred, and 1 or 2 is even more preferred.

[0153] M ＋ The monovalent radiation-sensitive onium cation represented by the formula (I) is not particularly limited as long as it is known as a radiation-sensitive onium cation in an onium salt used as a radiation-sensitive acid generator contained in a radiation-sensitive composition. For example, a sulfonium cation (S ＋ ), iodonium cation (I ＋ ) are listed.

[0154] M ＋ Examples of the monovalent radiation-sensitive onium cation represented by the formula (r-a) include monovalent cations represented by the following formulas (r-a) to (r-c) (hereinafter, also referred to as "cations (r-a) to (r-c)").

[0155]

[0156] 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 Ｂ１are 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. ｂ１ is an integer from 0 to 3.

[0157] 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.

[0158] In the above formula (rc), b6 is an integer of 0 to 5. When b6 is 1, R Ｂ９ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ９ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogeno group, or a plurality of R Ｂ９ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are bonded. b7 is an integer of 0 to 5. When b7 is 1, R Ｂ１０ is a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group, or a halogeno group. Ｂ１０ are the same or different and are a monovalent organic group having 1 to 20 carbon atoms, a hydroxy group, a nitro group or a halogeno group, or a plurality of R Ｂ１０ are combined with each other to form a ring structure having 4 to 20 ring members together with the carbon chain to which they are attached.

[0159] "Organic group" refers to a group containing at least one carbon atom.

[0160] R Ｂ１ , R Ｂ２ , R Ｂ３ , R Ｂ４ , R Ｂ５ , R Ｂ６ , R Ｂ７ , R Ｂ９ or R Ｂ１０Examples 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)").

[0161] Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include the above-mentioned 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 following formula are given below.

[0162] 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.

[0163] 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).

[0164] 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".

[0165] 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.

[0166] R Ｂ１ , R Ｂ２ , R Ｂ５ , RＢ６ , 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.

[0167] R Ｂ３ and R Ｂ４ is preferably a hydrogen atom or a single bond formed by combining these, and is preferably a hydrogen atom.

[0168] 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.

[0169] The radiation-sensitive onium cation is preferably the cation (ra) or the cation (rc).

[0170] Examples of the cation (ra) include cations represented by the following formulae (ra-1) to (ra-17).

[0171]

[0172] Examples of the cation (r-c) include cations represented by the following formulae (r-c-1) and (r-c-2).

[0173]

[0174] Examples of the structural unit (If) include structural units represented by the following formulae (If-1) to (If-17).

[0175]

[0176] In the above formulas (If-1) to (If-17), R １ and M ＋ has the same meaning as the above formula (If).

[0177] Specific examples of the structure of the monomer that provides the structural unit (If) include the monomers (U-1) to (U-17) in the examples described below.

[0178] The lower limit of the content of the structural unit (If) in the polymer [F] is preferably 1 mol%, more preferably 5 mol%, even more preferably 10 mol%, and even more preferably 20 mol%, based on the total structural units constituting the polymer [F]. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and even more preferably 45 mol%. When the content is 20 mol% or more, sensitivity and the reduction of development defects tend to be further improved. Furthermore, when the content is 45 mol% or less, LWR and film thickness uniformity tend to be further improved.

[0179] [Structural Unit (IIf)] The structural unit (IIf) is a structural unit other than the structural unit (If) (i.e., a structural unit different from the structural unit (If)) that contains a fluorine atom. By including the structural unit (IIf), the polymer [F] can have a higher fluorine atom content than the polymer [A].

[0180] Examples of the structural unit (IIf) include structural units represented by the following formula (IIf-1) or (IIf-2) (hereinafter also referred to as "structural unit (IIf-1) or (IIf-2)").

[0181]

[0182] In the above formulas (IIf-1) and (IIf-2), R ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ is a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic ring. ３ is a single bond, *-COO- or *-CONH-. * is R ８ The binding site is shown.

[0183] In the above formula (IIf-1), R ９ is a single bond, a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent fluorinated aliphatic hydrocarbon group having 1 to 10 carbon atoms. ４ is *-COO- or *-OCO-. * is R ９ The binding site with R １０is a monovalent hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ９ and R １０ is a group having a fluorine atom.

[0184] In the above formula (IIf-2), R １１ is a group having 1 to 10 carbon atoms (n ５ +1)-valent aliphatic hydrocarbon group. １２ and R １３ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. A is —OH or —COOH. n ５ is an integer from 1 to 3. ５ If there are two or more R １２ are the same or different, and multiple R １３ are the same or different from each other, and multiple A's are the same or different from each other.

[0185] R ７ As the alkyl group, a hydrogen atom or a methyl group is preferred from the viewpoint of copolymerizability of the monomer that gives the structural unit (IIf-1) or (IIf-2).

[0186] R ８ The number of ring members of the aromatic ring giving the formula (I) is preferably 5 to 30, and more preferably 6 to 30.

[0187] R ８ Examples of aromatic rings that give ２ Among the ring structures which give the following, those exemplified as aromatic rings are mentioned.

[0188] R ８ The ring structure that gives the above formula is preferably an aromatic hydrocarbon ring, more preferably a benzene ring.

[0189] R ８ Examples of the substituents that may be possessed by the aromatic ring that gives the formula include the above-mentioned Ar Ｐ Examples of the substituent that the aromatic hydrocarbon ring that gives the following may have include those exemplified above.

[0190] L ３may be a single bond, *-COO-, or *-CONH-. Comparing *-COO- with *-CONH-, *-COO- tends to improve LWR, and *-CONH- tends to improve sensitivity.

[0191] R ９ Examples of the divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms that gives the formula (I) include a divalent chain hydrocarbon group having 1 to 10 carbon atoms and a divalent alicyclic hydrocarbon group having 3 to 10 carbon atoms.

[0192] Examples of the divalent chain hydrocarbon group having 1 to 10 carbon atoms include the above-mentioned R Ｘ , R Ｙ , R Ｚ , R Ｂ , or R Ｃ Among the examples of the monovalent chain hydrocarbon group having 1 to 20 carbon atoms which gives the above formula, groups in which one hydrogen atom has been removed from those having 1 to 10 carbon atoms can be mentioned.

[0193] Examples of the divalent alicyclic hydrocarbon group having 3 to 10 carbon atoms include the above-mentioned R Ｘ , R Ｙ , R Ｚ , R Ｂ , or R Ｃ Among the examples of the monovalent alicyclic hydrocarbon group having 1 to 20 carbon atoms which gives the above formula, groups in which one hydrogen atom has been removed from those having 1 to 10 carbon atoms can be mentioned.

[0194] R ９ Examples of the divalent fluorinated aliphatic hydrocarbon group having 1 to 10 carbon atoms that gives the formula (I) include the above divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0195] R ９ may be a single bond, a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent fluorinated aliphatic hydrocarbon group having 1 to 10 carbon atoms. １０ is a monovalent hydrocarbon group having 1 to 20 carbon atoms, R ９ is a divalent fluorinated aliphatic hydrocarbon group having 1 to 10 carbon atoms.

[0196] L ４ may be *-COO- or *-OCO-.

[0197] R １０ Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms that gives the formula 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 following formula are given below.

[0198] R １０ Examples of the monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms that gives the formula (I) include those in which some or all of the hydrogen atoms of the monovalent hydrocarbon group having 1 to 20 carbon atoms have been substituted with fluorine atoms.

[0199] R １１ (n ５ Examples of the (+1)-valent aliphatic hydrocarbon group include the above-mentioned R Ｘ , R Ｙ , R Ｚ , R Ｂ , or R Ｃ Among the examples of monovalent alicyclic hydrocarbon groups having 1 to 20 carbon atoms that give the formula ５ Examples of such groups include groups in which one hydrogen atom has been removed.

[0200] n ５ As the number, 1 is preferred.

[0201] n ５ If is 1, R １１ As the group, an alkanediyl group is preferred. In this case, the film thickness uniformity tends to be further improved.

[0202] R １２ and R １３ As the alkyl group, a monovalent fluorinated alkyl group having 1 to 10 carbon atoms is preferred, a perfluoroalkyl group is more preferred, and a trifluoromethyl group is even more preferred.

[0203] A is preferably —OH.

[0204] Group -L in structural unit (IIf-1)４ -R １０ may correspond to a group containing an acid-dissociable group depending on its structure. Also, it may correspond to a group that gives a carboxy group upon reaction with a developer, or a group that gives a hydroxy group upon reaction with a developer. In particular, when it corresponds to a group that gives a carboxy group upon reaction with a developer, or a group that gives a hydroxy group upon reaction with a developer, there is a tendency that the film thickness uniformity can be further improved.

[0205] Examples of the structural unit (IIf-1) include structural units represented by the following formulae (IIf-1-1) to (IIf-1-13).

[0206]

[0207] In the above formulae (IIf-1-1) to (IIf-1-13), R ７ has the same meaning as formula (IIf-1) above.

[0208] Examples of the structural unit (IIf-2) include structural units represented by the following formulae (IIf-2-1) to (IIf-2-5).

[0209]

[0210] In the above formulae (IIf-2-1) to (IIf-2-5), R ７ has the same meaning as formula (IIf-2) above.

[0211] Specific structures of the monomers that provide the structural unit (IIf-1) include, for example, the monomers (F-1) to (F-5), (F-7) to (F-9), and (F-14) to (F-18) in the Examples described later. Specific structures of the monomers that provide the structural unit (IIf-2) include, for example, the monomers (F-6), and (F-10) to (F-13) in the Examples described later.

[0212] The lower limit of the content of the structural unit (IIf) in the polymer [F] is preferably 40 mol %, more preferably 50 mol %, and even more preferably 60 mol %, based on all structural units constituting the polymer [F]. The upper limit of the content is preferably 99 mol %, more preferably 95 mol %, and even more preferably 90 mol %.

[0213] [Other structural units] The other structural units are structural units other than the structural unit (If) and the structural unit (IIf). The structural unit (IIIf) containing a phenolic hydroxyl group, the structural unit (IVf) containing an acid-dissociable group, the structural unit (Vf) containing a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof, the structural unit (VIf) containing a carboxy group, and the structural unit (VIIf) containing an alcoholic hydroxyl group, which are exemplified as other structural units, correspond to the structural units (Ia) to (Va) described above in the section <Polymer [A]>, respectively.

[0214] When the polymer [F] has other structural units, the lower limit of the content of the other structural units is preferably 0.1 mol %, more preferably 0.5 mol %, even more preferably 1 mol %, and still more preferably 5 mol %, based on the total structural units constituting the polymer [F]. The upper limit of the content is preferably 20 mol %, more preferably 15 mol %, and even more preferably 10 mol %.

[0215] <[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.

[0216] Examples of the acid generated from the acid generator (B) include sulfonic acid, carboxylic acid, and imide acid.

[0217] 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.

[0218] Examples of the onium salt compound include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, and pyridinium salts.

[0219] Specific examples of the acid generator (B) include the compounds described in paragraphs

[0080] to

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

[0220] 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.

[0221] 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 (F)>.

[0222] 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.

[0223] 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.

[0224] Specific examples of the structure of the acid generator [B] include the acid generators (B-1) to (B-14) in the examples described later.

[0225] 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.

[0226] <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).

[0227] 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").

[0228] 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.

[0229] 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.

[0230] Examples of the radiation-sensitive onium cation in the photodegradable base include the radiation-sensitive onium cations described above in the section <[F] Polymer>.

[0231] 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.

[0232] 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.

[0233] Specific examples of the structure of the acid diffusion controller [C] include the acid diffusion controllers (C-1) to (C-9) in the examples described later.

[0234] 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 %.

[0235] <[D] Organic Solvent> The radiation-sensitive composition usually contains [D] an organic solvent. 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] and the polymer [F], as well as the acid generator [B] and the acid diffusion controller [C], and other optional components that may be contained as needed.

[0236] 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).

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents such as n-pentane and n-hexane; and aromatic hydrocarbon solvents such as toluene and xylene.

[0243] The organic solvent (D) is preferably an alcohol solvent, an ester solvent, or a combination thereof, more preferably a polyhydric alcohol partial ether solvent, a polyhydric alcohol partial ether carboxylate solvent, or a combination thereof, and even more preferably propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, or a combination thereof.

[0244] 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 %.

[0245] <Other Optional Components> Examples of other optional components include surfactants, etc. The radiation-sensitive composition may contain one or more other optional components.

[0246] <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").

[0247] 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 that is excellent in sensitivity, LWR, few development defects, and film thickness uniformity can be formed.

[0248] Each step of the resist pattern forming method will be described below.

[0249] [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.

[0250] In this step, the radiation-sensitive composition described above is used as the radiation-sensitive composition.

[0251] Substrates include, for example, silicon wafers, silicon dioxide, and aluminum coated wafers.

[0252] 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.

[0253] [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.

[0254] 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.

[0255] [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.

[0256] 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.

[0257] 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.

[0258] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0259] <Synthesis of Polymers> Polymers (A-1) to (A-54) and polymers (F-1) to (F-48) were synthesized according to the following method. Compounds represented by the following formulae (M-1) to (M-42), (U-1) to (U-17), and (F-1) to (F-18) (hereinafter also referred to as "monomers (M-1) to (M-42), (U-1) to (U-17), and (F-1) to (F-18)") were used for the synthesis of polymer [A] and polymer [F]. The Mw and Mw / Mn of the obtained polymers were confirmed by GPC as described above in the section [Method for measuring Mw and Mn].

[0260] In the following synthesis examples, "mol %" means a value when the total number of moles of the monomers used is taken as 100 mol %.

[0261]

[0262]

[0263]

[0264]

[0265] Synthesis Example 1-1 Synthesis of Polymer (A-1) Monomer (M-1) and monomer (M-12) were dissolved in methanol (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer obtained was 40 / 60. Next, azobisisobutyronitrile (AIBN) was added as an initiator in an amount of 8 mol% relative to the total amount of monomers to prepare a monomer solution. Meanwhile, propylene glycol monomethyl ether (100 parts by mass relative to the total amount of monomers) was added to an empty reaction vessel and heated to 85°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours, and then heated at 85°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature.

[0266] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, and then redissolved in propylene glycol monomethyl ether (300 parts by mass). Next, methanol (500 parts by mass), triethylamine (50 parts by mass), and ultrapure water (10 parts by mass) were added, and a hydrolysis reaction was carried out at 70°C for 6 hours with stirring. After completion of the reaction, the residual solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass). The resin was dropped into 500 parts by mass of water to coagulate, and the resulting solid was filtered off. The mixture was dried at 50°C for 12 hours to synthesize a white powdery polymer (A-1). The Mw of the polymer (A-1) was 6,400, and the Mw / Mn was 1.6.

[0267] [Synthesis Examples 1-2 to 1-14 and 1-17 to 1-42] Synthesis of polymers (A-2) to (A-14) and (A-17) to (A-42) Polymers (A-2) to (A-14) and (A-17) to (A-42) were synthesized in the same manner as in Synthesis Example 1-1, except that the types and ratios of the monomers were changed as shown in Table 1 below. The Mw and Mw / Mn of each of the obtained polymers are shown in Table 1 below.

[0268] Synthesis Example 1-15 Synthesis of Polymer (A-15) Monomer (M-10) and monomer (M-12) were dissolved in 2-butanone (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer obtained was 40 / 60. A monomer solution was prepared by adding 8 mol% of AIBN as an initiator relative to the total amount of monomers. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours. The mixture was then heated at 80°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the obtained polymerization solution and stirred. The lower layer was recovered, and the solvent was removed to obtain polymer (A-15). The Mw of polymer (A-15) was 5,900, and the Mw / Mn was 1.6.

[0269] [Synthesis Examples 1-16 and 1-43 to 1-54] Synthesis of polymers (A-16) and (A-43) to (A-54) Polymers (A-16) and (A-43) to (A-54) were synthesized in the same manner as in Synthesis Example 1-15, except that the types and ratios of monomers were changed as shown in Table 1 below. The Mw and Mw / Mn of each of the obtained polymers are shown in Table 1 below.

[0270] The types and amounts (unit: mol %) of monomers that provide each structural unit of the polymers obtained in Synthesis Examples 1-1 to 1-54, as well as Mw and Mw / Mn, are shown in the following Table 1. In the following Table 1, "-" indicates that the corresponding monomer was not used.

[0271]

[0272] Synthesis Example 2-1 Synthesis of Polymer (F-1) Monomer (U-1) and monomer (F-1) were dissolved in 2-butanone (200 parts by mass relative to the total amount of monomers) so that the molar ratio in the final polymer was 30 / 70. A 4 mol % AIBN initiator was added relative to the total amount of monomers to prepare a monomer solution. Meanwhile, 2-butanone (100 parts by mass) was placed in an empty reaction vessel and heated to 80°C with stirring. Next, the monomer solution prepared above was added dropwise over 3 hours. The mixture was then heated at 80°C for an additional 3 hours. After completion of the polymerization reaction, the polymerization solution was cooled to room temperature. Acetonitrile (100 parts by mass) and hexane (600 parts by mass) were added to the resulting polymerization solution and stirred. The lower layer was recovered, and the solvent was removed to obtain polymer (F-1). The Mw of polymer (F-1) was 15,290, and the Mw / Mn was 1.7.

[0273] [Synthesis Examples 2-2 to 2-50] Synthesis of Polymers (F-2) to (F-50) Polymers (F-2) to (F-50) were synthesized in the same manner as in Synthesis Example 2-1, except that the types and ratios of the monomers were changed as shown in Table 2. The Mw and Mw / Mn of each of the resulting polymers are shown in Table 2.

[0274]

[0275] <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.

[0276] [[B] Acid Generator] As the acid generator [B], compounds represented by the following formulas (B-1) to (B-14) (hereinafter also referred to as "acid generators (B-1) to (B-14)") were used.

[0277]

[0278] [[C] Acid Diffusion Controller] As the acid diffusion controller [C], compounds represented by the following formulas (C-1) to (C-9) (hereinafter also referred to as "acid diffusion controllers (C-1) to (C-9)") were used.

[0279]

[0280] [[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

[0281] Example 1 Preparation of Radiation-Sensitive Composition (R-1) 100 parts by mass of polymer (A-1), 0.1 part by mass of polymer (F-1), 20 parts by mass of acid generator (B-1), 20 mol % of acid diffusion controller (C-1) relative to acid generator (B-1), 4,800 parts by mass of organic solvent (D-1), and 2,000 parts by mass of organic solvent (D-2) were blended and mixed. The resulting mixture was then filtered through a membrane filter with a pore size of 0.20 μm to prepare radiation-sensitive composition (R-1).

[0282] [Examples 2 to 125 and Comparative Examples 1 to 5] Preparation of Radiation-Sensitive Compositions (R-2) to (R-125) and (CR-1) to (CR-5) Radiation-sensitive compositions (R-2) to (R-125) and (CR-1) to (CR-5) were prepared in the same manner as in Example 1, except that the types and blending amounts of each component shown in Tables 3 to 5 below were used.

[0283] In Tables 3 to 5 below, "-" indicates that the corresponding component is not used.

[0284] In Tables 3 to 5 below, the amount of the acid diffusion controller (C) refers to the molar ratio relative to the component having a radiation-sensitive acid-generating structure (when there are multiple components, the total amount).

[0285]

[0286]

[0287]

[0288] <Formation of Resist Pattern> Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (manufactured by Brewer Science)) 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 32 nm line and space pattern.

[0289] <Evaluation> The sensitivity, LWR, number of development defects, and film thickness uniformity were evaluated according to the following methods. The results are shown in Tables 6 to 8 below.

[0290] [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 If it is less than 25 mJ / cm, it is rated as "A" (very good). ２ More than 27.5mJ / cm ２ If it is less than 27.5 mJ / cm, it is rated as "B" (good). ２ 30mJ / cm or more ２ In the following cases, the rating is "C" (fairly good) and 30 mJ / cm ２ If it was over 100%, it was rated as "D" (poor).

[0291] [LWR] The resist pattern formed in the above section <Formation of Resist Pattern> was observed from above the pattern using a scanning electron microscope (Hitachi High-Tech Corporation's "CG-4100"). Line widths were measured at a total of 50 arbitrary points. A 3 sigma value was determined from the distribution of the measured values, and the determined 3 sigma value was taken as the LWR (unit: nm). The smaller the LWR value, the better the result. LWR was evaluated as "A" (very good) when it was less than 3.50 nm, "B" (good) when it was 3.50 nm or more but less than 3.75 nm, "C" (fairly good) when it was 3.75 nm or more but 4.00 nm, and "D" (poor) when it was more than 4.00 nm.

[0292] [Number of Development Defects] The number of defects (pieces) for the resist patterns formed in the above section <Formation of Resist Pattern> was measured using a defect inspection device (KLA-Tencor's "KLA2925"). The measured defects were then classified into those determined to be derived from the resist film and foreign matter derived from the external environment. The number of development defects was evaluated as "A" (very good) when the number of defects determined to be derived from the resist film was less than 40, "B" (good) when it was 40 to 50, "C" (fairly good) when it was 50 to 60, and "D" (poor) when it was more than 60.

[0293] [Film Thickness Uniformity] Each of the radiation-sensitive compositions prepared above was applied to the surface of a 12-inch silicon wafer using the spin coater. After 60 seconds of preheating at 100°C, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 45 nm. Next, using an optical interference film thickness measuring device ("VM-3210" manufactured by SCREEN), the film thickness was measured at 21 points at 1 cm intervals from the center of the wafer up to a radius of 10 cm in the vertical direction, and the variation (3σ) of the measured values ​​was determined to represent the film thickness uniformity. Film thickness uniformity was evaluated as "A" (very good) for a film thickness of less than 0.5 nm, "B" (good) for a film thickness of 0.5 nm or more but less than 1.0 nm, "C" (fairly good) for a film thickness of 1.0 nm or more but less than 1.5 nm, and "D" (poor) for a film thickness of 1.5 nm or more.

[0294]

[0295]

[0296]

Claims

1. A radiation-sensitive composition comprising: a first polymer having a structural unit (Ia) containing a phenolic hydroxyl group, and whose solubility in a developer changes under the action of an acid; and a second polymer having a higher fluorine atom content than the first polymer, wherein the second polymer has a structural unit (If) containing a group that generates sulfonic acid under the action of radiation, and a structural unit (IIf) other than the structural unit (If) that contains a fluorine atom.

2. The radiation-sensitive composition according to claim 1, wherein the structural unit (If) is represented by the following formula (If), and the structural unit (IIf) is represented by the following formula (IIf-1) or (IIf-2): (In formula (If), R １ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. １ is a single bond or *-COO-. * is R １ indicates the bonding site with the carbon atom to which R is attached. ２ is a group in which two hydrogen atoms have been removed from a substituted or unsubstituted ring structure. １ is 0 or 1. ２ is a single bond or a divalent linking group. ２ is an integer from 1 to 3. ２ If there are two or more R ２ are the same or different, and multiple L ２ are the same or different. ３ and R ４ are each independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 10 carbon atoms, or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ３ is an integer from 0 to 10. ３ If there are two or more R ３ are the same or different, and multiple R ４ are the same or different. ５ and R ６ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. ４ is an integer from 1 to 10. ４ If there are two or more R ５ are the same or different, and multiple R ６ are the same or different. ＋ is a monovalent radiation-sensitive onium cation. (In formulas (IIf-1) and (IIf-2), R ７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. ８ is a single bond or a group in which two hydrogen atoms have been removed from a substituted or unsubstituted aromatic ring. ３ is a single bond, *-COO- or *-CONH-. * is R ８ In formula (IIf-1), R ９ is a single bond, a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, or a divalent fluorinated aliphatic hydrocarbon group having 1 to 10 carbon atoms. ４ is *-COO- or *-OCO-. * is R ９ The binding site with R １０ is a monovalent hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. ９ and R １０ In formula (IIf-2), either one of R is a group having a fluorine atom. １１ is a group having 1 to 10 carbon atoms (n ５ +1)-valent aliphatic hydrocarbon group. １２ and R １３ are each independently a fluorine atom or a monovalent fluorinated alkyl group having 1 to 10 carbon atoms. A is —OH or —COOH. n ５ is an integer from 1 to 3. ５ If there are two or more R １２ are the same or different, and multiple R １３ are the same or different, and multiple A's are the same or different.

3. The radiation-sensitive composition according to claim 1, wherein the content of the second polymer is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the first polymer.

4. A method for forming a resist pattern, comprising the steps of: applying the radiation-sensitive composition according to any one of claims 1 to 3 directly or indirectly to a substrate; exposing the resist film formed by the application; and developing the exposed resist film.

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