Radiation-sensitive composition for alkaline development and pattern formation method

Abstract

To provide a radiation-sensitive composition capable of forming a resist film which exhibits good sensitivity and is excellent in LWR performance and pattern rectangularity.SOLUTION: A radiation-sensitive composition for alkali development contains: a polymer having a structural unit represented by formula (1); and a compound represented by formula (2). In formula (1), R1 represents a hydrogen atom, a fluorine atom, a methyl group or the like; A1 represents a C1-20 divalent hydrocarbon group or a C6-20 divalent cyclic organic group having a lactone structure, a cyclic carbonate structure or a sultone structure; X1 represents -O-, -COO-, -OCO-, -O-CO-O-, -NHCO- or -CONH-; R2-R8 each represent a hydrogen atom or a C1-5 alkyl group; k represents an integer of 0-2; m represents an integer of 1-10; and n represents an integer of 1-4.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a radiation-sensitive composition for alkali development and a pattern forming method. [Background technology]

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor devices. In a typical procedure, for example, positive tone development (PTD), a resist composition coating is first exposed to radiation through a mask pattern to generate acid, which then catalyzes a reaction that creates a difference in the solubility of the resin in an alkaline developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] In recent years, various resist compositions have been proposed that incorporate cyclic structures such as lactone structures, carbonate structures, and sultone structures into the resin component (see, for example, Patent Document 1). Patent Document 1 discloses a resist composition that uses an acid-dissociable group-containing resin that has a specific lactone structure in its side chain. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-2248 Summary of the Invention [Problem to be solved by the invention]

[0005] Photolithography techniques using resist compositions are progressing toward finer patterns by utilizing short-wavelength radiation such as ArF excimer lasers, or liquid immersion lithography, in which exposure is performed while the space between the lens of the exposure tool and the resist film is filled with a liquid medium. Lithography using shorter-wavelength radiation such as electron beams, X-rays, and extreme ultraviolet (EUV) is also being considered as next-generation technologies. Efforts toward these next-generation technologies require performance equal to or better than conventional performance in terms of radiation sensitivity, LWR (Line Width Roughness), which indicates the variation in line width of the resist pattern, and pattern rectangularity, which indicates the rectangularity of the cross-sectional shape of the resist pattern.

[0006] The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to provide a radiation-sensitive composition and a pattern forming method that are capable of forming a resist film that exhibits good sensitivity and is excellent in LWR performance and pattern rectangularity. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve this problem, and as a result have found that the above problem can be solved by using a radiation-sensitive composition having a specific composition in PTD development, thereby completing the present invention. Specifically, the present invention provides the following means.

[0008] In one embodiment, the present invention provides a radiation-sensitive composition for alkali development, which contains a polymer having a structural unit represented by the following formula (1) and a compound represented by the following formula (2): [ka] (In formula (1), R 1 A is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. 1X is a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent cyclic organic group having 6 to 20 carbon atoms and having a lactone structure, a cyclic carbonate structure, or a sultone structure. 1 is -O-, -COO-, -OCO-, -O-CO-O-, -NHCO- or -CONH-. 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, k is an integer of 0 to 2, m is an integer of 1 to 10, and n is an integer of 1 to 4. [ka] (In formula (2), W 1 is a monovalent cyclic organic group having 3 to 20 carbon atoms. 1 R is a single bond or a divalent linking group. 9 , R 10 and R 11 are each independently a hydrogen atom, a fluorine atom or a fluoroalkyl group. f is a fluorine atom or a fluoroalkyl group. a is an integer of 0 to 8. X + is a monovalent cation.)

[0009] In another embodiment, the present invention provides a pattern forming method, comprising: a step of applying the above-described radiation-sensitive composition for alkali development onto a substrate to form a resist film; a step of exposing the resist film; and a step of developing the exposed resist film with an alkali developer. [Effects of the Invention]

[0010] According to the present invention, by preparing a radiation-sensitive composition for alkali development that contains a polymer having a structural unit represented by the above formula (1) and a compound represented by the above formula (2), it is possible to exhibit high sensitivity during resist pattern formation, as well as to achieve excellent LWR performance and pattern rectangularity. DETAILED DESCRIPTION OF THE INVENTION

[0011] Matters related to the implementation of the present disclosure will be described in detail below. In this specification, a numerical range indicated using "to" means that the numerical values ​​before and after "to" are included as the lower and upper limits.

[0012] <Radiation-sensitive composition for alkali development> The radiation-sensitive composition for alkali development according to the present disclosure (hereinafter also referred to as "the composition") contains a polymer [A] and a compound [B]. The composition may also contain other optional components as long as the effects of the present disclosure are not impaired. Each component will be described in detail below.

[0013] In this specification, the term "hydrocarbon group" includes chain hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain hydrocarbon group" refers to a linear hydrocarbon group or a branched hydrocarbon group that does not contain a cyclic structure and is composed solely of a chain structure. However, it may be saturated or unsaturated. The term "alicyclic hydrocarbon group" refers to a hydrocarbon group that contains only an alicyclic hydrocarbon structure as a ring structure and does not contain an aromatic ring structure. However, it does not necessarily have to be composed solely of an alicyclic hydrocarbon structure and may also contain a chain structure as part of it. The term "aromatic hydrocarbon group" refers to a hydrocarbon group that contains an aromatic ring structure as a ring structure. However, it does not necessarily have to be composed solely of an aromatic ring structure and may contain a chain structure or an alicyclic hydrocarbon structure as part of it. The term "organic group" refers to an atomic group obtained by removing any hydrogen atom from a carbon-containing compound (i.e., an organic compound).

[0014] <[A] Polymer> The polymer [A] is a polymer having a structural unit represented by the following formula (1) (hereinafter also referred to as "structural unit (I)"). The lactone structure in the structural unit (I) is bonded to the polymer main chain at the carbon atom adjacent to the oxygen atom (-O-) in the lactone structure. By incorporating such a structural unit (I) into the polymer component, it is believed that the solubility of unexposed areas in an alkaline developer can be reduced in a resist film formed from this composition. As a result, a resist film with excellent LWR performance and pattern rectangularity can be obtained. [ka] (In formula (1), R 1 A is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. 1 X is a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent cyclic organic group having 6 to 20 carbon atoms and having a lactone structure, a cyclic carbonate structure, or a sultone structure. 1 is -O-, -COO-, -OCO-, -O-CO-O-, -NHCO- or -CONH-. 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, k is an integer of 0 to 2, m is an integer of 1 to 10, and n is an integer of 1 to 4.

[0015] (Structural unit (I)) In the above formula (1), R 1 From the viewpoint of copolymerizability of the monomer that gives the structural unit (I), is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

[0016] A 1 Examples of the divalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a divalent chain hydrocarbon group having 1 to 20 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, and a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms.

[0017] A 1 Examples of divalent cyclic organic groups represented by the formula (I) include groups in which any methylene group constituting the carbon ring of a divalent monocyclic or polycyclic saturated alicyclic hydrocarbon group is replaced with -COO-, -O-CO-O-, or -SO2-O-. Examples of monocyclic divalent saturated alicyclic hydrocarbon groups include groups in which two hydrogen atoms have been removed from the same or different carbon atoms constituting the ring of cyclopentane, cyclohexane, cycloheptane, or cyclooctane. Examples of polycyclic divalent saturated alicyclic hydrocarbon groups include bicyclo[2.2.1]heptane (norbornane), bicyclo[2.2.2]octane, or tricyclo[3.3.1.1]heptane. 3,7 ]A group in which two hydrogen atoms have been removed from the same or different carbon atoms constituting the ring of decane (adamantane) is included.

[0018] R 2 and R 3 The alkyl group having 1 to 5 carbon atoms represented by the formula (I) may be either linear or branched. The alkyl group is preferably linear. In terms of making it easier to adjust the solubility in an alkaline developer, R 2 and R 3 is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a methyl group or an ethyl group.

[0019] R 4 , R 5 , R 6 , R 7 and R 8 The alkyl group having 1 to 5 carbon atoms represented by the formula (I) may be either linear or branched. The alkyl group is preferably linear. In terms of improving the solubility of the exposed area in an alkaline developer, R 4 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom. 5 ~R 8 is preferably a hydrogen atom, a methyl group or an ethyl group, more preferably a hydrogen atom.

[0020] In order to impart appropriate solubility in an alkaline developer, k is preferably 0 or 1, and more preferably 0. In order to improve the solubility of the exposed area in an alkaline developer, m is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1. n is preferably 1 to 3, and more preferably 1 or 2.

[0021] Examples of the structural unit (I) include structural units represented by the following formula: [ka] (In the formula, R 1 is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group.

[0022] The content of the structural unit (I) is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more, based on all structural units constituting the polymer [A]. The content of the structural unit (I) is preferably 75 mol% or less, more preferably 70 mol% or less, and even more preferably 65 mol% or less, based on all structural units constituting the polymer [A]. By ensuring that the content of the structural unit (I) falls within the above range, the effect of improving the LWR performance and pattern rectangularity of a resist film formed using this composition can be enhanced.

[0023] (Other structural units) The polymer [A] may further contain, in addition to the structural unit (I), a structural unit different from the structural unit (I) (hereinafter also referred to as "other structural units"). Examples of the other structural units include the following structural units (II) to (V).

[0024] Structural Units (II) The polymer [A] preferably further contains a structural unit (II) having an acid-dissociable group. The acid-dissociable group is a group that substitutes a hydrogen atom of an acid group such as a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, or a sulfo group, and is a group that dissociates under the action of an acid. When the polymer [A] contains an acid-dissociable group, the acid-dissociable group is dissociated by the acid generated by exposure of the composition to light, generating an acidic group, which changes the solubility of the polymer component in a developer. As a result, the composition can be endowed with good lithography properties.

[0025] The structural unit (II) is not particularly limited as long as it contains an acid-dissociable group. Examples of the structural unit (II) include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which the hydrogen atom of a phenolic hydroxyl group is substituted with a tertiary alkyl group, and a structural unit having an acetal bond. From the viewpoint of further improving the pattern formability of the present composition, the structural unit (II) is preferably a structural unit having a tertiary alkyl ester moiety, and specifically, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (II-1)") is preferred. [ka] (In formula (3), R 12 R is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. 13 is a monovalent hydrocarbon group having 1 to 20 carbon atoms. 14 and R 15 are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic group having 3 to 20 carbon atoms, or R 14 and R 15 are aligned with each other and R 14 and R 15 represents a divalent alicyclic group having 3 to 20 carbon atoms formed together with the carbon atom to which it is bonded.)

[0026] In the above formula (3), R 12 From the viewpoint of copolymerizability of the monomer that gives the structural unit (II-1), is preferably a hydrogen atom or a methyl group, more preferably a methyl group.

[0027] R 13 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a monovalent chain hydrocarbon group having 1 to 10 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.

[0028] R 13 ~R 15 Examples of the monovalent chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms, and linear or branched unsaturated hydrocarbon groups having 1 to 10 carbon atoms. Of these, linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms are preferred.

[0029] R 13 ~R 15 Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms and represented by the formula (I) include groups in which one hydrogen atom has been removed from a saturated alicyclic hydrocarbon, an unsaturated alicyclic hydrocarbon, or an alicyclic polycyclic hydrocarbon having 3 to 20 carbon atoms. Specific examples of these alicyclic hydrocarbons include saturated alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; unsaturated alicyclic hydrocarbons such as cyclopentene, cyclohexene, cycloheptene, cyclooctene, and cyclodecene; and alicyclic polycyclic hydrocarbons such as bicyclo[2.2.1]heptane (norbornane), bicyclo[2.2.2]octane, tricyclo[3.3.1.1]heptane (norbornane), and cyclohexene. 3,7 ]decane (adamantane), etc.

[0030] R 13 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (I) include groups in which one hydrogen atom has been removed from an aromatic ring such as benzene, naphthalene, anthracene, indene, and fluorene.

[0031] From the viewpoint of thoroughly removing development residues and increasing the solubility of exposed areas in alkaline developer, R 13Among these, a monovalent hydrocarbon group having 1 to 8 carbon atoms is preferred, and a linear or branched monovalent saturated hydrocarbon group having 1 to 8 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 8 carbon atoms is more preferred.

[0032] R 14 and R 15 are aligned with each other and R 14 and R 15 The divalent alicyclic group having 3 to 20 carbon atoms formed together with the carbon atom to which R is bonded is not particularly limited as long as it is a group formed by removing two hydrogen atoms from the same carbon atom constituting a carbon ring of a monocyclic or polycyclic alicyclic hydrocarbon having the above carbon number. 14 and R 15 The divalent alicyclic group formed by combining these may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group. When the divalent alicyclic group is a polycyclic hydrocarbon group, the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a fused alicyclic hydrocarbon group, and may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. Note that a fused alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed in such a way that multiple alicyclic rings share a side (a bond between two adjacent carbon atoms).

[0033] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, and preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, and cyclooctanediyl groups. Preferred polycyclic alicyclic hydrocarbon groups are bridged alicyclic saturated hydrocarbon groups, including bicyclo[2.2.1]heptane-2,2-diyl (norbornane-2,2-diyl), bicyclo[2.2.2]octane-2,2-diyl, and tricyclo[3.3.1.1]heptane-2,2-diyl. 3,7 ]Decane-2,2-diyl group (adamantane-2,2-diyl group) and the like are preferred.

[0034] From the viewpoint of increasing the solubility of the exposed area in an alkaline developer, 14 and R 15is a monovalent chain hydrocarbon group having 1 to 8 carbon atoms or a monovalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms, or R 14 and R 15 are aligned with each other and R 14 and R 15 represents a divalent alicyclic hydrocarbon group having 3 to 12 carbon atoms formed together with the carbon atom to which it is bonded, and is preferably a monovalent chain hydrocarbon group having 1 to 8 carbon atoms or a monovalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms, or R 14 and R 15 are aligned with each other and R 14 and R 15 More preferably, represents a divalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms formed together with the carbon atom to which it is bonded.

[0035] The structural unit (II-1) is particularly preferably a structural unit represented by the following formula (4), since this can increase the solubility of the exposed area in an alkaline developer and enable the formation of a finer pattern. [ka] (In formula (4), R 12 R is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. 16 R is a monovalent hydrocarbon group having 1 to 8 carbon atoms. 17 and R 18 are each independently a monovalent chain hydrocarbon group having 1 to 8 carbon atoms or a monovalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms, or R 17 and R 18 are aligned with each other and R 17 and R 18 represents a divalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms formed together with the carbon atom to which it is bonded.)

[0036] In the above formula (4), R 12 From the viewpoint of copolymerizability of the monomer that gives the structural unit represented by the above formula (4), is preferably a hydrogen atom or a methyl group, more preferably a methyl group.

[0037] R16 , R 17 and R 18 is R in the above formula (3) 13 , R 14 and R 15 Examples of the corresponding carbon numbers can be adopted from the explanations of R 16 is preferably a linear or branched monovalent saturated hydrocarbon group having 1 to 5 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 8 carbon atoms, and more preferably a linear or branched monovalent saturated hydrocarbon group having 1 to 3 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 5 carbon atoms. 17 and R 18 is a monovalent chain saturated hydrocarbon group having 1 to 4 carbon atoms, or R 17 and R 18 are aligned with each other and R 17 and R 18 It is preferable that the group represents a divalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms, which is formed together with the carbon atom to which it is bonded.

[0038] Among these, R 16 is an alkyl group having 1 to 4 carbon atoms, and R 17 and R 18 is R 17 and R 18 are combined with each other and together with the carbon atoms to which they are bonded, forming a monocyclic cycloalkane structure having 3 to 6 carbon atoms.

[0039] Specific examples of the structural unit (II) include structural units represented by the following formulas (3-1) to (3-6). [ka] (In formulas (3-1) to (3-6), R 12 ~R 15 has the same meaning as in formula (3). i and j each independently represent an integer of 1 to 4. h and g each independently represent 0 or 1.

[0040] In the above formulas (3-1) to (3-6), i and j are preferably 1 or 2, and more preferably 1. 13 is preferably a methyl group, an ethyl group, or an isopropyl group. 14 and R 15 is preferably a methyl group or an ethyl group.

[0041] The content of the structural unit (II) is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, and even more preferably 35 mol% or more, based on the total structural units constituting the polymer [A]. The content of the structural unit (II) is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and even more preferably 65 mol% or less, based on the total structural units constituting the polymer [A]. By setting the content of the structural unit (II) within the above range, the pattern formability of the composition can be further improved. The polymer [A] may contain only one type of structural unit (II), or a combination of two or more types.

[0042] Structural unit (III) The polymer [A] may further contain a structural unit having a polar group (hereinafter also referred to as "structural unit (III)"). When the polymer [A] further contains the structural unit (III), it becomes easier to adjust the solubility in an alkaline developer, and it is possible to improve lithography performance such as resolution. Examples of the polar group contained in the structural unit (III) include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Of these, a hydroxy group and a carboxy group are preferred, and a hydroxy group (particularly an alcoholic hydroxyl group) is more preferred. Note that the structural unit (III) is a different structural unit from the structural unit (structural unit (IV)) having a phenolic hydroxyl group described below.

[0043] Here, in this specification, a "phenolic hydroxyl group" refers to a group in which a hydroxyl group is directly bonded to an aromatic hydrocarbon structure. An "alcoholic hydroxyl group" refers to a group in which a hydroxyl group is directly bonded to an aliphatic hydrocarbon structure. This aliphatic hydrocarbon structure may be a chain hydrocarbon group or an alicyclic hydrocarbon group.

[0044] Examples of the structural unit (III) include structural units represented by the following formulas: However, the structural unit (III) is not limited to these. [ka] (In the formula, R A is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group.

[0045] When the polymer [A] has the structural unit (III), the content of the structural unit (III) is preferably 2 mol% or more, more preferably 5 mol% or more, and even more preferably 10 mol% or more, based on the total structural units constituting the polymer [A]. The content of the structural unit (III) is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less, based on the total structural units constituting the polymer [A]. By setting the content of the structural unit (III) within the above range, the lithography performance of the composition, such as resolution, can be further improved.

[0046] Structural unit (IV) The polymer [A] may further have a structural unit having a phenolic hydroxyl group (hereinafter also referred to as "structural unit (IV)"). The polymer [A] having the structural unit (IV) is preferred in that it can improve etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. In particular, the polymer [A] having the structural unit (IV) is preferably applicable to pattern formation using exposure to radiation having a wavelength of 50 nm or less, such as electron beams or EUV. In this case, the polymer [A] preferably has the structural unit (II) in addition to the structural units (I) and (IV).

[0047] The structural unit (IV) is not particularly limited as long as it contains a phenolic hydroxyl group, and examples thereof include a structural unit derived from hydroxystyrene or a derivative thereof and a structural unit derived from a (meth)acrylic compound having a hydroxybenzene structure.

[0048] When obtaining a polymer having structural unit (IV) as polymer [A], it is preferable to carry out polymerization in a state in which the phenolic hydroxyl group is protected with a protecting group such as an alkali-dissociable group, and then to obtain structural unit (IV) by deprotection through hydrolysis. The structural unit that gives structural unit (IV) upon hydrolysis is preferably a structural unit represented by the following formula (4-1) or a structural unit represented by the following formula (4-2). [ka] (In formulas (4-1) and (4-2), R P1 R is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. P2 is a monovalent hydrocarbon group or alkoxy group having 1 to 20 carbon atoms.

[0049] R P2 The monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (II) is R 13 Examples of the alkoxy group include a methoxy group, an ethoxy group, and a tert-butoxy group. P2 Of these, is preferably an alkyl group or an alkoxy group, and more preferably a methyl group or a tert-butoxy group.

[0050] When a radiation-sensitive composition for exposure to radiation having a wavelength of 50 nm or less is obtained, the content of the structural unit (IV) in the polymer [A] is preferably 10 mol % or more, more preferably 20 mol % or more, based on all structural units constituting the polymer [A]. The content of the structural unit (IV) in the polymer [A] is preferably 70 mol % or less, more preferably 60 mol % or less, based on all structural units constituting the polymer [A].

[0051] Structural unit (V) The polymer [A] may further have a structural unit (hereinafter also referred to as "structural unit (V)") that is different from the structural unit (I), and that includes at least one structural unit selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. Introduction of the structural unit (V) can further adjust the solubility of the polymer [A] in a developer, improve the adhesion of the resist film, and further enhance the etching resistance.

[0052] Examples of the structural unit (V) include structural units represented by the following formulas (5-1) to (5-10). [ka] (In formulas (5-1) to (5-10), R L1 R is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. L2 and R L3 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group. L4 and R L5 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a cyano group, a trifluoromethyl group, a methoxy group, a methoxycarbonyl group, a hydroxy group, a hydroxymethyl group, or a dimethylamino group, or R L4 and R L5 are aligned with each other and R L4 and R L5is a divalent alicyclic group having 3 to 8 carbon atoms, which is formed together with the carbon atom to which L is bonded. 2 is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. p is an integer of 0 to 3. q is an integer of 1 to 3.

[0053] Above R L4 and R L5 are aligned with each other and R L4 and R L5 The divalent alicyclic group having 3 to 8 carbon atoms formed together with the carbon atom to which R is bonded includes R in the above formula (3). 14 and R 15 Examples include divalent alicyclic groups having 3 to 20 carbon atoms, which are formed by combining chain hydrocarbon groups or alicyclic hydrocarbon groups represented by the following formula (I) together with the carbon atoms to which they are bonded, and which have 3 to 8 carbon atoms. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0054] L 2 Examples of the divalent linking group represented by the formula (I) include a divalent linear or branched hydrocarbon group having 1 to 10 carbon atoms, a divalent alicyclic hydrocarbon group having 4 to 12 carbon atoms, or a group composed of one or more of these hydrocarbon groups and at least one group selected from -CO-, -O-, -NH-, and -S-.

[0055] When the polymer [A] has the structural unit (V), the content of the structural unit (V) is preferably 40 mol % or less, more preferably 35 mol % or less, and even more preferably 30 mol % or less, based on the total structural units constituting the polymer [A]. By setting the content of the structural unit (V) within the above range, the lithography performance such as resolution of the composition can be further improved.

[0056] [A] Polymer synthesis The polymer (A) can be synthesized, for example, by polymerizing monomers that provide the respective structural units in an appropriate solvent using a radical polymerization initiator or the like.

[0057] Examples of radical polymerization initiators include azo radical initiators such as azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobisisobutyrate; and peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, with AIBN being more preferred. These radical initiators can be used alone or in combination.

[0058] Examples of the solvent used in the polymerization include alkanes, cycloalkanes, aromatic hydrocarbons, halogenated hydrocarbons, saturated carboxylic acid esters, ketones, ethers, and alcohols. Specific examples of these include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. The solvent used in the polymerization may be one type alone or two or more types in combination.

[0059] The reaction temperature in the polymerization is usually 40° C. to 150° C., and preferably 50° C. to 120° C. The reaction time is usually 1 hour to 48 hours, and preferably 1 hour to 24 hours.

[0060] The weight-average molecular weight (Mw) of the polymer [A], as calculated on a polystyrene basis by gel permeation chromatography (GPC), is preferably 1,000 or more, more preferably 2,000 or more, even more preferably 3,000 or more, and even more preferably 4,000 or more. Furthermore, the Mw of the polymer [A] is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, and even more preferably 15,000 or less. Setting the Mw of the polymer [A] within the above range is advantageous in that it can improve the coatability of the composition, improve the heat resistance of the resulting resist film, and sufficiently suppress development defects.

[0061] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the polymer [A] determined by GPC is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less. Mw / Mn is usually 1 or more.

[0062] In the present composition, the content of the polymer [A] is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total amount of solids contained in the composition (i.e., the total mass of all components other than the solvent component contained in the composition). The content of the polymer [A] is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less, based on the total amount of solids contained in the composition. The polymer [A] typically constitutes the base resin of the present composition. In this specification, the term "base resin" refers to a polymer component that accounts for 50% by mass or more of the total amount of solids contained in the composition. The present composition may contain only one type of polymer [A], or two or more types.

[0063] <[B] Compound> The compound [B] is a compound represented by the following formula (2): The compound [B] is an onium salt compound that functions as a radiation-sensitive acid generator that generates an acid upon irradiation with radiation. [ka] (In formula (2), W 1 is a monovalent cyclic organic group having 3 to 20 carbon atoms. 1 R is a single bond or a divalent linking group. 9 , R 10 and R 11 are each independently a hydrogen atom, a fluorine atom or a fluoroalkyl group. f is a fluorine atom or a fluoroalkyl group. a is an integer of 0 to 8. X + is a monovalent cation.)

[0064] In the above formula (2), W 1 The monovalent cyclic organic group having 3 to 20 carbon atoms and represented by the formula (I) is not particularly limited as long as it is a group in which one hydrogen atom has been removed from a cyclic structure having 3 to 20 carbon atoms. Examples of the cyclic structure include an alicyclic structure having 3 to 20 carbon atoms, an aliphatic heterocyclic structure having 3 to 20 carbon atoms, and an aromatic ring structure having 6 to 20 carbon atoms. These cyclic structures may have a substituent. Examples of the substituent include an alkoxy group, an alkoxycarbonyl group, a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), a hydroxyl group, and a cyano group.

[0065] Examples of alicyclic structures having 3 to 20 carbon atoms include alicyclic monocyclic structures having 3 to 20 carbon atoms and alicyclic polycyclic structures having 6 to 20 carbon atoms. The alicyclic monocyclic structures having 3 to 20 carbon atoms and the alicyclic polycyclic structures having 6 to 20 carbon atoms may be either saturated or unsaturated hydrocarbon structures. The alicyclic polycyclic structures may be either bridged alicyclic hydrocarbon structures or fused alicyclic hydrocarbon structures. Here, "bridged alicyclic hydrocarbons" refer to polycyclic alicyclic hydrocarbons in which two non-adjacent carbon atoms constituting an alicyclic ring are bonded by a bond chain containing one or more carbon atoms. "Fused alicyclic hydrocarbons" refer to polycyclic alicyclic hydrocarbons in which multiple alicyclic rings share a common edge (a bond between two adjacent carbon atoms).

[0066] Among the alicyclic monocyclic structures, saturated hydrocarbon structures include cyclopentane, cyclohexane, cycloheptane, and cyclooctane. Unsaturated hydrocarbon structures include cyclopentene, cyclohexene, cycloheptene, cyclooctene, and cyclodecene. Preferred alicyclic polycyclic structures are bridged alicyclic saturated hydrocarbon structures, such as bicyclo[2.2.1]heptane (norbornane), bicyclo[2.2.2]octane, and tricyclo[3.3.1.1]. 3,7 ] Decane (adamantane), etc.

[0067] Examples of the aliphatic heterocyclic structure having 3 to 20 carbon atoms include a cyclic ether structure, a lactone structure, a cyclic carbonate structure, a sultone structure, and a thioxane structure. The aliphatic heterocyclic structure may be either a monocyclic structure or a polycyclic structure, and may also be any of a bridged structure, a fused ring structure, and a spiro ring structure. 1 The aliphatic heterocyclic structure having 3 to 20 carbon atoms represented by the formula (I) may be a combination of two or more of a bridged structure, a fused ring structure, and a spiro ring structure. The "spiro ring structure" refers to a polycyclic ring structure formed by two rings sharing one atom.

[0068] Examples of the aromatic ring structure having 6 to 20 carbon atoms include benzene, naphthalene, anthracene, indene, and fluorene.

[0069] From the viewpoint of improving the transparency of the resist film obtained from the present composition while increasing the hydrophobicity of the film, and thereby increasing the difference in solubility in an alkaline developer between the exposed and unexposed areas, W in the above formula (2) is 1 is preferably a monovalent group having an alicyclic structure or an aliphatic heterocyclic structure, and more preferably has a bridged alicyclic saturated hydrocarbon structure or a bridged aliphatic heterocyclic structure. 1 From the viewpoint of sensitivity, it is preferable that the compound does not contain a fluorine atom.

[0070] L 1 The divalent linking group represented by the formula (I) is preferably -O-, -CO-, -COO-, -OCO-, -O-CO-O-, -S-, -SO2-, -CONH- or -NHCO-.

[0071] R 9 , R 10 , R 11 and R f Examples of the fluoroalkyl group represented by the formula (I) include a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a pentafluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropyl group, a heptafluoro-n-propyl group, a heptafluoro-i-propyl group, a nonafluoro-n-butyl group, a nonafluoro-i-butyl group, a nonafluoro-t-butyl group, a 2,2,3,3,4,4,5,5-octafluoro-n-pentyl group, a tridecafluoro-n-hexyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group. 9 , R 10 , R 11 and R f The fluoroalkyl group represented by the following formula is preferably a fluoroalkyl group having 1 to 3 carbon atoms, more preferably a trifluoromethyl group.

[0072] Among these, R 9 , R 10 , R 11 and R fis preferably a fluorine atom or a trifluoromethyl group in that better sensitivity can be achieved. a is preferably 0 to 5, and more preferably 0 to 2.

[0073] Specific examples of the anion contained in the compound represented by the above formula (2) include anions represented by the following formulas. [ka]

[0074] X + is a monovalent cation. X + The monovalent cation represented by the formula (I) is preferably a monovalent radiation-sensitive onium cation, and examples thereof include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi. Specific examples of radiation-decomposable onium cations containing such elements include sulfonium cations, tetrahydrothiophenium cations, iodonium cations, phosphonium cations, diazonium cations, and pyridinium cations. Among these, X + is preferably a sulfonium cation or an iodonium cation, and specifically, is preferably a cation represented by each of the following formulas (X-1) to (X-6). [ka]

[0075] In the above formula (X-1), R a1 , R a2 and R a3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, a halogen atom, -OSO2-R P , -SO2-R Q , -SR Tor R a1 , R a2 and R a3 R represents a ring structure formed by combining two or more of the following. The ring structure may contain a heteroatom (such as an oxygen atom or a sulfur atom) between the carbon-carbon bonds that form the skeleton. P , R Q and R T are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted monovalent alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R a1 ~R a3 and R P , R Q and R T If there are multiple R a1 ~R a3 and R P , R Q and R T are the same or different.

[0076] In the above formula (X-2), R b1 is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. k is 0 or 1. n k When is 0, k4 is an integer from 0 to 4, and n k When is 1, k4 is an integer between 0 and 7. R b1 If there are multiple, multiple R b1 are the same or different, and multiple R b1 R may represent a ring structure formed by combining with each other. b2 L is a substituted or unsubstituted linear or branched alkyl group having 1 to 7 carbon atoms, or a substituted or unsubstituted monovalent aromatic hydrocarbon group having 6 or 7 carbon atoms. C is a single bond or a divalent linking group. k5 is an integer of 0 to 4. R b2If there are multiple, multiple R b2 are the same or different, and multiple R b2 may represent a ring structure formed by combining with each other, and q is an integer of 0 to 3. In the formula, S + The ring structure containing the following may contain a heteroatom (such as an oxygen atom or a sulfur atom) between the carbon-carbon bonds that form the skeleton.

[0077] In the above formula (X-3), R c1 , R c2 and R c3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms.

[0078] In the above formula (X-4), R g1 is a substituted or unsubstituted linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted acyl group having 2 to 8 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 8 carbon atoms, or a hydroxy group. k is 0 or 1. n k2 When is 0, k 10 is an integer from 0 to 4, and n k2 When is 1, k 10 is an integer between 0 and 7. g1 If there are multiple, multiple R g1 may be the same or different, and multiple R g1 R may represent a ring structure formed by combining with each other. g2 and R g3 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyloxy group, a substituted or unsubstituted monocyclic or polycyclic cycloalkyl group having 3 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a hydroxy group, or a halogen atom, or R g2 and R g3 represents a ring structure formed by combining with each other. k11 and k12 each independently represent an integer of 0 to 4. R g2 and R g3 If there are multiple Rg2 and R g3 may be the same or different from each other.

[0079] In the above formula (X-5), R d1 and R d2 are each independently a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, an alkoxy group or an alkoxycarbonyl group, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, a halogen atom, a halogenated alkyl group having 1 to 4 carbon atoms, or a nitro group, or a ring structure formed by combining two or more of these groups. k6 and k7 are each independently an integer of 0 to 5. R d1 and R d2 If there are multiple R d1 and R d2 may be the same or different.

[0080] In the above formula (X-6), R e1 and R e2 are each independently a halogen atom, a substituted or unsubstituted linear or branched alkyl group having 1 to 12 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k8 and k9 are each independently an integer of 0 to 4.

[0081] X + Specific examples of the monovalent cation represented by the formula include structures represented by the following formulas, but are not limited to these specific examples. [ka] [ka] [ka]

[0082] [ka]

[0083] Specific examples of the compound [B] include a compound selected from the specific examples of the anion in the formula (2) and X +

[0033] However, the compound [B] is not limited to these combinations. The compound [B] may be used singly or in combination of two or more.

[0084] The content of the [B] compound can be appropriately selected depending on the type of [A] polymer used, exposure conditions, the required sensitivity, etc., but is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the [A] polymer. The content of the [B] compound is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. By ensuring that the content of the [B] compound falls within the above range, high sensitivity, good LWR performance, and pattern rectangularity can be achieved during resist pattern formation.

[0085] Other optional components that may be contained in the composition include [C] an acid diffusion controller, [D] a solvent, and [E] a high fluorine-containing polymer.

[0086] <[C] Acid diffusion controller> The acid diffusion controller [C] is incorporated into the composition to inhibit the diffusion of the acid generated from the compound [B] upon exposure into the resist film, thereby suppressing chemical reactions caused by the acid in unexposed areas. The incorporation of the acid diffusion controller [C] into the composition is advantageous in that it can further improve the lithography properties of the composition and enhance the storage stability of the composition. Furthermore, it can suppress changes in the line width of the resist pattern due to variations in the exposure-to-development time, thereby enabling the production of a radiation-sensitive composition with excellent process stability. Examples of the acid diffusion controller [C] include nitrogen-containing compounds and photodegradable bases.

[0087] ·Nitrogen-containing compounds Examples of the nitrogen-containing compound include a compound represented by the following formula (5) (hereinafter also referred to as "nitrogen-containing compound (I)"), a compound having two nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compound (II)"), a compound having three nitrogen atoms in the same molecule (hereinafter also referred to as "nitrogen-containing compound (III)"), an amide group-containing compound, a urea compound, a nitrogen-containing heterocyclic compound, and a nitrogen-containing compound having an acid-dissociable group. [ka] (In formula (5), R N1 , R N2 and R N3 are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aralkyl group.

[0088] Specific examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine and tri-n-pentylamine; and aromatic amines such as aniline and 2,6-diisopropylaniline. Examples of the nitrogen-containing compound (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine. Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; polymers such as dimethylaminoethylacrylamide; and the like.

[0089] Examples of the amide group-containing compound include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, pyrrolidone, and N-methylpyrrolidone. Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea. Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecan-1-ylcarbonyloxyethyl)morpholine; pyrazine, pyrazole, and the like.

[0090] Examples of nitrogen-containing compounds having an acid-dissociable group include Nt-butoxycarbonylpiperidine, Nt-butoxycarbonylimidazole, Nt-butoxycarbonylbenzimidazole, Nt-butoxycarbonyl-2-phenylbenzimidazole, N-(t-butoxycarbonyl)di-n-octylamine, N-(t-butoxycarbonyl)diethanolamine, N-(t-butoxycarbonyl)dicyclohexylamine, N-(t-butoxycarbonyl)diphenylamine, Nt-butoxycarbonyl-4-hydroxypiperidine, and Nt-amyloxycarbonyl-4-hydroxypiperidine.

[0091] [C] The nitrogen-containing compound as the acid diffusion controller is preferably at least one selected from the group consisting of nitrogen-containing compound (I), nitrogen-containing heterocyclic compounds, and nitrogen-containing compounds having an acid-dissociable group, and more preferably a nitrogen-containing compound having an acid-dissociable group.

[0092] Photodegradable bases The photodegradable base is a compound that generates an acid upon irradiation with radiation. The acid generated by the photodegradable base is a weak acid that does not induce dissociation of an acid-dissociable group under normal conditions. Here, "normal conditions" refers to conditions in which post-exposure baking (PEB) is performed at 110°C for 60 seconds. Examples of the photodegradable base include compounds that generate an acid weaker than the acid generated by the acid generator [B] upon exposure. Among these, onium salts that generate a weak acid (preferably a carboxylic acid) upon irradiation with radiation are preferably used as the photodegradable base.

[0093] The photodegradable base functions as an acid diffusion controller in unexposed areas due to its basicity, but in exposed areas, a weak acid is generated from the protons produced by decomposition of the radiation-sensitive onium cation and the anion of the weak acid, resulting in a decrease in acid diffusion controllability. Therefore, in exposed areas of a resist film containing a photodegradable base, the generated acid efficiently dissociates acid-dissociable groups in the resist film. Meanwhile, in unexposed areas, the components in the resist film are not affected by the acid. This results in a more pronounced difference in solubility between exposed and unexposed areas, resulting in a resist film with even better LWR performance and pattern rectangularity.

[0094] Examples of the photodegradable base include sulfonium salt compounds represented by the following formula (6-1) and iodonium salt compounds represented by the following formula (6-2). [ka] (In the above formula (6-1) and formula (6-2), J + is a sulfonium cation. + is the iodonium cation. - and Q - are each independently OH - , R α -COO - , R α -SO3 - or R α -N - (SO2R f2 ) is a monovalent anion represented by R α is a monovalent hydrocarbon group, or any methylene group in the monovalent hydrocarbon group is -O-, -CO-, -COO-, -O-CO-O-, -S-, -SO2- or -CONR β R is a monovalent group A in which any hydrogen atom of the monovalent hydrocarbon group or the group A is replaced by a fluorine atom or a hydroxyl group. β is a hydrogen atom or a monovalent hydrocarbon group. f2 is a perfluoroalkyl group.

[0095] In the above formula (6-1), J + Examples of the sulfonium cation represented by the formula (X-1) to (X-4) include the sulfonium cations represented by the formula (X-1) to (X-4) given above as examples of the cation constituting the compound [B]. In the above formula (6-2), U + Examples of the iodonium cation represented by the formula (X-5) and (X-6) given above as examples of the cation constituting the compound [B] include the iodonium cation represented by the formula (X-5) and (X-6).

[0096] Examples of photodegradable bases include compounds represented by the following formulas, but are not limited to these compounds. [ka] [ka]

[0097] The photodegradable base used in the preparation of the present composition is preferably a sulfonium salt, more preferably a triarylsulfonium salt, and may be used alone or in combination of two or more.

[0098] When the composition contains an acid diffusion controller (C), the content of the acid diffusion controller (C) in the composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, based on 100 parts by mass of the polymer (A). The content of the acid diffusion controller (C) in the composition is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on 100 parts by mass of the polymer (A). By ensuring that the content of the acid diffusion controller (C) falls within the above range, the lithography performance of the composition can be further improved.

[0099] <[D] Solvent> The solvent [D] is not particularly limited as long as it can dissolve or disperse the components blended in the composition. Examples of the solvent [D] include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0100] Examples of alcohol-based solvents include aliphatic monoalcohol-based solvents having 1 to 18 carbon atoms, such as 4-methyl-2-pentanol and n-hexanol; alicyclic monoalcohol-based solvents having 3 to 18 carbon atoms, such as cyclohexanol; polyhydric alcohol-based solvents having 2 to 18 carbon atoms, such as 1,2-propylene glycol; and polyhydric alcohol partial ether-based solvents having 3 to 19 carbon atoms, such as propylene glycol monomethyl ether. Examples of ether-based solvents include dialkyl ether-based solvents, such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether, diisoamyl ether, dihexyl ether, and diheptyl ether; cyclic ether-based solvents, such as tetrahydrofuran and tetrahydropyran; and aromatic ring-containing ether-based solvents, such as diphenyl ether and anisole.

[0101] 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-iso-butyl ketone, 2-heptanone, ethyl-n-butyl ketone, methyl-n-hexyl ketone, di-iso-butyl ketone, and trimethylnonanone; cyclic ketone solvents such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, and methylcyclohexanone; 2,4-pentanedione, acetonylacetone, acetophenone, and diacetone alcohol. Examples of amide solvents 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.

[0102] Examples of ester solvents include monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate, polyhydric alcohol carboxylate solvents such as propylene glycol acetate, polyhydric alcohol partial ether carboxylate solvents such as propylene glycol monomethyl ether acetate, polycarboxylic acid diester solvents such as diethyl oxalate, carbonate solvents such as dimethyl carbonate and diethyl carbonate, and cyclic esters such as γ-butyrolactone. Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents having 5 to 12 carbon atoms such as n-pentane and n-hexane, and aromatic hydrocarbon solvents having 6 to 16 carbon atoms such as toluene and xylene.

[0103] The solvent [D] preferably contains at least one selected from the group consisting of ester solvents and ketone solvents, more preferably at least one selected from the group consisting of polyhydric alcohol partial ether carboxylate solvents and cyclic ketone solvents, and even more preferably at least one of propylene glycol monomethyl ether acetate, ethyl lactate, and cyclohexanone. One or more of the solvents [D] can be used.

[0104] <[E] Highly Fluorinated Polymer> The highly fluorine-containing polymer [E] (hereinafter also referred to simply as "polymer [E]") is a polymer having a higher mass content of fluorine atoms than polymer [A]. When the composition contains polymer [E], the polymer [E] can be unevenly distributed in the surface layer of the resist film relative to polymer [A], thereby enhancing the water repellency of the surface of the resist film during immersion lithography.

[0105] The fluorine atom content of the polymer [E] is not particularly limited as long as it is larger than that of the polymer [A], but is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 4% by mass or more, and particularly preferably 7% by mass or more. The fluorine atom content of the polymer [E] is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. The fluorine atom content (% by mass) of the polymer is 13 The polymer structure can be determined by C-NMR spectroscopy or the like, and the amount can be calculated from the structure.

[0106] Examples of the fluorine atom-containing structural unit (hereinafter also referred to as "structural unit (F)") contained in the polymer [E] include the structural unit (fa) and the structural unit (fb) shown below. The polymer [E] may contain either the structural unit (fa) or the structural unit (fb) as the structural unit (F), or may contain both the structural unit (fa) and the structural unit (fb).

[0107] Structural Unit (fa) The structural unit (fa) is a structural unit represented by the following formula (7-1): By having the structural unit (fa), the fluorine atom content of the polymer [E] can be adjusted. [ka] (In formula (7-1), R C is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2-O-NH-, -CONH-, or -O-CO-NH-. R E is a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms or a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0108] In the above formula (7-1), R CFrom the viewpoint of copolymerizability of the monomer that provides the structural unit (fa), G is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. From the viewpoint of copolymerizability of the monomer that provides the structural unit (fa), G is preferably a single bond or -COO-, and more preferably -COO-.

[0109] R E Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms and represented by the formula (R) include a linear or branched alkyl group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. E Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include monocyclic or polycyclic alicyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms. E is preferably a monovalent fluorinated chain hydrocarbon group, more preferably a monovalent fluorinated alkyl group, and further preferably a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group or a 5,5,5-trifluoro-1,1-diethylpentyl group.

[0110] When the polymer [E] contains the structural unit (fa), the content of the structural unit (fa) is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, based on all structural units constituting the polymer [E]. Furthermore, the content of the structural unit (fa) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on all structural units constituting the polymer [E]. By setting the content of the structural unit (fa) within the above range, the mass content of fluorine atoms in the polymer [E] can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, thereby further improving the water repellency of the resist film during immersion exposure.

[0111] Structural Units (fb) The structural unit (fb) is a structural unit represented by the following formula (7-2): The polymer [E] has improved solubility in an alkaline developer due to the structural unit (fb), which can further suppress the occurrence of development defects. [ka] (In formula (7-2), R F is a hydrogen atom, a fluoro group, a methyl group, or a trifluoromethyl group. 59 is a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), or R 60 R' is a group in which an oxygen atom, a sulfur atom, -NR'-, a carbonyl group, -CO-O-, or -CO-NH- is bonded to the terminal of the R 60 is a single bond or a divalent organic group having 1 to 20 carbon atoms. 12 A is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms. 11 is an oxygen atom, -NR"-, -CO-O-*, or -SO2-O-*. R" is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" is R 61 R indicates the binding site that binds to 61 is a hydrogen atom or a monovalent organic group having 1 to 30 carbon atoms. s is an integer of 1 to 3. However, when s is 2 or 3, multiple R 60 , X 12 , A 11 and R 61 are the same or different.)

[0112] The structural unit (fb) is divided into a case in which it has an alkali-soluble group and a case in which it has a group that dissociates under the action of an alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group").

[0113] When the structural unit (fb) has an alkali-soluble group, R 61 is a hydrogen atom, and A 11 is an oxygen atom, -COO-* or -S0-*. "*" is R 61indicates the binding site of X 12 A is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. 11 If is an oxygen atom, X 12 is A 11 is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. 60 is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R 60 , X 12 , A 11 and R 61 are the same or different. When the structural unit (fb) has an alkali-soluble group, it is possible to increase the affinity for an alkali developer and suppress development defects. Examples of the structural unit (fb) having an alkali-soluble group include: 11 is an oxygen atom, and X 12 It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0114] When the structural unit (fb) has an alkali-dissociable group, R 61 is a monovalent organic group having 1 to 30 carbon atoms, and A 11 is an oxygen atom, -NR"-, -COO-* or -S0-*. "*" is R 61 indicates the binding site of X 12 R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. 61 A is a single bond or a divalent organic group having 1 to 20 carbon atoms. 11 is -COO-* or -SO2O-*, X 12 or R 61 is A 11 A has a fluorine atom on the carbon atom bonded to or adjacent to A. 11 If is an oxygen atom, X 12 or R 61 is a single bond, and R 59 R is a hydrocarbon group with 1 to 20 carbon atoms 60 A carbonyl group is bonded to the end of the R 61 is an organic group having a fluorine atom. When s is 2 or 3, multiple R60 , X 12 , A 11 and R 61 are the same or different from each other. When the structural unit (fb) has an alkali dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkali development step. This can increase the affinity to the developer and more efficiently suppress development defects. Examples of the structural unit (fb) having an alkali dissociable group include A 11 is -COO-* and R 61 or X 12 It is particularly preferred that both of them have a fluorine atom.

[0115] When the polymer [E] has the structural unit (fb), the content of the structural unit (fb) is preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 60 mol% or more, based on all structural units constituting the polymer [E]. Furthermore, the content of the structural unit (fb) is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less, based on all structural units constituting the polymer [E]. By ensuring that the content of the structural unit (fb) falls within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0116] In addition to the structural unit (fa) and the structural unit (fb), the polymer [E] may also contain a structural unit (II) having an acid-dissociable group or a structural unit having an alicyclic structure represented by the following formula (8) (hereinafter also referred to as "structural unit (G)"). [ka] (In the above formula (8), R 1α is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 2α is a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0117] In the above formula (8), R 2αThe monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (3) is 13 ~R 15 Examples of the monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms include the groups exemplified above.

[0118] When the polymer [E] contains a structural unit represented by the formula (8), the content of the structural unit is preferably 10 mol % or more, more preferably 20 mol % or more, and even more preferably 30 mol % or more, based on all structural units constituting the polymer [E]. The content of the structural unit represented by the formula (8) is preferably 70 mol % or less, more preferably 60 mol % or less, and even more preferably 50 mol % or less, based on all structural units constituting the polymer [E].

[0119] When the polymer [E] has the structural unit (II), the content of the structural unit (II) is preferably 5 mol % or more, more preferably 10 mol % or more, based on all structural units constituting the polymer [E]. The content of the structural unit (II) is preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 30 mol % or less, based on all structural units constituting the polymer [E].

[0120] The Mw of the polymer [E] measured by GPC is preferably 1,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more. The Mw of the polymer [E] is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 20,000 or less. The molecular weight distribution (Mw / Mn) of the polymer [E] measured by GPC, expressed as the ratio of Mn to Mw, is preferably 1 or more and 5 or less, and more preferably 1 or more and 3 or less.

[0121] When the composition contains the polymer [E], the content of the polymer [E] in the composition is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, per 100 parts by mass of the polymer [A]. The content of the polymer [E] in the composition is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the polymer [A]. The composition may contain one type of polymer [E] alone, or two or more types in combination.

[0122] <Other optional ingredients> The composition may further contain a component (hereinafter also referred to as "other optional component") other than the polymer [A], the compound [B], the acid diffusion controller [C], the solvent [D], and the polymer [E]. Examples of the other optional component include a radiation-sensitive acid generator other than the compound [B], a surfactant, an alicyclic skeleton-containing compound (e.g., 1-adamantanecarboxylic acid, 2-adamantanone, t-butyl deoxycholate, etc.), a sensitizer, and a localization promoter. The content ratio of the other optional component in the composition can be appropriately selected depending on each component, as long as it does not impair the effects of the present disclosure.

[0123] <Method for producing radiation-sensitive composition> The composition can be produced, for example, by mixing the polymer [A] and, if necessary, other components such as the solvent [D] in the desired ratio, and filtering the resulting mixture, preferably using a filter (e.g., a filter with a pore size of approximately 0.2 μm). The solids concentration of the composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. The solids concentration of the composition is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 5% by mass or less. By setting the solids concentration of the composition within the above range, good coatability can be achieved, which is advantageous in that a good resist pattern shape can be obtained.

[0124] The composition thus obtained can be suitably used as a positive pattern-forming composition for forming a pattern using an alkaline developer.

[0125] <Method for forming a resist pattern> The method for forming a resist pattern according to the present disclosure includes the steps of applying the present composition to one surface of a substrate (hereinafter also referred to as the "coating step"), exposing the resist film obtained by the coating step (hereinafter also referred to as the "exposure step"), and developing the exposed resist film with an alkaline developer (hereinafter also referred to as the "developing step"). Examples of patterns formed by the resist pattern according to the present disclosure include line and space patterns and hole patterns. Since the resist film is formed using the present composition in the method for forming a resist pattern according to the present disclosure, a resist pattern with good sensitivity and lithography properties and few development defects can be formed. Each step will be described below.

[0126] [Coating process] In this process, the composition is applied to one side of a substrate to form a resist film on the substrate. Conventional substrates can be used for forming the resist film, including silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in JP-B-6-12452 and JP-A-59-93448, may be formed on the substrate. Examples of methods for applying the composition include spin coating, casting coating, and roll coating. After application, pre-baking (PB) may be performed to volatilize the solvent in the coating. The PB temperature is preferably 60°C or higher, more preferably 80°C or higher. The PB temperature is preferably 140°C or lower, more preferably 120°C or lower. The PB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter. The average thickness of the resist film formed is preferably from 10 to 1,000 nm, and more preferably from 20 to 500 nm.

[0127] When immersion exposure is performed in the subsequent exposure step, a protective film for immersion that is insoluble in the immersion liquid may be further provided on the resist film formed from the composition, regardless of whether or not the composition contains a water-repellent polymer additive such as polymer [E], in order to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion may be either a solvent-removable protective film that is removed with a solvent before the development step (see, for example, JP 2006-227632 A), or a developer-removable protective film that is removed simultaneously with development in the development step (see, for example, WO 2005 / 069076 and WO 2006 / 035790 A). From the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion.

[0128] [Exposure process] In this step, the resist film obtained in the coating step is exposed to light. This exposure is carried out by irradiating the resist film with radiation through a photomask, and optionally through an immersion medium such as water. Examples of radiation include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, extreme ultraviolet light (EUV), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Of these, the radiation irradiated onto the resist film formed using the composition is preferably far ultraviolet light, EUV, or electron beams, more preferably ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), EUV, or electron beams, and even more preferably ArF excimer laser light, EUV, or electron beams.

[0129] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the exposed areas of the resist film by the acid generated from the compound [B] upon exposure. This PEB can increase the difference in solubility in a developer between the exposed and unexposed areas. The PEB temperature is preferably 50°C or higher, more preferably 80°C or higher. The PEB temperature is preferably 180°C or lower, more preferably 130°C or lower. The PEB time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The PEB time is preferably 600 seconds or shorter, more preferably 300 seconds or shorter.

[0130] [Development process] In this step, the exposed resist film is developed with an alkaline developer (alkaline development), thereby forming a desired resist pattern. After development, the resist film is typically washed with a rinse solution such as water or alcohol, and then dried.

[0131] Examples of developers used in alkaline development include aqueous alkaline 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 (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, with 2.38% by mass aqueous TMAH solutions being more preferred.

[0132] Examples of development methods include a method in which a substrate is immersed in a tank filled with developer for a certain period of time (dip method), a method in which developer is piled up on the surface of the substrate by surface tension and left to stand for a certain period of time (puddle method), a method in which developer is sprayed onto the surface of the substrate (spray method), and a method in which developer is continuously dispensed onto a substrate rotating at a constant speed while a developer dispensing nozzle is scanned at a constant speed (dynamic dispense method).

[0133] The composition described above, which contains the polymer [A] and the compound [B], exhibits high sensitivity during resist pattern formation and exhibits excellent LWR performance and pattern rectangularity. The reason for this is presumed to be as follows, although it is not intended to limit the scope of the present invention. Taking the case where the lactone structure is a γ-butyrolactone structure as an example, when the lactone structure is bonded to the main chain of the polymer at the α-position or when the lactone structure is bonded to the main chain of the polymer at the β-position, a primary hydroxy group is generated by ring-opening of the lactone structure (see Schemes (A) and (B) below). Therefore, the ring-opening reaction of the lactone structure in the polymer is more likely to proceed, and the ring-opening of the lactone structure excessively increases the solubility of the unexposed areas in the developer. As a result, the shape of the upper part of the resist pattern becomes excessively rounded, which is likely to lead to deterioration in LWR performance and pattern rectangularity. [ka]

[0134] In contrast, when the lactone structure is bonded to the main chain of the polymer at the γ-position, a secondary hydroxy group is generated by ring-opening of the lactone structure (see Scheme (C) below), which is thought to make the ring-opening reaction of the lactone structure less likely to proceed. Therefore, the polymer [A] having the structural unit represented by the above formula (1) has low solubility in the developer in the unexposed areas, resulting in an appropriate difference in solubility. As a result, it is thought that excellent LWR performance and pattern rectangularity can be achieved. [ka]

[0135] Furthermore, since the present composition contains the compound [B] together with the polymer [A], the compound [B] acts as a radiation-sensitive photoacid generator in the exposed areas, and the acid generated from the compound [B] can favorably promote dissociation of the acid-dissociable group, thereby increasing the solubility of the exposed areas in an alkaline developer. Therefore, it is believed that the resist film formed using the present composition has a more pronounced difference in solubility in an alkaline developer between the exposed and unexposed areas, allowing for the formation of a resist film with even better LWR performance and pattern rectangularity. [Example]

[0136] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following examples, "parts" and "%" are by mass unless otherwise specified. Measurements in the examples and comparative examples were carried out by the following methods.

[0137] [Weight average molecular weight (Mw) and number average molecular weight (Mn)] The Mw and Mn of the polymer were measured by gel permeation chromatography (GPC) using Tosoh GPC columns (two G2000HXL columns, one G3000HXL column, and one G4000HXL column) under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection volume: 100 μL, column temperature: 40°C, detector: differential refractometer, with monodisperse polystyrene as the standard. The polydispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0138] [ 13 C-NMR analysis] polymer 13 In the C-NMR analysis, a nuclear magnetic resonance spectrometer (JNM-ECX400 manufactured by JEOL Ltd.) was used, and DMSO-d6 was used as the measurement solvent to determine the content (mol %) of each structural unit in each polymer.

[0139] <Synthesis of Compounds> [Synthesis Example 1A] (Synthesis of Monomer (M-1)) 20.0 mmol of 4-pentenoic acid, 30.0 mmol of metachloroperbenzoic acid, and 50 g of dichloromethane were added to a reaction vessel and stirred at room temperature for 12 hours. The reaction was then terminated by adding saturated aqueous sodium thiosulfate, followed by extraction with dichloromethane and separation of the organic layer. The resulting organic layer was washed with saturated aqueous sodium chloride and then with water. After drying over sodium sulfate, the solvent was distilled off. The alcohol was obtained in good yield by purification using column chromatography. To the alcohol, 30.0 mmol of triethylamine, 30.0 mmol of methacrylic acid chloride, and 50 g of tetrahydrofuran were added and stirred at 80°C for 1 hour. The reaction solution was then cooled to below 30°C, and a saturated aqueous solution of ammonium chloride was added to terminate the reaction. Ethyl acetate was then added for extraction, and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous solution of sodium chloride and then with water. After drying with sodium sulfate, the solvent was removed by distillation, and the residue was purified by column chromatography to obtain a compound represented by the following formula (M-1) (hereinafter sometimes referred to as "monomer (M-1)") in good yield. The synthesis scheme of monomer (M-1) is shown below. [ka]

[0140] [Synthesis examples 2A to 9A] (Synthesis of Monomers (M-2) to (M-9)) Compounds represented by the following formulae (M-2) to (M-9), respectively, were synthesized in the same manner as in Synthesis Example 1A, except that the raw materials and precursors were appropriately changed. The compounds represented by the following formulae (M-2) to (M-9) may be referred to as "monomer (M-2)" to "monomer (M-9)", respectively.

[0141] <Polymer synthesis> The monomers used in the synthesis of the polymers are shown below. In the following synthesis examples, unless otherwise specified, "parts by mass" refers to a value when the total mass of the monomers used in each polymerization is taken as 100 parts by mass. "% by mole" refers to a value when the total number of moles of the monomers used in each polymerization or all structural units constituting each polymer is taken as 100% by mole.

[0142] (Monomer that provides structural unit (I)) [ka]

[0143] (Monomers that give structural units (II) to (V), (F), and (G)) [ka] [ka]

[0144] [Synthesis Example 1] (Synthesis of Resin (A-1)) Monomer (m-1) and monomer (M-1) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 50 / 50 (mol %), and AIBN (azobisisobutyronitrile) (3 mol % relative to the total of 100 mol % of the monomers used) was added as an initiator to prepare a monomer solution. 2-butanone (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The polymerization reaction was initiated at the start of the dropwise addition and continued for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The white powder was washed twice with methanol, filtered off, and dried at 50°C for 24 hours to obtain white powdery resin (A-1) (yield: 83%). The Mw of resin (A-1) was 7,800, and the Mw / Mn was 1.58. 13As a result of C-NMR analysis, the content ratios of the structural units derived from the monomer (m-1) and the monomer (M-1) were 51.0 mol % and 49.0 mol %, respectively.

[0145] [Synthesis Examples 2 to 36] (Synthesis of Resins (A-2) to (A-36)) Resins (A-2) to (A-36) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Tables 1 and 2 below were used. The content ratio (mol %) of the structural unit, yield (%), and physical properties (Mw, Mw / Mn) of each resin obtained are also shown in Tables 1 and 2. In Tables 1 and 2, "-" indicates that the corresponding monomer was not used (the same applies to the following tables).

[0146] [Table 1]

[0147] [Table 2]

[0148] [Synthesis Example 37] (Synthesis of Resin (A-37)) Monomer (m-2), monomer (M-1), and monomer (m-24) were dissolved in 1-methoxy-2-propanol (200 parts by mass) to a molar ratio of 50 / 10 / 40 (mol%), and AIBN (5 mol%) was added as an initiator to prepare a monomer solution. 1-Methoxy-2-propanol (100 parts by mass) was placed in a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The start of the dropwise addition marked the start of the polymerization reaction, which was carried out for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The cooled polymerization solution was poured into hexane (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with hexane, filtered off, and dissolved in 1-methoxy-2-propanol (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 while stirring. After the reaction was completed, the remaining solvent was distilled off, and the resulting solid was dissolved in acetone (100 parts by mass) and added dropwise to water (500 parts by mass) to coagulate the resin. The resulting solid was filtered and dried at 50°C for 13 hours to obtain a white powdery resin (A-37) (yield: 79%). The Mw of the resin (A-37) was 5,200, and the Mw / Mn was 1.60. 13 As a result of C-NMR analysis, the content ratios of the structural units derived from the monomer (m-2), the monomer (M-1) and the monomer (m-24) were 51.3 mol %, 9.9 mol % and 38.8 mol %, respectively.

[0149] [Synthesis Examples 38 to 44] (Synthesis of Resins (A-38) to (A-44)) Resins (A-38) to (A-44) were synthesized in the same manner as in Synthesis Example 37, except that the types and blending ratios of monomers shown in Table 3 below were used. The structural unit content (mol %), yield (%), and physical properties (Mw, Mw / Mn) of each resin obtained are also shown in Table 3 below.

[0150] [Table 3]

[0151] [Synthesis Example 45] (Synthesis of High Fluorine-Containing Resin (E-1)) Monomer (m-2) and monomer (m-26) were dissolved in 2-butanone (200 parts by mass) at a molar ratio of 20 / 80 (mol%), and AIBN (4 mol%) was added as an initiator to prepare a monomer solution. 2-butanone (100 parts by mass) was added to a reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C and the monomer solution was added dropwise over 3 hours with stirring. The polymerization reaction was initiated at the start of the dropwise addition and continued for 6 hours. After completion of the polymerization reaction, the polymerization solution was cooled to below 30°C with water. The solvent was replaced with acetonitrile (400 parts by mass), and then hexane (100 parts by mass) was added, stirred, and the acetonitrile layer was collected. This process was repeated three times. The solvent was replaced with propylene glycol monomethyl ether acetate to obtain a solution of high-fluorine-containing resin (E-1) (yield: 69%). The Mw of the high fluorine-containing resin (E-1) was 6,000, and the Mw / Mn was 1.62. 13 As a result of C-NMR analysis, the content ratios of the structural units derived from the monomer (m-1) and the monomer (m-26) were 19.9 mol % and 80.1 mol %, respectively.

[0152] [Synthesis Examples 46 to 49] (Synthesis of High Fluorine-Containing Resins (E-2) to (E-5)) Highly fluorinated resins (E-2) to (E-5) were synthesized in the same manner as in Synthesis Example 45, except for using monomers of the types and blending ratios shown in Table 4 below. The content (mol %) of each structural unit, yield (%) and physical properties (Mw, Mw / Mn) of the obtained highly fluorinated resins are also shown in Table 4 below.

[0153] [Table 4]

[0154] <Preparation of Radiation-Sensitive Resin Composition> The acid generators [B], acid diffusion controllers [C], solvents [D] and highly fluorinated resins [E] used in preparing the radiation-sensitive resin compositions of Examples 1 to 51 and Comparative Examples 1 to 25 are shown below.

[0155] [B] Acid generator B-1 to B-8: Compounds represented by the following formulas (B-1) to (B-8) [ka]

[0156] [C] Acid diffusion control agent C-1 to C-5: Compounds represented by the following formulae (C-1) to (C-5) [ka]

[0157] [D] Solvent D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol monomethyl ether D-3: γ-butyrolactone D-4: Ethyl lactate

[0158] Preparation and evaluation of positive-tone radiation-sensitive resin compositions for ArF exposure [Example 1] A radiation-sensitive resin composition (J-1) was prepared by mixing 100 parts by mass of resin (A-1), 12.0 parts by mass of acid generator (B-1), 6.0 parts by mass of acid diffusion controller (C-1), 3.0 parts by mass (solids content) of high-fluorine-containing resin (E-1), and 3,230 parts by mass of a mixed solvent of solvent (D-1) / solvent (D-2) / solvent (D-3) (blending ratio: D-1 / D-2 / D-3 = 2240 / 960 / 30 (parts by mass)) and filtering the mixture through a membrane filter with a pore size of 0.2 μm.

[0159] [Examples 2 to 39 and Comparative Examples 1 to 13] Except for using the components of the types and contents shown in Tables 5 and 6 below, the radiation-sensitive resin compositions (J-2) to (J-39) and (CJ-1) to (CJ-13) were prepared in the same manner as in Example 1.

[0160]

Table 5

[0161]

Table 6

[0162] <Formation of a resist pattern using a positive-type ArF-exposure radiation-sensitive resin composition> On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" of Tokyo Electron Limited), a composition for forming an underlayer antireflection film ("ARC66" of Brewer Science, Inc.) was applied, and then heated at 205 °C for 60 seconds to form an underlayer antireflection film with an average thickness of 100 nm. On this underlayer antireflection film, a positive-type ArF-exposure radiation-sensitive resin composition was applied using the above spin coater, and PB (pre-bake) was performed at 100 °C for 60 seconds. Then, by cooling at 23 °C for 30 seconds, a resist film with an average thickness of 90 nm was formed. Next, for this resist film, using an ArF excimer laser immersion exposure apparatus ("TWINSCAN XT-1900i" of ASML), under the optical conditions of NA = 1.35 and Dipole (σ = 0.9 / 0.7), exposure was performed through a mask pattern of 40 nm line and space. After exposure, PEB (post-exposure bake) was performed at 100 °C for 60 seconds. Then, the resist film was alkali-developed using a 2.38 mass% aqueous TMAH solution as an alkali developer, washed with water after development, and further dried to form a positive-type resist pattern (40 nm line and space pattern).

[0163] <Evaluation> The resist patterns formed using the positive radiation-sensitive resin composition for ArF exposure were evaluated for sensitivity, LWR performance, and pattern rectangularity according to the following methods. The results are shown in Table 7. The resist patterns were measured using a scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation).

[0164] [sensitivity] In forming a resist pattern using the positive radiation-sensitive resin composition for ArF exposure, the exposure dose for forming a 40 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was determined as the sensitivity (mJ / cm 2 The sensitivity was 30 mJ / cm 2 The following cases are considered "good" and 30mJ / cm 2 When the value exceeded 100%, it was evaluated as "poor".

[0165] [LWR performance] A 40 nm line-and-space resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above. The formed resist pattern was observed from above using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values. This 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line roughness and the better the result. LWR performance was evaluated as "good" when it was 2.5 nm or less, and "poor" when it exceeded 2.5 nm.

[0166] Pattern Rectangularity The 40 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose determined in the sensitivity evaluation above was observed using the scanning electron microscope described above, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the bottom side length to the top side length in the cross-sectional shape was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0167] [Table 7]

[0168] As is clear from the results in Table 7, when the radiation-sensitive resin compositions of Examples 1 to 39 were used for ArF exposure, they had good sensitivity, LWR performance, and pattern rectangularity. On the other hand, in Comparative Examples 1 to 13, each characteristic was inferior to that of the Examples. From these results, when the radiation-sensitive resin compositions of Examples 1 to 39 containing the polymer having the structural unit represented by the above formula (1) and the compound represented by the above formula (2) were used for ArF exposure, it can be said that they showed high sensitivity and could form a resist pattern with good LWR performance and pattern rectangularity.

[0169] · Preparation and Evaluation of Radiation-Sensitive Resin Composition for Extreme Ultraviolet (EUV) Exposure [Example 40] 100 parts by mass of resin (A-37), 17.0 parts by mass of acid generator (B-1), 10.0 parts by mass of acid diffusion controller (C-1), 3.0 parts by mass (solid content) of highly fluorine-containing resin (E-5), and a mixed solvent of solvent (D-1) / solvent (D-4) of 6,110 parts by mass (mixing ratio: D-1 / D-4 = 4280 / 1830 (parts by mass)) were mixed and filtered through a membrane filter with a pore size of 0.2 μm to prepare a radiation-sensitive resin composition (J-40).

[0170] [Examples 41 to 51 and Comparative Examples 14 to 25] Radiation-sensitive resin compositions (J-41) to (J-51) and (CJ-14) to (CJ-25) were prepared in the same manner as in Example 40, except that the components of the types and contents shown in Table 8 below were used.

[0171] [Table 8]

[0172] <Formation of Resist Pattern Using Radiation-Sensitive Resin Composition for EUV Exposure> A 12-inch silicon wafer was coated with a composition for forming a bottom anti-reflective coating (Brewer Science's ARC66) using a spin coater (Tokyo Electron Limited's CLEAN TRACK ACT12), followed by heating at 205°C for 60 seconds to form a bottom anti-reflective coating with an average thickness of 105 nm. A radiation-sensitive resin composition for EUV exposure was then coated onto this bottom anti-reflective coating using the spin coater, followed by post-baking at 130°C for 60 seconds. This was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 55 nm. This resist film was then exposed to light using an EUV exposure system (ASML's NXE3300) with NA=0.33, illumination conditions: Conventional s=0.89, and a mask: imecDEFECT32FFR02. After exposure, post-baking was performed at 120°C for 60 seconds. Thereafter, the resist film was subjected to alkaline development using a 2.38% by mass aqueous solution of TMAH as an alkaline developer, and after development, the resist film was washed with water and further dried to form a positive resist pattern (32 nm line and space pattern).

[0173] <Evaluation> The resist patterns formed using the radiation-sensitive resin composition for EUV exposure were evaluated for sensitivity, LWR performance, and pattern rectangularity according to the following methods. The results are shown in Table 9. A scanning electron microscope (CG-5000 manufactured by Hitachi High-Technologies Corporation) was used to measure the resist pattern length.

[0174] [sensitivity] In forming a resist pattern using a radiation-sensitive resin composition for EUV exposure, the exposure dose required to form a 32 nm line and space pattern was defined as the optimum exposure dose, and this optimum exposure dose was used as the sensitivity (mJ / cm 2 The sensitivity was 30 mJ / cm 2 The following cases are considered "good" and 30mJ / cm 2 When the value exceeded 100%, it was evaluated as "poor".

[0175] [LWR performance] A resist pattern was formed by irradiating the resist with the optimal exposure dose determined in the sensitivity evaluation above, and adjusting the mask size to form a 32 nm line-and-space pattern. The formed resist pattern was observed from above using the scanning electron microscope described above. The line width variation was measured at a total of 500 points, and a 3 sigma value was calculated from the distribution of the measured values. This 3 sigma value was taken as the LWR (nm). The smaller the LWR value, the smaller the line wobble and the better the result. LWR performance was evaluated as "good" when it was 3.0 nm or less, and "poor" when it exceeded 3.0 nm.

[0176] Pattern Rectangularity The 32 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose determined in the sensitivity evaluation above was observed using the scanning electron microscope described above, and the cross-sectional shape of the line-and-space pattern was evaluated. The rectangularity of the resist pattern was evaluated as "A" (very good) if the ratio of the bottom side length to the top side length in the cross-sectional shape was 1 or more and 1.05 or less, "B" (good) if it was more than 1.05 and 1.10 or less, and "C" (poor) if it was more than 1.10.

[0177] [Table 9]

[0178] As is clear from the results in Table 9, when used for EUV exposure, the radiation-sensitive resin compositions of Examples 40 to 51 had good sensitivity, LWR performance, and pattern rectangularity. In contrast, in Comparative Examples 14 to 25, each property was inferior to that of Examples 40 to 51.

[0179] The radiation-sensitive resin composition and the method for forming a resist pattern described above can form a resist pattern that has good sensitivity to exposure light and excellent LWR performance and pattern shape performance, and therefore can be suitably used in the processing of semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. A polymer having a structural unit represented by the following formula (1) and a structural unit represented by the following formula (4): A compound represented by the following formula (2), Contains A radiation-sensitive composition for alkali development, wherein the content of a structural unit represented by the following formula (4) is 30 mol % or more and 80 mol % or less based on all structural units constituting the polymer: 【Chemistry 1】 (In formula (1), R １ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. １ X is a divalent hydrocarbon group having 1 to 20 carbon atoms, or a divalent cyclic organic group having 6 to 20 carbon atoms and having a lactone structure, a cyclic carbonate structure, or a sultone structure. １ is —O—, —COO—, —OCO—, —O—CO—O—, —NHCO—, or —CONH—. ２ , R ３ , R ４ , R ５ , R ６ , R ７ and R ８ are each independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; k is 0, m is 1, and n is an integer of 1 to 4. 【Chemistry 2】 (In formula (2), W １ is a monovalent cyclic organic group having 3 to 20 carbon atoms. １ is a single bond or a divalent linking group. ９ , R １０ and R １１ are each independently a hydrogen atom, a fluorine atom or a fluoroalkyl group. ｆ is a fluorine atom or a fluoroalkyl group. a is an integer of 0 to 8. X ＋ is a monovalent cation.) 【Transformation 3】 (In formula (4), R １２ is a hydrogen atom, a fluorine atom, a methyl group, a trifluoromethyl group, or an alkoxyalkyl group. １６ is a monovalent hydrocarbon group having 1 to 8 carbon atoms. １７ and R １８ is R １７ and R １８ are aligned with each other and R １７ and R １８ represents a divalent monocyclic aliphatic hydrocarbon group having 3 to 8 carbon atoms formed together with the carbon atom to which

2. W in the above formula (2) １ The radiation-sensitive composition for alkali development according to claim 1 , wherein represents a monovalent group having an alicyclic structure or an aliphatic heterocyclic structure.

3. W in the above formula (2) １ The radiation-sensitive composition for alkali development according to claim 1 or 2, wherein

4. a step of applying the radiation-sensitive composition for alkali development according to any one of claims 1 to 3 onto a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with an alkaline developer; A pattern forming method comprising:

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