Radiation-sensitive resin composition and pattern forming method

Abstract

Provided are: a radiation-sensitive resin composition that can form a resist film that exhibits satisfactory levels of sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity even when forming a resist pattern having a high aspect ratio; and a pattern formation method. This radiation-sensitive resin composition comprises: a first onium salt compound represented by formula (1); a second onium salt compound represented by formula (2); a resin containing a structural unit having an acid-dissociable group; and a solvent.　(In formula (1), R1 represents a C1-40 monovalent chain-shaped organic group. R2 and R3 are each a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group, or a monovalent fluorinated hydrocarbon group. Rf11 and RF12 are each a fluorine atom or a monovalent fluorinated hydrocarbon group. R4, R5, R6, R7 and R8 are each a hydrogen atom, a hydroxyl group, a halogen atom, or a C1-20 monovalent organic group. Alternatively, if a plurality of R8 are present, two of the plurality of R8 mutually combine to form a ring structure having 5-20 ring members and configured by also two carbon atoms of the benzene ring in formula (1) to which these moieties are bonded.)　(In formula (2), RB denotes a C3-40 monovalent organic group including a ring structure. Rf21 and Rf22 each denote a fluorine atom or a monovalent fluorinated hydrocarbon group. Z+ is a monovalent radiation-sensitive onium cation.)

Description

[Technical Field]

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

[0002] Photolithography techniques using resist compositions are used to form fine circuits in semiconductor elements. A typical procedure involves, for example, exposing a coating of the resist composition to radiation through a mask pattern to generate an acid, which is then catalyzed by a reaction that causes a difference in the solubility of the resin in an alkaline or organic developer between the exposed and unexposed areas, thereby forming a resist pattern on a substrate.

[0003] The photolithography technology mentioned above is promoting pattern miniaturization by using short-wavelength radiation such as ArF excimer lasers, and also by using liquid immersion lithography, in which exposure is performed with the space between the lens of the exposure device and the resist film filled with a liquid medium. Lithography using even shorter-wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation technology.

[0004] As efforts toward further technological advances continue, efforts are being made to improve the sensitivity and resolution of photoacid generators, which are a major component of resist compositions. For example, studies are being conducted on photoacid generators that can provide strong acidity by substituting fluorine for the proximal carbon of the sulfonic acid group (see Patent No. 5703702). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5703702 Summary of the Invention [Problem to be solved by the invention]

[0006] Further applications include the formation of high-aspect-ratio resist patterns with line widths and hole diameters of 100 nm or less and resist film thicknesses of 100 to 200 nm or even greater. Even when forming such high-aspect-ratio patterns, resist performance equivalent to or better than conventional performance is required in terms of critical dimension uniformity (CDU), which is an index of sensitivity and uniformity of line widths and hole diameters, pattern circularity, which indicates the circularity of hole shapes, 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.

[0007] An object of the present invention is to provide a radiation-sensitive resin composition and a pattern forming method that are capable of forming a resist film that exhibits sufficient levels of sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity, even when forming a resist pattern with a high aspect ratio. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problem, the present inventors have found that the above object can be achieved by employing the following configuration, and have thus completed the present invention.

[0009] That is, in one embodiment, the present invention provides: a first onium salt compound represented by the following formula (1); a second onium salt compound represented by the following formula (2); a resin including a structural unit having an acid-dissociable group; Solvent and The present invention relates to a radiation-sensitive resin composition comprising: [ka] (In formula (1), R 1 is a monovalent chain organic group having 1 to 40 carbon atoms. R 2 and R 3are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group, or a monovalent fluorinated hydrocarbon group. 2 and R 3 If there are multiple R 2 and R 3 are the same or different. R f11 and R f12 are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group. f11 and R f12 If there are multiple R f11 and R f12 are the same or different. m1 and m2 each independently represent an integer of 1 to 4. R 4 , R 5 , R 6 and R 7 are each independently a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms. 4 , R 5 , R 6 and R 7 If there are multiple R 4 , R 5 , R 6 and R 7 are the same or different. R 8 If there is one, R 8 R is a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms. 8 If there are multiple 8 are each independently a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms, or a plurality of R 8 Two of these are combined with each other to form a 5-20-membered ring structure formed together with the two carbon atoms of the benzene ring in formula (1) to which they are bonded. n1 and n2 each independently represent an integer of 1 to 4. n3 is an integer from 1 to 5. [ka] (In formula (2), R B is a monovalent organic group containing a cyclic structure and having 3 to 40 carbon atoms. R f21 and R f22 are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group. f21 and R f22 If there are multiple R f21 and R f22 are the same or different. p is an integer of 1 to 4. Z + is a monovalent radiation-sensitive onium cation.

[0010] The radiation-sensitive resin composition contains both a first onium salt compound and a second onium salt compound as radiation-sensitive acid generators, and therefore exhibits excellent sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity even when forming resist patterns with high aspect ratios. Without being bound by any theory, the reason for this is presumed to be as follows: The anion portion of the first onium salt compound has a chain structure, which reduces the influence of steric hindrance, resulting in a relatively long diffusion length of the generated acid. This allows the generated acid to be sufficiently distributed throughout the resist film, even if it is thick, without uneven distribution. Furthermore, the cation portion of the first onium salt compound has high transparency and high quantum efficiency due to its structure, allowing acid to be efficiently generated throughout the entire thickness of the resist film during exposure, even in thick resist films. Furthermore, the thioxane-like structure containing sulfur and oxygen makes the compound highly soluble and allows it to be uniformly dispersed in the resist film. By combining these unique properties of the first onium salt compound with a second onium salt compound whose anion moiety has a cyclic structure and generates a relatively short acid diffusion length, the effects of both compounds are complemented, making it possible to provide optimal acid diffusion length, solubility, and acidity for various pattern sizes that would be difficult to achieve with a single composition. As a result, desired resist performance can be achieved. The organic group refers to a group containing at least one carbon atom.

[0011] In another embodiment, the present invention provides a resist film production method, comprising: exposing the resist film to light; developing the exposed resist film with a developer; The present invention relates to a pattern forming method comprising the steps of:

[0012] The pattern formation method uses the radiation-sensitive resin composition described above, which is capable of forming a resist film that is excellent in sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity, and therefore can efficiently form a high-quality resist pattern. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0014] <Radiation sensitive resin composition> The radiation-sensitive resin composition according to this embodiment (hereinafter also simply referred to as the "composition") contains a first onium salt compound, a second onium salt compound, a resin containing a structural unit having an acid-dissociable group, and a solvent. It may further contain an acid diffusion controller as needed. The composition may contain other optional components as long as they do not impair the effects of the present invention. By including both the first onium salt compound and the second onium salt compound as radiation-sensitive acid generators, the radiation-sensitive resin composition can impart high levels of sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity to a resist film of the radiation-sensitive resin composition.

[0015] (First onium salt compound) The first onium salt compound is represented by the above formula (1) and functions as a radiation-sensitive acid generator that generates an acid upon irradiation with radiation.

[0016] R 1The monovalent chain organic group having 1 to 40 carbon atoms and represented by the formula (I) is not particularly limited as long as it has a chain structure. Examples of the chain structure include monovalent chain hydrocarbon groups having 1 to 40 carbon atoms, whether saturated or unsaturated, straight or branched, groups in which some or all of the hydrogen atoms contained in the chain hydrocarbon group have been substituted with substituents, groups containing -CO-, -CS-, -O-, -S-, -SO2-, -NR'- or a combination of two or more of these between carbon atoms or at the carbon chain terminal of these groups, or combinations thereof. R' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0017] Examples of the chain hydrocarbon group having 1 to 40 carbon atoms include linear or branched saturated hydrocarbon groups having 1 to 40 carbon atoms, and linear or branched unsaturated hydrocarbon groups having 1 to 40 carbon atoms. Examples of the linear or branched saturated hydrocarbon group having 1 to 40 carbon atoms include alkyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl, 2-methylpropyl, 1-methylpropyl, t-butyl, n-pentyl, isopentyl, and neopentyl. Examples of the linear or branched unsaturated hydrocarbon group having 1 to 40 carbon atoms include alkenyl groups such as ethenyl, propenyl, and butenyl; and alkynyl groups such as ethynyl, propynyl, and butynyl.

[0018] Examples of the substituent that substitutes some or all of the hydrogen atoms of the chain hydrocarbon group include halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms; hydroxy groups; carboxy groups; cyano groups; nitro groups; alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkoxycarbonyloxy groups, acyl groups, acyloxy groups, or groups in which the hydrogen atoms of these groups are substituted with halogen atoms; and oxo groups (=O).

[0019] Among them, R 1The monovalent chain organic group having 1 to 40 carbon atoms represented by the formula (I) is preferably the above-mentioned monovalent chain hydrocarbon group having 1 to 40 carbon atoms, a group in which at least one of an ether bond (-O-) and a carbonyl group (-CO-) (hence, including an ester bond) is incorporated into the chain or at the end of the chain of a monovalent chain hydrocarbon group having 1 to 40 carbon atoms, a group in which some or all of the hydrogen atoms of a monovalent chain hydrocarbon group having 1 to 40 carbon atoms have been substituted with fluorine atoms, or a combination thereof. Furthermore, a group in which at least one of an ether bond (-O-) and a carbonyl group (-CO-) is incorporated into the chain or at the end of the chain of a monovalent chain hydrocarbon group having 1 to 20 carbon atoms, a group in which some or all of the hydrogen atoms of a monovalent chain hydrocarbon group having 1 to 20 carbon atoms have been substituted with fluorine atoms, or a combination thereof. In particular, R 1 The monovalent chain organic group having 1 to 40 carbon atoms represented by the following formula is preferably a straight-chain organic group having 1 to 40 carbon atoms.

[0020] Examples of the monovalent linear hydrocarbon group having 1 to 20 carbon atoms and having at least one of an ether bond (-O-) and a carbonyl group (-CO-) incorporated into the chain or at the chain terminal thereof include alkoxyalkyl groups, alkylcarbonylalkyl groups, alkoxycarbonylalkyl groups, alkylcarbonyloxyalkyl groups, alkylcarbonyloxy groups, and alkoxy groups. The alkyl chains of these groups preferably each independently have 1 to 12 carbon atoms. At least one of an ether bond (-O-) and a carbonyl group (-CO-) may be repeatedly incorporated into the chain. Some or all of the hydrogen atoms of these groups may be substituted with halogen atoms.

[0021] The above-mentioned monovalent chain hydrocarbon group having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms is preferably a monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms.

[0022] Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms include fluorinated alkyl groups such as 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; fluorinated alkenyl groups such as a trifluoroethenyl group and a pentafluoropropenyl group; Examples include fluorinated alkynyl groups such as a fluoroethynyl group and a trifluoropropynyl group.

[0023] R 2 and R 3 The monovalent hydrocarbon group represented by the above R 1 In addition to the monovalent chain hydrocarbon group having 1 to 40 carbon atoms, examples thereof include a monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 40 carbon atoms, and a combination thereof.

[0024] Examples of the monovalent alicyclic hydrocarbon group having 3 to 40 carbon atoms include monocyclic or polycyclic saturated hydrocarbon groups, and monocyclic or polycyclic unsaturated hydrocarbon groups. Preferred examples of the monocyclic saturated hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. Preferred examples of the polycyclic cycloalkyl group include bridged alicyclic hydrocarbon groups such as a norbornyl group, an adamantyl group, a tricyclodecyl group, and a tetracyclododecyl group. Examples of the monocyclic unsaturated hydrocarbon group include monocyclic cycloalkenyl groups such as a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, and a cyclohexenyl group. Examples of the polycyclic unsaturated hydrocarbon group include polycyclic cycloalkenyl groups such as a norbornenyl group, a tricyclodecenyl group, and a tetracyclododecenyl group. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two non-adjacent carbon atoms constituting the alicyclic ring are bonded by a bond chain containing one or more carbon atoms.

[0025] Examples of the monovalent aromatic hydrocarbon group having 6 to 40 carbon atoms include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and anthryl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0026] R 2 and R 3 The monovalent fluorinated hydrocarbon group represented by the above R 1 In addition to the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms in the above, examples thereof include a monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms.

[0027] Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms include fluorinated cycloalkyl groups such as a fluorocyclopentyl group, a difluorocyclopentyl group, a nonafluorocyclopentyl group, a fluorocyclohexyl group, a difluorocyclohexyl group, an undecafluorocyclohexylmethyl group, a fluoronorbornyl group, a fluoroadamantyl group, a fluorobornyl group, a fluoroisobornyl group, and a fluorotricyclodecyl group; Examples include fluorinated cycloalkenyl groups such as a fluorocyclopentenyl group and a nonafluorocyclohexenyl group.

[0028] The fluorinated hydrocarbon group is preferably the monovalent fluorinated linear hydrocarbon group having 1 to 8 carbon atoms, more preferably a monovalent fluorinated linear hydrocarbon group having 1 to 5 carbon atoms.

[0029] R 2 and R 3 In terms of the degree of freedom of the structure around the sulfo group and the acidity of the generated acid, a hydrogen atom, a fluorine atom, or a monovalent fluorinated linear hydrocarbon group having 1 to 5 carbon atoms is preferred.

[0030] R f11 and R f12 The monovalent fluorinated hydrocarbon group represented by R 2 and R 3A monovalent fluorinated hydrocarbon group represented by the following formula can be suitably used.

[0031] m1 and m2 each independently represent an integer of 1 to 3, more preferably 1 or 2, and particularly preferably 1.

[0032] Specific examples of the anion portion of the first onium salt compound include, but are not limited to, structures of the following formulae (1-1-1) to (1-1-20).

[0033] [ka]

[0034] [ka]

[0035] R 4 , R 5 , R 6 and R 7 (Hereinafter referred to as “R 4 ~R 7 "). The monovalent organic group having 1 to 20 carbon atoms, represented by (I), may be any of a group corresponding to the structure of the monovalent chain organic group having 1 to 40 carbon atoms described above, a cyclic structure, or a combination thereof. Examples of the cyclic structure include cyclic hydrocarbon groups, regardless of whether they are alicyclic, aromatic, or heterocyclic. The cyclic structure is preferably an alicyclic structure having 3 to 20 carbon atoms, an aromatic ring structure having 6 to 20 carbon atoms, or a combination thereof. Other examples include groups in which some or all of the hydrogen atoms contained in a group having a cyclic structure have been substituted with a substituent, groups containing -CO-, -CS-, -O-, -S-, -SO2-, -NR"-, or a combination of two or more of these at the carbon-carbon interval or at the carbon chain terminal of such groups, or a combination thereof. R" is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms.

[0036] The substituents that substitute a part or all of the hydrogen atoms of the organic group include the above-mentioned R 1 Examples of substituents include those which substitute some or all of the hydrogen atoms of the chain hydrocarbon group in the above formula.

[0037] R 4 ~R 7 The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms in the above R 2 and R 3 Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms in the above, groups corresponding to those having 3 to 20 carbon atoms can be suitably used.

[0038] R 4 ~R 7 In the above, the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms is 2 and R 3 Among the monovalent aromatic hydrocarbon groups having 6 to 40 carbon atoms in the above, groups corresponding to those having 6 to 20 carbon atoms can be suitably used.

[0039] Above R 4 ~R 7 Examples of the heterocyclic cyclic hydrocarbon group in the above formula include a group in which one hydrogen atom has been removed from an aromatic heterocyclic structure and a group in which one hydrogen atom has been removed from an alicyclic heterocyclic structure. Five-membered aromatic structures that become aromatic due to the introduction of heteroatoms are also included in the heterocyclic structure. Examples of heteroatoms include oxygen atoms, nitrogen atoms, and sulfur atoms.

[0040] Examples of the aromatic heterocyclic structure include: Oxygen atom-containing aromatic heterocyclic structures such as furan, pyran, benzofuran, and benzopyran; nitrogen atom-containing aromatic heterocyclic structures such as pyrrole, imidazole, pyridine, pyrimidine, pyrazine, indole, quinoline, isoquinoline, acridine, phenazine, and carbazole; Sulfur-containing aromatic heterocyclic structures such as thiophene; Examples include aromatic heterocyclic structures containing multiple heteroatoms, such as thiazole, benzothiazole, thiazine, and oxazine.

[0041] Examples of the alicyclic heterocyclic structure include Oxygen atom-containing alicyclic heterocyclic structures such as oxirane, tetrahydrofuran, tetrahydropyran, dioxolane, and dioxane; Nitrogen atom-containing alicyclic heterocyclic structures such as aziridine, pyrrolidine, piperidine, and piperazine; Sulfur atom-containing alicyclic heterocyclic structures such as thietane, thiolane, and thiane; Examples include alicyclic heterocyclic structures containing multiple heteroatoms such as morpholine, 1,2-oxathiolane, and 1,3-oxathiolane.

[0042] The cyclic structure also includes a lactone structure, a cyclic carbonate structure, a sultone structure, and a structure containing a cyclic acetal.

[0043] R 8 As the monovalent organic group having 1 to 20 carbon atoms represented by the above R 4 ~R 7 A monovalent organic group having 1 to 20 carbon atoms and represented by the following formula can be suitably used.

[0044] R 8 In the case where there are multiple R 8 The cyclic structure having 5 to 20 ring members formed together with the two carbon atoms of the benzene ring in the above formula (1) to which R 4 ~R 7 Among the cyclic structures shown above, structures corresponding to 5 to 20 ring members can be suitably employed. Among them, from the viewpoint of transparency of the cation portion of the first onium salt compound, alicyclic hydrocarbon structures having 5 to 20 carbon atoms are preferred as the cyclic structure. Examples of the alicyclic hydrocarbon structure having 5 to 20 carbon atoms include R 4 ~R 7 Among the monovalent alicyclic hydrocarbon groups having 3 to 20 carbon atoms shown in the above, structures corresponding to those having 5 to 20 carbon atoms are exemplified.

[0045] R 4 , R 5 , R 6 , R 7 and R8 are preferably a hydrogen atom, a halogen atom, the above-mentioned monovalent chain hydrocarbon group having 1 to 20 carbon atoms, or the above-mentioned monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms. 4 , R 5 , R 6 and R 7 is a hydrogen atom, and R 8 is more preferably a chain hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 6 to 12 carbon atoms, a fluorine atom, or a fluorinated hydrocarbon group having 1 to 10 carbon atoms. As the monovalent chain hydrocarbon group having 1 to 10 carbon atoms, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, or a 1,1-dimethyl-1-propyl group is preferred. As the monovalent alicyclic hydrocarbon group having 6 to 12 carbon atoms, a cyclohexyl group or a cycloheptyl group is preferred. As the fluorinated hydrocarbon group having 1 to 10 carbon atoms, 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, or a heptafluoro-n-propyl group is preferred.

[0046] n1 and n2 are each independently preferably an integer of 2 to 4, more preferably 2 or 3. n3 is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 1 or 2.

[0047] Specific examples of the cation moiety of the first onium salt compound include, but are not limited to, structures of the following formulae (1-2-1) to (1-2-24).

[0048] [ka]

[0049] The first onium salt compound can be obtained by appropriately combining the above anion moiety and cation moiety. Specific examples include, but are not limited to, structures of the following formulae (1-1) to (1-22).

[0050] [ka]

[0051] [ka]

[0052] The lower limit of the content of the first onium salt compound (the total content when multiple types of first onium salt compounds are included) is preferably 0.1 parts by mass, more preferably 1 part by mass, even more preferably 3 parts by mass, and particularly preferably 5 parts by mass, per 100 parts by mass of the resin described below. The upper limit of the content is preferably 100 parts by mass, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 40 parts by mass. The content of the first onium salt compound is appropriately selected depending on the type of resin used, exposure conditions, desired sensitivity, and the like. This allows for excellent sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity to be exhibited during resist pattern formation.

[0053] (Method for synthesizing first onium salt compound) As a method for synthesizing the first onium salt compound, in the above formula (1), R 4 , R 5 , R 6 and R 7 An example will be explained below in which n1 is a hydrogen atom, n2 is both 2, and n3 is 1. A typical scheme is shown below.

[0054] [ka] (In the scheme, R 1 , R 2 , R 3 , R f11 , R f12 , m1, m2 and R 8 is the same as in formula (1) above. + is a monovalent metal ion.)

[0055] The (substituted) benzene ring is iodized under an acid catalyst, followed by oxidation of the (substituted) iodobenzene with peroxide and subsequent iodine oxide elimination to obtain an iodonium salt. This is then subjected to a nucleophilic substitution reaction with a thioxane or its analog to produce the cationic portion of the first onium salt compound represented by formula (ia). Finally, salt exchange with a sulfonate having the structure of the anionic portion of the first onium salt compound can be performed to synthesize the first onium salt compound represented by formula (1'). Other structures can also be synthesized by appropriately selecting the starting materials, thioxane analogs, and sulfonates.

[0056] (Second onium salt compound) The second onium salt compound is represented by the above formula (2) and functions as a radiation-sensitive acid generator that generates an acid upon irradiation with radiation.

[0057] R B The monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure represented by the formula (I) is not particularly limited, and may be either a group containing only a cyclic structure or a group combining a cyclic structure with a chain structure. The cyclic structure may be either a monocyclic or polycyclic ring. The cyclic structure may be an aromatic ring structure, an alicyclic structure, a heterocyclic structure, or a combination thereof. The heterocyclic structure includes a lactone structure, a cyclic carbonate structure, a sultone structure, or a combination thereof. These structures are preferably contained as the smallest basic skeleton of the cyclic structure. The number of cyclic structures as the basic skeleton in the organic group may be one or two or more. A heteroatom or a heteroatom-containing group may be present between the carbon atoms forming the skeleton of the cyclic structure or the chain structure or at the end of the carbon chain, and a hydrogen atom on a carbon atom of the cyclic structure or the chain structure may be substituted with another substituent.

[0058] The cyclic structure may be any of the above R 4 , R 5 , R 6 , R 7 and R 8 The cyclic structure in the above formula (R) can be preferably used. 1A monovalent chain organic group having 1 to 40 carbon atoms and represented by the following formula can be suitably used. Examples of the heteroatom or heteroatom-containing group include -CO-, -CS-, -O-, -S-, -SO2-, -NR'''-, and groups containing a combination of two or more of these. R''' is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the substituent that substitutes a hydrogen atom on a carbon atom of the cyclic structure or chain structure include the above-mentioned R 1 Examples of substituents include those which substitute some or all of the hydrogen atoms of the chain hydrocarbon group in the above formula.

[0059] R B The cyclic structure contained in is preferably an alicyclic polycyclic structure having 6 to 14 carbon atoms, and more preferably a norbornyl group or an adamantyl group.

[0060] R f21 and R f22 The monovalent fluorinated hydrocarbon group represented by the above R f11 and R f12 A monovalent fluorinated hydrocarbon group represented by the following formula can be suitably used.

[0061] p is preferably an integer of 1 to 3, and more preferably 1 or 2.

[0062] Specific examples of the anion portion of the second onium salt compound include, but are not limited to, structures of the following formulae (2-1-1) to (2-1-30).

[0063] [ka]

[0064] [ka]

[0065] In the above formula (2), the above Z +Examples of the monovalent radiation-sensitive onium cation represented by the formula (X) include radiation-decomposable onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi in addition to the cation moiety of the first onium salt compound. Examples of the radiation-decomposable onium cation include sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Among these, sulfonium cation or iodonium cation is preferred. The sulfonium cation or iodonium cation is preferably represented by the following formulae (X-1) to (X-6).

[0066] [ka]

[0067] In the above formula (X-1), R a1 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, a halogen atom, -OSO2-R P , -SO2-R Q or -SR T or a ring structure formed by combining two or more of these groups. The ring structure may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton. R 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 alicyclic hydrocarbon group having 5 to 25 carbon atoms, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms. k1, k2, and k3 are each independently an integer of 0 to 5. R a1 and R P , R Q and R TIf there are multiple R a1 and R P , R Q and R T may be the same or different.

[0068] 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 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 may be 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 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 b2 If there are multiple, multiple R b2 may be 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 may contain a heteroatom such as O or S between the carbon-carbon bonds that form the skeleton.

[0069] 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.

[0070] In the above formula (X-4), R g1is 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, k10 is an integer between 0 and 4, and n k2 When is 1, k10 is an integer between 0 and 7. R 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, a halogen atom, or a ring structure formed by combining these groups together. k11 and k12 are each independently an integer of 0 to 4. R g2 and R g3 If there are multiple R g2 and R g3 may be the same or different.

[0071] 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.

[0072] 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.

[0073] Specific examples of the radiation-sensitive onium cation include, but are not limited to, structures of the following formulae (2-2-1) to (2-2-32).

[0074] [ka]

[0075] [ka]

[0076] The second onium salt compound may have a structure in which the above-mentioned anion moiety and the above-mentioned radiation-sensitive onium cation are combined in any manner. Specific examples of the second onium salt compound include, but are not limited to, onium salt compounds represented by the following formulas (2-1) to (2-30):

[0077] [ka]

[0078] [ka]

[0079] The lower limit of the content of the second onium salt compound (the total content when multiple types of second onium salt compounds are included) is preferably 1 part by mass, more preferably 2 parts by mass, even more preferably 3 parts by mass, and particularly preferably 4 parts by mass, per 100 parts by mass of the resin described below. The upper limit of the content is preferably 40 parts by mass, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass. The content of the second onium salt compound is appropriately selected depending on the type of resin used, exposure conditions, desired sensitivity, and the like. This allows for excellent sensitivity, CDU performance, pattern circularity, LWR performance, and pattern rectangularity to be exhibited during resist pattern formation.

[0080] The lower limit of the ratio b / a, by mass, of the content b of the second onium salt compound to the content a of the first onium salt compound is preferably 0.05, more preferably 0.1, even more preferably 0.2, and particularly preferably 0.5.The upper limit of the ratio b / a is preferably 20, more preferably 15, even more preferably 10, and particularly preferably 5.

[0081] (resin) The resin is an aggregate of polymers containing a structural unit having an acid-dissociable group (hereinafter also referred to as "structural unit (I)") (hereinafter also referred to as "base resin"). The "acid-dissociable group" refers to a group that substitutes a hydrogen atom in a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, or the like, and that dissociates under the action of an acid. The radiation-sensitive resin composition has excellent pattern formability because the resin contains the structural unit (I).

[0082] In addition to the structural unit (I), the base resin preferably contains a structural unit (II) containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure, which will be described later, and may contain structural units other than the structural units (I) and (II). Each structural unit will be described below.

[0083] Structural Units The structural unit (I) is a structural unit containing an acid-dissociable group. The structural unit (I) is not particularly limited as long as it contains an acid-dissociable group, and examples thereof 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 improving the pattern formability of the radiation-sensitive resin composition, a structural unit represented by the following formula (3) (hereinafter also referred to as "structural unit (I-1)") is preferred.

[0084] [ka]

[0085] In the above formula (3), R 17 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 18 R is a monovalent hydrocarbon group having 1 to 20 carbon atoms. 19 and R 20 are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded.

[0086] Above R 17 As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (I-1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0087] Above R 18 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula (I) include a 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.

[0088] Above R 18 ~R 20 Examples of the chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula include a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, and a linear or branched unsaturated hydrocarbon group having 1 to 10 carbon atoms.

[0089] Above R 18 ~R 20 The alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is 2 and R 3 Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms in the above, groups corresponding to those having 3 to 20 carbon atoms can be suitably used.

[0090] Above R 18 The monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) is 2 and R 3 Among the monovalent aromatic hydrocarbon groups having 6 to 40 carbon atoms in the above, groups corresponding to 3 to 20 carbon atoms can be suitably used.

[0091] Above R 18 As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms, or an alicyclic hydrocarbon group having 3 to 20 carbon atoms is preferred.

[0092] Above R 19 and R 20 The divalent alicyclic group having 3 to 20 carbon atoms, which is formed by combining chain hydrocarbon groups or alicyclic hydrocarbon groups represented by the formula (I) together with the carbon atoms to which they are 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. Either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group may be used, and 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).

[0093] Among the monocyclic alicyclic hydrocarbon groups, preferred saturated hydrocarbon groups include cyclopentanediyl, cyclohexanediyl, cycloheptanediyl, and cyclooctanediyl groups, while preferred unsaturated hydrocarbon groups include cyclopentenediyl, cyclohexenediyl, cycloheptenediyl, cyclooctenediyl, and cyclodecenediyl groups. Preferred polycyclic alicyclic hydrocarbon groups include bridged alicyclic saturated hydrocarbon groups, such as 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.

[0094] Among these, R 18 is an alkyl group having 1 to 4 carbon atoms, and R 19 and R 20 The alicyclic structure formed by combining these together with the carbon atoms to which they are bonded is preferably a polycyclic or monocyclic cycloalkane structure.

[0095] Examples of the structural unit (I-1) include structural units represented by the following formulas (3-1) to (3-6) (hereinafter also referred to as "structural units (I-1-1) to (I-1-6)").

[0096] [ka]

[0097] In the above formulas (3-1) to (3-6), R 17 ~R 20 has the same meaning as in the above formula (3). i and j each independently represent an integer of 1 to 4. k and l are 0 or 1.

[0098] i and j are preferably 1. 18 R is preferably a methyl group, an ethyl group, an isopropyl group, or a cyclopentyl group. 19 and R 20 As the alkyl group, a methyl group or an ethyl group is preferred.

[0099] The base resin may contain one type of structural unit (I) or a combination of two or more types.

[0100] The lower limit of the content of the structural unit (I) (the total content when multiple types are included) relative to all structural units constituting the base resin is preferably 10 mol%, more preferably 20 mol%, even more preferably 30 mol%, and particularly preferably 35 mol%. The upper limit of the content is preferably 80 mol%, more preferably 75 mol%, even more preferably 70 mol%, and particularly preferably 65 mol%. By keeping the content of the structural unit (I) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0101] [Structural unit (II)] The structural unit (II) is a structural unit containing at least one selected from the group consisting of a lactone structure, a cyclic carbonate structure, and a sultone structure. By further including the structural unit (II), the base resin can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive resin composition. Furthermore, the adhesion between a resist pattern formed from the base resin and a substrate can be improved.

[0102] Examples of the structural unit (II) include structural units represented by the following formulae (T-1) to (T-10).

[0103] [ka]

[0104] In the above formula, R L1 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. L2 ~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.L4 and R L5 and may be combined together to form a divalent alicyclic group having 3 to 8 carbon atoms together with the carbon atoms to which they are bonded. 2 is a single bond or a divalent linking group. X is an oxygen atom or a methylene group. k is an integer of 0 to 3. m is an integer of 1 to 3.

[0105] Above R L4 and R L5 Examples of the divalent alicyclic group having 3 to 8 carbon atoms formed by combining these groups together with the carbon atoms to which they are bonded include R 19 and R 20 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.

[0106] The above 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-.

[0107] Of these, the structural unit (II) is preferably a structural unit containing a lactone structure, more preferably a structural unit containing a norbornane lactone structure, and even more preferably a structural unit derived from norbornane lactone-yl (meth)acrylate.

[0108] The lower limit of the content of the structural unit (II) is preferably 20 mol%, more preferably 30 mol%, and even more preferably 35 mol%, based on all structural units constituting the base resin. The upper limit of the content is preferably 75 mol%, more preferably 70 mol%, and even more preferably 65 mol%. By ensuring that the content of the structural unit (II) falls within the above range, the radiation-sensitive resin composition can further improve lithography performance such as resolution and adhesion of the formed resist pattern to the substrate.

[0109] [Structural unit (III)] The base resin optionally contains other structural units in addition to the structural units (I) and (II). Examples of the other structural units include a structural unit (III) containing a polar group (excluding those corresponding to the structural unit (II)). By further containing the structural unit (III), the base resin can adjust its solubility in a developer, thereby improving the lithography performance, such as resolution, of the radiation-sensitive resin composition. Examples of the polar group include a hydroxy group, a carboxy group, a cyano group, a nitro group, and a sulfonamide group. Among these, a hydroxy group and a carboxy group are preferred, and a hydroxy group is more preferred.

[0110] Examples of the structural unit (III) include structural units represented by the following formula:

[0111] [ka]

[0112] In the above formula, R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0113] When the base resin has the structural unit (III) having the polar group, the lower limit of the content of the structural unit (III) is preferably 5 mol%, more preferably 8 mol%, and even more preferably 10 mol%, based on the total structural units constituting the base resin. The upper limit of the content is preferably 40 mol%, more preferably 35 mol%, and even more preferably 30 mol%. By keeping the content of the structural unit (III) within the above range, the lithography performance, such as resolution, of the radiation-sensitive resin composition can be further improved.

[0114] Structural Unit (IV) In addition to the structural unit (III) having the polar group, the base resin optionally contains a structural unit derived from hydroxystyrene or a structural unit having a phenolic hydroxyl group (hereinafter, both of these are collectively referred to as "structural unit (IV)"). The structural unit (IV) contributes to improving etching resistance and the difference in developer solubility (dissolution contrast) between exposed and unexposed areas. This resin is particularly suitable for pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV. In this case, the resin preferably contains the structural unit (I) in addition to the structural unit (IV).

[0115] The structural units derived from hydroxystyrene are represented, for example, by the following formulas (4-1) to (4-2), and the structural units having a phenolic hydroxyl group are represented, for example, by the following formulas (4-3) to (4-4).

[0116] [ka]

[0117] In the above formulas (4-1) to (4-4), R 11 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group.

[0118] When obtaining the structural unit (IV), 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 (e.g., an acyl group), and then to obtain the structural unit (IV) by deprotecting the phenolic hydroxyl group by hydrolysis.

[0119] In the case of a resin for exposure to radiation having a wavelength of 50 nm or less, the lower limit of the content of the structural unit (IV) is preferably 10 mol %, more preferably 20 mol %, based on all structural units constituting the resin, and the upper limit of the content is preferably 70 mol %, more preferably 60 mol %.

[0120] (Method for synthesizing base resin) The base resin 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.

[0121] Examples of the radical polymerization initiator 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.

[0122] Examples of the solvent used in the polymerization 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, 2-butanone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; Examples of the solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 4-methyl-2-pentanol, etc. These solvents used in the polymerization may be used alone or in combination of two or more.

[0123] 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.

[0124] The molecular weight of the base resin is not particularly limited, but the lower limit of the weight average molecular weight (Mw) in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 1,000, more preferably 2,000, even more preferably 3,000, and particularly preferably 4,000. The upper limit of Mw is preferably 50,000, more preferably 30,000, even more preferably 15,000, and particularly preferably 12,000. If the Mw of the base resin is below the lower limit, the heat resistance of the resulting resist film may be reduced. If the Mw of the base resin is above the upper limit, the developability of the resist film may be reduced.

[0125] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base resin as determined by GPC is usually 1 or more and 5 or less, preferably 1 or more and 3 or less, and more preferably 1 or more and 2 or less.

[0126] The Mw and Mn of the resin in this specification are values ​​measured using gel permeation chromatography (GPC) under the following conditions.

[0127] GPC columns: 2 G2000HXL, 1 G3000HXL, 1 G4000HXL (all manufactured by Tosoh) Column temperature: 40℃ Elution solvent: tetrahydrofuran Flow rate: 1.0mL / min Sample concentration: 1.0% by mass Sample injection volume: 100 μL Detector: differential refractometer Standard material: monodisperse polystyrene

[0128] The content of the base resin is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the total solid content of the radiation-sensitive resin composition.

[0129] (other resins) The radiation-sensitive resin composition of this embodiment may contain, as an additional resin, a resin having a higher mass content of fluorine atoms than the base resin (hereinafter also referred to as a "high-fluorine content resin"). When the radiation-sensitive resin composition contains a high-fluorine content resin, the high-fluorine content resin can be unevenly distributed in the surface layer of the resist film relative to the base resin, thereby improving the water repellency of the surface of the resist film during immersion exposure.

[0130] The high-fluorine content resin preferably has, for example, a structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (V)"), and may also have the structural unit (I) or structural unit (III) of the above-mentioned base resin, as necessary.

[0131] [ka]

[0132] In the above formula (5), R 13 is a hydrogen atom, a methyl group, or a trifluoromethyl group. Lis a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH- or -OCONH-. 14 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.

[0133] Above R 13 As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred.

[0134] Above G L As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (V), a single bond and -COO- are preferred, and -COO- is more preferred.

[0135] Above R 14 Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula 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.

[0136] Above R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (I) include a monocyclic or polycyclic hydrocarbon group having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0137] Above R 14 As the alkyl group, a fluorinated chain hydrocarbon group is preferable, a fluorinated alkyl group is more preferable, and a 2,2,2-trifluoroethyl group, a 1,1,1,3,3,3-hexafluoropropyl group, and a 5,5,5-trifluoro-1,1-diethylpentyl group are even more preferable.

[0138] When the high-fluorine-content resin has the structural unit (V), the content of the structural unit (V) is preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 45 mol% or more, and particularly preferably 50 mol% or more, based on the total structural units constituting the high-fluorine-content resin. Also, the content is preferably 90 mol% or less, more preferably 85 mol% or less, and even more preferably 80 mol% or less. By setting the content of the structural unit (V) within the above range, the mass content of fluorine atoms in the high-fluorine-content resin can be more appropriately adjusted, further promoting uneven distribution of fluorine atoms in the surface layer of the resist film, and as a result, the water repellency of the resist film during immersion exposure can be further improved.

[0139] The high-fluorine-content resin may have a fluorine atom-containing structural unit represented by the following formula (f-2) (hereinafter also referred to as structural unit (VI)) in addition to or instead of the structural unit (V): By having the structural unit (f-2), the high-fluorine-content resin has improved solubility in an alkaline developer, and can suppress the occurrence of development defects.

[0140] [ka]

[0141] The structural unit (VI) is roughly classified into two types: (x) a case having an alkali-soluble group, and (y) a case having a group that dissociates under the action of alkali to increase the solubility in an alkali developer (hereinafter simply referred to as an "alkali-dissociable group"). In both (x) and (y), R C R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. D is a single bond, a hydrocarbon group having 1 to 20 carbon atoms and a valence of (s+1), and R of this hydrocarbon group E Oxygen atom, sulfur atom, -NR dd -, a carbonyl group, -COO-, or -CONH- is bonded to the hydrocarbon group, or a structure in which some of the hydrogen atoms in the hydrocarbon group are substituted with an organic group having a hetero atom. ddis a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s is an integer of 1 to 3.

[0142] When the structural unit (VI) has (x) an alkali-soluble group, R F is a hydrogen atom, and A 1 is an oxygen atom, -COO-* or -SO2O-*. * is R F The binding site of W is shown. 1 A is a single bond, a hydrocarbon group having 1 to 20 carbon atoms, or a divalent fluorinated hydrocarbon group. 1 is an oxygen atom, W 1 is A 1 is a fluorinated hydrocarbon group having a fluorine atom or a fluoroalkyl group on the carbon atom to which R is bonded. E is a single bond or a divalent organic group having 1 to 20 carbon atoms. When s is 2 or 3, multiple R E , W 1 , A 1 and R F may be the same or different. When the structural unit (VI) has (x) an alkali-soluble group, it is possible to increase the affinity for an alkaline developer and suppress development defects. As the structural unit (VI) having (x) an alkali-soluble group, A 1 is an oxygen atom and W 1 It is particularly preferred that is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0143] When the structural unit (VI) has an alkali-dissociable group (y), R F is a monovalent organic group having 1 to 30 carbon atoms, and A 1 is an oxygen atom, -NR aa -, -COO-* or -SO2O-*. R aa is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. * is R F The binding site of W is shown. 1 R is a single bond or a divalent fluorinated hydrocarbon group having 1 to 20 carbon atoms. E A is a single bond or a divalent organic group having 1 to 20 carbon atoms. 1 When is -COO-* or -S02O-*, W 1or R F is A 1 A has a fluorine atom on the carbon atom bonded to or adjacent to A. 1 is an oxygen atom, W 1 , R E is a single bond, and R D R is a hydrocarbon group with 1 to 20 carbon atoms E A carbonyl group is bonded to the end of the R F is an organic group having a fluorine atom. When s is 2 or 3, multiple R E , W 1 , A 1 and R F may be the same or different. When the structural unit (VI) has (y) an alkali-dissociable group, the surface of the resist film changes from hydrophobic to hydrophilic in the alkaline development step. As a result, the affinity to the developer is significantly increased, and development defects can be more efficiently suppressed. As the structural unit (VI) having (y) an alkali-dissociable group, A 1 is -COO-* and R F Or W 1 It is particularly preferred that both of them have a fluorine atom.

[0144] R C As the alkyl group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (VI), a hydrogen atom and a methyl group are preferred, and a methyl group is more preferred.

[0145] R E When is a divalent organic group, it is preferably a group having a lactone structure, more preferably a group having a polycyclic lactone structure, and more preferably a group having a norbornane lactone structure.

[0146] When the high-fluorine-content resin has the structural unit (VI), the content of the structural unit (VI) 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 high-fluorine-content resin. Also, it is preferably 95 mol% or less, more preferably 90 mol% or less, and even more preferably 85 mol% or less. By setting the content of the structural unit (VI) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0147] Other structural units The high fluorine content resin may contain a structural unit having an alicyclic structure represented by the following formula (6) as a structural unit other than the structural units listed above. [ka] (In the above formula (6), 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.

[0148] In the above formula (6), R 2α The monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) is 2 and R 3 Among the monovalent alicyclic hydrocarbon groups having 3 to 40 carbon atoms in the above, groups corresponding to those having 3 to 20 carbon atoms can be suitably used.

[0149] When the high-fluorine-content resin contains the structural unit having the alicyclic structure, the content of the structural unit having the alicyclic structure is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on the total structural units constituting the high-fluorine-content resin, and is preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 50 mol% or less.

[0150] The lower limit of Mw of the high-fluorine-content resin is preferably 1,000, more preferably 2,000, further preferably 3,000, and particularly preferably 5,000. The upper limit of Mw is preferably 50,000, more preferably 30,000, further preferably 20,000, and particularly preferably 15,000.

[0151] The Mw / Mn of the high fluorine content resin is usually 1 or more, more preferably 1.1 or more, and usually 5 or less, preferably 3 or less, more preferably 2 or less, and even more preferably 1.9 or less.

[0152] The content of the high-fluorine content resin is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 1.5 parts by mass or more, relative to 100 parts by mass of the base resin, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0153] By setting the content of the high-fluorine-containing resin within the above range, the high-fluorine-containing resin can be more effectively distributed unevenly on the surface layer of the resist film, thereby further improving the water repellency of the surface of the resist film during immersion lithography. The radiation-sensitive resin composition may contain one or more high-fluorine-containing resins.

[0154] (Method for synthesizing high fluorine content resin) The high fluorine content resin can be synthesized by the same method as the above-mentioned method for synthesizing the base resin.

[0155] (acid diffusion control agent) The radiation-sensitive resin composition may optionally contain an acid diffusion controller. The acid diffusion controller controls the diffusion of acids generated from the first onium salt compound and the second onium salt compound in the resist film upon exposure, thereby suppressing undesirable chemical reactions in unexposed areas. The storage stability of the resulting radiation-sensitive resin composition is also improved. Furthermore, the resolution of the resist pattern is further improved, and changes in the line width of the resist pattern due to variations in the exposure time between exposure and development can be suppressed, resulting in a radiation-sensitive resin composition with excellent process stability.

[0156] Examples of the acid diffusion controller include a compound represented by the following formula (7) (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 (hereinafter also referred to as "nitrogen-containing compound (III)"), an amide group-containing compound, a urea compound, and a nitrogen-containing heterocyclic compound.

[0157] [ka]

[0158] In the above formula (7), R 22 , R 23 and R 24 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.

[0159] Examples of the nitrogen-containing compound (I) include monoalkylamines such as n-hexylamine; dialkylamines such as di-n-butylamine; trialkylamines such as triethylamine; and aromatic amines such as aniline.

[0160] Examples of the nitrogen-containing compound (II) include ethylenediamine and N,N,N',N'-tetramethylethylenediamine.

[0161] Examples of the nitrogen-containing compound (III) include polyamine compounds such as polyethyleneimine and polyallylamine; polymers such as dimethylaminoethylacrylamide; and the like.

[0162] 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.

[0163] Examples of the urea compound include urea, methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3,3-tetramethylurea, 1,3-diphenylurea, and tributylthiourea.

[0164] Examples of the nitrogen-containing heterocyclic compound include pyridines such as pyridine and 2-methylpyridine; morpholines such as N-propylmorpholine and N-(undecylcarbonyloxyethyl)morpholine; pyrazine, pyrazole, and the like.

[0165] Furthermore, as the nitrogen-containing organic compound, a compound having an acid-dissociable group can also be used. Examples of such nitrogen-containing organic 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, Nt-butoxycarbonyl-4-acetoxypiperidine, and Nt-amyloxycarbonyl-4-hydroxypiperidine.

[0166] Alternatively, a radiation-sensitive weak acid generator that generates a weak acid upon exposure can be suitably used as the acid diffusion controller. The acid generated by the radiation-sensitive acid generator is a weak acid that does not induce dissociation of the acid-dissociable group in the resin under conditions that dissociate the acid-dissociable group. In this specification, "dissociation" of the acid-dissociable group refers to dissociation upon post-exposure baking at 110°C for 60 seconds.

[0167] Examples of the radiation-sensitive weak acid generator include onium salt compounds that decompose upon exposure to light and lose their ability to control acid diffusion. Examples of the onium salt compound include sulfonium salt compounds represented by the following formula (8-1) and iodonium salt compounds represented by the following formula (8-2).

[0168] [ka]

[0169] In the above formula (8-1) and formula (8-2), J + is a sulfonium cation, and U + is the iodonium cation. + Examples of the sulfonium cation represented by the formula (X-1) to (X-3) include the sulfonium cation represented by the formula (X-1) to (X-3), and U + Examples of the iodonium cation represented by the formula (X-4) to (X-5) include the iodonium cation represented by the formula (X-4) to (X-5). - and Q - are each independently OH - , R α -COO - , R α -SO3 - It is an anion represented by R α R is a monovalent chain organic group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure. α The monovalent chain organic group having 1 to 40 carbon atoms includes R 1 A monovalent chain organic group having 1 to 40 carbon atoms and represented by the following formula can be suitably used. αThe monovalent organic group having 3 to 40 carbon atoms is R B A monovalent organic group having 3 to 40 carbon atoms and containing a cyclic structure represented by the following formula can be suitably used.

[0170] Examples of the radiation-sensitive weak acid generator include compounds represented by the following formula:

[0171] [ka]

[0172] [ka]

[0173] Of these, the radiation-sensitive weak acid generator is preferably a sulfonium salt, more preferably a triarylsulfonium salt, and even more preferably triphenylsulfonium salicylate or triphenylsulfonium 10-camphorsulfonate.

[0174] The lower limit of the content of the acid diffusion controller is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, even more preferably 1 part by mass, and particularly preferably 2 parts by mass, relative to 100 parts by mass of the resin, and the upper limit of the content is preferably 20 parts by mass, more preferably 15 parts by mass, and even more preferably 10 parts by mass.

[0175] By setting the content of the acid diffusion controller within the above range, the lithography performance of the radiation-sensitive resin composition can be further improved. The radiation-sensitive resin composition may contain one or more types of acid diffusion controller.

[0176] (solvent) The radiation-sensitive resin composition according to this embodiment contains a solvent. The solvent is not particularly limited as long as it can dissolve or disperse at least Compound (1) and the resin, as well as the radiation-sensitive acid generator and other components that may be optionally contained therein.

[0177] Examples of the solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0178] Examples of alcohol-based solvents include: Monoalcohol solvents having 1 to 18 carbon atoms, such as iso-propanol, 4-methyl-2-pentanol, 3-methoxybutanol, n-hexanol, 2-ethylhexanol, furfuryl alcohol, cyclohexanol, 3,3,5-trimethylcyclohexanol, and diacetone alcohol; polyhydric alcohol solvents having 2 to 18 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, and tripropylene glycol; Examples of suitable polyhydric alcohol solvents include partially etherified polyhydric alcohol solvents in which some of the hydroxy groups of the above polyhydric alcohol solvents have been etherified.

[0179] Examples of ether solvents include: dialkyl ether solvents such as diethyl ether, dipropyl ether, and dibutyl ether; cyclic ether solvents such as tetrahydrofuran and tetrahydropyran; Aromatic ring-containing ether solvents such as diphenyl ether and anisole (methyl phenyl ether); Examples of the polyhydric alcohol solvent include polyhydric alcohol ether solvents obtained by etherifying the hydroxy groups of the above polyhydric alcohol solvents.

[0180] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, and methylcyclohexanone: Examples include 2,4-pentanedione, acetonylacetone, and acetophenone.

[0181] Examples of the amide solvent include cyclic amide solvents such as N,N'-dimethylimidazolidinone and N-methylpyrrolidone; Examples of the solvent include chain amide solvents such as N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, and N-methylpropionamide.

[0182] Examples of ester solvents include: Monocarboxylic acid ester solvents such as n-butyl acetate and ethyl lactate; polyhydric alcohol partial ether acetate solvents such as diethylene glycol mono-n-butyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate; Lactone solvents such as γ-butyrolactone and valerolactone; Carbonate solvents such as diethyl carbonate, ethylene carbonate, and propylene carbonate; Examples of the solvent include polycarboxylic acid diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

[0183] Examples of hydrocarbon solvents include Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, di-isopropylbenzene, and n-amylnaphthalene.

[0184] Among these, ester-based solvents and ketone-based solvents are preferred, polyhydric alcohol partial ether acetate-based solvents, cyclic ketone-based solvents and lactone-based solvents are more preferred, and propylene glycol monomethyl ether acetate, cyclohexanone and γ-butyrolactone are even more preferred. The radiation-sensitive resin composition may contain one or more solvents.

[0185] (Other optional ingredients) The radiation-sensitive resin composition may contain other optional components in addition to the above components. Examples of the other optional components include a crosslinking agent, a localization promoter, a surfactant, an alicyclic skeleton-containing compound, and a sensitizer. These other optional components may be used alone or in combination of two or more.

[0186] <Method for preparing radiation-sensitive resin composition> The radiation-sensitive resin composition can be prepared, for example, by mixing a first onium salt compound, a second onium salt compound, a resin, and optionally a high-fluorine-content resin, and a solvent in a predetermined ratio. After mixing, the radiation-sensitive resin composition is preferably filtered, for example, through a filter having a pore size of about 0.05 μm to 0.40 μm. The solids concentration of the radiation-sensitive resin composition is usually 0.1% to 50% by mass, preferably 0.5% to 30% by mass, and more preferably 1% to 20% by mass.

[0187] The lower limit of the viscosity of the radiation-sensitive resin composition is preferably 1.0 mPa·s, more preferably 1.2 mPa·s, and even more preferably 1.4 mPa·s, and the upper limit of the viscosity is preferably 15 mPa·s, more preferably 10 mPa·s, and even more preferably 5 mPa·s.

[0188] <Pattern formation method> A pattern forming method according to one embodiment of the present invention includes: a step (1) of directly or indirectly applying the radiation-sensitive resin composition onto a substrate to form a resist film (hereinafter also referred to as a "resist film forming step"); a step (2) of exposing the resist film to light (hereinafter also referred to as the "exposure step"); The method includes a step (3) of developing the exposed resist film (hereinafter also referred to as the "developing step").

[0189] According to the above-described resist pattern forming method, a high-quality resist pattern can be formed because the above-described radiation-sensitive resin composition is used, which is capable of forming a resist film that is excellent in sensitivity in the exposure step, LWR performance, CDU performance, pattern rectangularity, and etching resistance. Each step will be described below.

[0190] [Resist film formation process] In this step (step (1) above), a resist film is formed from the radiation-sensitive resin composition. Examples of substrates on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide wafers, and aluminum-coated wafers. Alternatively, an organic or inorganic anti-reflective coating, such as those disclosed in Japanese Patent Publication No. 6-12452 or Japanese Patent Application Laid-Open No. 59-93448, may be formed on the substrate. Examples of coating methods for forming the resist film include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed, if necessary, to volatilize the solvent in the coating film. The PB temperature is typically 60°C to 140°C, and preferably 80°C to 120°C. The PB time is typically 5 to 600 seconds, and preferably 10 to 300 seconds.

[0191] The lower limit of the thickness of the resist film to be formed is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm. The upper limit of the thickness is preferably 500 nm, more preferably 400 nm, and even more preferably 300 nm. In particular, when a thick resist film is exposed to ArF excimer laser light in the exposure step described below, the lower limit of the thickness may be 100 nm, 150 nm, or 200 nm.

[0192] When performing immersion exposure, regardless of whether the radiation-sensitive resin composition contains a water-repellent polymer additive such as a high-fluorine-content resin, a protective film for immersion exposure that is insoluble in the immersion liquid may be provided on the formed resist film to prevent direct contact between the immersion liquid and the resist film. The protective film for immersion exposure may be either a solvent-removable protective film that is removed with a solvent before the development step (see, for example, JP-A No. 2006-227632), or a developer-removable protective film that is removed simultaneously with development in the development step (see, for example, WO2005-069076 and WO2006-035790). However, from the viewpoint of throughput, it is preferable to use a developer-removable protective film for immersion exposure.

[0193] When the next exposure step is carried out using radiation with a wavelength of 50 nm or less, it is preferable to use a resin having the structural units (I) and (IV) as the base resin in the composition.

[0194] [Exposure process] In this step (step (2) above), the resist film formed in step (1), the resist film formation step, is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). The radiation used for exposure may be, depending on the line width of the desired pattern, electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet), X-rays, and gamma rays; or charged particle beams such as electron beams and alpha rays. Among these, far ultraviolet light, electron beams, and EUV are preferred, with ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV being more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, being even more preferred.

[0195] When exposure is performed by immersion exposure, examples of the immersion liquid used include water and fluorine-based inert liquids. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has as small a temperature coefficient of refractive index as possible so as to minimize distortion of the optical image projected onto the film. However, particularly when the exposure light source is an ArF excimer laser (wavelength 193 nm), water is preferred for its availability and ease of handling, in addition to the above considerations. When water is used, a small proportion of an additive that reduces the surface tension of water and increases its surfactant power may be added. This additive is preferably one that does not dissolve the resist film on the wafer and has negligible effect on the optical coating on the underside of the lens. Distilled water is preferred as the water used.

[0196] After the exposure, post-exposure baking (PEB) is preferably performed to promote dissociation of acid-dissociable groups in the resin or the like in the exposed portions of the resist film by the acid generated from the radiation-sensitive acid generator upon exposure. This PEB results in a difference in solubility in a developer between the exposed and unexposed portions. The PEB temperature is usually 50°C to 180°C, preferably 80°C to 130°C. The PEB time is usually 5 seconds to 600 seconds, preferably 10 seconds to 300 seconds.

[0197] [Development process] In this step (step (3) above), the resist film exposed in the exposure step (step (2) above) is developed. This allows a predetermined resist pattern to be formed. After development, the resist film is generally washed with a rinse liquid such as water or alcohol, and then dried.

[0198] In the case of alkaline development, the developer used for the development may be, for example, an alkaline aqueous solution containing at least one alkaline compound 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, or 1,5-diazabicyclo-[4.3.0]-5-nonene. Among these, a TMAH aqueous solution is preferred, and a 2.38 mass % TMAH aqueous solution is more preferred.

[0199] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, as well as solvents containing an organic solvent. Examples of the organic solvent include one or more of the solvents listed above as solvents for the radiation-sensitive resin composition. Among these, ether solvents, ester solvents, and ketone solvents are preferred. As ether solvents, glycol ether solvents are preferred, with ethylene glycol monomethyl ether and propylene glycol monomethyl ether being more preferred. As ester solvents, acetate ester solvents are preferred, with n-butyl acetate and amyl acetate being more preferred. As ketone solvents, chain ketones are preferred, with 2-heptanone being more preferred. The content of the organic solvent in the developer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 99% by mass or more. Examples of components other than the organic solvent in the developer include water and silicone oil.

[0200] As mentioned above, the developer may be either an alkaline developer or an organic solvent developer, and can be appropriately selected depending on whether the desired pattern is a positive or negative pattern.

[0201] 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 by scanning a developer dispensing nozzle at a constant speed over a substrate that is rotating at a constant speed (dynamic dispense method). [Example]

[0202] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Measurement methods for various physical properties are shown below.

[0203] [Weight average molecular weight (Mw) and number average molecular weight (Mn)] The Mw and Mn of the polymer were measured under the conditions described above, and the dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0204] [ 13 C-NMR analysis] polymer 13 C-NMR analysis was carried out using a nuclear magnetic resonance spectrometer (JNM-Delta400 manufactured by JEOL Ltd.).

[0205] <Resin synthesis> The monomers used in the synthesis of each resin in each example and comparative example are shown below. In the following synthesis examples, unless otherwise specified, parts by mass refer to a value where the total mass of the monomers used is taken as 100 parts by mass, and mol % refers to a value where the total number of moles of the monomers used is taken as 100 mol %.

[0206] [ka]

[0207] [Synthesis Example 1] (Synthesis of Resin (A-1)) Monomer (M-1), monomer (M-2), and monomer (M-13) were dissolved in 2-butanone (200 parts by mass) to a molar ratio of 40 / 15 / 45 (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 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 using water. The cooled polymerization solution was poured into methanol (2,000 parts by mass), and the precipitated white powder was filtered off. The filtered white powder was washed twice with methanol, filtered, and dried at 50°C for 24 hours to obtain a white powdery resin (A-1) (yield: 83%). The Mw of the resin (A-1) was 8,800, and the Mw / Mn was 1.50. 13 As a result of C-NMR analysis, the contents of the structural units derived from (M-1), (M-2) and (M-13) were 41.3 mol %, 13.8 mol % and 44.9 mol %, respectively.

[0208] [Synthesis Examples 2 to 11] (Synthesis of Resin (A-2) to Resin (A-11)) Resins (A-2) to (A-11) were synthesized in the same manner as in Synthesis Example 1, except that the types and blending ratios of monomers shown in Table 1 below were used. The content (mol %) of each structural unit, the yield (%), and physical properties (Mw and Mw / Mn) of the resulting resins are also shown in Table 1 below. In Table 1 below, "-" indicates that the corresponding monomer was not used (the same applies to the following tables).

[0209] [Table 1]

[0210] (Synthesis of Resin (A-12)) Monomer (M-1) and monomer (M-18) were dissolved in 1-methoxy-2-propanol (200 parts by mass) at a molar ratio of 50 / 50 (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 solidify the resin. The resulting solid was filtered and dried at 50°C for 13 hours to obtain a white powdery resin (A-12) (yield: 79%). The Mw of resin (A-12) 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 (M-1) and (M-18) were 51.3 mol % and 48.7 mol %, respectively.

[0211] [Synthesis Examples 13 to 15] (Synthesis of Resin (A-13) to Resin (A-15)) Resins (A-13) to (A-15) were synthesized in the same manner as in Synthesis Example 12, except that the types and blending ratios of monomers shown in Table 2 below were used. The alkali-dissociable groups of all monomers providing structural unit (IV) were hydrolyzed to phenolic hydroxyl groups. The content (mol %) of each structural unit, the yield (%), and physical properties (Mw and Mw / Mn) of the resulting resins are also shown in Table 2 below.

[0212] [Table 2]

[0213] [Synthesis Example 16] (Synthesis of high fluorine content resin (F-1)) Monomer (M-1) and monomer (M-20) 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 polymerized 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 content resin (F-1) (yield: 69%). The high fluorine content resin (F-1) had an Mw of 6,000 and an Mw / Mn ratio of 1.62. 13 As a result of C-NMR analysis, the content ratios of the structural units derived from (M-1) and (M-20) were 19.9 mol % and 80.1 mol %, respectively.

[0214] [Synthesis Examples 17-20] (Synthesis of High Fluorine Content Resin (F-2) to High Fluorine Content Resin (F-5)) High fluorine content resins (F-2) to (F-5) were synthesized in the same manner as in Synthesis Example 16, except for using monomers of the types and blending ratios shown in Table 3 below. The content (mol %) of each structural unit, yield (%) and physical properties (Mw and Mw / Mn) of the obtained high fluorine content resins are also shown in Table 3 below.

[0215] [Table 3]

[0216] <Synthesis of first onium salt compound B> [Synthesis Example 21] (Synthesis of Compound (B-1)) Compound (B-1) was synthesized according to the following synthesis scheme.

[0217] [ka]

[0218] 20.0 mmol of iodine, 40.0 mmol of tert-butylbenzene, 40.0 mmol of metachloroperbenzoic acid, 40.0 mmol of tosylic acid monohydrate, and 100 g of chloroform were added to a reaction vessel and stirred at room temperature for 24 hours. After dilution with water, the mixture was extracted with methylene chloride and the organic layer was separated. The resulting organic layer was washed with saturated aqueous sodium chloride. After drying with sodium sulfate, the solvent was removed by distillation, and the mixture was recrystallized and purified with diethyl ether to obtain an iodonium salt compound in good yield.

[0219] The iodonium salt was added with 20.0 mmol of 1,4-thioxane, 2.00 mmol of copper (II) acetate, and 50 g of chloroform, and the mixture was stirred for 24 hours under ice cooling. After removing impurities by filtration through Celite, the solvent was distilled off, and the residue was purified by column chromatography to obtain the compound (B-1-a) represented by the above formula (B-1-a) in good yield.

[0220] To the salt represented by the above formula (B-1-a), 20.0 mmol of potassium nonafluoro-1-butanesulfonate was added, and a mixture of water and dichloromethane (1:1 (mass ratio)) was added to prepare a 0.5 M solution. After vigorously stirring at room temperature for 3 hours, dichloromethane was added for extraction, and the organic layer was separated. The obtained organic layer was dried over sodium sulfate, the solvent was distilled off, and the solution was purified by column chromatography to obtain compound (B-1) represented by the above formula (B-1) in good yield.

[0221] [Synthesis Examples 22 to 27] (Synthesis of Compounds (B-2) to (B-7)) First onium salt compounds represented by the following formulae (B-2) to (B-7) were synthesized in the same manner as in Synthesis Example 21, except that the raw materials and precursors were changed as appropriate.

[0222] [ka]

[0223] [Synthesis Example 28] (Synthesis of Compound (B-8)) Compound (B-8) was synthesized according to the following synthesis scheme.

[0224] [ka]

[0225] A 1M solution was prepared by adding a mixture of acetonitrile and water (1:1 (mass ratio)) to 20.0 mmol of 6-bromo-5,5,6,6-tetrafluorohexan-1-ol, followed by the addition of 40.0 mmol of sodium dithionite and 60.0 mmol of sodium bicarbonate, and the mixture was allowed to react at 70°C for 4 hours. After extraction with acetonitrile and the solvent was distilled off, a 0.5M solution was prepared by adding a mixture of acetonitrile and water (3:1 (mass ratio)). 60.0 mmol of aqueous hydrogen peroxide and 2.00 mmol of sodium tungstate were added, and the mixture was heated and stirred at 50°C for 12 hours. A sodium sulfonate salt compound was obtained by extraction with acetonitrile and the distillation of the solvent. 20.0 mmol of the salt represented by the above formula (B-1-a) was added to the sodium sulfonate salt compound, and a 0.5M solution was prepared by adding a mixture of water and dichloromethane (1:3 (mass ratio)). After vigorously stirring for 3 hours at room temperature, dichloromethane was added for extraction, and the organic layer was separated. The organic layer was dried over sodium sulfate, the solvent was removed by distillation, and the onium salt was purified by column chromatography to obtain the onium salt in good yield.

[0226] The onium salt was added with 20.0 mmol of lauric acid, 30.0 mmol of dicyclohexylcarbodiimide, and 50 g of methylene chloride, and stirred at room temperature for 3 hours. After dilution with water, the mixture was extracted with methylene chloride and the organic layer was separated. The resulting organic layer was washed with a saturated aqueous sodium chloride solution 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 compound (B-8) represented by formula (B-8) in good yield.

[0227] [Synthesis Examples 29-37] (Synthesis of compounds (B-9) to (B-17)) First onium salt compounds represented by the following formulae (B-9) to (B-17) were synthesized in the same manner as in Synthesis Example 28, except that the raw materials and precursors were changed as appropriate.

[0228] [ka]

[0229] [Onium Salts Other Than the First Onium Salt Compounds (B-1) to (B-17)] b-1 to b-5: Compounds represented by the following formulas (b-1) to (b-5) (hereinafter, the compounds represented by formulas (b-1) to (b-5) may be referred to as "compound (b-1)" to "compound (b-5)", respectively).

[0230] [ka]

[0231] [Second onium salt compounds (C-1) to (C-15)] (C-1) to (C-15): Compounds represented by the following formulas (C-1) to (C-15) (hereinafter, the compounds represented by formulas (C-1) to (C-15) may be referred to as "compound (C-1)" to "compound (C-15)", respectively.)

[0232] [ka]

[0233] [[D] Acid diffusion control agent] D-1 to D-10: Compounds represented by the following formulas (D-1) to (D-10), and d-1 to d-9: Compounds represented by the following formulas (d-1) to (d-9):

[0234] [ka]

[0235] [ka]

[0236] [[E]Solvent] E-1: Propylene glycol monomethyl ether acetate E-2: Propylene glycol monomethyl ether E-3: γ-butyrolactone E-4: Ethyl lactate

[0237] [Preparation of Positive Radiation-Sensitive Resin Composition for ArF Exposure] [Example 1] A radiation-sensitive resin composition (J-1) was prepared by mixing 100 parts by mass of (A-1) as the resin [A], 6.0 parts by mass of (B-1) as the first onium salt compound [B], 6.0 parts by mass of (C-1) as the second onium salt compound [C], 6.0 parts by mass of (D-1) as the acid diffusion controller [D], 3.0 parts by mass (solids content) of (F-1) as the high fluorine content resin [F], and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent [E], and filtering the mixture through a membrane filter having a pore size of 0.2 μm.

[0238] [Examples 2 to 65 and Comparative Examples 1 to 10] Radiation-sensitive resin compositions (J-2) to (J-65) and (CJ-1) to (CJ-10) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Tables 4-1 and 4-2 below were used.

[0239]

Table 4-1

[0240]

Table 4-2

[0241] [Viscosity Measurement] The viscosity (mPa·s) of the radiation-sensitive resin composition was measured at 25 °C using a Cannon-Fenske viscometer.

[0242] [Formation of Resist Pattern Using Positive-Type Radiation-Sensitive Resin Composition for ArF Exposure] On a 12-inch silicon wafer, using a spin coater (「CLEAN TRACK ACT12」 of Tokyo Electron Limited), a composition for forming an anti-reflection film for the lower layer (「ARC66」 of Brewer Science, Inc.) was applied, and then heated at 205 °C for 60 seconds to form an anti-reflection film for the lower layer with an average thickness of 100 nm. On this anti-reflection film for the lower layer, the prepared positive-type radiation-sensitive resin composition for ArF exposure 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 160 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 Annular (σ = 0.8 / 0.6), exposure was performed through a mask pattern of contact holes with 80 nm holes and 150 nm pitch. 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 (contact hole pattern with 80 nm holes and 150 nm pitch).

[0243] [Evaluation] The resist patterns formed using the positive radiation-sensitive resin composition for ArF exposure were evaluated for sensitivity, CDU performance, and pattern circularity according to the following methods. The results are shown in Tables 5-1 and 5-2. The resist patterns were measured using a scanning electron microscope (CG-5000, manufactured by Hitachi High-Technologies Corporation).

[0244] [sensitivity] In forming a resist pattern using the positive radiation-sensitive resin composition for ArF exposure, the exposure dose for forming 80 nm holes and contact holes with a pitch of 150 nm 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 are considered "good" and 30mJ / cm 2 If it exceeded this, it was rated as "poor".

[0245] [CDU performance] Contact holes with an 80 nm hole pitch and a 150 nm pitch were 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 variation in the contact holes 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 CDU (nm). The smaller the CDU value, the smaller the hole roughness and the better it was. CDU performance was evaluated as "good" when it was less than 5.0 nm, and "poor" when it was 5.0 nm or greater.

[0246] [Pattern circularity] The 80 nm holes and 150 nm pitch contact holes formed by irradiating with the optimal exposure dose determined in the sensitivity evaluation above were observed using the above scanning electron microscope, and their vertical and horizontal sizes were measured. If the ratio of vertical size to horizontal size was 0.95 or more and less than 1.05, it was rated as "A" (very good); if it was 0.90 or more and less than 0.95, or 1.05 or more and less than 1.10, it was rated as "B" (good); and if it was less than 0.90 or more than 1.10, it was rated as "C" (poor).

[0247] [Table 5-1]

[0248] [Table 5-2]

[0249] As is clear from the results in Tables 5-1 and 5-2, when the radiation-sensitive resin compositions of the Examples were used for ArF exposure, they exhibited good sensitivity, CDU performance, and pattern circularity, whereas the Comparative Examples were inferior in each property to the Examples. Therefore, when the radiation-sensitive resin compositions of the Examples were used for ArF exposure, resist patterns with high sensitivity and good CDU performance and pattern circularity could be formed.

[0250] [Preparation of Positive-Working Radiation-Sensitive Resin Composition for Extreme Ultraviolet (EUV) Exposure] [Example 66] A radiation-sensitive resin composition (J-66) was prepared by mixing 100 parts by mass of (A-12) as a resin [A], 9.0 parts by mass of (B-1) as a first onium salt compound [B], 9.0 parts by mass of (C-1) as a second onium salt compound [C], 3.0 parts by mass of (D-5) as an acid diffusion controller [D], 3.0 parts by mass (solids content) of (F-5) as a high fluorine content resin [F], and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as a solvent, and filtering the mixture through a membrane filter having a pore size of 0.2 μm.

[0251] [Examples 67 to 82 and Comparative Examples 11 to 20] Radiation-sensitive resin compositions (J-67) to (J-82) and (CJ-11) to (CJ-20) were prepared in the same manner as in Example 66, except that the types and amounts of each component shown in Table 6 below were used.

[0252] [Table 6]

[0253] [Viscosity Measurement] The viscosity (mPa·s) of the radiation-sensitive resin composition was measured under the condition of 25 °C using a Canon Fenske viscometer.

[0254] [Formation of Resist Pattern Using EUV Exposure Positive-Type Radiation-Sensitive Resin Composition] On a 12-inch silicon wafer, using a spin coater ("CLEAN TRACK ACT12" of Tokyo Electron Limited), after applying a composition for forming an anti-reflection film for the lower layer ("ARC66" of Brewer Science), it was heated at 205 °C for 60 seconds to form an anti-reflection film for the lower layer with an average thickness of 105 nm. On this anti-reflection film for the lower layer, the prepared EUV exposure radiation-sensitive resin composition was applied using the above spin coater, and PB was performed at 130 °C for 60 seconds. Then, by cooling at 23 °C for 30 seconds, a resist film with an average thickness of 55 nm was formed. Next, this resist film was exposed using an EUV exposure apparatus ("NXE3300" of ASML) with NA = 0.33, illumination condition: Conventional s = 0.89, and mask: imecDEFECT32FFR02. After exposure, PEB was performed at 120 °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 (32 nm line and space pattern).

[0255] [Evaluation] Regarding the resist pattern formed using the above EUV exposure positive-type radiation-sensitive resin composition, the sensitivity, LWR performance, and pattern rectangularity were evaluated according to the following methods. The results are shown in Table 7 below. For the length measurement of the resist pattern, a scanning electron microscope ("CG-5000" of Hitachi High-Technologies Corporation) was used.

[0256] [Sensitivity] In forming a resist pattern using the positive-tone radiation-sensitive resin composition for EUV exposure, the exposure dose for forming a 32 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 are considered "good" and 30mJ / cm 2 If it exceeded this, it was rated as "poor".

[0257] [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.

[0258] Pattern Rectangularity The 32 nm line-and-space resist pattern formed by irradiating with the optimum exposure dose determined in the sensitivity evaluation was observed using the scanning electron microscope, 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.

[0259] [Table 7]

[0260] As is clear from the results in Table 7, the radiation-sensitive resin compositions of the Examples exhibited good sensitivity, LWR performance, and pattern rectangularity when used for EUV exposure, whereas the Comparative Examples were inferior to the Examples in each of the properties.

[0261] [Preparation of a negative-tone radiation-sensitive resin composition for ArF exposure, and formation and evaluation of a resist pattern using this composition] [Example 83] A radiation-sensitive resin composition (J-83) was prepared by mixing 100 parts by mass of (A-5) as the resin [A], 6.0 parts by mass of (B-1) as the first onium salt compound [B], 6.0 parts by mass of (C-7) as the second onium salt compound [C], 6.0 parts by mass of (D-1) as the acid diffusion controller [D], 3.0 parts by mass (solids content) of (F-4) as the high fluorine content resin [F], and 3,230 parts by mass of a mixed solvent of (E-1) / (E-2) / (E-3) as the solvent [E], and filtering the mixture through a membrane filter having a pore size of 0.2 μm.

[0262] 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 100 nm. The negative radiation-sensitive resin composition for ArF exposure (J-83) prepared above was then coated onto the bottom anti-reflective coating using the spin coater, followed by pre-baking at 100°C for 60 seconds. The wafer was then cooled at 23°C for 30 seconds to form a resist film with an average thickness of 90 nm. This resist film was then exposed to light using an ArF excimer laser immersion exposure system (ASML's TWINSCAN XT-1900i) under optical conditions of NA = 1.35 and annular (σ = 0.8 / 0.6) through a mask pattern with 40 nm holes and a 105 nm pitch. After the exposure, PEB (post-exposure bake) was performed for 60 seconds at 100° C. Then, the resist film was developed using n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (40 nm holes, 105 nm pitch).

[0263] The resist pattern formed using the negative-tone radiation-sensitive resin composition for ArF exposure was evaluated in the same manner as the resist pattern formed using the positive-tone radiation-sensitive resin composition for ArF exposure. As a result, the radiation-sensitive resin composition of Example 83 exhibited good sensitivity, CDU performance, and pattern circularity, even when a negative-tone resist pattern was formed by ArF exposure.

[0264] [Preparation of a negative-tone radiation-sensitive resin composition for EUV exposure, and formation and evaluation of a resist pattern using this composition] [Example 84] A radiation-sensitive resin composition (J-84) was prepared by mixing 100 parts by mass of (A-15) as a resin [A], 9.0 parts by mass of (B-1) as a first onium salt compound [B], 9.0 parts by mass of (C-11) as a second onium salt compound [C], 3.0 parts by mass of (D-5) as an acid diffusion controller [D], 3.0 parts by mass (solids content) of (F-5) as a high fluorine content resin [F], and 6,110 parts by mass of a mixed solvent of (E-1) / (E-4) as a solvent, and filtering the mixture through a membrane filter having a pore size of 0.2 μm.

[0265] 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. The negative radiation-sensitive resin composition for EUV exposure (J-84) prepared above 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: imecDEFECT32FFR15. After exposure, post-baking was performed at 120°C for 60 seconds. Thereafter, the resist film was developed with n-butyl acetate as an organic solvent developer and dried to form a negative resist pattern (40 nm holes, 105 nm pitch).

[0266] The resist pattern formed using the negative-tone radiation-sensitive resin composition for EUV exposure was evaluated in the same manner as the resist pattern formed using the positive-tone radiation-sensitive resin composition for EUV exposure. As a result, the radiation-sensitive resin composition of Example 84 exhibited good sensitivity, LWR performance, and pattern rectangularity, even when a negative-tone resist pattern was formed by EUV exposure. [Industrial Applicability]

[0267] 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 is excellent in CDU performance, pattern circularity, LWR performance, and pattern rectangularity. Therefore, these compositions can be suitably used in the fabrication processes of semiconductor devices, which are expected to become increasingly miniaturized in the future.

Claims

1. a first onium salt compound represented by the following formula (1); a second onium salt compound represented by the following formula (2); a resin including a structural unit having an acid-dissociable group; Solvent and A radiation-sensitive resin composition comprising: 【Chemistry 1】 (In formula (1), R １ is a monovalent chain organic group having 1 to 40 carbon atoms. R ２ and R ３ are each independently a hydrogen atom, a fluorine atom, a monovalent hydrocarbon group, or a monovalent fluorinated hydrocarbon group. ２ and R ３ If there are multiple R ２ and R ３ are the same or different. R ｆ１１ and R ｆ１２ are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group. ｆ１１ and R ｆ１２ If there are multiple R ｆ１１ and R ｆ１２ are the same or different. m １ and m ２ are each independently an integer of 1 to 4. R ４ , R ５ , R ６ and R ７ are each independently a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms. ４ , R ５ , R ６ and R ７ If there are multiple R ４ , R ５ , R ６ and R ７ are the same or different. R ８ If there is one ８ is a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms. ８ If there are multiple R ８ are each independently a hydrogen atom, a hydroxy group, a halogen atom, or a monovalent organic group having 1 to 20 carbon atoms, or a plurality of R ８ Two of these are combined with each other to form a cyclic structure having 5 to 20 ring members, which is formed together with the two carbon atoms of the benzene ring in formula (1) to which they are bonded. n １ and n ２ are each independently an integer of 1 to 4. n ３ is an integer from 1 to 5. 【Chemistry 2】 (In formula (2), R Ｂ is a monovalent organic group containing a cyclic structure and having 3 to 40 carbon atoms. R ｆ２１ and R ｆ２２ are each independently a fluorine atom or a monovalent fluorinated hydrocarbon group. ｆ２１ and R ｆ２２ If there are multiple R ｆ２１ and R ｆ２２ are the same or different. p is an integer of 1 to 4. Z ＋ is a monovalent radiation-sensitive onium cation.

2. In the above formula (1), R ２ , R ３ , R ｆ１１ and R ｆ１２ 2. The radiation-sensitive resin composition according to claim 1, wherein the total number of fluorine atoms in

3. In the above formula (1), R １ 2. The radiation-sensitive resin composition according to claim 1, wherein the monovalent chain organic group having 1 to 40 carbon atoms represented by the formula: is a straight-chain organic group having 1 to 40 carbon atoms.

4. In the above formula (1), R １ the monovalent chain organic group having 1 to 40 carbon atoms, represented by the formula (I), is a chain hydrocarbon group having 1 to 40 carbon atoms, a group in which at least one of an ether bond and a carbonyl group is incorporated into the chain or at an end of the chain of the chain hydrocarbon group having 1 to 40 carbon atoms, or a group in which some or all of the hydrogen atoms of a fluorinated chain hydrocarbon group having 1 to 40 carbon atoms have been substituted with fluorine atoms.

5. In the above formula (1), m １ and m ２ The radiation-sensitive resin composition according to claim 1 , wherein each of the formulas is independently 1 or 2.

6. In the above formula (1), R ８ is a chain hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 6 to 12 carbon atoms, a fluorine atom, or a fluorinated hydrocarbon group having 1 to 10 carbon atoms.

7. In the above formula (2), R Ｂ 2. The radiation-sensitive resin composition according to claim 1, wherein the cyclic structure contained in the formula (I) is an alicyclic polycyclic structure having 6 to 14 carbon atoms.

8. 2. The radiation-sensitive resin composition according to claim 1, wherein the monovalent radiation-sensitive onium cation in the formula (2) is a sulfonium cation or an iodonium cation.

9. 2. The radiation-sensitive resin composition according to claim 1, wherein the content of the first onium salt compound is 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the resin.

10. 2. The radiation-sensitive resin composition according to claim 1, wherein the ratio b / a, on a mass basis, of the content b of the second onium salt compound to the content a of the first onium salt compound is 0.05 or more and 20 or less.

11. 2. The radiation-sensitive resin composition according to claim 1, wherein the structural unit having an acid-dissociable group is represented by the following formula (3): 【Transformation 3】 (In the formula, R １７ is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. R １８ is a monovalent hydrocarbon group having 1 to 20 carbon atoms. R １９ and R ２０ are each independently a monovalent chain hydrocarbon group having 1 to 10 carbon atoms or a monovalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, or R １９ and R ２０ are combined together with the carbon atoms to which they are bonded to form a divalent alicyclic group having 3 to 20 carbon atoms.

12. The radiation-sensitive resin composition according to claim 1 , further comprising an acid diffusion controller.

13. 2. The radiation-sensitive resin composition according to claim 1, which has a viscosity of from 1.0 mPa·s to 15 mPa·s.

14. A step of directly or indirectly applying the radiation-sensitive resin composition according to any one of claims 1 to 13 onto a substrate to form a resist film; exposing the resist film to light; developing the exposed resist film with a developer; A pattern forming method comprising:

15. 15. The pattern forming method according to claim 14, wherein the exposure is carried out with an ArF excimer laser.

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