Radiation-sensitive resin composition and method for forming resist pattern

Abstract

To provide a radiation-sensitive resin composition that can exhibit sufficient levels of sensitivity, focal depth and process margins when subjected to the next-generation exposure techniques, and a method for forming a resist pattern.SOLUTION: A radiation-sensitive resin composition contains: a resin including a structural unit having a phenolic hydroxyl group; and a compound represented by formula (1). In formula (1), Ar is a substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms; n is an integer of 2 to 4; Z+ is a monovalent onium cation; a plurality of Ys are each independently a polar group; and at least one of the plurality of Ys is an -OH group or a -SH group bonded to a carbon atom adjacent to a carbon atom to which a COO- group is bonded.SELECTED DRAWING: None

Description

[Technical field]

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

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

[0003] The photolithography technology mentioned above promotes finer patterns by using short-wavelength radiation from ArF excimer lasers, etc., 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.

[0004] As efforts toward further technological advances continue, a technology has been proposed in which a photosensitive quencher is added to a resist composition, and acid that has diffused to unexposed areas is captured through an ion exchange reaction to improve lithography performance using ArF exposure (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-200560 A Summary of the Invention [Problem to be solved by the invention]

[0006] Lithography using shorter wavelength radiation such as electron beams, X-rays, and EUV (extreme ultraviolet) is also being considered as a next-generation exposure technology. Although these next-generation exposure technologies require resist performance equal to or greater than conventional ones in terms of sensitivity, depth of focus, etc., and a process margin that makes it easier to control conditions for finer patterns is also desired, these properties have not been achieved at a sufficient level with existing radiation-sensitive resin compositions.

[0007] An object of the present invention is to provide a radiation-sensitive resin composition and a method for forming a resist pattern that are capable of exhibiting sufficient levels of sensitivity, depth of focus, and process margin when next-generation exposure technology is applied. [Means for solving the problem]

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

[0009] That is, in one embodiment, the present invention relates to a resin including a structural unit having a phenolic hydroxyl group, and A compound represented by the following formula (1): The present invention relates to a radiation-sensitive resin composition comprising the above compound. [ka] In formula (1), Ar is a substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms. n is an integer of 2 to 4. Z + is a monovalent onium cation. Each of the multiple Y's is independently a polar group. However, at least one of the multiple Y's is COO - The carbon atom adjacent to the carbon atom to which the group is bonded is an -OH group or an -SH group.

[0010] In the radiation-sensitive resin composition, by blending a compound represented by the above formula (1) having a specific structure (hereinafter also referred to as "compound (B)") as a quencher, it is possible to exhibit excellent sensitivity, focal depth, and process margin. Although not bound by any theory, the reason is presumed as follows. When the exposure dose is less than the required amount (underdose case), the deprotection of the acid-dissociable group of the resin becomes insufficient, so the solubility of the exposed part in the developer tends to decrease, which may cause bridge defects and scum generation. By introducing multiple polar groups into compound (B) to increase the polarity, the solubility in the alkaline developer in the exposed part is increased, and the above-mentioned defects can be suppressed. In addition, when the cross-sectional shape of the pattern in the exposed part becomes T-shaped or inverted wedge-shaped (a state in which the bottom is narrower than the top) during defocusing, the pattern collapse is likely to occur. Since the thick part at the top of the pattern is considered to be a part where deprotection is insufficient, the solubility of the upper part of the pattern is increased by increasing the polarity of compound (B), as in the case of underexposure, and the above-mentioned defects can be suppressed. In this way, it is presumed that the insufficient solubility in the exposed area at low exposure doses or when defocused is compensated for by blending compound (B), and the radiation-sensitive resin composition can exhibit sufficient levels of sensitivity, depth of focus, and process margin.

[0011] In one embodiment, the COO - The polar group bonded to the carbon atom adjacent to the carbon atom to which the group is bonded is preferably an -OH group. By adopting an -OH group as the polar group, the polarity of the compound (B) can be further increased, so that the sensitivity, focal depth, and process margin can be exhibited at higher levels.

[0012] In one embodiment, the compound represented by the above formula (1) is preferably a compound represented by the following formula (1-1). [ka] (In formula (1-1), R p1is an alkoxy group, an alkoxycarbonyl group, a halogen atom, or an amino group. m is an integer of 0 to 3. When m is 2 or 3, multiple R p1 are the same or different. n and Z + is the same as the above formula (1). q is an integer of 0 to 2. When q is 0, m+n is 5 or less. However, at least one OH group is a COO - The carbon atom adjacent to the carbon atom to which the group is bonded is

[0013] By employing the compound represented by the above formula (1-1) (hereinafter also referred to as "compound (b)") as compound (B), the polarity of compound (B) can be efficiently increased, and the sensitivity, depth of focus, and process margin can be efficiently improved.

[0014] In one embodiment, q in the above formula (1-1) is preferably 0 or 1. This makes it possible to increase the solubility of the compound (b) in an alkaline developer while maintaining the affinity with the resin (A).

[0015] In one embodiment, n in the above formula (1-1) is preferably 2 or 3. This can enhance the polarity, stability, etc. of compound (b).

[0016] In one embodiment, the content of the compound represented by the formula (1) is preferably 3 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the resin, which allows the solubility improving effect of the compound (B) to be obtained at a sufficient level, and allows the sensitivity, depth of focus, and process margin to be exhibited at higher levels.

[0017] In one embodiment, the onium cation in the above formula (1) is preferably a sulfonium cation or an iodonium cation.

[0018] In one embodiment, the radiation-sensitive resin composition preferably further contains a radiation-sensitive acid generator that generates an acid having a smaller pKa than the acid generated from the compound represented by formula (1). By specifically including a radiation-sensitive acid generator in the radiation-sensitive resin composition, it becomes possible to deprotect the protecting group in the resin (A), and the lithography process can be suitably carried out.

[0019] In one embodiment, the content of the radiation-sensitive acid generator is preferably 10 parts by mass or more relative to 100 parts by mass of the resin. The content of the radiation-sensitive acid generator is preferably 10 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the resin. This can further improve the sensitivity, depth of focus, and process margin.

[0020] In one embodiment, the structural unit having a phenolic hydroxyl group is preferably a structural unit derived from hydroxystyrene.When using exposure to EUV or the like, the light absorption by base resin, which has been a problem in exposure to ArF excimer laser light, is not a problem, so that the structural unit derived from hydroxystyrene, which has high etching resistance, can be efficiently introduced.

[0021] In one embodiment, the content of the structural unit having a phenolic hydroxyl group in the resin is preferably 5 mol % or more and 70 mol % or less, which can further improve the etching resistance of the resulting pattern.

[0022] In another embodiment, the present invention provides a method for producing a photoresist film by using the radiation-sensitive resin composition, a step of exposing the resist film to light; and The present invention also relates to a method for forming a resist pattern, which comprises the step of developing the exposed resist film.

[0023] The method for forming a resist pattern uses the above-mentioned radiation-sensitive resin composition, which has excellent sensitivity, depth of focus and process margin, and therefore can efficiently form a high-quality resist pattern.

[0024] In another embodiment, by employing the radiation-sensitive resin composition having excellent sensitivity, depth of focus and process margin, the exposure can be suitably carried out using extreme ultraviolet rays or an electron beam, and a desired fine pattern can be efficiently formed.

[0025] In yet another embodiment, the present invention provides a resin comprising a structural unit having an acid dissociable group and no structural unit having a phenolic hydroxyl group. A compound represented by the following formula (1), and A radiation-sensitive acid generator that generates an acid having a lower pKa than the acid generated from the above compound. Including, The present invention relates to a radiation-sensitive resin composition in which the content of the radiation-sensitive acid generator is 10 parts by mass or more based on 100 parts by mass of the resin. [ka] In formula (1), Ar is a substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms. n is an integer of 2 to 4. Z + is a monovalent onium cation. Each of the multiple Y's is independently a polar group. However, at least one of the multiple Y's is COO - The carbon atom adjacent to the carbon atom to which the group is bonded is an -OH group or an -SH group. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0027] First Embodiment <Radiation sensitive resin composition> The radiation-sensitive resin composition according to this embodiment (hereinafter, simply referred to as the "composition") contains a resin (A) and a compound (B). If necessary, it further contains a radiation-sensitive acid generator (C) and a solvent (D). The composition may contain other optional components as long as they do not impair the effects of the present invention.

[0028] (Resin (A)) Resin (A) is an aggregate of polymers having structural units (a1) having a phenolic hydroxyl group (hereinafter, this resin is also referred to as "base resin"). Resin (A) as a base resin may have structural units (a2) having an acid-dissociable group and other structural units in addition to the structural units (a1). Each structural unit will be described below.

[0029] [Structural unit (a1)] The structural unit (a1) is a structural unit containing a phenolic hydroxyl group. The resin (A) can adjust the solubility in the developer more appropriately by having the structural unit (a1) and other structural units as necessary, and as a result, the sensitivity of the radiation-sensitive resin composition can be further improved. In addition, when KrF excimer laser light, EUV, electron beams, etc. are used as radiation to be irradiated in the exposure step in the resist pattern forming method, the structural unit (a1) in the resin (A) contributes to improving the etching resistance and the difference in solubility in the developer between the exposed and unexposed areas (dissolution contrast). In particular, it can be suitably applied to pattern formation using exposure to radiation with a wavelength of 50 nm or less, such as electron beams or EUV.

[0030] In the radiation-sensitive resin composition of this embodiment, the structural unit (a1) may be a structural unit derived from hydroxystyrene.

[0031] Examples of the structural unit (a1) include structural units represented by the following formula (af):

[0032] [ka]

[0033] In the above formula (af), R AF1 is a hydrogen atom or a methyl group. AF is a single bond, -COO-, -O- or -CONH-. AF2 is a monovalent organic group having 1 to 20 carbon atoms. f1 is an integer from 0 to 3. f1 If is 2 or 3, multiple R AF2 may be the same or different. f2 is an integer from 1 to 3. f1 +n f2 is less than or equal to 5. af is an integer from 0 to 2.

[0034] Above R AF1 From the viewpoint of copolymerizability of the monomer that gives the structural unit (a1), it is preferably a hydrogen atom.

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

[0036] The organic group in the resin (A) refers to a group containing at least one carbon atom.

[0037] Above R AF2 Examples of the monovalent organic group having 1 to 20 carbon atoms represented by the formula (I) include monovalent hydrocarbon groups having 1 to 20 carbon atoms, groups containing a divalent heteroatom-containing group between the carbon atoms of this hydrocarbon group or at the bond-side terminal of this hydrocarbon group, and groups in which some or all of the hydrogen atoms in this group and the hydrocarbon group have been substituted with monovalent heteroatom-containing groups.

[0038] Above R AF2 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms represented by the formula: Alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group; alkenyl groups such as ethenyl, propenyl, and butenyl; Chain hydrocarbon groups such as alkynyl groups, e.g., ethynyl, propynyl, butynyl, etc.; cycloalkyl groups such as a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a norbornyl group, and an adamantyl group; alicyclic hydrocarbon groups such as cycloalkenyl groups, e.g., cyclopropenyl, cyclopentenyl, cyclohexenyl, and norbornenyl; Aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, or an anthryl group; Examples include aromatic hydrocarbon groups such as aralkyl groups, eg, benzyl group, phenethyl group, and naphthylmethyl group.

[0039] Above R AF2 As the alkyl group, a chain hydrocarbon group or a cycloalkyl group is preferable, an alkyl group or a cycloalkyl group is more preferable, and a methyl group, an ethyl group, a propyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group or an adamantyl group is even more preferable.

[0040] Examples of the divalent heteroatom-containing group include -O-, -CO-, -CO-O-, -S-, -CS-, -SO2-, -NR'-, and combinations of two or more of these, where R' is a hydrogen atom or a monovalent hydrocarbon group.

[0041] Examples of the monovalent heteroatom-containing group include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom, hydroxyl group, carboxy group, cyano group, amino group, and sulfanyl group (-SH).

[0042] Among these, a monovalent chain hydrocarbon group is preferred, an alkyl group is more preferred, and a methyl group is even more preferred.

[0043] Above n f1 is preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

[0044] Above n f2 As the group, 1 and 2 are preferable, and 1 is more preferable.

[0045] Above n af As the number, 0 and 1 are preferable, and 0 is more preferable.

[0046] The structural unit (a1) is preferably any of structural units represented by the following formulas (a1-1) to (a1-6).

[0047] [ka]

[0048] In the above formulas (a1-1) to (a1-6), R AF1 is the same as the above formula (af).

[0049] Among these, the structural units (a1-1) and (a1-2) are preferred, with (a1-1) being more preferred.

[0050] The lower limit of the content of the structural unit (a1) in the resin (A) is preferably 5 mol%, more preferably 10 mol%, further preferably 15 mol%, and particularly preferably 20 mol%, based on the total structural units constituting the resin (A). The upper limit of the content is preferably 70 mol%, more preferably 60 mol%, further preferably 55 mol%, and particularly preferably 50 mol%. By setting the content of the structural unit (a1) within the above range, the radiation-sensitive resin composition can further improve the sensitivity, focal depth, and process margin.

[0051] When a monomer having a phenolic hydroxyl group such as hydroxystyrene is directly subjected to radical polymerization, the polymerization may be inhibited by the influence of the phenolic hydroxyl group. In this case, it is preferable to polymerize the phenolic hydroxyl group in a state in which the phenolic hydroxyl group is protected by a protecting group such as an alkali dissociable group, and then to obtain the structural unit (a1) by deprotection through hydrolysis. The structural unit that gives the structural unit (a1) through hydrolysis is preferably represented by the following formula (4).

[0052] [ka]

[0053] In the above formula (4), R 11 R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 12 R is a monovalent hydrocarbon group or alkoxy group having 1 to 20 carbon atoms. 12 Examples of the monovalent hydrocarbon group having 1 to 20 carbon atoms include monovalent hydrocarbon groups having 1 to 20 carbon atoms. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a tert-butoxy group.

[0054] Above R 12 As the alkyl group, an alkyl group and an alkoxy group are preferable, and among them, a methyl group and a tert-butoxy group are more preferable.

[0055] [Structural unit (a2)] The structural unit (a2) is a structural unit containing an acid dissociable group. In particular, the acid dissociable group in the structural unit (a2) preferably contains a cyclic structure. Examples of the acid dissociable group containing a cyclic structure include a structural unit having a tertiary alkyl ester moiety, a structural unit having a structure in which a 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, the structural unit represented by the following formula (5) (hereinafter also referred to as "structural unit (a2-1)") is preferred.

[0056] In the present invention, the term "acid dissociable group" refers to a group that substitutes a hydrogen atom of a carboxy group, a phenolic hydroxyl group, an alcoholic hydroxyl group, a sulfo group, etc., and dissociates by the action of an acid. The radiation-sensitive resin composition has excellent pattern formability because the resin has the structural unit (a2).

[0057] [ka]

[0058] In the above formula (5), R 7 R is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. 8 R is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. 9 and R 10 are each independently a monovalent linear hydrocarbon group having 1 to 10 carbon atoms, 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 atom to which they are bonded. 8 ~R 10 Among these, one or more may be combined with each other to form at least one cyclic structure. 1 represents a single bond or a divalent linking group.

[0059] Above R 7 From the viewpoint of copolymerizability of the monomer that gives the structural unit (a2-1), a hydrogen atom or a methyl group is preferable, and a methyl group is more preferable.

[0060] Above R 8 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.

[0061] Above R 8 ~R 10 Examples of the chain hydrocarbon group having 1 to 10 carbon atoms represented by the formula (I) include linear or branched saturated hydrocarbon groups having 1 to 10 carbon atoms, and linear or branched unsaturated hydrocarbon groups having 1 to 10 carbon atoms.

[0062] Above R 8 ~R 10Examples of the alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the formula (1) include monocyclic or polycyclic saturated hydrocarbon groups, or monocyclic or polycyclic unsaturated hydrocarbon groups. As the monocyclic saturated hydrocarbon group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, or a cyclooctyl group is preferable. As the monocyclic unsaturated hydrocarbon group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, or a cyclooctenyl group is preferable. As the polycyclic cycloalkyl group, a bridged alicyclic hydrocarbon group such as a norbornyl group, an adamantyl group, a tricyclodecyl group, or a tetracyclododecyl group is preferable. The bridged alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group in which two carbon atoms that are not adjacent to each other among the carbon atoms constituting the alicyclic ring are bonded by a bond chain containing one or more carbon atoms.

[0063] Above R 8 Examples of the monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms represented by the formula (1) include aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and an anthryl group; and aralkyl groups such as a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0064] Above R 8 As the alkyl group, a linear or branched saturated hydrocarbon group having 1 to 10 carbon atoms and an alicyclic hydrocarbon group having 3 to 20 carbon atoms are preferable.

[0065] Above R 8 ~R 10When any of a plurality of the above are combined with each other to have at least one or more cyclic structures, the divalent alicyclic group having 3 to 20 carbon atoms formed by combining chain hydrocarbon groups or alicyclic hydrocarbon groups with each other and the carbon atoms to which they are bonded is not particularly limited as long as it is a group obtained 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. It may be either a monocyclic hydrocarbon group or a polycyclic hydrocarbon group, and the polycyclic hydrocarbon group may be either a bridged alicyclic hydrocarbon group or a condensed alicyclic hydrocarbon group, or it may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. The condensed alicyclic hydrocarbon group refers to a polycyclic alicyclic hydrocarbon group formed in such a way that a plurality of alicyclic rings share a side (a bond between two adjacent carbon atoms).

[0066] 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.

[0067] The above L 1 Examples of the divalent linking group represented by the formula (I) include an alkanediyl group, a cycloalkanediyl group, an alkenediyl group, * -R LA O-, * -R LB COO- and the like (* indicates a bond on the oxygen side). A part or all of the hydrogen atoms of these groups may be substituted with halogen atoms such as fluorine atoms and chlorine atoms, cyano groups, and the like.

[0068] The alkanediyl group is preferably an alkanediyl group having 1 to 8 carbon atoms.

[0069] Examples of the cycloalkanediyl group include monocyclic cycloalkanediyl groups such as a cyclopentanediyl group and a cyclohexanediyl group, and polycyclic cycloalkanediyl groups such as a norbornanediyl group and an adamantanediyl group. The cycloalkanediyl group is preferably a cycloalkanediyl group having 5 to 12 carbon atoms.

[0070] Examples of the alkenediyl group include an ethenediyl group, a propenediyl group, a butenediyl group, etc. The alkenediyl group is preferably an alkenediyl group having 2 to 6 carbon atoms.

[0071] the above * -R LA O-R LA Examples of the alkyl group include the above-mentioned alkanediyl group, the above-mentioned cycloalkanediyl group, and the above-mentioned alkenediyl group. * -R LB COO-R LB Examples of the arenediyl group include the above-mentioned alkanediyl group, the above-mentioned cycloalkanediyl group, the above-mentioned alkenediyl group, and arenediyl group. Examples of the arenediyl group include a phenylene group, a tolylene group, and a naphthylene group. The arenediyl group is preferably an arenediyl group having 6 to 15 carbon atoms.

[0072] R 9 and R 10 The alicyclic group constituted by L and L together contains an unsaturated bond, 1 is a single bond, R 8 is preferably a hydrogen atom.

[0073] Examples of the structural unit (a2-1) include structural units represented by the following formulas (5-1) to (5-4) (hereinafter also referred to as "structural units (a2-1-1) to (a2-1-4)").

[0074] [ka]

[0075] In the above formula (5-1), R 7 and R 8 is the same as in the above formula (5), and i is an integer of 1 to 4.

[0076] In the above formula (5-2), R 7 is the same as the above formula (5). 8 is a hydrogen atom. 2T represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. i is an integer of 1 to 4.

[0077] In the above formulas (5-3) and (5-4), R 7 , R 9 and R 10 is the same as the above formula (5). 2T represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. i is an integer of 1 to 4.

[0078] Of these, the structural unit (a2-1) is preferably the structural unit (a2-1-1) or the structural unit (a2-1-2), and more preferably a structural unit having a cyclopentane structure, a structural unit having a cyclohexane structure, a structural unit having a cyclopentene structure, or a structural unit having a cyclohexene structure.

[0079] The resin (A) may contain one type of structural unit (a2) or a combination of two or more types.

[0080] The lower limit of the content of the structural unit (a2) is preferably 15 mol%, more preferably 20 mol%, even more preferably 25 mol%, and particularly preferably 30 mol%, based on the total structural units constituting the base resin (A). The upper limit of the content is preferably 90 mol%, more preferably 80 mol%, even more preferably 75 mol%, and particularly preferably 70 mol%. By setting the content of the structural unit (a2) within the above range, the pattern formability of the radiation-sensitive resin composition can be further improved.

[0081] [Structural unit (a3)] The structural unit (a3) ​​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. The base resin further contains the structural unit (a3), which allows the base resin to adjust its solubility in a developer, and as a result, the radiation-sensitive resin composition can improve lithography performance such as resolution. In addition, the adhesion between a resist pattern formed from the base resin and a substrate can be improved.

[0082] Examples of the structural unit (a3) ​​include structural units represented by the following formulas (T-1) to (T-10).

[0083] [ka]

[0084] In the above formula, R L1 R 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 L may be combined with each other to form a divalent alicyclic group having 3 to 8 carbon atoms together with the carbon atom to which they are bonded. 2is 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.

[0085] Above R L4 and R L5 Examples of the divalent alicyclic group having 3 to 8 carbon atoms formed by combining together with the carbon atom to which they are bonded include R 9 and R 10 Among divalent alicyclic groups having 3 to 20 carbon atoms constituted 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, groups having 3 to 8 carbon atoms are exemplified. One or more hydrogen atoms on this alicyclic group may be substituted with a hydroxy group.

[0086] 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-.

[0087] As the structural unit (a2), of these, a structural unit containing a lactone structure is preferable, a structural unit containing a norbornane lactone structure is more preferable, and a structural unit derived from norbornane lactone-yl (meth)acrylate is even more preferable.

[0088] When the resin (A) has the structural unit (a2), the lower limit of the content is preferably 5 mol%, more preferably 10 mol%, and even more preferably 15 mol%, based on the total structural units constituting the base resin. The upper limit of the content is preferably 40 mol%, more preferably 30 mol%, and even more preferably 20 mol%. By setting the content of the structural unit (II) within the above range, the radiation-sensitive resin composition can further improve the lithography performance such as resolution and the adhesion of the formed resist pattern to the substrate.

[0089] [Structural unit (a4)] The resin (A) may appropriately have a structural unit (also referred to as a structural unit (a4)) other than the above structural units (a1) to (a3). Examples of the structural unit (a4) include structural units having a fluorine atom, an alcoholic hydroxyl group, a carboxy group, a cyano group, a nitro group, a sulfonamide group, and the like. Among these, a structural unit having a fluorine atom, a structural unit having an alcoholic hydroxyl group, and a structural unit having a carboxy group are preferred, and a structural unit having a fluorine atom and a structural unit having an alcoholic hydroxyl group are more preferred.

[0090] Examples of the structural unit (a4) include structural units represented by the following formulas.

[0091] [ka]

[0092] In the above formula, R A is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group.

[0093] When the resin (A) has the structural unit (a4), the lower limit of the content ratio of the structural unit (a4) to the total structural units constituting the resin (A) is preferably 1 mol%, more preferably 3 mol%, and even more preferably 5 mol%. On the other hand, the upper limit of the content ratio is preferably 50 mol%, more preferably 40 mol%, and even more preferably 30 mol%. By setting the content ratio of other structural units within the above range, the solubility of the resin (A) in the developer can be made more appropriate. If the content ratio of other structural units exceeds the above upper limit, the pattern formability may be reduced.

[0094] Incidentally, the above structural units (a2) to (a4) and other structural units exclude those structural units that fall under the above structural unit (a1).

[0095] The content of the resin (A) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more, based on the total solid content of the radiation-sensitive resin composition. Here, the "solid content" refers to all components contained in the radiation-sensitive resin composition excluding the solvent.

[0096] (Method of synthesizing resin (A)) The resin (A) serving as the base resin can be synthesized, for example, by polymerizing monomers which provide the respective structural units in a suitable solvent using a radical polymerization initiator or the like.

[0097] 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; Examples of the radical initiator include peroxide radical initiators such as benzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide. Among these, AIBN and dimethyl 2,2'-azobisisobutyrate are preferred, and AIBN is more preferred. These radical initiators can be used alone or in combination of two or more.

[0098] Examples of the solvent used in the polymerization reaction include alkanes such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n-decane; cycloalkanes such as cyclohexane, cycloheptane, cyclooctane, decalin, and norbornane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and cumene; halogenated hydrocarbons such as chlorobutanes, bromohexanes, dichloroethanes, hexamethylene dibromide, and chlorobenzene; saturated carboxylic acid esters such as ethyl acetate, n-butyl acetate, i-butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, 4-methyl-2-pentanone, and 2-heptanone; ethers such as tetrahydrofuran, dimethoxyethanes, and diethoxyethanes; and alcohols such as methanol, ethanol, 1-propanol, 2-propanol, and 4-methyl-2-pentanol. The solvents used in these polymerization reactions may be used alone or in combination of two or more.

[0099] The reaction temperature in the above polymerization reaction 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.

[0100] The molecular weight of the base resin (A) is not particularly limited, but the weight average molecular weight (Mw) calculated based on polystyrene standards by gel permeation chromatography (GPC) is preferably 1,000 to 50,000, more preferably 2,000 to 30,000, even more preferably 3,000 to 15,000, and particularly preferably 4,000 to 12,000. If the Mw of the resin (A) is less than the lower limit, the heat resistance of the resulting resist film may be reduced. If the Mw of the resin (A) is greater than the upper limit, the developability of the resist film may be reduced.

[0101] The ratio (Mw / Mn) of Mw to the polystyrene-equivalent number average molecular weight (Mn) of the base resin (A) 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.

[0102] In this specification, the Mw and Mn of the resin are values ​​measured by gel permeation chromatography (GPC) under the following conditions. 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

[0103] The content of the resin (A) 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.

[0104] (Other resins) The radiation-sensitive resin composition of the present embodiment may contain, as another 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, and as a result, the state of the resist film surface and the component distribution in the resist film can be controlled to a desired state.

[0105] The high fluorine content resin preferably has, for example, the structural unit (a1) and the structural unit (a2) in the above-mentioned base resin, and also has a structural unit represented by the following formula (6) (hereinafter also referred to as "structural unit (a5)"). [ka]

[0106] In the above formula (6), R 13is a hydrogen atom, a methyl group, or a trifluoromethyl group. G is a single bond, an oxygen atom, a sulfur atom, -COO-, -SO2ONH-, -CONH-, or -OCONH-. R 14 represents 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.

[0107] Above R 13 From the viewpoint of copolymerizability of the monomer that gives the structural unit (a5), a hydrogen atom or a methyl group is preferable, and a methyl group is more preferable.

[0108] Above G L As the group, from the viewpoint of copolymerizability of the monomer that gives the structural unit (a5), a single bond and -COO- are preferable, and -COO- is more preferable.

[0109] Above R 14 Examples of the monovalent fluorinated chain hydrocarbon group having 1 to 20 carbon atoms represented by the formula (1) include linear or branched alkyl groups having 1 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0110] Above R 14 Examples of the monovalent fluorinated alicyclic hydrocarbon group having 3 to 20 carbon atoms represented by the following formula include monocyclic or polycyclic hydrocarbon groups having 3 to 20 carbon atoms in which some or all of the hydrogen atoms have been substituted with fluorine atoms.

[0111] 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 further preferable.

[0112] When the high fluorine content resin has the structural unit (a5), the lower limit of the content of the structural unit (a5) is preferably 10 mol%, more preferably 15 mol%, further preferably 20 mol%, and particularly preferably 25 mol% based on the total structural units constituting the high fluorine content resin. The upper limit of the content is preferably 60 mol%, more preferably 50 mol%, and further preferably 40 mol%. By setting the content of the structural unit (a5) within the above range, the mass content of fluorine atoms in the high fluorine content resin can be more appropriately adjusted, and the uneven distribution of fluorine atoms in the surface layer of the resist film can be further promoted.

[0113] The high fluorine content resin may have a fluorine atom-containing structural unit represented by the following formula (f-1) (hereinafter also referred to as structural unit (a6)) in addition to the structural unit (a5). By having the structural unit (f-1), the high fluorine content resin has improved solubility in an alkaline developer, and can suppress the occurrence of development defects. [ka]

[0114] The structural unit (a6) 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 an 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 (s+1)-valent hydrocarbon group having 1 to 20 carbon atoms, and R of this hydrocarbon group E At the end of the side, there is an oxygen atom, a sulfur atom, and -NR dd R is a structure in which -, a carbonyl group, -COO- or -CONH- is bonded, or a structure in which some of the hydrogen atoms in the hydrocarbon group are replaced by an organic group having a hetero atom. dd represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. s represents an integer of 1 to 3.

[0115] When the structural unit (a6) has an alkali-soluble group (x), 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 If is an oxygen atom, W 1 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 (a6) has an alkali-soluble group (x), it is possible to increase the affinity for an alkali developer and suppress development defects. As the structural unit (a6) having an alkali-soluble group (x), A 1 is an oxygen atom and W 1 It is particularly preferred that R is a 1,1,1,3,3,3-hexafluoro-2,2-methanediyl group.

[0116] When the structural unit (a6) has an alkali dissociable group (y), R F is a monovalent organic group having 1 to 30 carbon atoms, 1 is an oxygen atom, -NR aa -, -COO-* or -SO2O-*. 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 -S0-*, W 1 or R F A 1 A has a fluorine atom on the carbon atom bonded to or adjacent to the carbon atom. 1If is an oxygen atom, W 1 , R E is a single bond, and R D R is a hydrocarbon group having 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 (a6) has an alkali dissociable group (y), 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 (a6) having an alkali dissociable group (y), A 1 is -COO-* and R F Or W 1 or both of these have fluorine atoms The above are particularly preferred.

[0117] R C From the viewpoint of the copolymerizability of the monomer that gives the structural unit (a6), a hydrogen atom or a methyl group is preferable, and a methyl group is more preferable.

[0118] 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.

[0119] When the high fluorine content resin has the structural unit (a6), the lower limit of the content of the structural unit (a6) is preferably 10 mol%, more preferably 20 mol%, further preferably 30 mol%, and particularly preferably 35 mol%, based on the total structural units constituting the high fluorine content resin. The upper limit of the content is preferably 90 mol%, more preferably 75 mol%, and further preferably 60 mol%. By setting the content of the structural unit (a6) within the above range, the water repellency of the resist film during immersion exposure can be further improved.

[0120] 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.

[0121] The lower limit of Mw / Mn of the high fluorine content resin is usually 1, and more preferably 1.1. The upper limit of the Mw / Mn is usually 5, and is preferably 3, more preferably 2, and even more preferably 1.7.

[0122] The lower limit of the content of the high fluorine content resin is preferably 0.1 mass%, more preferably 0.5 mass%, further preferably 1 mass%, and even more preferably 1.5 mass%, based on the total solid content in the radiation-sensitive resin composition. The upper limit of the content is preferably 20 mass%, more preferably 15 mass%, further preferably 10 mass%, and particularly preferably 7 mass%.

[0123] The lower limit of the content of the high fluorine content resin is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, even more preferably 1 part by mass, and particularly preferably 1.5 parts by mass, relative to 100 parts by mass of the base resin. The upper limit of the content is preferably 15 parts by mass, more preferably 10 parts by mass, even more preferably 8 parts by mass, and particularly preferably 5 parts by mass.

[0124] By setting the content of the high fluorine content resin within the above range, the high fluorine content resin can be more effectively unevenly distributed in the surface layer of the resist film, and as a result, the water repellency of the surface of the resist film during immersion exposure can be further improved. The radiation-sensitive resin composition may contain one or more types of high fluorine content resins.

[0125] (Method of 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.

[0126] (Compound (B)) The compound (B) can function as a quencher (photodegradable base) that captures acid in the unexposed or pre-exposed area. The compound (B) is represented by the following formula (1). [ka] In formula (1), Ar is a substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms. n is an integer of 2 to 4. Z + is a monovalent onium cation. Each of the multiple Y's is independently a polar group. However, at least one of the multiple Y's is COO - The carbon atom adjacent to the carbon atom to which the group is bonded is an -OH group or an -SH group.

[0127] The inclusion of compound (B) improves the solubility of the resin in an alkaline developer, thereby suppressing problems caused by fluctuations in the exposure dose or focus position, thereby imparting high levels of sensitivity, depth of focus, and process margin to the radiation-sensitive resin composition.

[0128] In the above formula (1), the substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms is not particularly limited, and may be a monocyclic or polycyclic ring, and may have an aromatic heterocyclic structure in which a carbon atom forming the skeleton is substituted with a heteroatom, and a hydrogen atom on the carbon atom may be substituted with a substituent other than the above polar group.

[0129] Examples of the aromatic ring include groups having a benzene ring structure, a naphthalene ring structure, a phenanthrene ring structure, an anthracene ring structure, and the like.

[0130] Examples of the heteroatom in the aromatic heterocyclic structure include an oxygen atom, a nitrogen atom, and a sulfur atom. Examples of the aromatic heterocyclic structure include oxygen atom-containing heterocyclic structures such as a furan ring structure, a pyran ring structure, a benzofuran ring structure, and a benzopyran ring structure; Nitrogen atom-containing heterocyclic structures such as a pyridine ring structure, a pyrimidine ring structure, an indole ring structure, etc. Examples of the heterocyclic structure include a sulfur atom-containing heterocyclic structure such as a thiophene ring structure. Can be obtained.

[0131] Examples of the polar group include a hydroxy group, a sulfanyl group, a carboxy group, a cyano group, a nitro group, an amino group, a group having an ester bond, and a halogen atom.

[0132] Examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, an alkyl group, an alkoxy group, an alkoxycarbonyl group, an alkoxycarbonyloxy group, an acyl group and an acyloxy group.

[0133] The monovalent onium cation includes, for example, radiolytic onium cations containing elements such as S, I, O, N, P, Cl, Br, F, As, Se, Sn, Sb, Te, and Bi, such as sulfonium cation, tetrahydrothiophenium cation, iodonium cation, phosphonium cation, diazonium cation, and pyridinium cation. Among them, sulfonium cation or iodonium cation is preferred. The sulfonium cation or iodonium cation is preferably represented by the following formulas (X-1) to (X-5).

[0134] [ka]

[0135] [ka]

[0136] [ka]

[0137] [ka]

[0138] [ka]

[0139] In the above formula (X-1), R a1 , R a2 and R a3 each independently represents 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, -OSO2-R P , -SO2-R Q Or -SR T or a ring structure formed by combining two or more of these groups together. 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 ~R a3 And R P , R Q and R T If there are multiple R a1 ~R a3 And R P , R Q and R T may be the same or different.

[0140] 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. k When is 0, k4 is an integer from 0 to 4, and nk When is 1, k4 is an integer from 0 to 7. 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 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. 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 combine with each other to form a ring structure. q is an integer of 0 to 3.

[0141] 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, or a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms.

[0142] In the above formula (X-4), 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, a nitro group, or a ring structure formed by combining two or more of these groups together. 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.

[0143] In the above formula (X-5), R e1 and R e2are 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.

[0144] The compound (B) is preferably a compound represented by the following formula (1-1) (that is, compound (b)). [ka] (In formula (1-1), R p1 is an alkoxy group, an alkoxycarbonyl group, a halogen atom, or an amino group. m is an integer of 0 to 3. When m is 2 or 3, multiple R p1 are the same or different. n and Z + is the same as the above formula (1). q is an integer of 0 to 2. When q is 0, m+n is 5 or less. However, at least one OH group is a COO - The carbon atom adjacent to the carbon atom to which the group is bonded is

[0145] By employing the compound (b) represented by the above formula (1-1) as the compound (B), the polarity can be increased, and the sensitivity, depth of focus, and process margin can be efficiently improved.

[0146] In the above formula (1-1), examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. Examples of the alkoxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, and a propoxycarbonyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0147] In the above formula (1-1), m is preferably an integer of 0 to 2, and more preferably 0 or 1. q is preferably 0 or 1. Furthermore, n is preferably 2 or 3.

[0148] Suitable specific examples of the compound represented by formula (1-1) include the following formulae (1-1a) to (1-1i).

[0149] [ka]

[0150] The content of the compound (B) is preferably 0.5 parts by mass or more and 100 parts by mass or less relative to 100 parts by mass of the resin. The upper limit of the content is more preferably 50 parts by mass, and even more preferably 25 parts by mass. The lower limit of the content is more preferably 1 part by mass, and even more preferably 2 parts by mass. The content of the compound (B) is appropriately selected according to the type of the resin (A) used, the exposure conditions, the required sensitivity, and the type and content of the radiation-sensitive acid generator (C) described later. This allows the solubility of the resin (A) to be obtained at a sufficient level, and allows the sensitivity, depth of focus, and process margin to be exhibited at higher levels.

[0151] When the radiation-sensitive resin composition according to the present embodiment contains a radiation-sensitive acid generator described later, the upper limit of the molar ratio of the content of the compound (B) to the content of the radiation-sensitive acid generator is preferably 250 mol%, more preferably 200 mol%, further preferably 100 mol%, and particularly preferably 50 mol%, while the lower limit of the molar ratio is preferably 3 mol%, more preferably 5 mol%, further preferably 10 mol%, and particularly preferably 15 mol%.

[0152] (Method of synthesizing compound (B)) Compound (B) can be typically synthesized by reacting a benzoic acid derivative corresponding to the anion moiety with a sulfonium chloride corresponding to the cation moiety under basic conditions to allow salt exchange to proceed. Compounds (B) having other structures can also be synthesized by appropriately selecting precursors corresponding to the anion moiety and the cation moiety in the same manner.

[0153] (Radiation-sensitive acid generator (C)) The radiation-sensitive acid generator (C) is a component that generates an acid upon exposure. When the resin contains a structural unit (a2) having an acid-dissociable group, the acid generated upon exposure can dissociate the acid-dissociable group of the structural unit (a2) to generate a carboxyl group or the like. This function is different from the function of the compound (B) that does not substantially dissociate the acid-dissociable group of the structural unit (a2) of the resin under the pattern formation conditions using the radiation-sensitive resin composition, and suppresses the diffusion of the acid generated from the radiation-sensitive acid generator (C) in the unexposed area. It can be said that the acid generated from the radiation-sensitive acid generator (C) is a relatively stronger acid (acid with a smaller pKa) than the acid generated from the compound (B). The difference between the functions of the compound (B) and the radiation-sensitive acid generator (C) is determined by the energy required for dissociating the acid-dissociable group of the structural unit (a2) of the resin, and the thermal energy conditions applied when forming a pattern using the radiation-sensitive resin composition. The form in which the radiation-sensitive acid generator is contained in the radiation-sensitive resin composition may be a form in which it exists as a compound alone (isolated from the polymer), a form in which it is incorporated as part of the polymer, or both of these forms, but a form in which it exists as a compound alone is preferred.

[0154] When the radiation-sensitive resin composition contains the radiation-sensitive acid generator (C), the polarity of the resin in the exposed area increases, and the resin in the exposed area becomes soluble in the developer in the case of development with an aqueous alkali solution, whereas it becomes poorly soluble in the developer in the case of development with an organic solvent.

[0155] Examples of the radiation-sensitive acid generator (C) include onium salt compounds, sulfonimide compounds, halogen-containing compounds, diazoketone compounds, etc. Examples of the onium salt compounds include sulfonium salts, tetrahydrothiophenium salts, iodonium salts, phosphonium salts, diazonium salts, pyridinium salts, etc. Among these, sulfonium salts and iodonium salts are preferred.

[0156] The acid generated by exposure can be one that generates a sulfonic acid by exposure. Such an acid can be a compound in which one or more fluorine atoms or fluorinated hydrocarbon groups are substituted on the carbon atom adjacent to the sulfo group. Among them, the radiation-sensitive acid generator (C) is particularly preferably one having a cyclic structure.

[0157] These radiation-sensitive acid generators may be used alone or in combination of two or more. The content of the radiation-sensitive acid generator may be 5 parts by mass or more per 100 parts by mass of the resin from the viewpoint of ensuring the sensitivity and developability as a resist, but is preferably 10 parts by mass or more from the viewpoint of sensitivity, focal depth, and process margin. The lower limit of the content is more preferably 12 parts by mass, and even more preferably 15 parts by mass. The upper limit of the content is preferably 60 parts by mass, more preferably 50 parts by mass, and even more preferably 40 parts by mass.

[0158] (Solvent (D)) The radiation-sensitive resin composition according to the present embodiment contains a solvent (D). The solvent (D) is not particularly limited as long as it is a solvent capable of dissolving or dispersing at least the resin (A) and the compound (B), as well as the radiation-sensitive acid generator (C) that is optionally contained therein.

[0159] Examples of the solvent (D) include alcohol-based solvents, ether-based solvents, ketone-based solvents, amide-based solvents, ester-based solvents, and hydrocarbon-based solvents.

[0160] 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 the polyhydric alcohol partially etherified solvents include those obtained by etherifying some of the hydroxy groups of the above-mentioned polyhydric alcohol solvents.

[0161] 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 hydroxyl groups of the above-mentioned polyhydric alcohol solvents.

[0162] Examples of ketone solvents include chain ketone solvents such as acetone, butanone, and methyl-iso-butyl ketone: Cyclic ketone solvents such as cyclopentanone, cyclohexanone, methylcyclohexanone, etc. Examples include 2,4-pentanedione, acetonylacetone, and acetophenone.

[0163] Examples of the amide solvents 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.

[0164] Examples of ester-based 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 polyvalent carboxylate diester solvents such as propylene glycol diacetate, methoxytriglycol acetate, diethyl oxalate, ethyl acetoacetate, ethyl lactate, and diethyl phthalate.

[0165] Examples of the hydrocarbon solvent include Aliphatic hydrocarbon solvents such as n-hexane, cyclohexane, and methylcyclohexane; Examples of the solvent include aromatic hydrocarbon solvents such as benzene, toluene, di-iso-propylbenzene, and n-amylnaphthalene.

[0166] 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.

[0167] (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.

[0168] (Crosslinking agent) The crosslinking agent is a compound having two or more functional groups, which (1) induces a crosslinking reaction in the polymer component by an acid catalysis in the baking step after the floodwise exposure step, and (1) increases the molecular weight of the polymer component, thereby decreasing the solubility of the patternwise exposed area in the developer. Examples of the functional group include a (meth)acryloyl group, a hydroxymethyl group, an alkoxymethyl group, an epoxy group, and a vinyl ether group.

[0169] (Uneven distribution promoter) The uneven distribution promoter has the effect of making the high fluorine content resin unevenly distributed on the resist film surface more efficiently. By incorporating this uneven distribution promoter in the radiation-sensitive resin composition, the amount of the high fluorine content resin added can be reduced compared to the conventional case. Therefore, while maintaining the lithography performance of the radiation-sensitive resin composition, it is possible to further suppress the elution of components from the resist film into the immersion medium, and perform immersion exposure at a higher speed by high-speed scanning, thereby improving the hydrophobicity of the resist film surface, which suppresses immersion-induced defects such as watermark defects. Examples of the uneven distribution promoter that can be used include low-molecular compounds having a relative dielectric constant of 30 to 200 and a boiling point of 100° C. or higher at 1 atmospheric pressure. Specific examples of such compounds include lactone compounds, carbonate compounds, nitrile compounds, polyhydric alcohols, and the like.

[0170] Examples of the lactone compound include γ-butyrolactone, valerolactone, mevalonic lactone, and norbornane lactone.

[0171] Examples of the carbonate compound include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, and the like.

[0172] The nitrile compound may, for example, be succinonitrile.

[0173] An example of the polyhydric alcohol is glycerin.

[0174] The lower limit of the content of the uneven distribution promoter is preferably 10 parts by mass, more preferably 15 parts by mass, further preferably 20 parts by mass, and further preferably 25 parts by mass, relative to 100 parts by mass of the total amount of the resin in the radiation-sensitive resin composition. The upper limit of the content is preferably 300 parts by mass, more preferably 200 parts by mass, further preferably 100 parts by mass, and particularly preferably 80 parts by mass. The radiation-sensitive resin composition may contain one or more kinds of uneven distribution promoters.

[0175] (Surfactant) The surfactant has the effect of improving the coating property, striation, developability, etc. Examples of the surfactant include nonionic surfactants such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene n-octylphenyl ether, polyoxyethylene n-nonylphenyl ether, polyethylene glycol dilaurate, and polyethylene glycol distearate; commercially available products include KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), Polyflow No. 75, and No. Examples include F-TOP EF301, EF303, and EF352 (all manufactured by Tochem Products), Megafac F171 and F173 (all manufactured by DIC), Fluorad FC430 and FC431 (all manufactured by Sumitomo 3M), Asahiguard AG710, Surflon S-382, SC-101, SC-102, SC-103, SC-104, SC-105, and SC-106 (all manufactured by Asahi Glass Co., Ltd.). The content of the surfactant in the radiation-sensitive resin composition is usually 2 parts by mass or less per 100 parts by mass of the resin.

[0176] (Alicyclic skeleton-containing compounds) The alicyclic skeleton-containing compound exhibits the effect of improving dry etching resistance, pattern shape, adhesion to a substrate, and the like.

[0177] Examples of the alicyclic skeleton-containing compound include Adamantane derivatives such as 1-adamantanecarboxylic acid, 2-adamantanone, and t-butyl 1-adamantanecarboxylate; Deoxycholic acid esters such as t-butyl deoxycholate, t-butoxycarbonylmethyl deoxycholate, and 2-ethoxyethyl deoxycholate; Lithocholic acid esters such as t-butyl lithocholic acid, t-butoxycarbonylmethyl lithocholic acid, and 2-ethoxyethyl lithocholic acid; Examples include 3-[2-hydroxy-2,2-bis(trifluoromethyl)ethyl]tetracyclo[4.4.0.1(2,5).1(7,10)]dodecane, 2-hydroxy-9-methoxycarbonyl-5-oxo-4-oxa-tricyclo[4.2.1.0(3,7)]nonane, etc. The content of the alicyclic skeleton-containing compound in the radiation-sensitive resin composition is usually 5 parts by mass or less based on 100 parts by mass of the resin.

[0178] (sensitizer) The sensitizer acts to increase the amount of acid generated from the radiation-sensitive acid generator or the like, and exerts the effect of improving the "apparent sensitivity" of the radiation-sensitive resin composition.

[0179] Examples of the sensitizer include carbazoles, acetophenones, benzophenones, naphthalenes, phenols, biacetyl, eosin, rose bengal, pyrenes, anthracenes, and phenothiazines. These sensitizers may be used alone or in combination of two or more. The content of the sensitizer in the radiation-sensitive resin composition is usually 2 parts by mass or less per 100 parts by mass of the resin.

[0180] <Method for preparing radiation-sensitive resin composition> The radiation-sensitive resin composition can be prepared, for example, by mixing the resin (A), the compound (B), the radiation-sensitive acid generator (C), and, if necessary, a high-fluorine content resin, and the solvent (D) 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. The solid content concentration of the radiation-sensitive resin composition is usually 0.1% by mass to 50% by mass, preferably 0.5% by mass to 30% by mass, and more preferably 1% by mass to 20% by mass.

[0181] <Method of forming resist pattern> The method for forming a resist pattern according to the present invention comprises the steps of: A step (1) of forming a resist film by directly or indirectly applying the radiation-sensitive resin composition onto a substrate (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 an "exposure step"); and The method includes a step (3) of developing the exposed resist film (hereinafter also referred to as the "developing step").

[0182] According to the above-mentioned method for forming a resist pattern, since the above-mentioned radiation-sensitive resin composition, which is excellent in sensitivity, depth of focus, and process margin in the exposure step, is used, a high-quality resist pattern can be formed. Each step will now be described.

[0183] [Resist film formation process] In this step (step (1) above), a resist film is formed from the radiation-sensitive resin composition. Examples of the substrate on which the resist film is formed include conventionally known substrates such as silicon wafers, silicon dioxide, and aluminum-coated wafers. In addition, an organic or inorganic anti-reflective film disclosed in, for example, JP-B-6-12452 and JP-A-59-93448 may be formed on the substrate. Examples of the coating method include spin coating, casting coating, and roll coating. After coating, pre-baking (PB) may be performed as necessary to volatilize the solvent in the coating film. The PB temperature is usually 60° C. to 140° C., and preferably 80° C. to 120° C. The PB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds. The thickness of the resist film formed is preferably 10 nm to 1,000 nm, and more preferably 10 nm to 500 nm.

[0184] When performing immersion exposure, regardless of the presence or absence of the water-repellent polymer additive such as the high fluorine content resin in the radiation-sensitive resin composition, a protective film for immersion that is insoluble in the immersion liquid may be provided on the formed resist film in order to prevent direct contact between the immersion liquid and the resist film. As the protective film for immersion, either a solvent-peelable protective film that is peeled off with a solvent before the development step (see, for example, JP-A-2006-227632) or a developer-peelable protective film that is peeled off simultaneously with development in the development step (see, for example, WO2005-069076 and WO2006-035790) may be used. However, from the viewpoint of throughput, it is preferable to use a developer-peelable protective film for immersion.

[0185] When the next exposure step is carried out with radiation having a wavelength of 50 nm or less, it is preferable to use a resin having the structural units (a1) and (a2) as the base resin in the composition.

[0186] [Exposure process] In this step (step (2) above), the resist film formed in the resist film forming step (1) above is exposed to radiation through a photomask (or, in some cases, through an immersion medium such as water). Examples of radiation used for exposure include electromagnetic waves such as visible light, ultraviolet light, far ultraviolet light, EUV (extreme ultraviolet light), X-rays, and gamma rays; and charged particle beams such as electron beams and alpha rays, depending on the line width of the desired pattern. Among these, far ultraviolet light, electron beams, and EUV are preferred, ArF excimer laser light (wavelength 193 nm), KrF excimer laser light (wavelength 248 nm), electron beams, and EUV are more preferred, and electron beams and EUV with wavelengths of 50 nm or less, which are positioned as next-generation exposure technologies, are even more preferred.

[0187] When the exposure is performed by immersion exposure, the immersion liquid used may be, for example, water or a fluorine-based inert liquid. The immersion liquid is preferably a liquid that is transparent to the exposure wavelength and has a temperature coefficient of refractive index as small as possible so as to minimize distortion of the optical image projected onto the film, but when the exposure light source is an ArF excimer laser light (wavelength 193 nm), in addition to the above-mentioned viewpoint, water is preferably used from the viewpoint of ease of availability and ease of handling. When water is used, a small proportion of an additive that reduces the surface tension of water and increases the surfactant power may be added. It is preferable that this additive does not dissolve the resist film on the wafer and has a negligible effect on the optical coating on the lower surface of the lens. Distilled water is preferably used as the water to be used.

[0188] After the exposure, it is preferable to perform post-exposure baking (PEB) to promote dissociation of acid-dissociable groups of resins and the like by the acid generated from the radiation-sensitive acid generator by exposure in the exposed parts of the resist film. This PEB causes a difference in solubility in a developer between the exposed parts and the unexposed parts. The PEB temperature is usually 50°C to 180°C, and preferably 80°C to 130°C. The PEB time is usually 5 seconds to 600 seconds, and preferably 10 seconds to 300 seconds.

[0189] [Development process] In this step (step (3) above), the resist film exposed in the exposure step (2) above is developed. This allows a desired 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.

[0190] In the case of alkaline development, examples of the developer used in the development include an alkaline aqueous solution in which at least one of alkaline compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene is dissolved. Among these, an aqueous TMAH solution is preferred, and a 2.38 mass % aqueous TMAH solution is more preferred.

[0191] In the case of organic solvent development, examples of the organic solvent include hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents, or solvents containing organic solvents. Examples of the organic solvent include one or more of the solvents listed as the solvents for the radiation-sensitive resin composition described above. Among these, ester solvents and ketone solvents are preferred. As the ester solvent, acetate solvents are preferred, and n-butyl acetate and amyl acetate are more preferred. As the ketone solvent, chain ketones are preferred, and 2-heptanone is 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.

[0192] 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 (paddle method), a method in which developer is sprayed onto the substrate surface (spray method), and a method in which developer is continuously dispensed by scanning a developer dispensing nozzle at a constant speed over a substrate rotating at a constant speed (dynamic dispense method).

[0193] Another embodiment Hereinafter, another embodiment will be described focusing on the differences from the first embodiment. As another embodiment, there is a resin containing the structural unit (a2) and not containing a structural unit having a phenolic hydroxyl group, a radiation-sensitive resin composition containing a compound (B) and a radiation-sensitive acid generator (C), the content of the radiation-sensitive acid generator (C) being 10 parts by mass or more relative to 100 parts by mass of the resin, and a method for forming a resist pattern using the radiation-sensitive resin composition and ArF excimer laser light. In this embodiment, the resin is preferably a resin containing the structural unit (a2) and at least one structural unit selected from the group consisting of the structural unit (a3) ​​and the structural unit (a4). The content ratio of these structural units may be proportionally allocated to each structural unit based on the content ratio in the resin (A), with the amount of the resin (A) excluding the structural unit (a1) being 100 mol %. The preferable lower limit and upper limit of the above content are the same as those of the first embodiment, except that the content of the radiation-sensitive acid generator (C) is 10 parts by mass or more relative to 100 parts by mass of the resin. Moreover, preferred aspects of the types and contents of the compound (B), the solvent (D) and other optional components are the same as those in the first embodiment. With regard to the method for forming a resist pattern using the radiation-sensitive resin composition, preferred aspects of steps (1) to (3) are the same as those in the first embodiment, except that an ArF excimer laser beam is used in step (2). EXAMPLES

[0194] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Physical properties in the examples were measured as follows.

[0195] [Weight average molecular weight (Mw) and number average molecular weight (Mn)] The measurements were performed by gel permeation chromatography (GPC) using Tosoh GPC columns (G2000HXL: 2, G3000HXL: 1, G4000HXL: 1) under the following analytical conditions: flow rate: 1.0 mL / min, elution solvent: tetrahydrofuran, sample concentration: 1.0 mass%, sample injection amount: 100 μL, column temperature: 40° C., detector: differential refractometer, with monodisperse polystyrene as the standard. The dispersity (Mw / Mn) was calculated from the measurement results of Mw and Mn.

[0196] <Synthesis of resin (A)> The monomers used in the synthesis of each resin (A) in each of the Examples, Comparative Examples and Reference Examples are shown below. [ka]

[0197] [Synthesis Example 1] Synthesis of Resin (A-1) Compound (M-1) and compound (M-3) were dissolved in 1-methoxy-2-propanol (200 parts by mass relative to the total monomer amount) so that the molar ratio was 40 / 60. Next, azobisisobutyronitrile was added as an initiator at 6 mol% relative to the total monomer amount to prepare a monomer solution. Meanwhile, 1-methoxy-2-propanol (100 parts by mass relative to the total monomer amount) was added to an empty reaction vessel and heated to 85°C while stirring. Next, the monomer solution prepared above was dropped over 3 hours, and then heated at 85°C for another 3 hours, and the polymerization reaction was carried out for a total of 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled to room temperature.

[0198] The cooled polymerization solution was poured into hexane (500 parts by mass relative to the polymerization solution), and the precipitated white powder was filtered off. The filtered white powder was washed twice with 100 parts by mass of hexane relative to the polymerization solution, and then 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 the hydrolysis reaction was carried out at 70°C for 6 hours while stirring.

[0199] After the reaction was completed, the remaining solvent was distilled off, and the obtained solid was dissolved in acetone (100 parts by mass). The solution was dropped into 500 parts by mass of water to coagulate the resin, and the obtained solid was filtered off. The mixture was dried at 50° C. for 12 hours to synthesize a white powdery resin (A-1).

[0200] [Synthesis Examples 2-9] Resins (A-2) to (A-9) were synthesized in the same manner as in Synthesis Example 1 above, except that the monomer types and ratios were changed to the compositions shown in Table 1.

[0201] [Table 1]

[0202] [Synthesis Example 10] (Synthesis of Resin (A-10)) Monomer (M-3) and monomer (M-12) were dissolved in 2-butanone (200 parts by mass relative to the total amount of monomers) so that the molar ratio was 60 / 40, and AIBN (azobisisobutyronitrile) (3 mol% relative to the total of all monomers used, 100 mol%) was added as an initiator to prepare a monomer solution. 2-butanone (100 parts by mass relative to the total amount of monomers) was placed in an empty reaction vessel, and after purging with nitrogen for 30 minutes, the reaction vessel was heated to 80°C, and the monomer solution was dropped over 3 hours while stirring. The start of the dropwise addition was set as the start time of the polymerization reaction, and the polymerization reaction was carried out for 6 hours. After the polymerization reaction was completed, the polymerization solution was cooled with water to 30°C or less. 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 polymer (A-10) (yield: 80%). The Mw of the polymer (A-10) was 7,800, and the Mw / Mn was 1.51. 13 As a result of C-NMR analysis, the contents of the structural units derived from (M-3) and (M-12) were 58.9 mol % and 41.1 mol %, respectively.

[0203] [Synthesis Examples 11-12] Resins (A-11) and (A-12) were synthesized in the same manner as in Synthesis Example 10 above, except that the monomer types and ratios were changed to the compositions shown in Table 2.

[0204] [Table 2]

[0205] <Synthesis of compound (B)> (Synthesis of compound (B-1)) Compound (B-1) was synthesized according to the following reaction scheme. [ka]

[0206] 97.4 mmol of sodium hydrogen carbonate and 200 g of water were added to a reaction vessel. After confirming dissolution, 64.9 mmol of 2,6-dihydroxybenzoic acid was added. After stirring at room temperature for 1 hour, 300 g of dichloromethane and 64.9 mmol of triphenylsulfonium chloride were added. After stirring at room temperature for 2 hours, the organic layer was separated. The obtained organic layer was washed with water. After drying with sodium sulfate, the solvent was distilled off and recrystallization was performed to obtain the target compound (B-1).

[0207] (Synthesis of Compounds (B-2) to (B-9)) By appropriately selecting precursors and selecting the same recipe as in Example 1, onium salt compounds represented by the following formulas (B-2) to (B-6) were synthesized. [ka]

[0208] In the comparative example, a compound represented by the following formula (CB-1) was used as an acid diffusion controller. [ka]

[0209] <Radiation-sensitive acid generator (C)> As the radiation-sensitive acid generator (C), compounds represented by the following formulas (C-1) to (C-6) were used. [ka]

[0210] <Solvent (D)> As the solvent (D), the following solvent was used. D-1: Propylene glycol monomethyl ether acetate D-2: Propylene glycol 1-monomethyl ether D-3: Cyclohexanone D-4: γ-butyrolactone

[0211] [Example 1] A radiation-sensitive resin composition (R-1) was prepared by blending 100 parts by mass of resin (A-1), 20 parts by mass of (C-1) as a radiation-sensitive acid generator, 20 mol % of compound (B-1) as an acid diffusion controller relative to (C-1), 4,800 parts by mass of (D-1) as a solvent (D), and 2,000 parts by mass of (D-2).

[0212] [Examples 2 to 21 and Comparative Example 1] Radiation-sensitive resin compositions (R-2) to (R-21) and (CR-1) were prepared in the same manner as in Example 1, except that the types and amounts of each component shown in Table 3 below were used.

[0213] [Table 3]

[0214] <Resist pattern formation (1)> (EUV exposure, alkaline development) The radiation-sensitive resin composition prepared above was applied to the surface of a 12-inch silicon wafer on which a 20-nm-thick underlayer film (AL412 (Brewer Science)) was formed, using a spin coater (CLEAN TRACK ACT12, Tokyo Electron). After PB was performed at 130°C for 60 seconds, the wafer was cooled at 23°C for 30 seconds to form a resist film with a thickness of 50 nm. Next, the resist film was irradiated with EUV light using an EUV exposure machine (model "NXE3300", ASML, NA=0.33, illumination conditions: Conventional s=0.89, mask imecDEFECT32FFR02). The resist film was subjected to PEB at 130°C for 60 seconds. Then, the wafer was developed at 23°C for 30 seconds using a 2.38 wt% TMAH aqueous solution to form a positive 32 nm line and space pattern.

[0215] <Evaluation> The sensitivity, focal depth, and process window of each radiation-sensitive resin composition were evaluated by measuring each resist pattern formed as described above according to the following methods. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-4100") was used to measure the resist patterns. The evaluation results are shown in Table 4 below.

[0216] [sensitivity] In the above resist pattern formation (1), the exposure dose for forming a 32 nm line and space pattern was determined as the optimum exposure dose, and this optimum exposure dose was defined as the sensitivity (mJ / cm 2 The sensitivity was 30 mJ / cm 2 The following are considered "good": 30mJ / cm 2 If it exceeds this, it can be rated as "poor".

[0217] [depth of focus] In the resist pattern resolved at the above-mentioned optimum exposure dose, the dimensions were observed when the focus was changed in the depth direction, and the margin in the depth direction where the pattern dimensions were within 90% to 110% of the standard without bridges or residues was measured, and this measurement result was taken as the depth of focus. The depth of focus can be evaluated as good when it exceeds 50 nm, and as poor when it is 50 nm or less.

[0218] [Process Window] Patterns were formed from low to high exposure doses using a mask that forms 32 nm lines and spaces (1L / 1S). Generally, defects such as connection between patterns are seen on the low exposure dose side, and pattern collapse are seen on the high exposure dose side. The difference between the upper and lower limit values ​​of the resist dimensions where these defects are not seen is defined as the "CD margin", and a CD margin of 30 nm or more was judged to be good, and one less than 30 nm was judged to be bad. It is believed that the larger the CD margin value, the wider the process window.

[0219] [Table 4]

[0220] As is clear from the results in Table 4, the radiation-sensitive resin compositions of the Examples were all superior in sensitivity, depth of focus and process window (process margin) to the radiation-sensitive resin compositions of the Comparative Examples.

[0221] [Reference example 1] A radiation-sensitive resin composition (R-22) was prepared by mixing 100 parts by mass of (A-10) as a resin, 12 parts by mass of (C-1) as a radiation-sensitive acid generator, 20 mol % of (B-1) as an acid diffusion inhibitor relative to (C-1), 2,240 parts by mass of (D-1), 960 parts by mass of (D-3), and 30 parts by mass of (D-4) as a solvent, and filtering the mixture through a 0.2 μm membrane filter.

[0222] [Reference examples 2~6] Radiation-sensitive resin compositions (R-23) to (R-24) and (CR-1) to (CR-3) were prepared in the same manner as in Reference Example 1, except that the types and amounts of each component shown in Table 5 below were used.

[0223] [Table 5]

[0224] <Resist pattern formation (2)> (ArF exposure, alkaline development) A composition for forming a lower anti-reflective coating ("ARC66" by Brewer Science) was applied to the surface of a 12-inch silicon wafer using a spin coater ("CLEAN TRACK ACT12" by Tokyo Electron Co., Ltd.), and then heated at 205°C for 60 seconds to form a lower anti-reflective coating with a thickness of 105 nm. Each radiation-sensitive resin composition was applied onto this lower anti-reflective coating using the spin coater, and PB was performed at 100°C for 50 seconds. Then, it was cooled at 23°C for 30 seconds to form a resist film with a thickness of 90 nm. Next, this coating film was exposed through a mask pattern for forming a 38 nm line and space (1L / 1S) resist pattern using an ArF excimer laser immersion exposure device ("TWINSCAN XT-1900i" by ASML Co., Ltd.) under optical conditions of NA=1.35, Dipole35X (σ=0.97 / 0.77). After exposure, PEB was performed at 90°C for 50 seconds. Thereafter, paddle development was performed at 23°C for 30 seconds using a 2.38 mass% TMAH aqueous solution, followed by rinsing with ultrapure water for 7 seconds, and then spin drying at 2,000 rpm for 15 seconds to form a 40 nm line and space (1L / 1S) resist pattern.

[0225] <Evaluation> The formed resist patterns were measured according to the following methods to evaluate the sensitivity, CDU, and LWR of each radiation-sensitive resin composition. A scanning electron microscope (Hitachi High-Technologies Corporation's "CG-5000") was used to measure the resist patterns. The evaluation results are shown in Table 6 below.

[0226] [sensitivity] In the above resist pattern formation (2), the exposure dose required to form lines with a line width of 40 nm formed through a mask pattern for forming a pattern with a target dimension of 40 nm line and space was defined as the optimum exposure dose (Eop).

[0227] [CDU performance] A hole pattern formed by irradiating with the same exposure dose as the Eop calculated above was observed from above using the above scanning electron microscope. The hole diameter was measured at 16 points within an area of ​​400 nm on each side to calculate the average value, and this average value was then measured at any point for a total of 500 points. The 3 sigma value was calculated from the distribution of the measured values, and this was taken as the CDU performance (nm). The smaller the value, the smaller the variation in hole diameter over a long period and the better the CDU performance. CDU performance was evaluated as "good" when it was 6.0 nm or less, and "poor" when it exceeded 6.0 nm.

[0228] [LWR performance] A line and space pattern formed by irradiating with the same exposure dose as the Eop obtained in forming the resist pattern was observed from above the pattern using the above scanning electron microscope. A total of 500 points of line width variation were measured, and the 3 sigma value was calculated from the distribution of the measured values, which was taken as the LWR performance (nm). The smaller the LWR value, the smaller the line wobble and the better the performance. LWR performance was evaluated as "good" when it was 4.0 nm or less, and "poor" when it exceeded 4.0.

[0229] [Table 6]

[0230] As is clear from the results in Table 6 above, the radiation-sensitive resin compositions of Reference Examples 1 to 3 had good sensitivity, CDU performance, and LWR performance. [Industrial Applicability]

[0231] The radiation-sensitive resin composition and the method for forming a resist pattern of the present invention can improve sensitivity, depth of focus, and process margin compared to conventional methods, and can therefore be suitably used for forming fine resist patterns in the lithography process of various electronic devices such as semiconductor devices and liquid crystal devices.

Claims

1. A resin including a structural unit having a phenolic hydroxyl group and a structural unit having an acid dissociable group, A compound represented by the following formula (1): Including, The structural unit having an acid-dissociable group is a structural unit represented by the following formula (5): However, this radiation-sensitive resin composition excludes a resist composition containing Resin P-3 having repeating units represented by the following formulas M-3, M-8, M-22, and M-27 in a mass ratio of 30 / 30 / 10 / 30, a weight-average molecular weight of 4,000, and a dispersity of 1.4, and Compound Y represented by the following formula Q-3. 【Chemistry 1】 In formula (1), Ar is a substituted or unsubstituted aromatic ring having 6 to 20 carbon atoms. n is an integer of 2 to 4. Z + is a monovalent onium cation. Each of the multiple Y's is independently a polar group. However, at least one of the multiple Y's is COO - The carbon atom adjacent to the carbon atom to which the group is bonded is an —OH group or an —SH group. 【Chemistry 2】 (In the above formula (5): R 7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, R 8 is a hydrogen atom, R 9 and R 10 are combined with each other to represent a divalent alicyclic unsaturated hydrocarbon group having 3 to 20 carbon atoms constituted together with the carbon atom to which they are bonded, and L 1 represents a single bond or a divalent linking group; or R 7 is a hydrogen atom, a fluorine atom, a methyl group or a trifluoromethyl group, R 8 is a monovalent aromatic hydrocarbon group having 6 to 20 carbon atoms, R 9 and R 10 are each a divalent alicyclic group having 3 to 20 carbon atoms formed by combining these groups together with the carbon atom to which they are bonded, and L 1 is a single bond or a divalent linking group. 【Chemistry 3】 【Chemistry 4】

2. The radiation-sensitive resin composition according to claim 1, wherein the structural unit having the acid-dissociable group is a structural unit represented by the following formula (5-2): 【Chemistry 5】 (In the above formula (5-2), R 7 is the same as in the above formula (5). R 8 is a hydrogen atom. R 2T is a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms. i is an integer of 1 to 4.)

3. The above COO - 3. The radiation-sensitive resin composition according to claim 1, wherein the polar group bonded to the carbon atom adjacent to the carbon atom to which the group is bonded is an --OH group.

4. The radiation-sensitive resin composition according to any one of claims 1 to 3, wherein the compound represented by the formula (1) is a compound represented by the following formula (1-1): 【Chemistry 6】 (In formula (1-1), R p1 is an alkoxy group, an alkoxycarbonyl group, a halogen atom, or an amino group. m is an integer from 0 to 3. When m is 2 or 3, multiple R p1 are the same or different. + is the same as the above formula (1). q is an integer of 0 to 2. When q is 0, m+n is 5 or less. However, at least one OH group is a COO - The carbon atom adjacent to the carbon atom to which the group is bonded is

5. The radiation-sensitive resin composition according to claim 4, wherein q in the formula (1-1) is 0 or 1.

6. The radiation-sensitive resin composition according to claim 4 or 5, wherein n in the formula (1-1) is 2 or 3.

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

8. The radiation-sensitive resin composition according to any one of claims 1 to 7, further comprising a radiation-sensitive acid generator that generates an acid having a lower pKa than the acid generated from the compound represented by formula (1).

9. 9. The radiation-sensitive resin composition according to claim 8, wherein the content of the radiation-sensitive acid generator is 10 parts by mass or more based on 100 parts by mass of the resin.

10. 10. The radiation-sensitive resin composition according to claim 9, wherein the content of the radiation-sensitive acid generator is 10 parts by mass or more and 60 parts by mass or less based on 100 parts by mass of the resin.

11. 11. The radiation-sensitive resin composition according to claim 9, wherein the molar ratio of the content of the compound represented by formula (1) to the content of the radiation-sensitive acid generator is 3 mol % or more and 250 mol % or less.

12. 12. The radiation-sensitive resin composition according to claim 1, wherein the structural unit having a phenolic hydroxyl group is a structural unit derived from a hydroxystyrene.

13. 13. The radiation-sensitive resin composition according to claim 1, wherein the content of the structural unit having a phenolic hydroxyl group in the resin is from 5 mol % to 70 mol %.

14. A step of forming a resist film from the radiation-sensitive resin composition according to any one of claims 1 to 13; a step of exposing the resist film to light; and A method for forming a resist pattern comprising the step of developing the exposed resist film.

15. 15. The method for forming a resist pattern according to claim 14, wherein the exposure is carried out using extreme ultraviolet rays or electron beams.

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