Sulfonium salt, and acid generator comprising sulfonium salt

Abstract

To provide a novel photosensitive compound capable of exhibiting prompt decomposition and generating an acid under irradiation with light at a wavelength of 20 nm or less.SOLUTION: There is provided a sulfonium salt represented by formula (1), wherein Rf1 to Rf4 and Rf11 to Rf14 are the same or different and represent F, a fluoroalkyl group, H, a hydroxyl group, or an alkyl group; provided that at least two groups selected from Rf1 to Rf4 and Rf11 to Rf14 represent a fluorine atom or a fluoroalkyl group, n represents 0 or 1, and X- represents a monovalent counter anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel sulfonium salt, an acid generator containing the sulfonium salt, a photoresist containing the sulfonium salt, and a method for producing an electronic or optical device using the photoresist. [Background technology]

[0002] There is a demand for electronic and optical devices to be smaller while still maintaining a high capacity, and to achieve this, efforts are being made to increase the density and integration of semiconductor integrated circuits.

[0003] Photolithography is a well-known method for increasing the density and integration of semiconductor integrated circuits. Photolithography involves exposing a chemically amplified photoresist coating containing an acid generator (sometimes referred to as a "resist film") to light in a pattern, followed by a development process to form a resist film with the pattern formed. The resulting resist film with the pattern formed on it can be used as a mask to etch a substrate, thereby forming fine wiring and other features on the substrate.

[0004] In recent years, in the photolithography technology, there has been a demand for shorter wavelength exposure light in order to form finer patterns, and studies are underway to develop acid generators that are sensitive to ultrashort wavelength light (e.g., light with a wavelength of 20 nm or less) such as electron beams (EB) and extreme ultraviolet rays (EUV).

[0005] Patent Document 1 describes that, as acid generators sensitive to ultrashort wavelength light, salts of triarylsulfonium cations, such as [bis(p-fluorophenyl)](p-iodophenyl)sulfonium cations, which have an iodine atom and a fluorine atom or a fluoroalkyl group at the para-position relative to the position where the sulfur atom is bonded, and a counter anion, are sensitive to EB, and that when a resist film containing the salt is exposed to EB patternwise, a resist film having a fine pattern can be obtained. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-123579 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the salt described in Patent Document 1 still has insufficient sensitivity to light of ultrashort wavelengths. Furthermore, in photoresists, acid generators are generally present together with quenchers that are added to enhance the pattern resolution of the resist film, but the salts described in Patent Document 1 rapidly decompose in the presence of quenchers, resulting in a decrease or loss of photosensitivity. As a result, photoresists containing the salts and quenchers have poor storage stability, and although good patterns can be formed immediately after preparation, the problem is that pattern precision deteriorates significantly over time.

[0008] Therefore, an object of the present invention is to provide a novel compound having photosensitivity and acid generating ability, which is rapidly decomposed to generate an acid when irradiated with light having a wavelength of 20 nm or less. Another object of the present invention is to provide a novel compound that has photosensitivity, acid generating ability, and quencher resistance. Another object of the present invention is to provide a novel acid generator which is sensitive to light having a wavelength of 20 nm or less. Another object of the present invention is to provide a novel acid generator that is sensitive to light having a wavelength of 20 nm or less and has resistance to quenchers. Another object of the present invention is to provide a photoresist that can be used in photolithography using light having a wavelength of 20 nm or less. Another object of the present invention is to provide a method for manufacturing an electronic device or an optical device using the photoresist. [Means for solving the problem]

[0009] As a result of intensive investigations to solve the above-mentioned problems, the present inventors have found that when a fluorine atom or a fluoroalkyl group is bonded to a benzene ring contained in a triarylsulfonium cation at a position para to the position to which the sulfur atom is bonded, the fluorine atom or the fluoroalkyl group is specifically highly reactive and is easily decomposed in the presence of a quencher, making it impossible to obtain the effects (for example, photosensitivity or acid generating ability) that are attributable to the presence of a fluorine atom or a fluoroalkyl group. In the case of a sulfonium salt represented by the following formula (1), in which a fluorine atom or a fluoroalkyl group is bonded to a position that is ortho and / or meta to the position where the sulfur atom is bonded on the benzene ring contained in the triarylsulfonium cation, decomposition of the fluorine atom or the fluoroalkyl group is suppressed even in the presence of a quencher (i.e., it has quencher resistance), and it has excellent sensitivity to light with a wavelength of 20 nm or less, and when irradiated with light of the wavelength, it quickly decomposes to give an acid (H + X - ) was found to occur. The present invention was completed based on these findings.

[0010] That is, the present invention provides a sulfonium salt represented by the following formula (1): [ka] (In the formula, Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , Rf 14 are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf13 , and Rf 14 At least two selected from the group consisting of a fluorine atom and a fluoroalkyl group are selected. n is 0 or 1. X - indicates a monovalent counter anion)

[0011] The present invention also provides the above sulfonium salt, wherein the monovalent counter anion is a sulfonate anion or a nitrogen anion.

[0012] The present invention also provides an acid generator containing the sulfonium salt.

[0013] The present invention also provides a photoresist comprising the acid generator and an acid-reactive compound.

[0014] The present invention also provides the above photoresist, further comprising a quencher.

[0015] The present invention also provides a method for producing an electronic device or an optical device, which comprises a step of forming a pattern by photolithography using the photoresist. [Effects of the Invention]

[0016] The sulfonium salt represented by the above formula (1) (hereinafter, sometimes referred to as "sulfonium salt (1)") has excellent sensitivity to light with a wavelength of 20 nm or less, and when irradiated with light of this wavelength, it easily decomposes to form an acid (H + X - :X - is derived from the monovalent counter anion contained in the sulfonium salt (1). In other words, it has excellent photosensitivity and acid generating ability.

[0017] In addition, while general acid generators easily decompose in the presence of a quencher, resulting in a loss of photosensitivity or a decrease in photosensitivity, the sulfonium salt (1) is quencher-resistant and is inhibited from decomposing even in the presence of a quencher, thereby enabling the photosensitivity to be maintained at a high level.

[0018] Furthermore, the photoresist containing the sulfonium salt (1) and a quencher has excellent storage stability, and therefore can be prepared in advance and used at any time.

[0019] By using a photoresist containing the sulfonium salt (1) and performing photolithography using light with a wavelength of 20 nm or less, a resist film having a highly accurate fine pattern can be formed. By using the resulting resist film as an etching mask, it becomes possible to realize further increases in capacity and further miniaturization of electronic and optical devices. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Sulfonium salts] The sulfonium salt (1) of the present invention is a compound represented by the following formula (1). [ka] (In the formula, Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , Rf 14 are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , and Rf 14 At least two selected from the group consisting of a fluorine atom and a fluoroalkyl group are selected. n is 0 or 1. X - indicates a monovalent counter anion)

[0021] The alkyl group may be, for example, C 1-5The alkyl group (i.e., an alkyl group having 1 to 5 carbon atoms) includes a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, and a pentyl group. 1-3 Alkyl groups (i.e., alkyl groups having 1 to 3 carbon atoms) are preferred, and C 1-2 Alkyl groups (ie, alkyl groups having 1 to 2 carbon atoms) are particularly preferred.

[0022] The fluoroalkyl group is a group in which at least one hydrogen atom of an alkyl group has been substituted with a fluorine atom, and examples of the alkyl group include the same as those of the alkyl group.

[0023] The fluoroalkyl group may be a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms, that is, a perfluoroalkyl group (for example, perfluoro C 1-5 alkyl group) is preferred.

[0024] Among the compounds represented by the above formula (1), Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , and Rf 14 A compound in which 2 to 4 selected from the group consisting of: 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , and Rf 14 Particularly preferred are compounds in which two or four selected from the group represent a fluorine atom or a fluoroalkyl group.

[0025] Among the compounds represented by the above formula (1), Rf 1 , Rf 2 , Rf 3 , and Rf4 at least one selected from represents a fluorine atom or a fluoroalkyl group, and Rf 11 , Rf 12 , Rf 13 , and Rf 14 A compound in which at least one selected from the group represents a fluorine atom or a fluoroalkyl group is preferred in terms of excellent photosensitivity and / or decomposition efficiency.

[0026] Rf in the above formula (1) 1 , Rf 2 , Rf 3 , Rf 4 , Rf 11 , Rf 12 , Rf 13 , and Rf 14 Among these, the groups other than the groups representing a fluorine atom or a fluoroalkyl group are preferably hydrogen atoms or alkyl groups, with hydrogen atoms being particularly preferred, in terms of excellent photosensitivity and / or decomposition efficiency.

[0027] In the above formula (1), n represents 0 or 1. In particular, n preferably represents 1 in terms of particularly excellent quencher resistance. When n = 1, the position at which the iodine atom shown in parentheses is bonded is preferably the meta position relative to the position at which the sulfur atom shown in formula (1) is bonded, in terms of a large molecular dipole moment and excellent solubility in process solvents.

[0028] As the compound represented by the above formula (1), in view of excellent photosensitivity and / or decomposition efficiency, compounds in which the cationic moiety in formula (1) is represented by the following formulae (c1) to (c6) are preferred, and compounds in which the cationic moiety is represented by the following formulae (c1), (c2), (c4), and (c5) are particularly preferred. Furthermore, in view of particularly excellent quencher resistance, compounds in which the cationic moiety in formula (1) is represented by the following formulae (c4) to (c6) are preferred, and compounds in which the cationic moiety is represented by the following formulae (c4) and (c5) are particularly preferred, in view of particularly excellent quencher resistance and excellent photosensitivity and / or decomposition efficiency. [ka]

[0029] In the above formula, Rf 1 , Rf 2 , Rf 3 , Rf 11 , Rf 12 , Rf 13 is the same as above.

[0030] Examples of the counter anion include a halogen ion, a halogen oxo acid anion, a boron anion, a phosphate anion, a sulfate anion, a sulfonate anion, a nitrogen anion, a carboxylate anion, a methide anion, and SbF6. - , O.H. - , SCN - , NO2 - , NO3 - etc.

[0031] Examples of the halogen ions include Cl - , Br - , I - etc.

[0032] Examples of the halogen oxo acid anion include ClO4 - , IO3 - , BrO3 - etc.

[0033] The boron anion may be, for example, BF4 - Inorganic boron anions such as (C6F5)4B - , ((CF3)2C6H3)4B - , tetraphenylborate, tetrakis(monofluorophenyl)borate, tetrakis(difluorophenyl)borate, tetrakis(trifluorophenyl)borate, and other organic boron anions.

[0034] The phosphate anion may be, for example, PF6 - , PO4 3- Inorganic phosphate anions such as (CF3CF2)5PF -, (CF3CF2)4PF2 - , (CF3CF2)3PF3 - , (CF3CF2)2PF4 - , (CF3CF2)PF5 - and other organic phosphate anions.

[0035] The sulfonate anion is represented by, for example, the following formula (s1). R s1 -SO3 - (s1) (In the formula, R s1 indicates an organic group)

[0036] R s1 Examples of the organic group in the formula (I) include a hydrocarbon group which may have a substituent, a heterocyclic group which may have a substituent, and a group in which two or more of the groups are a single bond, -O-, -CO2-, -S-, -SO3-, and -SON(R s2 )-. s2 is a hydrogen atom or an alkyl group (e.g., C 1-30 The substituent represents an alkyl group. Examples of the substituent include a halogen atom such as a fluorine atom.

[0037] The hydrocarbon group includes a saturated hydrocarbon group and an unsaturated hydrocarbon group.

[0038] The hydrocarbon group may be, for example, C 1-30 It is a hydrocarbon group. 1-30 The hydrocarbon group may be, for example, C 1-30 Aliphatic hydrocarbon group, C 3-30 Alicyclic hydrocarbon group, C 6-30 Aromatic hydrocarbon groups and groups in which two or more of these are combined are included.

[0039] Said C 1-30 The hydrocarbon group is C 1-30 Alkyl group, C 2-30 Alkenyl group, C 6-15 Aryl group, C 6-15 Cycloalkylene group, C 6-15Bridged cyclic hydrocarbon groups and groups in which two of these are bonded together are preferred.

[0040] The heterocyclic group is a group in which one hydrogen atom has been removed from the structural formula of a heterocycle. The heterocycle includes aromatic heterocycles and non-aromatic heterocycles. Examples of such heterocycles include 3- to 10-membered rings (preferably 4- to 6-membered rings) containing carbon atoms and at least one heteroatom (e.g., oxygen atom, sulfur atom, nitrogen atom, etc.) as ring-constituting atoms, and condensed rings thereof.

[0041] Specific examples of the sulfonate anion include CH3SO3 - , C4H9SO3 - , CF3SO3 - , C2F5C4H4SO3 - , C4F9SO3 - , benzenesulfonate anion, p-toluenesulfonate anion, and camphorsulfonate anion.

[0042] Examples of the nitrogen anion include sulfonylimide anions represented by the following formula (n1). (R n1 SO2)2N - (n1) (Wherein, two R n1 are the same or different and represent organic groups)

[0043] R n1 The organic group in s1 Examples of the organic group are the same as those in the above.

[0044] Specific examples of the nitrogen anion include (FSO2)2N - , (CF3SO2)2N - , (C4F9SO2)2N - , (C2F5SO2)2N - etc.

[0045] The carboxylate anion is represented by, for example, the following formula (c1). R c1-COO - (c1) (In the formula, R c1 indicates an organic group)

[0046] R c1 The organic group in s1 Examples of the organic group are the same as those in the above.

[0047] Specific examples of the carboxylic acid anion include CF3CO2 - , CH3CO2 - , C2H5CO2 - , PhCO2 - etc.

[0048] The methide anion includes, for example, a sulfonylmethide anion represented by the following formula (m1). (R m1 SO2)3C - (m1) (wherein three R m1 are the same or different and represent organic groups)

[0049] R m1 The organic group in s1 Examples of the organic group are the same as those in the above.

[0050] Specific examples of the methide anion include (CF3SO2)3C - etc.

[0051] In addition to the above, the counter anion includes, for example, the anions described in JP-A-2013-47211, JP-A-2021-81708, JP-A-2013-80245, JP-A-2013-80240, and JP-A-2013-33161.

[0052] The counter anion is preferably a sulfonate anion or a nitrogen anion, because of its excellent solubility.

[0053] The chemical structure of the sulfonium salt (1) is, for example, 1 H-, 11B-, 13 C-, 19 F-, or 31 The compound can be identified by P-nuclear magnetic resonance spectroscopy, infrared absorption spectroscopy, elemental analysis, or the like.

[0054] The sulfonium salt (1) has excellent solubility in organic solvents, and its solubility in organic solvents (e.g., propylene glycol monomethyl ether acetate) at room temperature (e.g., 25°C) and normal pressure is, for example, 2% by weight or more (e.g., 2 to 50% by weight), preferably 3% by weight or more, more preferably 4% by weight or more, and particularly preferably 5% by weight or more.

[0055] Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; carbonates such as propylene carbonate, ethylene carbonate, 1,2-butylene carbonate, dimethyl carbonate, and diethyl carbonate; linear or cyclic esters such as ethyl acetate, butyl acetate, and ethyl lactate, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone; ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and diethylene glycol monobutyl ether. glycol diethers such as ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate; and ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl isoamyl ketone, and 2-heptanone. These can be used alone or in combination of two or more.

[0056] The organic solvent preferably contains at least one selected from the group consisting of ketones, chain esters, and glycol monoether monoesters.

[0057] The sulfonium salt (1) has high photosensitivity to light rays with wavelengths of 20 nm or less, such as EUV (extreme ultraviolet), EB (electron beam), and X-rays. Even without using a photosensitizer, light energy is directly transmitted to the sulfonium salt (1) by simply irradiating it with light of the wavelengths mentioned above, and photodecomposition proceeds rapidly, resulting in the formation of an acid (H + X - ) occurs.

[0058] Furthermore, sulfonium salt (1) has excellent stability (or quencher resistance or base resistance), and decomposition is suppressed even in the presence of a quencher when not irradiated with light. The residual rate of sulfonium salt (1), as determined by the method described in the Examples, is, for example, 35% or more, preferably 55% or more, and particularly preferably 70% or more.

[0059] The sulfonium salt (1) has the above properties and can therefore be suitably used as an acid generator (for example, a photoacid generator).

[0060] [Acid generator] The acid generator of the present invention contains at least the sulfonium salt (1). The acid generator may contain one type of the sulfonium salt (1) alone or two or more types in combination. The acid generator may also contain components other than the sulfonium salt (1). However, the proportion of the sulfonium salt (1) relative to all compounds (100% by weight) contained in the acid generator that decompose upon light irradiation to generate an acid is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0061] The acid generator has excellent solubility in organic solvents, and the amount of the acid generator (or the sulfonium salt (1)) that dissolves in 100 parts by weight of organic solvent at room temperature (e.g., 25°C) and normal pressure is, for example, 5 parts by weight or more, preferably 10 parts by weight or more, particularly preferably 15 parts by weight or more, and most preferably 20 parts by weight or more. Examples of the organic solvent include the same organic solvents in which the sulfonium salt (1) is soluble.

[0062] The acid generator has excellent sensitivity not only to light rays on the longer wavelength side but also to light rays with wavelengths of 20 nm or less, and when irradiated with the light rays, it easily decomposes to generate an acid (H + X - ) occurs.

[0063] Because the acid generator has the above properties, it can be suitably used as an acid generator for photoresists (particularly as an acid generator for photoresists used in photolithography using light having a wavelength of 20 nm or less).

[0064] Furthermore, the acid generator has excellent stability (or quencher resistance or base resistance), and decomposition is suppressed even in the presence of a quencher when not irradiated with light. The residual rate of the acid generator, as determined by the method described in the Examples, is, for example, 35% or more, preferably 55% or more, and particularly preferably 70% or more.

[0065] Therefore, the photoresist containing the acid generator and the quencher has excellent storage stability. The preparation time of the photoresist is not limited to immediately before use, but the photoresist can be prepared in advance and used at any time.

[0066] [Photoresist] The photoresist of the present invention contains the acid generator (or the sulfonium salt (1)) and an acid-reactive compound.

[0067] The content of the acid generator (or the sulfonium salt (1)) is, for example, 0.001 to 20% by weight, preferably 0.01 to 15% by weight, and particularly preferably 0.05 to 7% by weight, of the total amount of the acid-reactive compounds.

[0068] When the content of the acid generator (or the sulfonium salt (1)) is 0.001% by weight or more of the total amount of the acid-reactive compound, excellent sensitivity can be exhibited not only to light rays on the longer wavelength side but also to light rays with wavelengths of 20 nm or less. Furthermore, when the content is 20% by weight or less of the total amount of the acid-reactive compound, the effect of improving the resolution of the photoresist can be obtained.

[0069] (acid-reactive compounds) The acid-reactive compound is a compound whose solubility in an alkaline developer changes under the action of an acid. The photoresist of the present invention may contain one acid-reactive compound alone or two or more acid-reactive compounds in combination.

[0070] Acid-reactive compounds include negative-type photosensitive resins (QN) that are originally easily soluble in alkaline developers but become slightly soluble or insoluble in alkaline developers when exposed to an acid, and positive-type photosensitive resins (QP) that are originally slightly soluble or insoluble in alkaline developers but become soluble in alkaline developers when exposed to an acid.

[0071] Therefore, the photoresist contains the following composition (1) and composition (2). Composition (1): A composition containing the acid generator and a negative photosensitive resin (QN). Composition (2): A composition containing the acid generator and a positive photosensitive resin (QP).

[0072] The negative photosensitive resin (or negative chemically amplified resin; QN) may be, for example, a composition containing a phenolic hydroxyl group-containing resin (QN1) and a crosslinking agent (QN2).

[0073] The phenolic hydroxyl group-containing resin (QN1) is a resin containing a phenolic hydroxyl group that is readily soluble in an alkaline developer and becomes poorly soluble or insoluble in the alkaline developer upon reaction with a crosslinking agent, and examples thereof include novolak resins, polyhydroxystyrenes, copolymers of hydroxystyrene and styrene, copolymers of hydroxystyrene, styrene and a (meth)acrylic acid derivative, phenol-xylylene glycol condensation resins, cresol-xylylene glycol condensation resins, polyimides containing phenolic hydroxyl groups, polyamic acids containing phenolic hydroxyl groups, and phenol-dicyclopentadiene condensation resins. These may be used alone or in combination of two or more.

[0074] The phenolic hydroxyl group-containing resin (QN1) may contain a phenolic low molecular weight compound as part of its components.

[0075] The phenolic hydroxyl group-containing resin (QN1) has a weight average molecular weight (Mw) of, for example, 2,000 to 20,000 in terms of polystyrene as measured by GPC.

[0076] The crosslinking agent (QN2) is a compound that can crosslink the phenolic hydroxyl group-containing resin (QN1) with, for example, an acid generated from an acid generator, thereby making it difficult to dissolve or insolubilize it. Examples include bisphenol A-based epoxy compounds, bisphenol F-based epoxy compounds, bisphenol S-based epoxy compounds, novolac resin-based epoxy compounds, resol resin-based epoxy compounds, poly(hydroxystyrene)-based epoxy compounds, oxetane compounds, methylol group-containing melamine compounds, methylol group-containing benzoguanamine compounds, methylol group-containing urea compounds, methylol group-containing phenolic compounds, alkoxyalkyl group-containing melamine compounds, alkoxyalkyl group-containing benzoguanamine compounds, alkoxyalkyl group-containing urea compounds, alkoxyalkyl group-containing phenolic compounds, carboxymethyl group-containing melamine resins, carboxymethyl group-containing benzoguanamine resins, carboxymethyl group-containing urea resins, carboxymethyl group-containing phenolic resins, carboxymethyl group-containing melamine compounds, carboxymethyl group-containing benzoguanamine compounds, carboxymethyl group-containing urea compounds, and carboxymethyl group-containing phenolic compounds. These may be used alone or in combination of two or more.

[0077] The content of the crosslinking agent (QN2) is, for example, 10 to 40 mol % relative to the total acidic functional groups in the phenolic hydroxyl group-containing resin (QN1), from the viewpoint of efficiently making the phenolic hydroxyl group-containing resin (QN1) less soluble or insoluble in an alkaline developer.

[0078] Examples of the positive photosensitive resin (or positive chemically amplified resin; QP) include an alkali-soluble resin into which an acid-dissociable group has been introduced as a protecting group (protected group-introduced resin; QP1).

[0079] The protecting group-introduced resin (QP1) is a resin in which some or all of the hydrogen atoms of acidic functional groups (such as phenolic hydroxyl groups, carboxyl groups, sulfonyl groups, etc.) in an alkali-soluble resin have been substituted with acid-dissociable groups.

[0080] The protecting group-introduced resin (QP1) is a resin that is insoluble or poorly soluble in alkaline developers, and the acid (H + X - When the acid-dissociable group dissociates due to the reaction with the hydroxyl group, the resin changes to an alkali-soluble resin that is readily soluble in an alkaline developer.

[0081] The alkali-soluble resin is, for example, a resin having an HLB value of 4 to 19 (preferably 5 to 18, particularly preferably 6 to 17).

[0082] The alkali-soluble resins include phenolic hydroxyl group-containing resins, carboxyl group-containing resins, and sulfonic acid group-containing resins.

[0083] Examples of the phenolic hydroxyl group-containing resin include the same resins as the above-mentioned phenolic hydroxyl group-containing resin (QN1).

[0084] The carboxyl group-containing resin is not particularly limited as long as it is a polymer having a carboxyl group, and examples thereof include a homopolymer of a carboxyl group-containing vinyl monomer (Ba) and a copolymer of a carboxyl group-containing vinyl monomer (Ba) and a hydrophobic group-containing vinyl monomer (Bb).

[0085] An example of the carboxyl group-containing vinyl monomer (Ba) is (meth)acrylic acid.

[0086] The hydrophobic group-containing vinyl monomer (Bb) is C 1-20 Examples thereof include (meth)acrylic acid esters (Bb1) such as alkyl (meth)acrylates and alicyclic group-containing (meth)acrylates, and aromatic hydrocarbon monomers (Bb2) such as hydrocarbon monomers having a styrene skeleton and vinylnaphthalene.

[0087] The sulfonic acid group-containing resin is not particularly limited as long as it is a polymer having a sulfonic acid group, and examples thereof include copolymers of a sulfonic acid group-containing vinyl monomer (Bc) such as vinyl sulfonic acid or styrene sulfonic acid and a hydrophobic group-containing vinyl monomer (Bb).

[0088] Examples of the acid-dissociable group possessed by the protecting group-introduced resin (QP1) include 1-substituted methyl groups such as a methoxymethyl group, a benzyl group, and a tert-butoxycarbonylmethyl group; 1-substituted ethyl groups such as a 1-methoxyethyl group and a 1-ethoxyethyl group; 1-branched alkyl groups such as a tert-butyl group; silyl groups such as a trimethylsilyl group; germyl groups such as a trimethylgermyl group; alkoxycarbonyl groups such as a tert-butoxycarbonyl group; acyl groups; and cyclic acid-dissociable groups such as a tetrahydropyranyl group, a tetrahydrofuranyl group, a tetrahydrothiopyranyl group, and a tetrahydrothiofuranyl group. These groups may be contained alone or in combination of two or more.

[0089] The introduction rate of acid-dissociable groups in the protecting group-introduced resin (QP1) {the ratio of the number of acid-dissociable groups to the total number of unprotected acidic functional groups and acid-dissociable groups in the protecting group-introduced resin (QP1)} cannot be generally defined depending on the type of acid-dissociable group and the alkali-soluble resin into which the group is introduced, but is, for example, 10 to 100%, and preferably 15 to 100%.

[0090] The weight average molecular weight (Mw) of the protecting group-introduced resin (QP1) measured by GPC in terms of polystyrene is, for example, 1,000 to 150,000, and preferably 3,000 to 100,000.

[0091] (Other ingredients) In addition to the above components, the photoresist of the present invention may contain one or more other components as needed, such as a quencher, organic solvent, pigment, dye, photosensitizer, dispersant, surfactant, filler, leveling agent, antifoaming agent, antistatic agent, UV absorber, pH adjuster, surface modifier, plasticizer, drying accelerator, etc.

[0092] (Quencher) A quencher is a compound that neutralizes the acid generated from the acid generator in the resist film, thereby preventing the acid from diffusing and resulting in a decrease in the pattern resolution of the resist film.

[0093] As the quencher, a basic substance can be used. + X - A salt that generates an acid weaker than the quencher may also be used.

[0094] Examples of basic substances include nitrogen-containing organic compounds such as amines, ammonium salts, etc. These may be used alone or in combination of two or more.

[0095] The amines include aliphatic and aromatic amines.

[0096] Examples of aliphatic amines include primary amines such as hexylamine and octylamine; secondary amines such as dibutylamine, dipentylamine and dihexylamine; and tertiary amines such as trimethylamine, tributylamine, trihexylamine, trioctylamine, N,N-diisopropylethylamine and ethylenediamine.

[0097] Examples of aromatic amines include compounds in which an amino group is bonded to an aromatic hydrocarbon ring, such as naphthylamine, aniline, and diisopropylaniline; and heteroaromatic amines, such as pyridine, methylpyridine, and bipyridine.

[0098] Examples of ammonium salts include tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrabutylammonium lactate.

[0099] As the quencher, an amine is preferred, and an aliphatic amine or an aromatic amine is particularly preferred. The content of the quencher is, for example, 0.01 to 50 parts by weight, and preferably 0.5 to 30 parts by weight, relative to 100 parts by weight of the acid generator (or the sulfonium salt (1)), from the viewpoint of improving the resolution of the photoresist.

[0100] The content of the quencher is, for example, 0.0005 to 10% by weight, and preferably 0.005 to 5% by weight, based on the total amount of the acid-reactive compounds, from the viewpoint of improving the resolution of the photoresist.

[0101] (organic solvent) The organic solvent may be any solvent capable of dissolving the photosensitive resin and imparting good coating properties to the photoresist, but it is preferable to use a solvent with a boiling point of 200°C or less, as this allows the photoresist to be easily dried after application. Preferred organic solvents include aromatic hydrocarbons such as toluene; alcohols such as ethanol and methanol; ketones such as cyclohexanone, methyl ethyl ketone, and acetone; esters such as ethyl acetate, butyl acetate, and ethyl lactate; and glycol monoether monoesters such as propylene glycol monomethyl ether acetate. These may be used alone or in combination of two or more.

[0102] The photoresist of the present invention can be prepared, for example, by dissolving the acid generator (or the sulfonium salt (1)) in an organic solvent, and then adding and mixing a photosensitive resin and, if necessary, other components thereto.

[0103] The photoresist of the present invention contains a sulfonium salt (1) that has high sensitivity to light with a wavelength of 20 nm or less. Therefore, even when irradiated with light with a wavelength of 20 nm or less, the photoresist efficiently converts acid (H + X - ) can be generated. The generated acid (H + X - ), the solubility of the photosensitive resin in the exposed area in the developer changes. When the photosensitive resin is a negative photosensitive resin, the acid (H + X - On the other hand, when the photosensitive resin is a positive photosensitive resin, the solubility is reduced by the addition of an acid (H + X -) increases the solubility. Therefore, by using the photoresist of the present invention, an etching mask can be formed with high precision by photolithography.

[0104] The photoresist of the present invention also contains a sulfonium salt (1) that is resistant to quenchers, and therefore has excellent storage stability and can stably exhibit excellent photosensitivity over a long period of time.The photoresist can be prepared in advance and used at any time.

[0105] [Method of manufacturing electronic or optical devices] The method for producing an electronic device or an optical device of the present invention includes a step of forming a pattern by photolithography using the photoresist.

[0106] The step of forming a pattern by photolithography using the photoresist is preferably a step of forming an etching mask on a substrate through the following steps 1 to 3.

[0107] Step 1: forming a coating of the photoresist on a substrate Step 2: A step of irradiating the coating film with light in a pattern shape Step 3: Alkaline development

[0108] (Process 1) This step is a step of forming a coating film of the photoresist on a substrate to be etched. The coating film can be formed by applying the photoresist to the substrate by a known method such as spin coating, curtain coating, roll coating, spray coating, or screen printing, and then drying the applied photoresist.

[0109] (Process 2) In this step, the coating film obtained through step 1 is irradiated with light in a pattern shape, for example, by irradiating the coating film with light through a patterned photomask. The light used for the light irradiation is not particularly limited as long as it can decompose the sulfonium salt (1) to generate a strong acid, but from the viewpoint of forming a fine pattern, it is preferable to use light having a wavelength of 20 nm or less, such as EUV (extreme ultraviolet), EB (electron beam), or X-ray.

[0110] After the light irradiation, it is preferable to heat the film at a temperature of 60 to 200°C for about 0.1 to 120 minutes, since this can increase the difference in solubility in an alkaline developer between the exposed and unexposed areas, thereby obtaining the effect of improving the resolution of the pattern.

[0111] (Step 3) In this step, the photoresist coating film that has been subjected to step 2 is subjected to an alkaline development treatment.

[0112] The alkaline development treatment is carried out by applying the alkaline developer to the coating film by, for example, a dipping method, a shower method, a spray method or the like.

[0113] The alkaline developer may contain methanol, ethanol, isopropyl alcohol, tetrahydrofuran, N-methylpyrrolidone, or the like.

[0114] The alkaline development treatment is carried out by applying the alkaline developer to the coating film by a method such as dipping, showering, or spraying.

[0115] The temperature of the alkaline developer is, for example, 25 to 40° C. The alkaline development time is determined appropriately depending on the thickness of the coating film, but is, for example, about 1 to 5 minutes.

[0116] A resist film having a pattern can be formed on a substrate through step 3. By etching a substrate using the resist film having a pattern thus obtained as an etching mask, an electronic device or an optical device having a highly accurate wiring pattern or the like can be manufactured.

[0117] Examples of the electronic device include display devices such as organic EL displays and liquid crystal displays; input devices such as touch panels; light-emitting devices; sensor devices; and MEMS (Micro Electro Mechanical Systems) devices such as optical scanners, optical switches, acceleration sensors, pressure sensors, gyroscopes, microchannels, and inkjet heads.

[0118] The optical devices include, for example, optical waveguides, metalenses, semiconductor lasers, and the like.

[0119] The above-described configurations and combinations of the present invention are merely examples, and additions, omissions, substitutions, and modifications of the configurations are possible as appropriate without departing from the spirit of the present invention. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Furthermore, the present disclosure is not limited by the embodiments. [Example]

[0120] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0121] Example 1 Bis(2-trifluoromethylphenyl) sulfoxide was synthesized in the same manner as described in JP 2022-126072 A.

[0122] To 1.0 g of the obtained bis(2-trifluoromethylphenyl) sulfoxide, 18 g of iodobenzene was added and stirred to obtain a dispersion. 2.2 g of trifluoromethanesulfonic acid was added dropwise to the resulting dispersion, followed by adding 1.2 g of phosphoric anhydride in three portions to the dispersion, and stirring at room temperature for 2 hours to complete the reaction. After 5.4 g of ion-exchanged water was added to the reaction system to stop the reaction, 27 g of toluene was added and the precipitated solid was collected by filtration to obtain 1.2 g of a sulfonium salt [acid generator (1)], which is a salt of a cation and anion shown in the table below.

[0123] Example 2 The same procedure as in Example 1 was carried out except that iodobenzene was changed to 29 g of o-diiodobenzene, to obtain 1.4 g of a sulfonium salt [acid generator (2)], which is a salt of a cation and an anion shown in the table below.

[0124] Example 3 Using 96.5 g of 1-bromo-3,5-difluorobenzene, 13.4 g of magnesium, and 400 g of tetrahydrofuran, a tetrahydrofuran solution of 3,5-difluorophenylmagnesium bromide was obtained by a conventional method.

[0125] To the resulting solution, a diluted solution prepared by diluting 28.6 g of thionyl chloride with 50 g of tetrahydrofuran was added dropwise at a rate such that the temperature in the system did not exceed −5° C. After the addition was completed, the reaction was continued at room temperature for 1 hour to complete the reaction. The reaction solution was added to 500 g of ion-exchanged water at a rate that did not cause the system temperature to exceed 15°C, and the mixture was stirred for 1 hour. Then, 300 g of ethyl acetate was added, and the mixture was stirred for 1 hour. The aqueous layer was removed, and the organic layer was washed three times with 300 g of ion-exchanged water. The organic layer was then desolvated, and the resulting brown residue was recrystallized with cyclohexane. This yielded 26.0 g of bis(3,5-difluorophenyl) sulfoxide.

[0126] 6.86 g of the obtained bis(3,5-difluorophenyl) sulfoxide was dissolved in 78.3 g of iodobenzene, and 8.46 g of trifluoromethanesulfonic anhydride was added dropwise at a rate such that the temperature in the system did not exceed -5°C. After the dropwise addition was completed, the reaction was continued at room temperature for 1 hour to complete the reaction. The supernatant was removed, and the oily precipitate was added to 50 g of ion-exchanged water at a rate that did not cause the system temperature to exceed 15°C. Then, 75 g of tetrahydrofuran and 30 g of toluene were added, and the mixture was stirred for 1 hour. The upper layer was removed, and the remaining liquid was washed twice with 30 g of toluene. The washed solution was neutralized with sodium bicarbonate, extracted with 100 g of dichloromethane, and the aqueous layer was removed to obtain an organic layer. The resulting organic layer was then washed three times with 50 g of ion-exchanged water and the solvent was removed. When crystals began to precipitate, 150 g of methyl tert-butyl ether was added to precipitate white crystals. The crystals were collected by filtration and dried under reduced pressure to obtain 8.23 g of a sulfonium salt [acid generator (3)], a salt of the cation and anion shown in the table below.

[0127] Example 4 To 1.0 g of bis(3,5-difluorophenyl) sulfoxide, 2.2 g of m-diiodobenzene and 1.4 g of dichloromethane were added and stirred to obtain a dispersion. To the resulting dispersion, 2.7 g of trifluoromethanesulfonic acid was added dropwise. Subsequently, 0.58 g of phosphoric anhydride was added in two portions. The mixture was then stirred at room temperature for 1.5 hours to complete the reaction, and 30 g of deionized water was added to terminate the reaction. 17 g of toluene was then added and stirred, and the precipitated solid was collected by filtration to obtain 1.6 g of a sulfonium salt [acid generator (4)], which is a salt of a cation and anion shown in the table below.

[0128] Example 5 2.2 g of o-diiodobenzene was added to 1.0 g of bis(3,5-difluorophenyl) sulfoxide and stirred to obtain a dispersion. To the resulting dispersion, 2.7 g of trifluoromethanesulfonic acid was added dropwise. Subsequently, 0.68 g of phosphoric anhydride was added in two portions. The mixture was then stirred at room temperature for 1.5 hours to complete the reaction, and 30 g of deionized water was added to terminate the reaction. 17 g of toluene was then added and stirred, and the precipitated solid was collected by filtration to obtain 1.8 g of a sulfonium salt [acid generator (5)], which is a salt of a cation and anion shown in the table below.

[0129] (evaluation) The acid generators obtained in the examples and the acid generators shown in the comparative examples in Table 2 were evaluated for solvent solubility, photosensitivity, and quencher resistance by the following methods. The results are shown in the table below.

[0130] <Solvent solubility> 0.1 g of an acid generator was placed in a test tube, and propylene glycol monomethyl ether acetate was added in 0.2 g increments under normal pressure and at a temperature controlled at 25°C until the acid generator was completely dissolved. The concentration of the acid generator when completely dissolved was determined, and the solvent solubility was evaluated according to the following criteria. Evaluation criteria Good (◎): Acid generator concentration is 5% by weight or more Acceptable (○): Acid generator concentration is 2% by weight or more and less than 5% by weight Unacceptable (×): Acid generator concentration is less than 2% by weight

[0131] <Light sensitivity> The acid generator was diluted with acetonitrile to a molar concentration of 2.5 mM, and rhodamine B base (an acid coloring reagent, manufactured by Sigma-Aldrich) was added to a molar concentration of 2.5 mM to prepare a sample solution.

[0132] The obtained sample solution was placed in a quartz cell with an optical path length of 1 cm, and then exposed to light at an accelerating voltage of 100 kV and an integrated light intensity of 50 μC / cm using an exposure system (JEOL JBX-9300, manufactured by JEOL Ltd.). 2 The electron beam exposure was carried out under the following conditions. When the acid generator in the sample solution decomposes upon exposure to light and generates acid, the generated acid reacts with the rhodamine B base, increasing the absorbance at 556 nm. Therefore, the amount of acid generated can be determined by measuring the absorbance at 556 nm after exposure. The absorbance was measured using a spectrophotometer (UV-vis). The acid concentration in the sample solution after exposure was determined from the absorbance at 556 nm of the sample solution after exposure using a calibration curve (standard substance: p-toluenesulfonic acid). The acid generation rate was calculated from the following formula, and the photosensitivity was evaluated from the calculated acid generation rate according to the following criteria. Acid generation rate (%) = acid concentration after exposure (mM) / acid generator concentration before exposure (mM) × 100 (Evaluation criteria) Excellent (◎): Acid generation rate is 50% or more Good (○): Acid generation rate is 40% or more but less than 50% Acceptable (△): Acid generation rate is 20% or more but less than 40% Unacceptable (×): Acid generation rate is less than 20%

[0133] <Quencher resistance> A 5% solution of the acid generator in propylene glycol monomethyl ether was prepared, to which was added an equimolar amount of tetramethylammonium hydroxide (10% solution) to the acid generator, and the mixture was shaken to obtain a test liquid. Immediately after preparing the test solution, 0.05 g was sampled, diluted 50 times, and subjected to HPLC analysis, and the initial area (Ar1) of the acid generator was recorded. Furthermore, after storing the test solution at room temperature for one day, HPLC analysis was carried out in the same manner as above, and the area (Ar2) of the acid generator after storage was recorded. The residual rate of the acid generator was calculated from the following formula, and the quencher resistance was evaluated according to the following criteria. Acid generator remaining rate (%) = [Ar2 / Ar1] x 100 The higher the residual rate of the acid generator, the more stable it is against the base component of the quencher, and the higher the quencher resistance. (Evaluation criteria) Excellent (◎): Residual rate of acid generator is 70% or more Good (○): Residual rate of acid generator is 55% or more but less than 70% Acceptable (△): Residual rate of acid generator is 35% or more but less than 55% Unacceptable (×): Less than 35% of the acid generator remains

[0134] [Table 1]

[0135] [Table 2]

[0136] As can be seen from Tables 1 and 2, the acid generator (or sulfonium salt (1)) of the present invention has significantly improved solvent solubility and improved photosensitivity to electron beams compared to the case where it does not contain an iodine atom. Furthermore, the acid generator (or sulfonium salt (1)) of the present invention has superior quencher resistance compared to a compound containing a fluorine atom or a fluoroalkyl group at the para-position relative to the sulfur atom. Furthermore, the photosensitivity to electron beams is also improved.

[0137] The acid generator (or sulfonium salt (1)) of the present invention has the above-mentioned properties and can therefore be suitably used as an acid generator for photoresists (particularly as an acid generator for photoresists used in photolithography using light having a wavelength of 20 nm or less). Furthermore, photoresists containing the acid generator (or sulfonium salt (1)) of the present invention have excellent storage stability. Furthermore, by performing photolithography (particularly photolithography using light having a wavelength of 20 nm or less) using a photoresist containing the acid generator (or sulfonium salt (1)) of the present invention, fine patterns can be formed with high precision, thereby realizing increased capacity and miniaturization of electronic and optical devices.

Claims

1. A sulfonium salt represented by the following formula (1): 【Chemical 1】 (wherein, Rf １ , Rf ２ , Rf ３ , Rf ４ , Rf １１ , Rf １２ , Rf １３ , Rf １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. １ , Rf ２ , Rf ３ , Rf ４ , Rf １１ , Rf １２ , Rf １３ , and Rf １４ At least two selected from the above represent a fluorine atom or a fluoroalkyl group, and n represents 0 or 1. － indicates a monovalent counter anion)

2. 2. The sulfonium salt according to claim 1, wherein the monovalent counter anion is a sulfonate anion or a nitrogen anion.

3. An acid generator comprising the sulfonium salt according to claim 1 or 2.

4. A photoresist comprising the acid generator of claim 3 and an acid-reactive compound.

5. The photoresist of claim 4 further comprising a quencher.

6. A method for manufacturing an electronic device, comprising the step of forming a pattern by photolithography using the photoresist according to claim 4.

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