Sulfonium salt and acid generator

Abstract

To provide a novel sulfonium salt which has superior solvent solubility and sensitivity to ultra-short wavelength light, and which exhibits acid generation by rapid decomposition upon ultra-short wavelength light irradiation.SOLUTION: The present invention provides a sulfonium salt represented by formula (1), wherein Rf1, Rf2, Rf11, and Rf12 represent F or a fluoroalkyl group; R1 and R11 represent a hydrogen atom, an alkyl group, etc.; n represents an integer of 1 to 3; 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 manufacturing an electronic device or an optical device using the photoresist.

Background Art

[0002] The increase in capacity and miniaturization of electronic devices and optical devices are achieved by increasing the density and integration of semiconductor integrated circuits. And, as a method for increasing the density and integration of semiconductor integrated circuits, there is a method of forming a fine pattern on a semiconductor by making full use of photolithography technology.

[0003] In photolithography technology, pattern formation is performed by performing an exposure process and a development process on a coating film of a chemically amplified photoresist containing a photoacid generator and an acid-reactive compound (this may be referred to as a "resist film"). And, by shortening the wavelength of the light beam used in the exposure process, the pattern can be miniaturized.

[0004] Triphenylsulfonium salts are known as photoacid generators (see Patent Document 1). And, by performing an exposure process using a KrF excimer laser or an ArF excimer laser on a coating film of a photoresist containing a triphenylsulfonium salt, a pattern can be formed with high accuracy. However, the photoresist has low sensitivity to light beams with ultra-short wavelengths such as EUV (extreme ultraviolet rays), EB (electron beams), and X-rays, and it was difficult to use in photolithography using EUV or the like.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Then, the inventors of the present invention have found that when a fluorine atom or a fluoroalkyl group is added to a triarylsulfonium cation, the sensitivity to ultra-short wavelength light is improved but still not sufficient, and when an iodine atom is added together with the fluorine atom or the fluoroalkyl group, sufficient sensitivity to ultra-short wavelength light can be obtained. However, it has been found that when an iodine atom is added to a triarylsulfonium cation together with a fluorine atom or a fluoroalkyl group, the solvent solubility decreases.

[0007] In addition, in a photoresist, an acid generator generally coexists with a quencher added to improve pattern resolution. However, a salt of a triarylsulfonium cation having an iodine atom and having a fluorine atom or a fluoroalkyl group at a position para to the position where a sulfur atom is bonded, such as [bis(p-fluorophenyl)](p-iodophenyl)sulfonium cation, and a counter anion, has been found to rapidly decompose in the presence of a quencher, resulting in a decrease in photosensitivity or a loss of photosensitivity.

[0008] Therefore, an object of the present invention is to provide a novel sulfonium salt having excellent solvent solubility, sensitivity to ultra-short wavelength light, and the property of rapidly decomposing upon irradiation with ultra-short wavelength light to generate an acid. Another object of the present invention is to provide a novel sulfonium salt having excellent solvent solubility, sensitivity to ultra-short wavelength light, and quencher resistance. Another object of the present invention is to provide a novel acid generator having excellent solvent solubility, sensitivity to ultra-short wavelength light, and the property of rapidly decomposing upon irradiation with ultra-short wavelength light to generate an acid. Another object of the present invention is to provide a novel acid generator having excellent solvent solubility, sensitivity to ultra-short wavelength light, and quencher resistance. Another object of the present invention is to provide a novel photoresist that can be used in photolithography using light rays of an ultrashort wavelength. 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 Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that among the three benzene rings contained in a triarylsulfonium cation having a fluorine atom or a fluoroalkyl group and an iodine atom, when a specific polar group is imparted to the benzene ring having a fluorine atom or a fluoroalkyl group, it is possible to improve the sensitivity to light rays of an ultrashort wavelength while suppressing a decrease in solvent solubility, and when a sulfonium salt containing the cation to which the polar group is imparted is blended into a photoresist in a state of being dissolved in a solvent, the sulfonium salt can be uniformly dispersed in the photoresist, and when an exposure treatment and a development treatment are performed, it is possible to form a pattern with good accuracy. And, the sulfonium salt represented by the following formula (1) has excellent solvent solubility and sensitivity to light rays of an ultrashort wavelength, and also has quencher resistance in which decomposition is suppressed even in the coexistence of a quencher. It has been found that a photoresist containing the sulfonium salt represented by the following formula (1) and a quencher is excellent in storage stability and can maintain excellent pattern accuracy not only immediately after preparation but also after a lapse of time from the preparation. The present invention has been completed based on these findings.

[0010] That is, the present invention provides a sulfonium salt represented by the following formula (1).

Chemical Formula

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

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

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

[0014] The present invention also provides a method for manufacturing an electronic device or an optical device, including a step of forming a pattern by photolithography using the photoresist.

Advantages of the Invention

[0015] The sulfonium salt represented by the above formula (1) (hereinafter sometimes referred to as "sulfonium salt (1)") has excellent sensitivity to light rays of an extremely short wavelength, and by irradiating with light rays of said wavelength, it easily decomposes to generate an acid (H + X - :X - derived from the monovalent counter anion contained in the sulfonium salt (1)). Further, the sulfonium salt (1) has excellent solvent solubility.

[0016] Since the sulfonium salt (1) has both the above characteristics, when it is blended into a photoresist in a dissolved state in a solvent, it can be uniformly dispersed in the photoresist. When an exposure treatment and a development treatment using light rays of an extremely short wavelength are performed on the resist film obtained using the photoresist, a fine pattern can be formed with high accuracy.

[0017] Furthermore, general acid generators are prone to decomposition and loss of photosensitivity, or a decrease in photosensitivity, in the presence of a quencher. However, sulfonium salt (1) has quencher resistance, and its decomposition is suppressed even in the presence of a quencher, allowing it to maintain high photosensitivity. When a quencher is added to a photoresist containing sulfonium salt (1), a resist film with improved pattern resolution can be obtained.

[0018] Moreover, a photoresist containing sulfonium salt (1) and a quencher has excellent storage stability, so it can be prepared in advance and used at any timing.

[0019] If the obtained resist film is used as an etching mask, it becomes possible to achieve further increased capacity and further miniaturization of electronic devices and optical devices.

Mode for Carrying Out the Invention

[0020] [Sulfonium Salt] The sulfonium salt (1) of the present invention is a compound represented by the following formula (1).

Chemical Formula

[0021] Furthermore, the symbols A, B, and C attached to the benzene ring in the above formula are symbols attached to distinguish the three benzene rings in the formula. Hereinafter, the benzene ring to which A is attached is referred to as "benzene ring A", the benzene ring to which B is attached is referred to as "benzene ring B", and the benzene ring to which C is attached is referred to as "benzene ring C".

[0022] Said n is the number of iodine atoms bonded to benzene ring C, and represents an integer of 1 to 3. Among them, from the viewpoint of improving the sensitivity to light of ultra-short wavelengths, 1 or 2 is preferable as said n, and 1 is particularly preferable from the viewpoint of suppressing the decrease in solvent solubility while improving the sensitivity to light of ultra-short wavelengths.

[0023] In benzene ring C, the position where the iodine atom is bonded is preferably changed according to the number of iodine atoms to be bonded. When n = 1, it is preferably bonded to the para-position with respect to the position where the sulfur atom shown in formula (1) is bonded. When n = 2, it is preferably bonded to the meta-position, or to the ortho-position and the meta-position with respect to the position where the sulfur atom shown in formula (1) is bonded. When n = 3, it is preferably bonded to the ortho-position and the para-position with respect to the position where the sulfur atom shown in formula (1) is bonded.

[0024] Therefore, as the sulfonium salt (1), compounds represented by the following formulas (1-1), (1-2), (1-3), and (1-4) are preferable. As the sulfonium salt (1), from the viewpoint of suppressing the decrease in solvent solubility while improving the sensitivity to light of ultra-short wavelengths, compounds represented by the following formulas (1-1), (1-2), and (1-3) are particularly preferable, and from the viewpoint of significantly improving the sensitivity to light of ultra-short wavelengths, compounds represented by the following formulas (1-2) and (1-3) are most preferable. Also, from the viewpoint of significantly improving the solvent solubility, the compound represented by the following formula (1-1) is most preferable.

Chemical formula

[0025] Rf in the above formula1 , Rf 2 , Rf 11 , Rf 12 , R 1 , R 11 , X - is the same as described above.

[0026] The alkyl group is, for example, C 1-5 alkyl group (i.e., an alkyl group having 1 to 5 carbon atoms), preferably C 1-3 alkyl group (i.e., an alkyl group having 1 to 3 carbon atoms). Specific examples of the alkyl group include linear or branched alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, and the like.

[0027] The fluoroalkyl group is a group in which at least one of the hydrogen atoms of the alkyl group is substituted with a fluorine atom. Examples of the alkyl group are the same as those described above.

[0028] As the fluoroalkyl group, from the viewpoint of easy availability of raw materials, fluoro C 1-5 alkyl group is preferred, fluoro C 1-3 alkyl group is more preferred, and fluoro C 1-2 alkyl group is particularly preferred.

[0029] As the fluoroalkyl group, a group in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms, that is, a perfluoroalkyl group is preferred, perfluoro C 1-5 alkyl group is more preferred, perfluoro C 1-3 alkyl group is still more preferred, and perfluoro C 1-2 alkyl group is particularly preferred.

[0030] The trialkylsilyl group is a group represented by the general formula [-Si(R) 3 . The three Rs in the above formula represent the same or different alkyl groups. Examples of the alkyl group are the same as those of the alkyl group in the above formula (1).

[0031] As for the trialkylsilyl group, from the viewpoint of improving solvent solubility, it is preferable that at least one of the three Rs is a branched-chain alkyl group, and it is particularly preferable that at least one of the three Rs is a tert-butyl group.

[0032] As for the trialkylsilyl group, it is preferably a group represented by the general formula [-Si(R’) 2 (tert-butyl)] (wherein R’ is the same or different and represents a methyl group or an ethyl group), and particularly preferably a tert-butyldimethylsilyl group.

[0033] The hydroxy(poly)alkyleneoxy group is a group represented by the general formula [-(OR) m -OH]. In the formula, m Rs are the same or different and represent an alkylene group, and m represents an integer of 1 or more.

[0034] As for m, an integer of 1 to 4 is particularly preferable.

[0035] The alkylene group is, for example, an alkylene group having 1 to 5 carbon atoms, and examples thereof include linear or branched alkylene groups such as a methylene group, an ethylene group, a propylene group, and a butylene group. Among them, an ethylene group or a propylene group is preferable, and an ethylene group is particularly preferable.

[0036] As for the hydroxy(poly)alkyleneoxy group, among others, a hydroxy(poly)ethyleneoxy group or a hydroxy(poly)propyleneoxy group is preferable, and a hydroxy(poly)ethyleneoxy group is particularly preferable.

[0037] OR 1 group and OR 11 group are polar groups and exhibit the effect of improving solvent solubility. R 1 and R 11 constituting the polar group are preferably a hydrogen atom, an alkyl group, or a trialkylsilyl group, particularly preferably an alkyl group or a trialkylsilyl group, in terms of particularly excellent effect of improving solvent solubility, C1-5 An alkyl group or tri-C 1-5 An alkylsilyl group is most preferred.

[0038] The benzene rings A, B, and C in the above formula (1) may have other substituents in addition to the groups shown in the formula. Examples of other substituents include an alkyl group (e.g., an alkyl group having 1 to 3 carbon atoms). Further, the benzene ring C may have a fluorine atom and a fluoroalkyl group as other substituents.

[0039] The chemical structure of the sulfonium salt (1) can be identified, for example, 1 H-, 11 B-, 13 C-, 19 F-, or 31 P-nuclear magnetic resonance spectrum, infrared absorption spectrum, or elemental analysis, etc.

[0040] In the above formula, X - represents a monovalent counter anion, for example, a halogen ion, a halogen oxoacid anion, a boron anion, a phosphate anion, a sulfate anion, a sulfonate anion, a sulfonylimide anion, a carboxylate anion, a methide anion, an antimony anion, OH - SCN - NO 2 - NO 3 - etc.

[0041] Examples of the halogen ion include Cl - Br - I - etc.

[0042] Examples of the halogen oxoacid anion include ClO 4 - IO 3 - BrO 3 - etc.

[0043] Examples of the boron anion include inorganic boron anions such as BF 4 - and organic boron anions such as (C 6 F 5 ) 4 B - , ((CF 3 ) 2 C 6 H 3 ) 4 B - , tetraphenylborate, tetrakis(monofluorophenyl)borate, tetrakis(difluorophenyl)borate, tetrakis(trifluorophenyl)borate, and the like.

[0044] Examples of the phosphate anion include inorganic phosphate anions such as PF 6 - , PO 4 3- and organic phosphate anions such as (CF 3 CF 2 ) 5 PF - , (CF 3 CF 2 ) 4 PF 2 - , (CF 3 CF 2 ) 3 PF 3 - , (CF 3 CF 2 ) 2 PF 4 - , (CF 3 CF 2 )PF 5 - and the like.

[0045] The sulfonate anion is represented by, for example, the following formula (s1). R s1 -SO 3 - (s1) (In the formula, R s1 represents an organic group)

[0046] Rs1 Examples of the organic group in [description] 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 above groups are bonded via a linking group selected from a single bond or -O-, -CO 2 -, -S-, -SO 3 -, and -SO 2 N(R s2 ). Examples of the R s2 include a hydrogen atom or an alkyl group (e.g., a C 1-30 alkyl group). Examples of the substituent include a halogen atom such as a fluorine atom.

[0047] The hydrocarbon group includes a saturated hydrocarbon group and an unsaturated hydrocarbon group.

[0048] The hydrocarbon group is, for example, a C 1-30 hydrocarbon group. The C 1-30 hydrocarbon group includes, for example, a C 1-30 aliphatic hydrocarbon group, a C 3-30 cycloaliphatic hydrocarbon group, a C 6-30 aromatic hydrocarbon group, and a group in which two or more of these are bonded.

[0049] Examples of the C 1-30 hydrocarbon group preferably include a C 1-30 alkyl group, a C 2-30 alkenyl group, a C 6-15 aryl group, a C 6-15 cycloalkyl group, a C 6-15 bridged cyclic hydrocarbon group, and a group in which two or more of these are bonded.

[0050] The heterocyclic group is a group obtained by removing one hydrogen atom from the structural formula of the heterocycle. The heterocycle includes an aromatic heterocycle and a non-aromatic heterocycle. Examples of such a heterocycle include a 3- to 10-membered ring (preferably a 4- to 6-membered ring) having a carbon atom and at least one kind of hetero atom (e.g., an oxygen atom, a sulfur atom, a nitrogen atom, etc.) in the atoms constituting the ring, and a condensed ring thereof.

[0051] Specific examples of the sulfonic acid anion include CH 3 SO 3 - 、C 4 H 9 SO 3 - 、CF 3 SO 3 - 、C 2 F 5 C 4 H 4 SO 3 - 、C 4 F 9 SO 3 - 、benzenesulfonic acid anion, p-toluenesulfonic acid anion, camphorsulfonic acid anion, etc.

[0052] The sulfonylimide anion is represented by, for example, the following formula (n1). (R n1 SO 2 ) 2 N - (n1) (In the formula, two Rs n1 are the same or different and represent organic groups)

[0053] Examples of the organic group in R n1 are the same as those in R s1 .

[0054] Specific examples of the sulfonylimide anion include (FSO 2 ) 2 N - 、(CF 3 SO 2 ) 2 N - 、(C 4 F 9 SO 2 ) 2 N - 、(C 2 F 5 SO 2 ) 2 N - etc.

[0055] The carboxylic acid anion is represented by, for example, the following formula (c1). R c1 -COO - (c1) (In the formula, R c1 represents an organic group)

[0056] R c1 Examples of the organic group in R s1 are the same as those in R

[0057] Specific examples of the carboxylic acid anion include, for example, CF 3 CO 2 - , CH 3 CO 2 - , C 2 H 5 CO 2 - , C 6 H 5 CO 2 - and the like.

[0058] Examples of the methide anion include, for example, the sulfonylmethide anion represented by the following formula (m1). (R m1 SO 2 ) 3 C - (m1) (In the formula, the three Rs m1 are the same or different and represent organic groups)

[0059] R m1 Examples of the organic group in R s1 are the same as those in R

[0060] Specific examples of the methide anion include (CF 3 SO 2 ) 3 C - and the like.

[0061] Examples of the antimony anion include, for example, SbF6 - include the following.

[0062] In addition to the above, the monovalent counter anion includes anions described in JP-A-2013-47211, JP-A-2021-81708, JP-A-2013-80245, JP-A-2013-80240, and JP-A-2013-33161.

[0063] As the monovalent counter anion, a sulfonic acid anion or a sulfonylimide anion is preferable in terms of excellent solvent solubility and fine pattern forming property.

[0064] The sulfonium salt (1) is excellent in solubility in an organic solvent.

[0065] 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; chain or cyclic esters such as ethyl acetate, butyl acetate, ethyl lactate, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone; glycol diethers such as ethylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, triethylene glycol diethyl ether, and tripropylene glycol dibutyl ether; glycol monoether monoesters such as ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), 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.

[0066] As the organic solvent, it is preferably contained at least one selected from among ketones, chain esters, and glycol monoether monoesters.

[0067] The solubility of the sulfonium salt (1) in an organic solvent (e.g., PGMEA) 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. Therefore, if the sulfonium salt (1) is added to the photoresist together with the solvent, the sulfonium salt (1) can be uniformly dispersed in the photoresist.

[0068] Further, the sulfonium salt (1) has high photosensitivity to light rays of ultra-short wavelengths such as EUV (extreme ultraviolet rays), EB (electron beams), and X-rays. And without using a photosensitizer, just by irradiating the light rays of the above wavelength, the light energy directly propagates to the sulfonium salt (1) and the photolysis proceeds rapidly, generating an acid (H + X - ).

[0069] Also, the sulfonium salt (1) is excellent in stability (or quencher resistance or base resistance), and decomposition is suppressed even in the coexistence of a quencher when not irradiated with the above light rays. The residual ratio of the sulfonium salt (1) determined by the method described in the examples is, for example, 35% or more, preferably 55% or more, and particularly preferably 70% or more.

[0070] Since the sulfonium salt (1) has the above characteristics, it can be suitably used as an acid generator (e.g., a photoacid generator, preferably a photoacid generator for photoresist).

[0071] [Acid generator] The acid generator of the present invention contains at least the sulfonium salt (1). The acid generator may contain one kind of the sulfonium salt (1) alone, or may contain a combination of two or more kinds.

[0072] The acid generator may contain components other than the sulfonium salt (1), but the proportion of the sulfonium salt (1) in the total amount (100% by weight) of the compounds (hereinafter sometimes referred to as "photoacid generating compounds") 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, still more preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, especially preferably 95% by weight or more.

[0073] That is, the acid generator may contain a photoacid generating compound other than the sulfonium salt (1), but the content of other photoacid generating compounds is preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 30% by weight or less, particularly preferably 20% by weight or less, most preferably 10% by weight or less, especially preferably 5% by weight or less, based on the total amount (100% by weight) of the photoacid generating compounds contained in the acid generator.

[0074] Also, the acid generator may contain components other than the sulfonium salt (1), but the proportion of the sulfonium salt (1) in the total amount (100% by weight) of the acid generator is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, particularly preferably 80% by weight or more, most preferably 90% by weight or more, especially preferably 95% by weight or more.

[0075] The acid generator has excellent solubility in an organic solvent, and at normal temperature (e.g., 25 °C) and normal pressure, its solubility in an organic solvent (e.g., PGMEA) is, for example, 2% by weight or more (e.g., 2 - 50% by weight), preferably 3% by weight or more, more preferably 4% by weight or more, particularly preferably 5% by weight or more.

[0076] The acid generator is excellent in sensitivity not only to light rays on the longer wavelength side but also to extreme ultraviolet rays. When irradiated with the light rays, it easily decomposes to generate an acid (H + X - ).

[0077] Further, the acid generator is excellent in stability (or quencher resistance or base resistance), and decomposition is suppressed even in the coexistence of a quencher under non-irradiation of the light beam. The residual ratio of the acid generator determined by the method described in the examples is, for example, 35% or more, preferably 55% or more, particularly preferably 70% or more.

[0078] Therefore, the photoresist containing the acid generator and the quencher is excellent in storage stability. And the preparation time of the photoresist is not limited to immediately before use, and it can be prepared in advance and used at any timing.

[0079] Since the acid generator has the above characteristics, it can be suitably used as an acid generator for photoresists (particularly, an acid generator for photoresists used in photolithography utilizing light beams of ultra-short wavelengths).

[0080] [Photoresist] The photoresist of the present invention contains the acid generator (or sulfonium salt (1)) and an acid-reactive compound.

[0081] The total content of the acid generator (or sulfonium salt (1)) and the acid-reactive compound is, for example, 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, particularly preferably 90% by weight or more, most preferably 95% by weight or more of the total non-volatile content contained in the photoresist. Incidentally, the non-volatile content means a residue obtained by removing volatile components, and is, for example, a substance having a boiling point exceeding 155 ° C under normal pressure.

[0082] The content of the acid generator (or sulfonium salt (1)) is, for example, 0.001 to 20% by weight, preferably 0.01 to 15% by weight, particularly preferably 0.05 to 7% by weight of the content of the acid-reactive compound.

[0083] If the content of the acid generator (or sulfonium salt (1)) is 0.001% by weight or more of the content 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 of ultra-short wavelengths. Further, if the content is 20% by weight or less of the content of the acid-reactive compound, the effect of improving the resolution of the photoresist can be obtained.

[0084] (Acid-reactive compound) An acid-reactive compound is a compound whose solubility in an alkaline developer changes by the action of an acid. The photoresist of the present invention may contain one kind of acid-reactive compound alone or may contain a combination of two or more kinds.

[0085] Acid-reactive compounds include a negative-type photosensitive resin (QN) that is originally easily soluble in an alkaline developer and becomes poorly soluble or insoluble in an alkaline developer by the action of an acid, and a positive-type photosensitive resin (QP) that is originally poorly soluble or insoluble in an alkaline developer and becomes soluble in an alkaline developer by the action of an acid.

[0086] Therefore, the photoresist includes the following composition (1) and composition (2). Composition (1): A composition containing the acid generator and a negative-type photosensitive resin (QN) Composition (2): A composition containing the acid generator and a positive-type photosensitive resin (QP)

[0087] Examples of the negative-type photosensitive resin (or negative-type chemically amplified resin; QN) include a composition containing a phenolic hydroxyl group-containing resin (QN1) and a crosslinking agent (QN2).

[0088] The phenolic hydroxyl group-containing resin (QN1) is a resin containing a phenolic hydroxyl group that exhibits high solubility in an alkaline developer, and is a resin that reacts with a crosslinking agent to become less soluble or insoluble in an alkaline developer. Examples thereof include novolak resins, polyhydroxystyrene, copolymers of hydroxystyrene, copolymers of hydroxystyrene and styrene, copolymers of hydroxystyrene and (meth)acrylic acid derivatives, phenol-xylene glycol condensation resins, cresol-xylene glycol condensation resins, polyimides containing phenolic hydroxyl groups, polyamic acids containing phenolic hydroxyl groups, phenol-dicyclopentadiene condensation resins, and the like. These can be used alone or in combination of two or more.

[0089] The phenolic hydroxyl group-containing resin (QN1) may contain a phenolic low molecular compound as a part of the components.

[0090] The polystyrene-reduced weight average molecular weight (Mw) of the phenolic hydroxyl group-containing resin (QN1) measured by GPC is, for example, 2000 to 20000.

[0091] The crosslinking agent (QN2) is a compound that can crosslink a phenolic hydroxyl group-containing resin (QN1) to insolubilize or make it insoluble by, for example, an acid generated from an acid generator. Examples thereof include bisphenol A-based epoxy compounds, bisphenol F-based epoxy compounds, bisphenol S-based epoxy compounds, novolak 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 phenol compounds, alkoxyalkyl group-containing melamine compounds, alkoxyalkyl group-containing benzoguanamine compounds, alkoxyalkyl group-containing urea compounds, alkoxyalkyl group-containing phenol compounds, carboxymethyl group-containing melamine resins, carboxymethyl group-containing benzoguanamine resins, carboxymethyl group-containing urea resins, carboxymethyl group-containing phenol resins, carboxymethyl group-containing melamine compounds, carboxymethyl group-containing benzoguanamine compounds, carboxymethyl group-containing urea compounds, and carboxymethyl group-containing phenol compounds. These can be used alone or in combination of two or more.

[0092] From the viewpoint of efficiently insolubilizing or making insoluble the phenolic hydroxyl group-containing resin (QN1) in an alkaline developer, the content of the crosslinking agent (QN2) is, for example, 10 to 40 mol% with respect to all acidic functional groups in the phenolic hydroxyl group-containing resin (QN1).

[0093] Examples of the positive photosensitive resin (or positive chemically amplified resin; QP) include an alkali-soluble resin (a protecting group-introduced resin; QP1) into which an acid-dissociable group is introduced as a protecting group.

[0094] The protecting group-introduced resin (QP1) is a resin in which some or all of the hydrogen atoms of acidic functional groups (for example, phenolic hydroxyl groups, carboxyl groups, sulfonyl groups, etc.) in the alkali-soluble resin are substituted with acid-dissociable groups.

[0095] The protecting group-introduced resin (QP1) is originally a resin that is insoluble or hardly soluble in an alkaline developer, and when the acid-labile group dissociates by the acid (H + X - ) generated from the acid generator, it changes to an alkali-soluble resin that shows easy solubility in an alkaline developer.

[0096] 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).

[0097] The alkali-soluble resin includes a phenolic hydroxyl group-containing resin, a carboxyl group-containing resin, and a sulfonic acid group-containing resin.

[0098] Examples of the phenolic hydroxyl group-containing resin include the same resins as the above-mentioned phenolic hydroxyl group-containing resin (QN1).

[0099] 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).

[0100] Examples of the carboxyl group-containing vinyl monomer (Ba) include (meth)acrylic acid.

[0101] Examples of the hydrophobic group-containing vinyl monomer (Bb) include C 1-20 (meth)acrylate esters (Bb1) such as alkyl (meth)acrylate and alicyclic group-containing (meth)acrylate, and hydrocarbon monomers having a styrene skeleton and aromatic hydrocarbon monomers (Bb2) such as vinylnaphthalene.

[0102] 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 a copolymer of a sulfonic acid group-containing vinyl monomer (Bc) such as vinylsulfonic acid and styrenesulfonic acid and a hydrophobic group-containing vinyl monomer (Bb).

[0103] Examples of the acid dissociable group of the protecting group-introduced resin (QP1) include 1-substituted methyl groups such as methoxymethyl group, benzyl group, tert-butoxycarbonylmethyl group; 1-substituted ethyl groups such as 1-methoxyethyl group, 1-ethoxyethyl group; 1-branched alkyl groups such as tert-butyl group; silyl groups such as trimethylsilyl group; germyl groups such as trimethylgermyl group; alkoxycarbonyl groups such as tert-butoxycarbonyl group; acyl groups; cyclic acid dissociable groups such as tetrahydropyranyl group, tetrahydrofuranyl group, tetrahydrothiopyranyl group, tetrahydrothiofuranyl group, etc. These may be contained alone or in combination of two or more.

[0104] The introduction rate of the acid dissociable group 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 the acid dissociable group and the alkali-soluble resin into which the group is introduced, but is, for example, 10 to 100%, preferably 15 to 100%.

[0105] The polystyrene-reduced weight average molecular weight (Mw) of the protecting group-introduced resin (QP1) measured by GPC is, for example, 1000 to 150000, preferably 3000 to 100000.

[0106] The photoresist of the present invention can be prepared, for example, by dissolving the acid generator (or sulfonium salt (1)) in an organic solvent and mixing it with an acid-reactive compound.

[0107] The photoresist of the present invention can contain, if necessary, one or more other components in addition to the acid generator (or sulfonium salt (1)) and the acid-reactive compound. Examples of other components include quenchers, organic solvents, pigments, dyes, photosensitizers, dispersants, surfactants, fillers, leveling agents, antifoaming agents, antistatic agents, ultraviolet absorbers, pH adjusters, surface modifiers, plasticizers, drying accelerators, etc.

[0108] (Quencher) A quencher is a compound that suppresses the diffusion of acid generated from an acid generator in a resist film and the resulting reduction in the pattern resolution of the resist film by neutralizing the acid.

[0109] As the quencher, a basic substance can be used. Also, a salt that generates an acid with a lower acidity than the acid (H + X - ) generated from the acid generator can also be used as the quencher.

[0110] Examples of the basic substance include nitrogen-containing organic compounds such as amines and ammonium salts. These can be used alone or in combination of two or more.

[0111] Amines include aliphatic amines and aromatic amines.

[0112] 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.

[0113] 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.

[0114] Examples of ammonium salts include tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrabutylammonium lactate.

[0115] As the quencher, amines are preferred, and aliphatic amines or aromatic amines are particularly preferred.

[0116] From the viewpoint of improving the resolution of the photoresist, the content of the quencher is, for example, 0.01 to 50 parts by weight, preferably 0.5 to 30 parts by weight, based on 100 parts by weight of the acid generator (or sulfonium salt (1)) contained in the photoresist.

[0117] From the viewpoint of improving the resolution of the photoresist, the content of the quencher is, for example, 0.0005 to 10% by weight, preferably 0.005 to 5% by weight, based on the total amount of the acid-reactive compounds contained in the photoresist.

[0118] (Organic solvent) As the organic solvent, any solvent that can dissolve the acid-reactive compound and impart good coatability to the photoresist may be used. Among them, it is preferable to use a solvent having a boiling point of 200°C or lower because the photoresist can be easily dried after coating. Examples of such 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 (PGMEA). These can be used alone or in combination of two or more.

[0119] The photoresist of the present invention contains a sulfonium salt (1) having high sensitivity to light rays of ultra-short wavelengths. Therefore, even when irradiated with light rays of ultra-short wavelengths, without containing a photosensitizer, acid (H + X - ) can be efficiently generated in the exposed area. Then, the solubility of the acid-reactive compound in the exposed area changes due to the generated acid (H + X - ). When the acid-reactive compound is a negative photosensitive resin, the solubility decreases due to the acid (H + X - ). On the other hand, when the acid-reactive compound is a positive photosensitive resin, the acid (H + X -) increases solubility. Therefore, by using the photoresist of the present invention, an etching mask with good accuracy can be formed by photolithography.

[0120] The photoresist of the present invention also contains a sulfonium salt (1) having quencher resistance. Therefore, it has excellent storage stability and exhibits excellent photosensitivity stably over a long period. Therefore, it can be prepared in advance and used at any timing.

[0121] [Method for manufacturing an electronic device or an optical device] The method for manufacturing an electronic device or an optical device of the present invention includes a step of forming a pattern by photolithography using the photoresist.

[0122] 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. Step 1: A step of forming a coating film of the photoresist on a substrate Step 2: A step of performing light irradiation in a pattern shape on the coating film Step 3: A step of performing alkali development

[0123] (Step 1) This step is a step of forming a coating film of the photoresist on the substrate to be etched. The coating film can be formed by applying the photoresist to the substrate using a known method such as spin coating, curtain coating, roll coating, spray coating, screen printing, etc., and then drying it.

[0124] (Step 2) This step is a step of performing light irradiation in a pattern shape on the coating film obtained through Step 1 by a method such as light irradiation through a photomask having a pattern. As the light beam used for light irradiation, the sulfonium salt (1) is decomposed to form an acid (H + X -There is no particular limitation as long as it is possible to generate ), but from the viewpoint of forming a fine pattern, it is preferable to use light rays with an ultra-short wavelength such as EUV (extreme ultraviolet ray), EB (electron beam), or X-ray.

[0125] After light irradiation, heating at a temperature of 60 to 200 °C for about 0.1 to 120 minutes can increase the difference in solubility between the exposed portion and the unexposed portion in the alkaline developer, and is preferable in that the resolution of the pattern can be improved.

[0126] (Step 3) This step is a step of subjecting the photoresist coating film that has undergone Step 2 to an alkali development treatment.

[0127] Examples of the alkaline developer used for the alkali development treatment include an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium hydrogen carbonate solution, an aqueous tetramethylammonium salt solution, and the like.

[0128] Methanol, ethanol, isopropyl alcohol, tetrahydrofuran, N-methylpyrrolidone, etc. may be added to the alkaline developer.

[0129] The alkali development treatment is performed, for example, by applying the alkaline developer to the coating film by a method such as a dip method, a shower method, or a spray method.

[0130] The temperature of the alkaline developer is, for example, 25 to 40 °C. Also, the alkali development time is appropriately determined according to the thickness of the coating film, but is, for example, 1 to 5 minutes.

[0131] After Step 3, a resist film having a pattern can be formed on the substrate. If the substrate is etched using the resist film having the pattern thus obtained as an etching mask, an electronic device or an optical device having a high-precision wiring pattern or the like can be manufactured.

[0132] The electronic device includes, for example, display devices such as organic EL displays and liquid crystal displays; input devices such as touch panels; light-emitting devices; sensor devices; MEMS (Micro Electro Mechanical Systems) devices such as optical scanners, optical switches, acceleration sensors, pressure sensors, gyroscopes, microfluidic channels, and inkjet heads, etc.

[0133] The optical device includes, for example, optical waveguides, metalenses, semiconductor lasers, etc.

[0134] As described above, each configuration of the present invention and their combinations, etc. are examples, and additions, omissions, substitutions, and changes to the configuration can be made as appropriate without departing from the gist of the present invention. In addition, each aspect disclosed in this specification can be combined with any other features disclosed in this specification. Furthermore, the present disclosure is not limited by the embodiments.

Example

[0135] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited by these examples.

[0136] Example 1 (Preparation of acid generator; sulfonium reaction) Using 10 g of 4-bromo-2,6-difluoroanisole, 1.2 g of magnesium, and 40 g of tetrahydrofuran, a tetrahydrofuran solution of 2,6-difluoroanisole magnesium bromide was prepared by a conventional method.

[0137] To the obtained tetrahydrofuran solution of 2,6-difluoroanisole magnesium bromide, a solution prepared by diluting 2.5 g of thionyl chloride with 5 g of tetrahydrofuran was added dropwise at a rate such that the system temperature did not exceed -5°C. After the addition was completed, the reaction was allowed to proceed at room temperature for 1 hour to complete the reaction. Thereafter, the reaction solution was added to 50 g of ion-exchanged water at a rate such that the temperature inside the system did not exceed 15°C, and the mixture was stirred for 1 hour. Next, 30 g of ethyl acetate was added and the mixture was stirred for 1 hour. After removing the aqueous layer, the organic layer was washed three times with 30 g of ion-exchanged water. The organic layer was desolvated, and the resulting brown residue was recrystallized from cyclohexane to obtain 7.3 g of bis(2,6-difluoroanisole)sulfoxide.

[0138] 5.0 g of the obtained bis(2,6-difluoroanisole)sulfoxide was dissolved in 20 g of dichloromethane together with 4.6 g of iodobenzene, and 4.2 g of trifluoromethanesulfonic anhydride was added dropwise at a rate such that the temperature inside the system did not exceed -5°C. After completion of the dropwise addition, the reaction mixture was held at room temperature for 1 hour to complete the reaction. 150 g of methyl-tert-butyl ether was added to the reaction solution to precipitate brown crystals. These crystals were separated by filtration, dissolved in 30 g of dichloromethane, and washed three times with 50 g of ion-exchanged water.

[0139] The washed organic layer was desolvated to obtain crude crystals, which were purified by silica gel column chromatography to obtain 4.1 g of a sulfonium salt that is a salt of the cation and anion described in the following table. The obtained sulfonium salt was used as acid generator (1).

[0140] (Preparation of Photoresist) 1 part by weight of the obtained acid generator (1) and 100 parts by weight of a copolymer of p-hydroxystyrene and tert-butyl acrylate as an acid-reactive compound were uniformly dissolved in PGMEA and filtered through a membrane filter with a pore size of 1 μm to obtain photoresist (1).

[0141] Example 2 (Preparation of Acid Generator; Demethylation Reaction) 3.0 g of acid generator (1) obtained by performing a sulfoniumation reaction in the same manner as in Example 1 was dissolved in dichloromethane, and 20 g of a 17% dichloromethane solution of boron tribromide was added dropwise thereto at a rate such that the temperature inside the system did not exceed 10°C. After completion of the dropwise addition, the reaction mixture was held at room temperature for 1 hour to complete the reaction (demethylation reaction). Subsequently, 30 g of ion-exchanged water was added to the reaction solution, neutralized with sodium hydrogen carbonate, and then the aqueous layer was removed. Further, the organic layer was washed three times with 30 g of ion-exchanged water. The washed organic layer was desolventized to obtain crude crystals, and the obtained crude crystals were purified by silica gel column chromatography to obtain 1.3 g of a sulfonium salt, which is a salt of the cation and anion described in the following table. The obtained sulfonium salt was used as the acid generator (2).

[0142] (Preparation of Photoresist) A photoresist (2) was obtained in the same manner as in Example 1, except that the acid generator (2) obtained was used instead of the acid generator (1).

[0143] Example 3 (Preparation of Acid Generator; Sulfonium Reaction) Bis(2,6-difluoroanisole)(2,5-diiodophenyl)sulfonium trifluoromethanesulfonate was obtained in the same manner as in Example 1, except that p-diiodobenzene was used instead of iodobenzene.

[0144] (Preparation of Acid Generator; Demethylation Reaction) A sulfonium salt, which is a salt of the cation and anion described in the following table, was obtained in the same manner as in Example 2, except that bis(2,6-difluoroanisole)(2,5-diiodophenyl)sulfonium trifluoromethanesulfonate was used instead of the acid generator (1). The obtained sulfonium salt was used as the acid generator (3).

[0145] (Preparation of Photoresist) A photoresist (3) was obtained in the same manner as in Example 1, except that the acid generator (3) obtained was used instead of the acid generator (1).

[0146] Example 4 (Preparation of Acid Generator; Sulfonium Reaction) Except for using 1,3,5-triiodobenzene instead of iodobenzene, bis(2,6-difluoroanisole)(2,4,6-triiodophenyl)sulfonium trifluoromethanesulfonate was obtained in the same manner as in Example 1.

[0147] (Preparation of acid generator; demethylation reaction) Except for using bis(2,6-difluoroanisole)(2,4,6-triiodophenyl)sulfonium trifluoromethanesulfonate instead of acid generator (1), a sulfonium salt which is a salt of the cation and anion described in the following table was obtained in the same manner as in Example 2. The obtained sulfonium salt was used as acid generator (4).

[0148] (Preparation of photoresist) Except for using acid generator (4) obtained by replacing acid generator (1), photoresist (4) was obtained in the same manner as in Example 1.

[0149] Example 5 (Preparation of acid generator) 3.0 g of acid generator (2) obtained in the same manner as in Example 2 was dissolved in 10 g of dimethylformamide, and 2.9 g of potassium carbonate and 1.2 g of isopropyl iodide were added. After the addition was completed, the temperature was raised to 50 °C and the temperature was maintained for 5 hours to complete the reaction. Thereafter, 30 g of ion-exchanged water and 30 g of dichloromethane were added to the reaction solution for washing. After removing the aqueous layer, the organic layer was further washed 3 times with 30 g of ion-exchanged water. The washed organic layer was desolvated to obtain an oily substance, and the obtained oily substance was purified by silica gel chromatography to obtain 2.4 g of a sulfonium salt which is a salt of the cation and anion described in the following table. The obtained sulfonium salt was used as acid generator (5).

[0150] (Preparation of photoresist) Except for using acid generator (5) obtained by replacing acid generator (1), photoresist (5) was obtained in the same manner as in Example 1.

[0151] Example 6 (Preparation of Acid Generator) A sulfonium salt, which is a salt of the cation and anion described in the following table, was obtained in the same manner as in Example 5 except that tert-butyldimethylchlorosilane was used instead of isopropyl iodide. The obtained sulfonium salt was used as acid generator (6).

[0152] (Preparation of Photoresist) A photoresist (6) was obtained in the same manner as in Example 1 except that acid generator (6) obtained above was used instead of acid generator (1).

[0153] Example 7 (Preparation of Acid Generator; Sulfonium Reaction) A sulfonium salt, which is a salt of the cation and anion described in the following table, was obtained in the same manner as in Example 1 except that 4-bromo-2,6-bis(trifluoromethyl)anisole was used instead of 4-bromo-2,6-difluoroanisole. The obtained sulfonium salt was used as acid generator (7).

[0154] (Preparation of Photoresist) A photoresist (7) was obtained in the same manner as in Example 1 except that acid generator (7) obtained above was used instead of acid generator (1).

[0155] Comparative Examples 1 - 6 (Preparation of Photoresist) A photoresist was obtained in the same manner as in Example 1 except that the acid generators described in the following table were used.

[0156] (Evaluation) The acid generators of the examples and comparative examples were evaluated for photosensitivity, solvent solubility, and quencher resistance by the following methods. Also, the photoresists of the examples and comparative examples were evaluated for alkali developability by the following methods. The results are shown in the following table.

[0157] <Photosensitivity> The acid generator was diluted with acetonitrile to a molar concentration of 2.5 mM, and rhodamine B base (an acid chromogenic reagent, manufactured by Sigma-Aldrich) was added to a molar concentration of 2.5 mM to obtain a sample solution.

[0158] The obtained sample solution was placed in a quartz cell with an optical path length of 1 cm, and using an EB exposure apparatus (JEOL JBX-9300, manufactured by JEOL Ltd.), electron beam exposure was performed under the conditions of an acceleration voltage of 100 kV and an integrated light quantity of 100 μC / cm 2 of. Upon exposure, when the acid generator in the sample solution decomposes to generate acid, the generated acid reacts with rhodamine B base and the absorbance at 556 nm increases. Therefore, by measuring the absorbance at 556 nm after exposure, the amount of acid generated can be determined. The absorbance was measured using a spectrophotometer (UV-vis). From the absorbance at 556 nm of the sample solution after exposure, the acid concentration in the sample solution after exposure was quantified using a calibration curve (standard substance: p-toluenesulfonic acid). The acid generation rate was calculated from the following formula, and the photosensitivity was evaluated according to the following criteria from the obtained acid generation rate. Acid generation rate (%) = Acid concentration after exposure (mM) / Acid generator concentration before exposure (mM) × 100

[0159] (Evaluation criteria) Excellent (◎): Acid generation rate is 50% or more Good (○): Acid generation rate is 40% or more and less than 50% Fair (△): Acid generation rate is 20% or more and less than 40% Poor (×): Acid generation rate is less than 20%

[0160] <Solvent solubility> Under normal pressure and at a temperature of 25 °C, 0.1 g of the acid generator was charged into a test tube, and 0.2 g of PGMEA was added each time until the acid generator was completely dissolved. The concentration of the acid generator when it was completely dissolved was determined, and the solvent solubility was evaluated according to the following criteria. (Evaluation criteria) Good (◎): Acid generator concentration is 5 wt% or more Fair (○): Acid generator concentration is 2 wt% or more and less than 5 wt% Not acceptable (×): Acid generator concentration is less than 2% by weight

[0161] <Quencher resistance> A 5% solution of the acid generator in propylene glycol monomethyl ether was prepared, and an equimolar amount of tetramethylammonium hydroxide (10% solution) was added thereto and shaken to obtain a test solution. Immediately after the preparation of the test solution, 0.05 g was sampled, diluted 50-fold, and subjected to HPLC analysis to record the initial area (Ar1) of the acid generator. Also, after storing the test solution at room temperature for 1 day, HPLC analysis was performed in the same manner as above to record the area (Ar2) of the acid generator after storage. Then, the residual ratio of the acid generator was calculated from the following formula, and the quencher resistance was evaluated according to the following criteria. Residual ratio of acid generator (%) = [Ar2 / Ar1] × 100 Note that the higher the residual ratio of the acid generator, the more stable it is with respect to the basic component of the quencher, and the higher the quencher resistance. (Evaluation criteria) Excellent (◎): Residual ratio of acid generator is 70% or more Good (○): Residual ratio of acid generator is 55% or more and less than 70% Fair (△): Residual ratio of acid generator is 35% or more and less than 55% Not acceptable (×): Residual ratio of acid generator is less than 35%

[0162] <Alkaline developability> The photoresist was spin-coated on a glass plate (rotation speed 700 rpm, 20 seconds), heated on a hot plate at 85 °C for 10 minutes, and then heated on a hot plate at 120 °C for 10 minutes. Thereby, a resist film was obtained. Using an exposure apparatus (high-pressure mercury lamp, mask aligner MA-10), the obtained resist film was irradiated with 1000 mJ / cm² through a lattice-shaped pattern mask with a line width of 100 μm. 2It was exposed with the integrated light quantity, and after air cooling for 5 minutes, it was immersed in an alkaline developer (2.38% aqueous solution of TMAH) for 360 seconds. Then, it was washed with water and heated on a hot plate at 80 °C for 30 minutes. As a result, an evaluation sample having a pattern with a line width of 100 μm and a film thickness of 50 μm was obtained. The obtained evaluation sample was visually observed, and further observed using a laser microscope (OLS4000 manufactured by Olympus Corporation) to confirm the pattern shape and the degree of resin remaining undissolved due to development. Then, the alkali developability was evaluated according to the following criteria. (Evaluation Criteria) Good (○): There was no remaining undissolved portion at all, and uniform pattern formation was possible. Fair (△): There was a locally remaining undissolved portion, but uniform pattern formation was possible. Poor (×): There was a remaining undissolved portion over a wide range, and uniform pattern formation was impossible.

[0163] [Table 1]

[0164] [Table 2]

[0165] [Table 3]

[0166] From the above table, it can be seen that the acid generator (or sulfonium salt (1)) of the present invention has a polar group (hydroxy group, alkoxy group, or trialkylsilyl group) that has an effect of improving solvent solubility, together with a fluorine atom or a fluoroalkyl group that imparts a function of improving sensitivity to light rays of an ultrashort wavelength to benzene rings A and B, and contains an iodine atom in benzene ring C. Therefore, it has high sensitivity to light rays of an ultrashort wavelength and is excellent in solvent solubility and quencher resistance.

[0167] In addition, since the acid generator (or sulfonium salt (1)) of the present invention has excellent solvent solubility, quencher resistance, and photosensitivity as described above, it can be suitably used as an acid generator for photoresists (particularly, an acid generator for photoresists used in photolithography utilizing light of an extremely short wavelength). When photolithography (particularly, photolithography utilizing light of an extremely short wavelength) is performed using a photoresist containing the acid generator (or sulfonium salt (1)) of the present invention and alkali development treatment is carried out, it can be seen that a fine pattern can be accurately formed, and an increase in the capacity and miniaturization of electronic devices and optical devices can be achieved.

[0168] On the other hand, from the comparative examples, it can be seen that in the case of a sulfonium salt in which benzene rings A and B have neither a fluorine atom nor a fluoroalkyl group and a polar group, the sensitivity to light of an extremely short wavelength, solvent solubility, and alkali developability are all low. Also, in the case of a sulfonium salt in which benzene rings A and B have a fluorine atom or a fluoroalkyl group but do not have a polar group, it can be seen that the sensitivity to light of an extremely short wavelength is high, but the solvent solubility and alkali developability are low. Furthermore, even when benzene rings A and B have a fluorine atom or a fluoroalkyl group and a polar group, if benzene ring C does not have an iodine atom, it can be seen that the sensitivity to light of an extremely short wavelength and the solvent solubility are low. Furthermore, by comparing Comparative Example 6 with the examples, it can be seen that the sulfonium salt containing a fluorine atom or a fluoroalkyl group at the ortho-position or meta-position (particularly, the meta-position) with respect to the position where the sulfur atom is bonded is significantly inferior in quencher resistance compared to the sulfonium salt (1) of the present application containing a fluorine atom or a fluoroalkyl group at the para-position with respect to the position where the sulfur atom is bonded.

Claims

1. A sulfonium salt represented by the following formula (1): 【Chemistry 1】 (wherein, Rf １ , Rf ２ , Rf １１ and Rf １２ R may be the same or different and represents a fluorine atom or a fluoroalkyl group. １ , R １１ are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, or a trialkylsilyl group. The substituent is a hydroxy group or a hydroxy(poly)alkyleneoxy group. n represents an integer of 1 to 3, and X － 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 sulfonylimide 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. A method for manufacturing an electronic device, comprising the step of forming a pattern by photolithography using the photoresist according to claim 4.