Sulfonium salt and acid generation agent

Abstract

Provided is a novel sulfonium salt which rapidly decomposes to generate an acid when irradiated with a light beam having a wavelength of 20 nm or less.　A sulfonium salt according to the present invention is represented by formula (1). In the formula, RF 1, RF 2, RF 3, RF 4, RF 11, RF 12, RF 13, and RF 14 are the same or different, and each represents a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. However, at least two selected from RF 1, RF 2, RF 3, RF 4, RF 11, RF 12, RF 13, and RF 14 represent a fluorine atom or a fluoroalkyl group. n represents an integer of 1 or more. X- represents a monovalent counter anion.

Description

Sulfonium salts and acid generators

[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.

[0002] There is a demand for electronic and optical devices to be smaller while still increasing their 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 achieving high density and integration of semiconductor integrated circuits. Photolithography involves patternwise exposure of a coating of a chemically amplified photoresist (sometimes referred to as a "resist film") containing an acid generator and an acid-reactive compound, followed by development to form a pattern. The resulting resist film with the pattern formed thereon can be used as a mask to etch a substrate, thereby forming fine wiring and the like on the substrate.

[0004] Triphenylsulfonium salts are known as acid generators (see Patent Document 1). When a photoresist coating containing a triphenylsulfonium salt is exposed to a KrF excimer laser or an ArF excimer laser, a pattern can be formed with high precision.

[0005] Known acid generators include salts of a triarylsulfonium cation having 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, such as [bis(p-fluorophenyl)](p-iodophenyl)sulfonium cation, and a counter anion. Patent Document 2 discloses that the salt is sensitive to EB (electron beam), and that when a photoresist containing the salt is patternwise exposed to EB, a resist film having a fine pattern can be obtained.

[0006] JP 2011-191741 A JP 2021-123579 A

[0007] In recent years, in photolithography technology, there has been a demand for shorter wavelength exposure light in order to form finer patterns, and therefore, studies have been conducted on acid generators that are sensitive to light rays with ultrashort wavelengths, such as electron beams (EB) and extreme ultraviolet rays (EUV).

[0008] However, photoresists containing triphenylsulfonium salts have low sensitivity to light rays with ultrashort wavelengths such as EUV (extreme ultraviolet), EB, and X-rays, making them difficult to use in photolithography using such light rays with ultrashort wavelengths. Furthermore, the salts described in Patent Document 2 also have insufficient sensitivity to such light rays with ultrashort wavelengths.

[0009] Furthermore, in photoresists, acid generators are generally present together with quenchers that are added to enhance pattern resolution, but the salts described in Patent Document 2 rapidly decompose in the presence of quenchers, resulting in a decrease in 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.

[0010] Furthermore, in order to form a pattern with high accuracy, it is necessary to uniformly incorporate an acid generator into the photoresist. Then, by dissolving the acid generator in a solvent and then adding it to the photoresist, the acid generator can be easily incorporated uniformly into the photoresist. Therefore, the acid generator is required to have solvent solubility. However, triphenylsulfonium salts have low solvent solubility, so it has been difficult to incorporate them uniformly into the photoresist.

[0011] Therefore, an object of the present invention is to provide a novel sulfonium salt having photosensitivity and acid-generating ability, which rapidly decomposes to generate acid upon irradiation with light having a wavelength of 20 nm or less. Another object of the present invention is to provide a novel sulfonium salt having photosensitivity, acid-generating ability, and quencher resistance. Another object of the present invention is to provide a novel sulfonium salt having photosensitivity, acid-generating ability, and solvent solubility. Another object of the present invention is to provide a novel acid generator having sensitivity to light having a wavelength of 20 nm or less. Another object of the present invention is to provide a novel acid generator having sensitivity to light having a wavelength of 20 nm or less and quencher resistance. Another object of the present invention is to provide a novel acid generator having sensitivity to light having a wavelength of 20 nm or less and solvent solubility. 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 or optical device using the photoresist.

[0012] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they found that sulfonium salts containing a triarylsulfonium cation having a fluorine atom or a fluoroalkyl group and an iodine atom have excellent sensitivity to light having a wavelength of 20 nm or less, but when the fluorine atom or fluoroalkyl group is bonded to the triarylsulfonium cation at the para-position relative to the position at which the sulfur atom is bonded, the reactivity of the fluorine atom or fluoroalkyl group is specifically enhanced, and therefore the fluorine atom or fluoroalkyl group is easily decomposed in the presence of a quencher, and the effects (for example, photosensitivity and acid generating ability) attributable to the presence of a fluorine atom or fluoroalkyl group cannot be obtained.

[0013] The sulfonium salt represented by the following formula (1), that is, a triarylsulfonium cation having a fluorine atom or a fluoroalkyl group and an iodine atom, in which the fluorine atom or the fluoroalkyl group is bonded to the ortho-position and / or meta-position relative to the position where the sulfur atom is bonded, can suppress decomposition even in the presence of a quencher (i.e., has quencher resistance), has excellent sensitivity to light having a wavelength of 20 nm or less, and when irradiated with light having the wavelength, quickly decomposes to form an acid (H ＋ X － ) was found to occur.

[0014] Furthermore, the inventors have found that, of the three benzene rings contained in the cation in the following formula (1), adding a specific polar group to a benzene ring having a fluorine atom or a fluoroalkyl group can improve sensitivity to ultrashort wavelength light while suppressing a decrease in solvent solubility, and that when a sulfonium salt containing a cation having the polar group added thereto is dissolved in a solvent and blended with a photoresist, the sulfonium salt can be uniformly dispersed in the photoresist, and by performing exposure treatment and development treatment, a resist film having a highly accurate pattern can be formed.

[0015] Furthermore, the inventors have found that by adding a hydroxyl group, a hydroxyalkyl group, an alkoxy group, or a carboxyl group, which has the effect of improving solvent solubility, to the benzene ring containing the iodine atom among the three benzene rings constituting the cation in the following formula (1), it is possible to suppress a decrease in solvent solubility, and that when a sulfonium salt containing such a cation is dissolved in a solvent and blended with a photoresist, it becomes uniformly dispersed in the photoresist, and when exposure treatment and development treatment are carried out, a pattern with high precision can be obtained. The present invention was completed based on these findings.

[0016] That is, the present invention provides a sulfonium salt represented by the following formula (1): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the formula (I) represent a fluorine atom or a fluoroalkyl group, and n represents an integer of 1 or more. The benzene ring in the formula (I) may have a substituent bonded thereto in addition to the above groups. － indicates a monovalent counter anion)

[0017] The sulfonium salt represented by the formula (1) is preferably a sulfonium salt represented by the following formula (1-1): (wherein, Rf １ , Rf ２ , Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. １ , R １１ are the same or different and represent 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. n1 represents an integer of 1 to 3. X － indicates a monovalent counter anion)

[0018] The sulfonium salt represented by the formula (1) is preferably a sulfonium salt represented by the following formula (1-2): (wherein, Rf １ , Rf ２, Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. ａ represents a hydroxy group, a hydroxyalkyl group, an alkoxy group, or a carboxyl group. m1 and m2 each represent an integer of 1 or more, provided that m1 + m2 is an integer of 5 or less. X － indicates a monovalent counter anion)

[0019] The sulfonium salt represented by the formula (1) is preferably a sulfonium salt represented by the following formula (1-3): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the above represent a fluorine atom or a fluoroalkyl group, and m represents 0 or 1. X － indicates a monovalent counter anion)

[0020] The monovalent counter anion is preferably a sulfonate anion or a nitrogen anion.

[0021] The present invention also provides an acid generator containing the sulfonium salt.

[0022] The present invention also provides a photoresist comprising the acid generator and an acid-reactive compound.

[0023] The photoresist preferably further contains a quencher.

[0024] 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.

[0025] 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 the above wavelength, it easily decomposes to produce 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. In addition, the sulfonium salt (1) has excellent solvent solubility. Furthermore, while general acid generators easily decompose and lose or decrease their photosensitivity in the presence of a quencher, the sulfonium salt (1) has quencher resistance and is inhibited from decomposing even in the presence of a quencher, allowing it to maintain high photosensitivity.

[0026] Because sulfonium salt (1) possesses the above properties, when dissolved in a solvent and incorporated into a photoresist, it can be uniformly dispersed in the photoresist. When a resist film formed using the photoresist is subjected to exposure and development using ultrashort wavelength light, a fine pattern can be formed with high precision. Furthermore, adding a quencher to a photoresist containing sulfonium salt (1) can produce a resist film with improved pattern resolution. The resulting resist film can be used to further improve the precision of wiring patterns in electronic and optical devices. Furthermore, because the photoresist containing sulfonium salt (1) and a quencher has excellent storage stability, it can be prepared in advance and used at any time.

[0027] Furthermore, by performing photolithography using a photoresist obtained by adding sulfonium salt (1) and a light beam having a wavelength of 20 nm or less, a resist film having a highly accurate fine pattern can be formed. By using the obtained resist film as an etching mask, it becomes possible to realize further increases in capacity and further miniaturization of electronic devices and optical devices.

[0028] [Sulfonium Salt (1)] The sulfonium salt (1) of the present invention is a compound represented by the following formula (1). (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the formula (I) represent a fluorine atom or a fluoroalkyl group, and n represents an integer of 1 or more. The benzene ring in the formula (I) may have a substituent bonded thereto in addition to the above groups. － indicates a monovalent counter anion)

[0029] In this specification, the symbols A, B, and C attached to the benzene rings in the above formula (1) and the below-described formulas (1-1) and (1-2) are symbols attached to distinguish the three benzene rings in the formulas. Hereinafter, the benzene ring attached with A will be referred to as "benzene ring A," the benzene ring attached with B will be referred to as "benzene ring B," and the benzene ring attached with C will be referred to as "benzene ring C."

[0030] The alkyl group may be, for example, an alkyl group having 1 to 5 carbon atoms (i.e., C １－５ The alkyl group is a straight-chain or branched-chain 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, or a pentyl group. The alkyl group is preferably an alkyl group having 1 to 3 carbon atoms (i.e., C １－３ alkyl group), and alkyl groups having 1 or 2 carbon atoms (i.e., C １－２ alkyl groups) are particularly preferred.

[0031] 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.

[0032] As the fluoroalkyl group, fluoro C １－５ Alkyl groups are preferred, and fluoro C １－３ Alkyl groups are more preferred, and fluoro C １－２ Alkyl groups are particularly preferred.

[0033] The fluoroalkyl group is preferably a group in which all of the hydrogen atoms of the alkyl group have been substituted with fluorine atoms, i.e., a perfluoroalkyl group. １－５ Alkyl groups are more preferred, and perfluoro C １－３ Alkyl groups are more preferred, and perfluoro C １－２ Alkyl groups are particularly preferred.

[0034] In addition to the groups shown in the formula (1), other substituents may be bonded to the benzene ring A and the benzene ring B. Examples of the other substituents include an alkyl group and an iodine atom.

[0035] The benzene ring C in the formula (1) may have other substituents bonded thereto in addition to the groups shown in the formula. Examples of the other substituents include an alkyl group, a fluorine atom, and a fluoroalkyl group.

[0036] The sulfonium salt (1) of the present invention includes a sulfonium salt represented by the following formula (1-1) (hereinafter, may be referred to as "sulfonium salt (1-1)"), a sulfonium salt represented by the following formula (1-2) (hereinafter, may be referred to as "sulfonium salt (1-2)"), and a sulfonium salt represented by the following formula (1-3) (hereinafter, may be referred to as "sulfonium salt (1-3)").

[0037] (Sulfonium Salt (1-1)) The sulfonium salt (1-1) is a compound represented by the following formula (1-1). (wherein, Rf １ , Rf ２ , Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. １ , R １１ are the same or different and represent 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. n1 represents an integer of 1 to 3. X － indicates a monovalent counter anion)

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

[0039] Examples of the alkyl group and fluoroalkyl group include the same alkyl group and fluoroalkyl group as those in the formula (1) above.

[0040] The trialkylsilyl group has the general formula [—Si(R) ３In the formula, the three Rs may be the same or different and each represent an alkyl group. Examples of the alkyl group include the same as those in formula (1).

[0041] In terms of improving solvent solubility, it is preferable that at least one of the three R in the trialkylsilyl group is a branched alkyl group, and it is particularly preferable that at least one of the three R is a tert-butyl group.

[0042] The trialkylsilyl group may be a group represented by the general formula: —Si(R′) ２ (tert-butyl)] (R' may be the same or different and represents a methyl group or an ethyl group), and particularly preferred is a tert-butyldimethylsilyl group.

[0043] The hydroxy(poly)alkyleneoxy group is a group represented by the general formula [-(OR)s-OH], where s Rs, which may be the same or different, represent alkylene groups, and s represents an integer of 1 or greater.

[0044] The s is preferably an integer of 1 to 4.

[0045] 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, a butylene group, etc. As the alkylene group, an ethylene group or a propylene group is preferred, and an ethylene group is particularly preferred.

[0046] The hydroxy(poly)alkyleneoxy group is preferably a hydroxy(poly)ethyleneoxy group or a hydroxy(poly)propyleneoxy group, and particularly preferably a hydroxy(poly)ethyleneoxy group.

[0047] OR １ group and OR １１ The group is a polar group and acts to improve solvent solubility.

[0048] OR １ group and OR １１ R constituting the group １ and R １１is a hydrogen atom, an alkyl group, or a trialkylsilyl group. １ and R １１ As the alkyl group, an alkyl group or a trialkylsilyl group is particularly preferred in that it has a particularly excellent effect of improving solvent solubility. １－５ Alkyl group or tri C １－５ Alkylsilyl groups are most preferred.

[0049] The n1 is the number of iodine atoms bonded to the benzene ring C and represents an integer of 1 to 3. The n1 is preferably 1 or 2 from the viewpoint of improving sensitivity to ultrashort wavelength light, and particularly preferably 1 from the viewpoint of improving sensitivity to ultrashort wavelength light while suppressing a decrease in solvent solubility.

[0050] The position at which the iodine atom is bonded in the benzene ring C is preferably changed depending on the number of iodine atoms to be bonded. When n1=1, it is preferably bonded to the para position relative to the position at which the sulfur atom shown in formula (1-1) is bonded. When n1=2, it is preferably bonded to the meta position or the ortho and meta positions relative to the position at which the sulfur atom shown in formula (1-1) is bonded. When n1=3, it is preferably bonded to the ortho and para positions relative to the position at which the sulfur atom shown in formula (1-1) is bonded.

[0051] Therefore, as the sulfonium salt (1-1), compounds represented by the following formulas (1-1-1), (1-1-2), (1-1-3), and (1-1-4) are preferred. As the sulfonium salt (1-1), from the viewpoint of improving sensitivity to ultrashort wavelength light while suppressing a decrease in solvent solubility, compounds represented by the following formulas (1-1-1), (1-1-2), and (1-1-3) are particularly preferred, and from the viewpoint of significantly improving sensitivity to ultrashort wavelength light, compounds represented by the following formulas (1-1-2) and (1-1-3) are most preferred. Furthermore, from the viewpoint of significantly improving solvent solubility, compounds represented by the following formula (1-1-1) are most preferred. Rf in the following formulas １ , Rf ２ , Rf １１ , Rf １２ , R １ , R １１ , X － is the same as above.

[0052] (Sulfonium Salt (1-2)) The sulfonium salt (1-2) is a compound represented by the following formula (1-2). (wherein, Rf １ , Rf ２ , Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. ａ represents a hydroxy group, a hydroxyalkyl group, an alkoxy group, or a carboxyl group. m1 and m2 each represent an integer of 1 or more, provided that m1 + m2 is an integer of 5 or less. X － indicates a monovalent counter anion)

[0053] Examples of the fluoroalkyl group include the same as the fluoroalkyl group in the formula (1) above.

[0054] The hydroxyalkyl group is a group represented by the general formula [-R-OH], where R represents a group in which one hydrogen atom has been removed from the structural formula of an alkyl group.

[0055] The alkoxy group is a group represented by the general formula [—OR], where R represents an alkyl group.

[0056] Examples of the alkyl group include the same alkyl groups as those in the formula (1) above.

[0057] The hydroxyalkyl group may be a hydroxy C １－５ Alkyl groups are preferred, and hydroxy C １－３ Alkyl groups are more preferred, and hydroxy C １－２ Alkyl groups are particularly preferred.

[0058] The alkoxy group may be C １－５ An alkoxy group is preferred, and C １－３ An alkoxy group is more preferred, and C １－２ Alkoxy groups are particularly preferred.

[0059] The m1 represents the number of iodine atoms bonded to the benzene ring C and represents an integer of 1 or more (for example, an integer from 1 to 4). The m1 is preferably an integer from 1 to 3 from the viewpoint of improving sensitivity to ultrashort wavelength light, and is particularly preferably 1 or 2, and especially preferably 2, from the viewpoint of improving sensitivity to ultrashort wavelength light while suppressing a decrease in solvent solubility.

[0060] In the benzene ring C, the bonding position of the iodine atom is preferably changed depending on the number of iodine atoms to be bonded. For example, when m = 1, the bonding position may be any of the ortho, meta, or para positions relative to the bonding position of the sulfur atom shown in formula (1-2). When m = 2, the bonding position is preferably meta to the bonding position of the sulfur atom shown in formula (1-2). When m = 3, the bonding position is preferably ortho or para to the bonding position of the sulfur atom shown in formula (1-2).

[0061] The m2 is R bonded to the benzene ring C. ａ m2 is the number of groups and represents an integer of 1 or more (for example, an integer of 1 to 4). From the viewpoint of suppressing a decrease in solvent solubility, m2 is preferably an integer of 1 to 3, and from the viewpoint of suppressing a decrease in solvent solubility while improving sensitivity to ultrashort wavelength light, 1 or 2 is particularly preferred, and 1 is especially preferred.

[0062] When m2 is an integer of 2 or more, two or more R ａ may be the same or different.

[0063] The m1+m2 represents an integer of 5 or less (more specifically, an integer of 2 or more and 5 or less), and from the viewpoint of improving sensitivity to ultrashort wavelength light while suppressing a decrease in solvent solubility, the m1+m2 is preferably an integer of 2 to 4, and particularly preferably 2 or 3.

[0064] In addition to the groups shown in the formula (1-2), other substituents may be bonded to the benzene ring A and the benzene ring B. Examples of the other substituents include an alkyl group and an iodine atom.

[0065] The benzene ring C in the above formula (1-2) may have other substituents bonded thereto in addition to the groups shown in the above formula. Examples of other substituents include alkyl groups.

[0066] Among the sulfonium salts (1-2), Rf １ , Rf ２ , Rf １１ , and Rf １２ Specific examples of compounds in which all of X are fluorine atoms are shown below. － , R ａ In the sulfonium salt (1-2), Rf １ , Rf ２ , Rf １１ , and Rf １２ Specific examples of when all of are fluoroalkyl groups or when they are a combination of fluorine atoms and fluoroalkyl groups include compounds corresponding to the compounds represented by the following formulas:

[0067]

[0068]

[0069]

[0070] (Sulfonium Salt (1-3)) The sulfonium salt (1-3) is a compound represented by the following formula (1-3). (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the above represent a fluorine atom or a fluoroalkyl group, and m represents 0 or 1. X － indicates a monovalent counter anion)

[0071] Examples of the alkyl group and fluoroalkyl group include the same alkyl group and fluoroalkyl group as those in the formula (1) above.

[0072] Among the compounds represented by the above formula (1-3), R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ In terms of excellent photosensitivity and / or decomposition efficiency, compounds in which two to four selected from the group consisting of: Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ Particularly preferred are compounds in which two or four selected from the group represent a fluorine atom or a fluoroalkyl group.

[0073] Among the compounds represented by the above formula (1-3), R Ｆ １ , RＦ ２ , R Ｆ ３ , and R Ｆ ４ At least one selected from represents a fluorine atom or a fluoroalkyl group, and R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ 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.

[0074] R in the above formula (1-3) Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ Among these, the groups other than the group representing a fluorine atom or a fluoroalkyl group are preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom, in terms of excellent photosensitivity and / or decomposition efficiency.

[0075] In the above formula (1-3), m represents 0 or 1. In particular, m preferably represents 1 in terms of particularly excellent quencher resistance. When m = 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 (1-3) is bonded, in terms of a large molecular dipole moment and excellent solubility in process solvents.

[0076] As the compound represented by formula (1-3), compounds represented by the following formulae (1-3-1) to (1-3-6) are preferred in terms of excellent photosensitivity and / or decomposition efficiency, and compounds represented by the following formulae (1-3-1), (1-3-2), (1-3-4), and (1-3-5) are particularly preferred. Furthermore, compounds represented by the following formulae (1-3-4) to (1-3-6) are preferred in terms of particularly excellent quencher resistance, and compounds represented by the following formulae (1-3-4) and (1-3-5) are particularly preferred in terms of particularly excellent quencher resistance and excellent photosensitivity and / or decomposition efficiency.

[0077] In the above formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ is the same as above.

[0078] 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, an antimony anion, and an OH － , SCN － , NO ２ － , NO ３ － etc.

[0079] Examples of the halogen ions include Cl － ,Br － , I － etc.

[0080] Examples of the halogen oxo acid anion include ClO ４ － , I.O. ３ － , BrO ３ － etc.

[0081] The boron anion may be, for example, BF４ － Inorganic 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 other organic boron anions.

[0082] Examples of the phosphate anion include PF ６ － , P.O. ４ ３－ Inorganic 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 other organic phosphate anions.

[0083] The sulfonate anion is represented by, for example, the following formula (s1): ｓ１ -SO ３ － (s1) (wherein, R ｓ１ indicates an organic group)

[0084] R ｓ１Examples of the organic group in the formula 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-, -CO ２ -, -S-, -SO ３ - and -SO ２ N (R ｓ２ )- is a group linked by a linking group selected from the group consisting of R ｓ２ is a hydrogen atom or an alkyl group (e.g., C １－３０ The substituents include, for example, halogen atoms such as fluorine atoms.

[0085] The hydrocarbon group includes a saturated hydrocarbon group and an unsaturated hydrocarbon group.

[0086] 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 bonded together are included.

[0087] Said C １－３０ The hydrocarbon group includes C １－３０ Alkyl group, C ２－３０ Alkenyl group, C ６－１５ Aryl group, C ６－１５ Cycloalkylene group, C ６－１５ Bridged cyclic hydrocarbon groups and groups in which two or more of these are bonded together are preferred.

[0088] 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. 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.

[0089] Specific examples of the sulfonate anion include CH ３ SO ３ － , C ４ H９ SO ３ － , C.F. ３ SO ３ － , C ２ F ５ C ４ H ４ SO ３ － , C ４ F ９ SO ３ － , benzenesulfonate anion, p-toluenesulfonate anion, camphorsulfonate anion, and the like.

[0090] Examples of the nitrogen anion include a sulfonylimide anion represented by the following formula (n1): (R ｎ１ SO ２ ) ２ N － (n1) (wherein two R ｎ１ are the same or different and represent an organic group.

[0091] R ｎ１ The organic group in ｓ１ Examples of the organic group are the same as those in the above.

[0092] Specific examples of the nitrogen 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.

[0093] The carboxylate anion is represented by, for example, the following formula (c1): ｃ１ -COO － (c1) (wherein, R ｃ１ indicates an organic group)

[0094] R ｃ１ The organic group in ｓ１ Examples of the organic group are the same as those in the above.

[0095] Specific examples of the carboxylate anion include CF ３ CO ２ － , C.H. ３ CO ２ － , C ２ H ５ CO ２ － , PhCO ２ － etc.

[0096] The methide anion may, for example, be a sulfonylmethide anion represented by the following formula (m1): (R ｍ１ SO ２ ) ３ C － (m1) (wherein three R ｍ１ are the same or different and represent an organic group.

[0097] R ｍ１ The organic group in ｓ１ Examples of the organic group are the same as those in the above.

[0098] Specific examples of the methide anion include (CF ３ SO ２ ) ３ C － etc.

[0099] The antimony anion may be, for example, SbF ６ － etc.

[0100] 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.

[0101] As the counter anion, a sulfonate anion or a nitrogen anion is preferred, and a sulfonate anion or a sulfonylimide anion is particularly preferred, in terms of excellent solubility.

[0102] The chemical structure of the sulfonium salt (1) is, for example, １ H-, １１ B-, 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.

[0103] The sulfonium salt (1) has excellent solubility in organic solvents.

[0104] 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, ethyl lactate, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone; and ethylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monobutyl ether, and diisopropyl ether. Examples of such glycol diethers include propylene 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, 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 may be used alone or in combination of two or more.

[0105] The organic solvent preferably contains at least one selected from the group consisting of ketones, chain esters, and glycol monoether monoesters.

[0106] The solubility of the sulfonium salt (1) in an organic solvent (e.g., propylene glycol monomethyl ether acetate) at room temperature (e.g., 25°C) and atmospheric 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.

[0107] 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 rays with the wavelengths, and photodecomposition proceeds rapidly, resulting in the formation of an acid (H ＋ X).

[0108] 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.

[0109] The sulfonium salt (1) has the above properties and can therefore be suitably used as an acid generator (for example, a photoacid generator).

[0110] [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.

[0111] That is, the acid generator of the present invention may contain an acid-generating compound other than the sulfonium salt (1) as a compound that decomposes upon irradiation with light to generate an acid (hereinafter, may be referred to as an "acid-generating compound"). However, the content of the other acid-generating compound is preferably 50% by weight or less, more preferably 40% by weight or less, even more preferably 30% by weight or less, particularly preferably 20% by weight or less, most preferably 10% by weight or less, and especially preferably 5% by weight or less, based on the total amount (100% by weight) of the acid-generating compounds contained in the acid generator.

[0112] 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 the 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.

[0113] 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 produce an acid (H ＋ X － ) occurs.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] [Photoresist] The photoresist of the present invention contains the acid generator (or the sulfonium salt (1)) and an acid-reactive compound.

[0118] 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.

[0119] 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 compounds, 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 of the acid generator is 20% by weight or less of the total amount of the acid-reactive compounds, the effect of improving the resolution of the photoresist can be obtained.

[0120] (Acid-Reactive Compound) 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 or more of the acid-reactive compounds alone or in combination.

[0121] The acid-reactive compound includes a negative-type photosensitive resin (QN) that is originally easily soluble in an alkaline developer but becomes slightly soluble or insoluble in the alkaline developer upon the action of an acid, and a positive-type photosensitive resin (QP) that is originally slightly soluble or insoluble in an alkaline developer but becomes soluble in the alkaline developer upon the action of an acid.

[0122] Therefore, the photoresist contains the following composition (1) and composition (2): composition (1): a composition containing the acid generator and a negative-type photosensitive resin (QN); and composition (2): a composition containing the acid generator and a positive-type photosensitive resin (QP).

[0123] 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).

[0124] 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, 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.

[0125] The phenolic hydroxyl group-containing resin (QN1) may contain a phenolic low molecular weight compound as part of its components.

[0126] The phenolic hydroxyl group-containing resin (QN1) has a weight average molecular weight (Mw) of, for example, 2,000 to 20,000, as converted into polystyrene, as measured by GPC.

[0127] The crosslinking agent (QN2) is a compound that can crosslink the phenolic hydroxyl group-containing resin (QN1) with the acid generated from the acid generator to make it difficult to dissolve or insolubilize, such as 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, carboxymethyl group-containing phenolic compounds, etc. These can be used alone or in combination of two or more.

[0128] 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.

[0129] Examples of the positive photosensitive resin (or positive chemically amplified resin; QP) include a resin (protecting group-introduced resin; QP1) in which part or all of the hydrogen atoms of an alkali-soluble resin having an acidic functional group (e.g., a phenolic hydroxyl group, a carboxyl group, a sulfonyl group, etc.) have been substituted with an acid-dissociable group.

[0130] The protecting group-introduced resin (QP1) is a resin that is inherently insoluble or poorly soluble in an alkaline developer, and is soluble in the acid (H ＋ X － When the acid-dissociable group is dissociated by the reaction with the hydroxy group, the resin is converted into an alkali-soluble resin that is readily soluble in an alkali developer.

[0131] The alkali-soluble resin is, for example, a resin having an HLB value of 4 to 19 (preferably 5 to 18, and particularly preferably 6 to 17).

[0132] The alkali-soluble resins include phenolic hydroxyl group-containing resins, carboxyl group-containing resins, and sulfonic acid group-containing resins.

[0133] Examples of the phenolic hydroxyl group-containing resin include the same resins as the phenolic hydroxyl group-containing resin (QN1) described above.

[0134] 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).

[0135] An example of the carboxyl group-containing vinyl monomer (Ba) is (meth)acrylic acid.

[0136] The hydrophobic group-containing vinyl monomer (Bb) may be 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.

[0137] 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).

[0138] Examples of the acid-dissociable group contained in 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.

[0139] 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 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%.

[0140] 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.

[0141] (Other Components) In addition to the components described above, 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.

[0142] (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.

[0143] As the quencher, a basic substance can be used. ＋ X －A salt that generates an acid weaker than the quencher may also be used.

[0144] 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.

[0145] The amines include aliphatic and aromatic amines.

[0146] 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.

[0147] 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.

[0148] Examples of ammonium salts include tetramethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrabutylammonium lactate.

[0149] As the quencher, an amine is preferred, and an aliphatic amine or an aromatic amine is particularly preferred.

[0150] From the viewpoint of improving the resolution of the photoresist, the content of the quencher is, for example, preferably 0.01 to 50 parts by weight, and particularly preferably 0.5 to 30 parts by weight, per 100 parts by weight of the acid generator (or the sulfonium salt (1)) contained in the photoresist.

[0151] The content of the quencher is, for example, 0.0005 to 10% by weight, and preferably 0.005 to 5% by weight, of the total amount of acid-reactive compounds contained in the photoresist, from the viewpoint of improving the resolution of the photoresist.

[0152] (Organic Solvent) The organic solvent may be any solvent capable of dissolving the acid-reactive compound and imparting good coating properties to the photoresist, but it is particularly preferred to use a solvent with a boiling point of 200°C or less, as this allows the photoresist to be easily dried after coating. 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.

[0153] 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 an acid-reactive compound and, if necessary, other components (e.g., a quencher) thereto.

[0154] 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 can efficiently convert acid (H ＋ X － ) can be generated. ＋ X － When the acid-reactive compound is a negative photosensitive resin, the acid (H ＋ X － On the other hand, when the acid-reactive compound is a positive photosensitive resin, the solubility is reduced by the 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.

[0155] The photoresist of the present invention also contains a sulfonium salt (1) that is resistant to quenchers. Therefore, the photoresist has excellent storage stability and can stably exhibit excellent photosensitivity over a long period of time. Therefore, the photoresist can be prepared in advance and used at any time.

[0156] [Method for Manufacturing an Electronic or Optical Device] The method for manufacturing an electronic or optical device of the present invention includes a step of forming a pattern by photolithography using the photoresist.

[0157] 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.

[0158] Step 1: forming a coating film of the photoresist on a substrate; Step 2: irradiating the coating film with light in a pattern shape; and Step 3: performing alkaline development.

[0159] (Step 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 using a known method such as spin coating, curtain coating, roll coating, spray coating, or screen printing, and then drying the applied photoresist.

[0160] (Step 2) In this step, the coating film obtained through step 1 is irradiated with light in a pattern shape by a method such as irradiating the coating film with light through a photomask having a pattern. The light used for the light irradiation is a light beam that decomposes the sulfonium salt (1) to produce an acid (H ＋ X － However, from the viewpoint of forming a fine pattern, it is preferable to use an ultrashort wavelength light beam (e.g., a light beam having a wavelength of 20 nm or less) such as EUV (extreme ultraviolet light), EB (electron beam), or X-ray.

[0161] 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.

[0162] (Step 3) This step is a step in which the photoresist coating film that has been subjected to step 2 is subjected to an alkaline development treatment.

[0163] Examples of the alkaline developer used in the alkaline development treatment include an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, sodium hydrogen carbonate, and an aqueous solution of tetramethylammonium salt.

[0164] The alkaline developer may contain methanol, ethanol, isopropyl alcohol, tetrahydrofuran, N-methylpyrrolidone, or the like.

[0165] The alkaline development treatment is carried out by applying the alkaline developer to the coating film by, for example, a dipping method, a showering method, a spraying method or the like.

[0166] The temperature of the alkaline developer is, for example, 25 to 40° C. The alkaline development time is appropriately determined depending on the thickness of the coating film, but is, for example, about 1 to 5 minutes.

[0167] 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.

[0168] 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.

[0169] The optical devices include, for example, optical waveguides, metalenses, semiconductor lasers, and the like.

[0170] 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.

[0171] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0172] Example 1-1 (Preparation of Acid Generator: Sulfonium Formation 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 obtained by a conventional method.

[0173] To the resulting solution, 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 temperature in the system did not exceed -5°C. After completion of the addition, the system was maintained 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 in 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 mixture was washed three times with 30 g of ion-exchanged water. The organic layer was desolvated, and the resulting brown residue was recrystallized with cyclohexane to obtain 7.3 g of bis(2,6-difluoroanisole) sulfoxide.

[0174] 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 in the system did not exceed -5°C. After the dropwise addition was completed, the mixture was maintained at room temperature for 1 hour to complete the reaction. 150 g of methyl tert-butyl ether was added to the reaction solution, causing brown crystals to precipitate. The crystals were separated by filtration, dissolved in 30 g of dichloromethane, and washed three times with 50 g of ion-exchanged water.

[0175] 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 [acid generator (1-1a)], which is a salt of a cation and anion shown in the table below.

[0176] (Preparation of Photoresist) 1 part by weight of the obtained acid generator (1-1a) 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 the solution was filtered through a membrane filter with a pore size of 1 μm to obtain a photoresist.

[0177] Example 1-2 (Preparation of Acid Generator; Demethylation Reaction) 3.0 g of acid generator (1-1a) obtained by a sulfonation reaction in the same manner as in Example 1-1 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 in the system did not exceed 10°C. After completion of the dropwise addition, the mixture was maintained at room temperature for 1 hour to complete the demethylation reaction. Thereafter, 30 g of ion-exchanged water was added to the reaction solution, and the mixture was neutralized with sodium bicarbonate. The aqueous layer was then removed, and the organic layer was washed three times with 30 g of ion-exchanged water. The washed organic layer was desolvated to obtain crude crystals, which were then purified by silica gel column chromatography to obtain 1.3 g of a sulfonium salt [acid generator (1-1b)], which is a salt of a cation and anion shown in the table below.

[0178] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1b).

[0179] Example 1-3 (Preparation of Acid Generator: Sulfonation Reaction) Bis(2,6-difluoroanisole)(2,5-diiodophenyl)sulfonium trifluoromethanesulfonate was obtained in the same manner as in Example 1-1, except that p-diiodobenzene was used instead of iodobenzene.

[0180] (Preparation of Acid Generator: Demethylation Reaction) A sulfonium salt [acid generator (1-1c)], which is a salt of a cation and an anion shown in the table below, was obtained in the same manner as in Example 1-2, except that bis(2,6-difluoroanisole)(2,5-diiodophenyl)sulfonium trifluoromethanesulfonate was used instead of acid generator (1-1a).

[0181] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1c).

[0182] Example 1-4 (Preparation of Acid Generator: Sulfonation Reaction) Bis(2,6-difluoroanisole)(2,4,6-triiodophenyl)sulfonium trifluoromethanesulfonate was obtained in the same manner as in Example 1-1, except that 1,3,5-triiodobenzene was used instead of iodobenzene.

[0183] (Preparation of Acid Generator: Demethylation Reaction) A sulfonium salt [acid generator (1-1d)], which is a salt of a cation and an anion shown in the table below, was obtained in the same manner as in Example 1-2, except that bis(2,6-difluoroanisole)(2,4,6-triiodophenyl)sulfonium trifluoromethanesulfonate was used instead of acid generator (1-1a).

[0184] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1d).

[0185] Example 1-5 (Preparation of Acid Generator) 3.0 g of acid generator (1-1b) obtained by the same method as in Example 1-2 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 maintained at that temperature 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 three times with 30 g of ion-exchanged water. The organic layer after washing was desolvated to obtain an oily product, which was then purified by silica gel chromatography to obtain 2.4 g of a sulfonium salt [acid generator (1-1e)], which is a salt of a cation and an anion shown in the table below.

[0186] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1e).

[0187] Example 1-6 (Preparation of Acid Generator) The same procedure as in Example 1-5 was carried out except that tert-butyldimethylchlorosilane was used instead of isopropyl iodide, to obtain a sulfonium salt [acid generator (1-1f)], which is a salt of a cation and an anion shown in the table below.

[0188] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1f).

[0189] Example 1-7 (Preparation of Acid Generator; Sulfonium Formation Reaction) A sulfonium salt [acid generator (1-1g)], which is a salt of a cation and an anion shown in the table below, was obtained in the same manner as in Example 1-1, except that 4-bromo-2,6-bis(trifluoromethyl)anisole was used instead of 4-bromo-2,6-difluoroanisole.

[0190] (Preparation of Photoresist) A photoresist was prepared in the same manner as in Example 1-1, except that the acid generator (1-1a) was replaced with the acid generator (1-1g).

[0191] Comparative Examples 1-1 to 1-5 (Preparation of Photoresist) Photoresists were obtained in the same manner as in Example 1-1, except that the acid generators shown in the table below were used instead.

[0192] Example 2-1 (Preparation of Acid Generator) 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.

[0193] To the resulting solution, a solution prepared by diluting 28.6 g of thionyl chloride with 50 g of tetrahydrofuran was added dropwise, so that the temperature in the system did not exceed -5°C. After the completion of the dropwise addition, the reaction was continued at room temperature for 1 hour to complete the reaction. This solution was added to 500 g of ion-exchanged water so that the temperature in the system did not exceed 15°C, and the mixture was stirred for 1 hour. Thereafter, 300 g of ethyl acetate was added, and the mixture was stirred for 1 hour. After removing the aqueous layer, the mixture was washed three times with 300 g of ion-exchanged water. The organic layer was desolvated, and the resulting brown residue was recrystallized from cyclohexane, yielding 26.0 g of bis(3,5-difluorophenyl) sulfoxide.

[0194] 6.86 g of the obtained bis(3,5-difluorophenyl) sulfoxide was dissolved in 20 g of dichloromethane together with 5.40 g of 3-iodoanisole, and 8.46 g of trifluoromethanesulfonic anhydride was added dropwise thereto so that the system temperature 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. 150 g of methyl tert-butyl ether was added to the reaction solution, causing precipitation of brown crystals. These crystals were separated by filtration and dissolved in 30 g of dichloromethane, to which 100 g of a 17% dichloromethane solution of boron tribromide was added dropwise so that the system temperature did not exceed 10°C. After the dropwise addition was completed, the reaction was continued at room temperature for 1 hour to complete the reaction. Thereafter, 50 g of ion-exchanged water was added to the reaction solution, and the mixture was neutralized with sodium bicarbonate, after which the aqueous layer was removed, and the organic layer was further washed three times with 50 g of ion-exchanged water.

[0195] The washed organic layer was desolvated to obtain crude crystals, which were purified by silica gel column chromatography to obtain 7.18 g of a sulfonium salt [acid generator (1-2a)], which is a salt of a cation and anion shown in the table below.

[0196] (Preparation of Photoresist) 1 part by weight of the obtained acid generator (1-2a) and 100 parts by weight of a copolymer of p-hydroxystyrene and t-butyl acrylate as an acid-reactive compound were uniformly dissolved in PGMEA, and the solution was filtered through a membrane filter having a pore size of 1 μm to obtain a photoresist.

[0197] Examples 2-2 to 2-13 and Comparative Examples 2-1 to 2-4 Acid generators listed in the following table were obtained in the same manner as in Example 2-1. Photoresists were also obtained in the same manner as in Example 2-1, except that the acid generators obtained were used instead of acid generator (1-2a).

[0198] Example 3-1 (Preparation of Acid Generator) Bis(2-trifluoromethylphenyl)sulfoxide was synthesized in the same manner as described in JP-A 2022-126072.

[0199] 18 g of iodobenzene was added to 1.0 g of the obtained bis(2-trifluoromethylphenyl) sulfoxide, and the mixture was stirred to obtain a dispersion. 2.2 g of trifluoromethanesulfonic acid was added dropwise to the obtained dispersion. Subsequently, 1.2 g of phosphoric anhydride was added to the dispersion in three portions, and the mixture was stirred at room temperature for 2 hours to complete the reaction. 5.4 g of ion-exchanged water was added to the reaction system to terminate the reaction, after which 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 (1-3a)], which is a salt of a cation and anion shown in the table below.

[0200] Example 3-2 (Preparation of Acid Generator) 1.4 g of a sulfonium salt [acid generator (1-3b)], which is a salt of a cation and an anion shown in the table below, was obtained in the same manner as in Example 3-1, except that iodobenzene was changed to 29 g of o-diiodobenzene.

[0201] Example 3-3 (Preparation of Acid Generator) 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.

[0202] 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 completion of the dropwise addition, 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 such that the temperature in the system did not 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.

[0203] 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 system temperature did not exceed -5°C. After the completion of the dropwise addition, 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 such that the system temperature did not exceed 15°C. 75 g of tetrahydrofuran and 30 g of toluene were then 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 obtained 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, and white crystals were precipitated. The crystals were collected by filtration and dried under reduced pressure to obtain 8.23 ​​g of a sulfonium salt [acid generator (1-3c)], which is a salt of a cation and an anion shown in the table below.

[0204] Example 3-4 (Preparation of Acid Generator) 2.2 g of m-diiodobenzene and 1.4 g of dichloromethane were added to 1.0 g of bis(3,5-difluorophenyl)sulfoxide, and the mixture was stirred to obtain a dispersion. 2.7 g of trifluoromethanesulfonic acid was added dropwise to the obtained dispersion. Subsequently, 0.58 g of phosphoric anhydride was added in two divided 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 the mixture was stirred. The precipitated solid was collected by filtration to obtain 1.6 g of a sulfonium salt [acid generator (1-3e)], which is a salt of a cation and anion shown in the table below.

[0205] Example 3-5 (Preparation of Acid Generator) 2.2 g of o-diiodobenzene was added to 1.0 g of bis(3,5-difluorophenyl)sulfoxide and stirred to obtain a dispersion. 2.7 g of trifluoromethanesulfonic acid was added dropwise to the obtained dispersion. Subsequently, 0.68 g of phosphoric anhydride was added in two divided 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 (1-3f)], which is a salt of a cation and anion shown in the table below.

[0206] Comparative Examples 3-1 to 3-4 The compounds shown in the table below were used as acid generators.

[0207] (Evaluation) The acid generators of the Examples and Comparative Examples were evaluated for solvent solubility, photosensitivity, and quencher resistance by the following methods. The photoresists of the Examples and Comparative Examples were also evaluated for alkaline developability by the following method. The results are shown in the table below.

[0208] <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 controlled temperature of 25°C until the acid generator was completely dissolved. The concentration of the acid generator at the time of complete dissolution 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 but less than 5 wt%. Poor (×): Acid generator concentration is less than 2 wt%.

[0209] <Photosensitivity> 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.

[0210] The obtained sample solution was placed in a quartz cell with an optical path length of 1 cm, and exposed to light at an acceleration voltage of 100 kV and an integrated light dose of 50 μC / cm using an exposure device (JEOL JBX-9300, manufactured by JEOL Ltd.). ２ The sample was exposed to electron beams under the following conditions. Upon exposure, the acid generator in the sample solution decomposes to generate acid, and 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 quantified 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 using 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 and less than 50% Passable (△): Acid generation rate is 20% or more and less than 40% Poor (×): Acid generation rate is less than 20%

[0211] <Quencher Resistance> A 5% solution of an acid generator in propylene glycol monomethyl ether was prepared, to which an equimolar amount of tetramethylammonium hydroxide (10% solution) relative to the acid generator was added, followed by shaking to obtain a test solution. Immediately after preparation of the test solution, 0.05 g of the solution was sampled and diluted 50-fold. The sample was subjected to HPLC analysis to record the initial area (Ar1) of the acid generator. After storing the test solution at room temperature for one day, HPLC analysis was performed in the same manner as above to record the area (Ar2) of the acid generator after storage. The residual rate of the acid generator was calculated using the following formula, and the quencher resistance was evaluated according to the following criteria: Residual rate of acid generator (%) = [Ar2 / Ar1] × 100. Note that the higher the residual rate of the acid generator, the more stable it is to 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% Fair (△): Residual rate of acid generator is 35% or more but less than 55% Poor (×): Residual rate of acid generator is less than 35%

[0212] <Alkali developability> The photoresist was spin-coated (700 rpm, 20 seconds) onto a glass plate, and then heated on a hot plate heated to 85°C for 10 minutes, and then heated on a hot plate heated to 120°C for 10 minutes to obtain a resist film. The obtained resist film was exposed to 1000 mJ / cm2 of light using an exposure device (high-pressure mercury lamp, mask alignment device MA-10) through a lattice-shaped pattern mask with a line width of 100 μm. ２ The sample was exposed to an integrated light amount of 100 μm, cooled in air for 5 minutes, and then immersed in an alkaline developer (2.38% aqueous TMAH solution) for 360 seconds. The sample was then washed with water and heated on a hot plate at 80° C. for 30 minutes. This resulted in an evaluation sample having a pattern with a line width of 100 μm and a film thickness of 50 μm. The obtained evaluation sample was visually observed and further observed using a scanning electron microscope to confirm the pattern shape and the degree of undissolved resin due to development. The alkaline developability was then evaluated according to the following criteria. (Evaluation criteria) Good (○): No undissolved resin was present, and a uniform pattern could be formed. Fair (Δ): Undissolved resin was present locally, but a uniform pattern could be formed. Poor (×): Undissolved resin was present over a wide area, and a uniform pattern could not be formed.

[0213]

[0214]

[0215]

[0216] From Tables 1-1, 1-2, and 1-3 above, it can be seen that the acid generator (or sulfonium salt (1-1)) of the present invention has a fluorine atom or a fluoroalkyl group in the benzene rings A and B, which imparts a function of improving sensitivity to ultrashort wavelength light, at the meta position relative to the position where the sulfur atom is bonded, and also has a polar group (a hydroxy group, an alkoxy group, or a trialkylsilyl group) that has the effect of improving solvent solubility, and also contains an iodine atom in the benzene ring C, and therefore has high sensitivity to ultrashort wavelength light and, in addition, excellent solvent solubility and quencher resistance.

[0217] Furthermore, the acid generator (or sulfonium salt (1-1)) of the present invention has excellent solvent solubility and photosensitivity as described above, and therefore can be suitably used as an acid generator for photoresists (particularly as an acid generator for photoresists used in photolithography using ultrashort wavelength light). It can also be seen that when photolithography (particularly photolithography using ultrashort wavelength light) is performed using a photoresist containing the acid generator (or sulfonium salt (1-1)) of the present invention, followed by an alkali development treatment, fine patterns can be formed with high precision, enabling larger capacities and smaller sizes of electronic and optical devices to be achieved.

[0218] On the other hand, the comparative examples show that sulfonium salts in which the benzene rings A and B have neither a fluorine atom or a fluoroalkyl group nor a polar group all have low sensitivity to ultrashort wavelength light, solvent solubility, and alkaline developability. Furthermore, it is also shown that sulfonium salts in which the benzene rings A and B have a fluorine atom or a fluoroalkyl group but no polar group have high sensitivity to ultrashort wavelength light but low solvent solubility and alkaline developability. Furthermore, it is also shown that even if the benzene rings A and B have a fluorine atom or a fluoroalkyl group and a polar group, when the benzene ring C does not have an iodine atom, the sensitivity to ultrashort wavelength light and solvent solubility are low.

[0219]

[0220]

[0221]

[0222] Tables 2-1, 2-2, and 2-3 show that the acid generator (or sulfonium salt (1-2)) of the present invention has three groups [1], [2], and [3] below, and has the group [1] below at the meta position relative to the position where the sulfur atom is bonded, and therefore has high sensitivity to ultrashort wavelength light and, in addition, excellent solvent solubility and quencher resistance: [1] fluorine atom or fluoroalkyl group [2] iodine atom [3] group selected from hydroxy group, hydroxyalkyl group, alkoxy group, and carboxyl group

[0223] As described above, the acid generator (or sulfonium salt (1-2)) of the present invention has excellent solvent solubility, photosensitivity, and quencher resistance, and therefore can be suitably used as an acid generator for photoresists (particularly, an acid generator for photoresists used in photolithography using ultrashort wavelength light). It can also be seen that when photolithography (particularly, photolithography using ultrashort wavelength light) is performed using a photoresist containing the acid generator (or sulfonium salt (1-2)) of the present invention, fine patterns can be formed with high precision, thereby enabling electronic devices and optical devices to have larger capacities and smaller sizes.

[0224] On the other hand, Comparative Example 2-1 shows that sulfonium salts having no groups [1], [2], or [3] in the cation all have low sensitivity to ultrashort wavelength light, low solvent solubility, and low alkaline developability. Furthermore, Comparative Example 2-3 shows that sulfonium salts having groups [1] and [2] in the cation but no group [3] have high sensitivity to ultrashort wavelength light but low solvent solubility and low alkaline developability. Furthermore, it shows that sulfonium salts having groups [1] and [2] in the cation but no group [2] have high solvent solubility but low sensitivity to ultrashort wavelength light and low alkaline developability.

[0225]

[0226]

[0227] As can be seen from Tables 3-1 and 3-2, the acid generator (or sulfonium salt (3-1)) of the present invention has significantly improved solvent solubility and improved photosensitivity to electron beams compared to when it does not contain an iodine atom. Furthermore, since the acid generator (or sulfonium salt (3-1)) of the present invention contains a fluorine atom or a fluoroalkyl group at the ortho- and / or meta-position relative to the position where the sulfur atom is bonded, it has superior quencher resistance compared to when a fluorine atom or a fluoroalkyl group is contained at the para-position relative to the position where the sulfur atom is bonded. Furthermore, photosensitivity to electron beams is also improved.

[0228] Because the acid generator (or sulfonium salt (3-1)) of the present invention has the above-described 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). Furthermore, photoresists containing the acid generator (or sulfonium salt (3-1)) 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 (3-1)) of the present invention, fine patterns can be formed with high precision, enabling increased capacity and miniaturization of electronic and optical devices.

[0229] In summary, the configuration of the present disclosure and its variations are described below: [1] A sulfonium salt represented by the following formula (1): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the formula (I) represent a fluorine atom or a fluoroalkyl group, and n represents an integer of 1 or more. The benzene ring in the formula (I) may have a substituent bonded thereto in addition to the above groups. － represents a monovalent counter anion) [2] A sulfonium salt represented by the following formula (1-1): (wherein, Rf １ , Rf ２ , Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. １ , R １１ are the same or different and represent 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. n1 represents an integer of 1 to 3. X －represents a monovalent counter anion) [3] A sulfonium salt represented by the following formula (1-2): (wherein, Rf １ , Rf ２ , Rf １１ , and Rf １２ are the same or different and represent a fluorine atom or a fluoroalkyl group. ａ represents a hydroxy group, a hydroxyalkyl group, an alkoxy group, or a carboxyl group. m1 and m2 each represent an integer of 1 or more, provided that m1 + m2 is an integer of 5 or less. X － represents a monovalent counter anion) [4] A sulfonium salt represented by the following formula (1-3): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and represent a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the above represent a fluorine atom or a fluoroalkyl group, and m represents 0 or 1. X －represents a monovalent counter anion). [5] The sulfonium salt according to any one of [1] to [4], wherein the monovalent counter anion is a sulfonate anion or a nitrogen anion. [6] An acid generator comprising the sulfonium salt according to any one of [1] to [5]. [7] Use of the sulfonium salt according to any one of [1] to [5] as an acid generator. [8] A photoresist comprising the acid generator according to [6] and an acid-reactive compound. [9] The photoresist according to [8], further comprising a quencher.

[10] A method for producing an electronic or optical device, comprising a step of forming a pattern by photolithography using the photoresist according to [8] or [9].

[0230] The sulfonium salt (1) of the present invention has excellent photosensitivity and acid generating ability. It also has excellent solvent solubility and quencher resistance. Therefore, when the sulfonium salt (1) is dissolved in a solvent and incorporated into a photoresist, it can be uniformly dispersed in the photoresist. By carrying out exposure and development using ultrashort wavelength light, fine patterns can be formed with high precision. Furthermore, by using a photoresist obtained by adding the sulfonium salt (1) and performing photolithography using light with a wavelength of 20 nm or less, fine patterns can be formed with high precision, enabling further increases in capacity and further miniaturization of electronic or optical devices.

Claims

1. A sulfonium salt represented by the following formula (1): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and each represents a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the above represent a fluorine atom or a fluoroalkyl group. n represents an integer of 1 or more. The benzene ring in the formula may have a substituent bonded thereto in addition to the above groups. X － indicates a monovalent counter anion) 2. The sulfonium salt according to claim 1, wherein the sulfonium salt represented by formula (1) is a sulfonium salt represented by the following formula (1-1): (In the formula, 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. n1 represents an integer of 1 to 3. X － indicates a monovalent counter anion) 3. The sulfonium salt according to claim 1, wherein the sulfonium salt represented by formula (1) is a sulfonium salt represented by the following formula (1-2): (In the formula, 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. ａ represents a hydroxy group, a hydroxyalkyl group, an alkoxy group, or a carboxyl group. m1 and m2 each represent an integer of 1 or more, provided that m1 + m2 is an integer of 5 or less. X － indicates a monovalent counter anion) 4. The sulfonium salt according to claim 1, wherein the sulfonium salt represented by formula (1) is a sulfonium salt represented by the following formula (1-3): (In the formula, R Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , R Ｆ １４ are the same or different and each represents a fluorine atom, a fluoroalkyl group, a hydrogen atom, a hydroxyl group, or an alkyl group. Ｆ １ , R Ｆ ２ , R Ｆ ３ , R Ｆ ４ , R Ｆ １１ , R Ｆ １２ , R Ｆ １３ , and R Ｆ １４ At least two selected from the group consisting of a fluorine atom or a fluoroalkyl group, and m is 0 or 1. － indicates a monovalent counter anion) 5. The sulfonium salt according to any one of claims 1 to 4, wherein the monovalent counter anion is a sulfonate anion or a nitrogen anion.

6. An acid generator comprising the sulfonium salt according to any one of claims 1 to 4.

7. A photoresist comprising the acid generator of claim 6 and an acid-reactive compound.

8. The photoresist of claim 7 further comprising a quencher.

9. A method for producing an electronic device or an optical device, comprising the step of forming a pattern by photolithography using the photoresist according to claim 7.

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