JP2016056168A - Process for producing sulfonium salt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a sulfonium salt, which can suppress formation of a monosulfonium salt.SOLUTION: Provided is a process for producing a sulfonium salt comprising: forming a first sulfonium salt containing a sulfonium cation and a first anion; forming a second sulfonium salt by exchanging the first anion with a halide ion; and forming a third sulfonium salt by exchanging the halide ion with a second anion.SELECTED DRAWING: Figure 1

Description

  Some aspects of the present invention relate to a process for producing sulfonium salts useful as photoacid generators.

Conventionally, a salt of triarylsulfonium and a fluorine-containing anion (such as BF ₄ , PF ₆ , AsF _6, and SbF ₆ ) is known as a polymerization initiator having high photocationic polymerization initiating ability.
However, in the conventionally proposed method for producing a sulfonium salt, for example, a sulfide and a sulfoxide are condensed in the presence of at least one of an inorganic acid such as sulfuric acid and a strong organic acid such as methanesulfonic acid. Thereafter, a method of exchanging an anion derived from a strong organic acid with a fluorine-containing anion (for example, see Patent Document 1) is known. In this method, a bissulfonium salt having two sulfonio groups in one molecule is formed in addition to a monosulfonium salt having one sulfonio group in one molecule.

JP-A-61-100557

    According to the study by the present inventors, the bissulfonium salt has a higher water solubility than the monosulfonium salt. For this reason, the monosulfonium salt is more preferable as the sulfonium salt added to the photoresist used in the step of immersing the photoresist in water such as the electrolytic plating step. However, in the prior art, the bissulfonium salt is generated by a side reaction, and it is not easy to reduce the ratio.

  Some aspects of the present invention have been made in view of such circumstances, and provide a method for producing a sulfonium salt capable of suppressing the formation of a monosulfonium salt.

  According to some embodiments of the present invention, a first sulfonium salt containing a sulfonium cation and a first anion is produced, and the first anion is exchanged with a halide ion to produce a second sulfonium salt, and the halogen There is provided a method for producing a sulfonium salt comprising the step of exchanging a fluoride ion with a second anion to produce a third sulfonium salt.

  When the present inventor studied to suppress the formation of a bissulfonium salt, instead of directly exchanging the first anion of the sulfonium salt with the second anion, the first anion was exchanged with a halide ion, and a halide ion was obtained. It was found that the production of bissulfonium salt can be suppressed by exchanging for the second anion, and the present invention has been completed. The sulfonium salt obtained by the method of the present invention functions as a photoacid generator. Such a photoacid generator can be added to a photoresist and used as a cationic polymerization initiator. Moreover, you may add to the composition containing the polymer decomposed | disassembled by an acid, and may use it for the use which starts the decomposition reaction of a polymer by irradiation of light. Further, it may be added to a composition containing a precursor that reacts with another substance in the presence of an acid, and used for the purpose of initiating the reaction by light irradiation.

Hereinafter, various embodiments of the present invention will be exemplified. The following embodiments can be combined with each other.
Preferably, the sulfonium cation has at least one aryl group.
Preferably, the first sulfonium salt is produced by condensing a sulfoxide compound and an aryl compound in the presence of an acid.
Preferably, the sulfoxide compound is an optionally substituted diaryl sulfoxide compound.
Preferably, the aryl compound is an optionally substituted diaryl sulfide compound.
Preferably, the acid is sulfuric acid or sulfonic acid.
Preferably, the second sulfonium salt is produced by reacting a halide containing the halide ion with the first sulfonium salt.
Preferably, the third sulfonium salt is produced by reacting a metal salt containing a second anion with a second sulfonium salt.
Preferably, the second anion contains at least one fluorine atom.
Preferably, the second anion is CF ₃ SO ₃ ⁻ , CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ ⁻ , AsF ₆ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , BF ₄ ⁻ and B (C ₆ F ₅ ). ₄ ^- it is one selected from the group consisting of.

(A)-(e) shows the electroplating process included in the manufacturing process which manufactures devices, such as an integrated circuit (IC), using the photoresist containing a photo-acid generator. (A)-(c) shows the electroplating process following FIG.1 (e). (A)-(c) shows the electroplating process following FIG.2 (c).

  Embodiments of the present invention will be described below. Various characteristic items shown in the following embodiments can be combined with each other. In addition, the invention is independently established for each feature.

1. Method for Producing Sulphonium Salt A method for producing a sulfonium salt according to an embodiment of the present invention generates a first sulfonium salt containing a sulfonium cation and a first anion, and exchanges the first anion with a halide ion to produce a second sulfonium salt. Forming a sulfonium salt and exchanging the halide ions with a second anion to produce a third sulfonium salt.

<Step of producing first sulfonium salt>
In this step, a first sulfonium salt containing a sulfonium cation and a first anion is generated. The sulfonium cation is represented by the following general formula (1). The first anion is an anion that becomes a counter anion of the sulfonium cation and generates a weaker acid than the conjugate acid of the second anion.

(Wherein R ^{1 to} R ³ may be the same as or different from each other, and each may be a hydrogen atom, a hydrocarbon group that may be substituted with a substituent, or a substituent that may be substituted with a substituent). Any of the good heterocyclic groups, two or three of R ^{1 to} R ³ may be bonded to each other to form a ring.)

  Examples of the hydrocarbon group include alkyl groups such as methyl group, ethyl group, butyl group and octyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; aryl groups such as phenyl group, naphthyl group and anthryl group. Examples of the heterocyclic group include aromatic heterocyclic groups such as a pyridyl group and a furfuryl group.

  Examples of the substituent include an alkyl group such as a methyl group and an ethyl group; an aryl group such as a phenyl group, a naphthyl group and an anthryl group; an alkyloxy group such as a methoxy group; an aryloxy group such as a phenoxy group; an alkylthio group such as a methylthio group An arylthio group such as a phenylthio group; an acyl group such as an acetyl group; an aroyl group such as a benzoyl group; an acyloxy group such as an acetoxy group; an alloyoxy group such as a benzoyloxy group; a nitrile group, a nitro group, a hydroxy group, and a halogen An atom etc. are mentioned.

  In one example, the sulfonium cation is a sulfonium cation having at least one aryl group, more specifically a triarylsulfonium cation, and more specifically, diphenyl [4- (phenylthio) phenyl] -sulfonium cation. It is. In one example, the conjugate acid of the first anion is sulfonic acid, more specifically alkyl sulfonic acid, more specifically alkyl sulfonic acid having 1 to 8 carbon atoms, and more specifically, Methanesulfonic acid.

  The production method of the first sulfonium salt is not particularly limited, and for example, it can be produced by condensing a sulfoxide compound and an aryl compound in the presence of an acid. For example, the condensation reaction can be allowed to proceed by adding a sulfoxide compound and an aryl compound to a reaction solvent composed of an acid and stirring. In addition, when the first sulfonium salt is produced by this method, the anion composed of the conjugate base of the acid becomes the first anion of the first sulfonium salt. Moreover, you may use the mixture of the solvent and acid which do not inhibit a condensation reaction as a reaction solvent.

  The sulfoxide compound is represented by the following general formula (2).

(In the formula, R ^{1 to} R ² are defined in the same manner as in the general formula (1). R ¹ and R ² may be bonded to each other to form a ring.)

  Specific examples of the sulfoxide compound include dimethyl sulfoxide, methyl ethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfoxide, dibenzothiophene-S-oxide, (4-methylphenyl) phenyl sulfoxide, 4,4′-dimethyldiphenyl sulfoxide, 4,4. '-Dimethoxydiphenyl sulfoxide, 4-methylthiodiphenyl sulfoxide, (4-phenylthiophenyl) phenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-difluorodiphenyl sulfoxide, 4,4'-dichlorodiphenyl sulfoxide, 4 4,4′-dinitrodiphenyl sulfoxide, 4-benzoyldiphenyl sulfoxide, 4,4′-carboxydiphenyl sulfoxide, and the like. These sulfoxide compounds may be used alone or in combination of two or more.

  Among the sulfoxide compounds, preferred are optionally substituted diaryl sulfoxide compounds, particularly diphenyl sulfoxide, dibenzothiophene-S-oxide, 4,4′-dimethyldiphenyl sulfoxide, 4,4′-dimethoxydiphenyl sulfoxide, 4 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-difluorodiphenyl sulfoxide, 4,4′-dichlorodiphenyl sulfoxide.

The aryl compound is a compound that functions to introduce R ³ in the general formula (1). In order to produce the first sulfonium salt by a condensation reaction between the sulfoxide compound and the aryl compound, the aryl compound preferably has at least one hydrogen atom that is eliminated during the condensation. In addition, when the aryl compound has two or more hydrogen atoms that are eliminated during the condensation, a bissulfonium salt is easily generated. In such a case, the technical advantage of the present invention is remarkably increased. Become.

  Examples of the aryl compound include monocyclic or condensed polycyclic unsubstituted aryl compounds such as benzene, naphthalene, anthracene, phenanthrene, naphthacene, and pyrene; aryl compounds substituted with an alkyl group such as toluene, cumene, tert -Butylbenzene, xylene, ethylbenzene, dodecylbenzene, 1-methylnaphthalene, 1H-indene; aryl compounds substituted with an aryl group, such as biphenyl, biphenylene, 1,2'-binaphthyl, 2-phenylnaphthalene; substituted Aryl compounds substituted with an optionally substituted alkoxy group, for example, anisole, ethoxybenzene, 1-methoxynaphthalene, benzylphenyl ether, benzofuran; aryl compounds substituted with an optionally substituted aryloxy group, For example, diphenyl ether, 2-ethoxynaphthalene, 4-phenoxyphenol, xanthene; aryl compounds substituted with an alkylsulfonyl group, such as methylphenylsulfone; aryl compounds substituted with an arylsulfonyl group, such as diphenylsulfone; substituted Aryl compounds substituted with an optionally substituted alkylthio group, for example, thioanisole, ethylthiobenzene, benzothiophene, benzylphenyl sulfide, phenacylphenyl sulfide; aryl compounds substituted with an optionally substituted arylthio group (ie, Diaryl sulfide compounds), for example, diphenyl sulfide, dibenzothiophene, (2-methylphenyl) phenyl sulfide, (4-methylphenyl) phenyl sulfide, 2, '-Ditolyl sulfide, 2,3'-ditolyl sulfide, 2-phenylthionaphthalene, 9-phenylthioanthracene, (3-chlorophenyl) phenyl sulfide, (4-chlorophenyl) phenyl sulfide, 3,3'-dichlorodiphenyl Sulfide, (3-bromophenyl) phenyl sulfide, 2,2′-dibromodiphenyl sulfide, 3,3′-dibromodiphenyl sulfide, (2-methoxyphenyl) phenyl sulfide, phenoxathiin, thioxanthone, 2-isopropylthioxanthone, 2 -Methoxythioxanthone, 4,4'-diphenylthiobenzophenone, 4,4'-diphenylthiodiphenyl ether, 4,4'-diphenylthiobiphenyl, (4-phenylthiophenyl) phenyl sulfide, (4-benzo Ilphenyl) phenyl sulfide, (2-chloro-4-benzoylphenyl) phenyl sulfide, (2-methylthiobenzoylphenyl) phenyl sulfide and the like.

  The acid promotes the condensation reaction between the sulfoxide compound and the aryl compound and serves as a reaction solvent for the condensation reaction. Usable acids include organic acids such as sulfonic acid and carboxylic acid, and inorganic acids such as sulfuric acid.

  Examples of the sulfonic acid include alkyl sulfonic acid and aromatic sulfonic acid. Among these, alkylsulfonic acid is preferable, and alkylsulfonic acid having 1 to 8 carbon atoms is more preferable. Specific examples include methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, butane sulfonic acid, pentane sulfonic acid, and octane sulfonic acid.

  Examples of the carboxylic acid include alkyl carboxylic acids and aromatic carboxylic acids. Among these, alkyl carboxylic acids are preferable, and alkyl carboxylic acids having 1 to 8 carbon atoms are more preferable. Specific examples include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid and the like.

  Moreover, it is preferable to add a dehydrating agent in the reaction solvent. In this case, water generated by the condensation reaction is removed from the reaction system, and the condensation reaction is promoted. Examples of the dehydrating agent include inorganic oxides such as phosphorus pentoxide, inorganic acids such as polyphosphoric acid, and organic acid anhydrides such as acetic anhydride, propionic anhydride, and phthalic anhydride. These dehydrating agents may be used alone or in combination of two or more. Of these, preferred are organic acid anhydrides such as acetic anhydride, especially acetic anhydride.

<Step of producing second sulfonium salt>
In this step, the first anion of the first sulfonium salt is exchanged with a halide ion to produce a second sulfonium salt.

  The second sulfonium salt can be produced, for example, by reacting a halide containing the halide ion with the first sulfonium salt. This reaction can be caused, for example, by adding and stirring the first sulfonium salt and halide in a solvent that forms an aqueous layer and an organic layer. For example, when the solubility of the second sulfonium salt composed of a sulfonium cation and a halide ion in the organic layer is larger than the solubility of the halide salt composed of a counter cation and a first anion in the organic layer, By stirring the first sulfonium salt and halide in the solvent, the second sulfonium salt can be selectively taken into the organic layer.

  Examples of the organic solvent constituting the organic layer include an organic solvent capable of dissolving the second sulfonium salt, such as dichloromethane.

  Examples of the halide (fluoride, chloride, bromide, iodide) include hydrogen halide and alkali metal (lithium, sodium, potassium, etc.) salts of halogen. In one example, the hydrogen halide includes hydrogen chloride and hydrogen bromide, and the alkali metal salt of the halogen includes sodium chloride and sodium bromide.

<Step of producing third sulfonium salt>
In this step, the halide ion of the second sulfonium salt is exchanged with the second anion to produce a third sulfonium salt.

  The conjugate acid of the second anion is preferably a stronger acid than the conjugate acid of the first anion. In this case, the strength of the acid generated when the sulfonium salt functions as a photoacid generator is increased by exchanging the first anion of the sulfonium salt with the second anion.

  Examples of the conjugated acid of the second anion include inorganic acids and organic acids. Inorganic acids include hexafluoroantimonic acid, hexafluoroarsenic acid, hexafluorophosphoric acid, pentafluorohydroxoantimonic acid, tetrafluoroboric acid, trifluorotristrifluoromethylphosphoric acid, trifluorotrispentafluoroethyl phosphoric acid, Fluorotrisheptafluoropropyl phosphate, tetrakis (pentafluorophenyl) boric acid, tetrakis (trifluoromethylphenyl) boric acid, trifluoro (pentafluorophenyl) boric acid, tetrakis (difluorophenyl) boric acid, difluorobis (pentafluoro) Phenyl) boric acid and the like. Examples of the organic acid include alkyl sulfonic acids having 1 to 8 carbon atoms, or those in which part or all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms. Examples of the alkyl sulfonic acid include methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, butane sulfonic acid, pentane sulfonic acid, octane sulfonic acid and the like.

In other words, the second anion preferably contains at least one fluorine atom, and is CF ₃ SO ₃ ⁻ , CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ ⁻ , AsF ₆ ⁻ , PF ₆ ⁻ , SbF ₆ ^−. , BF ₄ ^- and _{B (C 6 F 5) 4} - made of is more preferable.

  The third sulfonium salt can be produced, for example, by reacting a metal salt containing a second anion with the second sulfonium salt. This reaction can be caused, for example, by adding and stirring the second sulfonium salt and the metal salt in a solvent that forms the aqueous layer and the organic layer. For example, when the solubility of the third sulfonium salt composed of the sulfonium cation and the second anion in the organic layer is larger than the solubility of the salt composed of the counter anion of the second anion and the halide ion in the organic layer The third sulfonium salt can be selectively taken into the organic layer by stirring in a state where the second sulfonium salt and the metal salt are present in the solvent.

  Examples of the organic solvent constituting the organic layer include an organic solvent capable of dissolving the third sulfonium salt, such as dichloromethane. The metal salt of the second anion is preferably an alkali metal salt such as a lithium salt, a sodium salt, or a potassium salt.

  Through the above steps, the production of the sulfonium salt of this embodiment is completed. The present embodiment is characterized in that instead of directly exchanging the first anion of the sulfonium salt with the second anion, the first anion is exchanged with a halide ion, and the halide ion is exchanged with the second anion. Production of a bissulfonium salt can be suppressed by producing a sulfonium salt through such a process. This point is demonstrated in the examples described later.

  Further, since the bissulfonium salt has a higher solubility in water than the monosulfonium salt, the sulfonium salt of the present embodiment having a low content of the bissulfonium salt is a step of immersing a photoresist in water, such as an electrolytic plating step. It can be suitably used as a photoacid generator to be added to the photoresist used in the above.

2. Electrolytic Plating Step Here, an electrolytic plating step using a photoresist containing the sulfonium salt produced by the above method as a photoacid generator will be described. The photoresist includes a polymer and the sulfonium salt. In one example, the polymer includes the following polymer A and polymer B. An example of the sulfonium salt is diphenyl [4- (phenylthio) phenyl] -sulfonium nonaflate obtained in Examples described later. The electrolytic plating process is a process included in a manufacturing process of a device such as an integrated circuit (IC). In this electrolytic plating process, a conductive portion is formed in a through hole formed by a photolithography process.

  First, a core substrate 1 is prepared as shown in FIG. 1A, and a patterned conductor layer 2 is formed on the surface of the core substrate 1 as shown in FIG.

  Next, as shown in FIG. 1C, a solder resist layer having a thickness of about 20 μm is applied by applying a thermosetting resin so as to cover the conductor layer 2 and the core substrate 1 and thermosetting the thermosetting resin. 3 is formed.

  Next, as shown in FIG. 1 (d), the solder resist layer 3 is irradiated with laser light to form the first through hole 4 to expose a part of the conductor layer 2. The smear remaining in the first through hole 4 is removed by a desmear process.

  Next, as shown in FIG.1 (e), the member in which the 1st through hole 4 was formed in the said process is immersed in the solution containing nickel salt, copper sulfate, sodium hydroxide, a complexing agent, and a chelating agent. Thus, the first conductive portion 5 is formed.

  Next, as shown in FIG. 2A, an intervening layer 6 and an electroless plating layer 7 are formed by an electroless plating process.

  Next, as shown in FIG. 2B, a photoresist layer 8 is formed to a thickness of 20 μm or more so as to cover the intervening layer 6 and the electroless plating layer 7. The thickness of the photoresist layer 8 is preferably 30 μm or more, and preferably 40 μm or more.

  Next, as shown in FIG. 2C, the second through hole 9 is formed by a photolithography process so that the intervening layer 6 is exposed on the surface. Specifically, the photoresist layer 8 is exposed and cured in a state where the portion corresponding to the second through hole 9 is covered with the light shielding pattern, and then the second through hole is dissolved by dissolving the portion covered with the light shielding pattern. 9 is formed. When the photoresist layer 8 is exposed, for example, with light having a wavelength of 365 nm, the photoacid generator absorbs the light and is decomposed to generate a conjugate acid of the second anion. This acid initiates cationic polymerization of the polymers A and B, and the photoresist layer 8 is cured.

Next, as shown to Fig.3 (a), the 2nd electroconductive part 10 is formed by electroplating by applying a voltage using the electroless-plating layer 7 as an electrode. In this electrolytic plating, the photoresist layer 8 is immersed in an electrolytic solution using water as a solvent. For this reason, if the ratio of the water-soluble component in the sulfonium salt is small, the plating solution is not contaminated, and further, the generation of acid in the plating solution is suppressed, thereby suppressing the contamination of the apparatus and the working environment. There is. The sulfonium salt of this embodiment has the above-mentioned advantages because the proportion of the water-soluble bissulfonium salt is very small.

  Next, as shown in FIG. 3B, the photoresist layer 8 is removed by immersing the member in which the second conductive portion 10 is formed in the above-described step in a stripping solution containing amine.

  Next, as shown in FIG.3 (c), the conductive post 11 is formed by performing a reflow process with respect to the member obtained at the said process. The reflow process is performed in a reflow furnace having a temperature higher than the melting point of at least one component of the second conductive portion 10.

  The manufacturing method of the conductive part or conductive post described above can be applied to the manufacture of devices such as electronic devices and electro-optical devices. The electronic device includes an IC chip, and the electro-optical device includes a display device.

  In particular, the manufacturing method of the conductive part or the conductive post is suitable for high-density mounting.

  According to the experimental procedure shown below, diphenyl [4- (phenylthio) phenyl] -sulfonium nonaflate (PSDPS-Nf) was synthesized by a direct salt exchange method (Method A) and an indirect salt exchange method (Method B). The ratio of the bissulfonium salt contained in was compared.

(1) Synthesis of PSDPS-Nf by direct salt exchange method (Method A)

  10.0 g diphenyl sulfoxide and 11.1 g diphenyl sulfide were dissolved in 26.5 g methanesulfonic acid. 3.16 g of phosphorous oxide was added to the methanesulfonic acid solution containing diphenyl sulfoxide and diphenyl sulfide over 10 minutes. The resulting mixture was stirred at 25 ° C. for 3 hours. Thereafter, the obtained mixture was cooled to 5 ° C., 60.0 g of water was added, and the mixture was further stirred for 10 minutes. Thereafter, the obtained solution was washed with 20 g of ethyl acetate, and the aqueous layer was recovered. This aqueous layer contains diphenyl [4- (phenylthio) phenyl] -sulfonium methanesulfonate produced by the condensation reaction of diphenyl sulfoxide and diphenyl sulfide.

  Next, 17.5 g of potassium nonaflate (potassium nonafluorobutanesulfonate) and 40 g of dichloromethane were added to the aqueous solution consisting of the aqueous layer and stirred at 25 ° C. for 1 hour, whereby PSDPS-Nf was dissolved in dichloromethane. Extract into the layer and collect the dichloromethane layer. Then, the dichloromethane solution which consists of a dichloromethane layer was wash | cleaned 4 times with water, and the dichloromethane was distilled off. This gave 27.1 g PSDPS-Nf. Thereafter, the purity of the product was measured by HPLC using an internal standard method. As a result, it was confirmed that 2.4% of bis- [4- (diphenylsulfonio) phenyl] -sulfide bis-nonaflate was contained as an impurity in the product.

The structural formula of PSDPS-Nf is shown below.

(2) Synthesis of diphenyl [4- (phenylthio) phenyl] -sulfonium bromide (PSDPS-Br)

  20.0 g diphenyl sulfoxide and 22.1 g diphenyl sulfide were dissolved in 57.0 g methanesulfonic acid. 6.32 g of phosphorus oxide was added to the methanesulfonic acid solution containing diphenyl sulfoxide and diphenyl sulfide over 10 minutes. The resulting mixture was stirred at 25 ° C. for 3 hours. The resulting mixture was then cooled to 5 ° C. and stirred for an additional 10 minutes after adding 120.0 g of water. Thereafter, the obtained solution was washed with 40 g of ethyl acetate, and the aqueous layer was recovered. This aqueous layer contains diphenyl [4- (phenylthio) phenyl] -sulfonium methanesulfonate produced by the condensation reaction of diphenyl sulfoxide and diphenyl sulfide.

  Next, 16.67 g of a 48% hydrogen bromide aqueous solution and 180 g of dichloromethane were added to the aqueous solution consisting of the aqueous layer, and the mixture was stirred at 25 ° C. for 1 hour to extract PSDPS-Br into the dichloromethane layer. The dichloromethane layer was collected. Then, the dichloromethane solution which consists of a dichloromethane layer was wash | cleaned twice with water, and the dichloromethane was distilled off. This gave 48.2 g PSDPS-Br.

(3) Synthesis of PSDPS-Nf by the indirect salt exchange method (Method B) 20.0 g of PSDPS-Br obtained in (2) above and 15.7 g of potassium nonaflate consisted of 40 g of water and 80 g of dichloromethane. Added to bilayer solvent. The resulting mixture was stirred at 25 ° C. for 1 hour to extract PSDPS-Nf into the dichloromethane layer, and the dichloromethane layer was recovered. Then, the dichloromethane solution which consists of a dichloromethane layer was wash | cleaned twice with water, and the dichloromethane was distilled off. This gave 26.3 g PSDPS-Nf. The purity of the product was measured by internal standard method using HPLC. As a result, it was confirmed that 0.2% of bis- [4- (diphenylsulfonio) phenyl] -sulfide bis-nonaflate was contained in the product as an impurity.

(4) Experimental procedure for water solubility measurement

  0.1 g PSDPS-Nf was added to 10.0 g water. The resulting mixture was stirred at 80 ° C. for 1 hour. Thereafter, the obtained mixture was cooled to 25 ° C., and 0.02 g of sodium benzoate was added as an internal standard substance, followed by further stirring for 10 minutes. Then, the obtained mixture was filtered and the filtrate was recovered. Thereafter, the water solubility of PSDPS-Nf was measured by an internal standard method using HPLC.

  The results are shown in Table 1. Table 1 shows the solubility (wt%) in water of the products obtained by methods A and B.

  Evaluation sample 1 synthesized by method A was higher in water solubility than evaluation sample 2 synthesized by method B. This indicates that bis- [4- (diphenylsulfonio) phenyl] -sulfide bis-nonaflate is the main water-soluble component in the evaluation sample. In other words, for water, the dicationic structure is more easily eluted than the monocationic structure. The low water solubility of the organic salt containing a monocation is advantageous in a plating process including a process applied to the formation of a conductive part such as a Cu pillar structure by a photolithography patterning process or the like.

Claims (10)

Producing a first sulfonium salt comprising a sulfonium cation and a first anion;
Exchanging the first anion with a halide ion to produce a second sulfonium salt;
A method for producing a sulfonium salt, comprising the step of exchanging the halide ion with a second anion to produce a third sulfonium salt. The method of claim 1, wherein the sulfonium cation has at least one aryl group. The method according to claim 1 or 2, wherein the first sulfonium salt is produced by condensing a sulfoxide compound and an aryl compound in the presence of an acid. The method according to claim 3, wherein the sulfoxide compound is an optionally substituted diaryl sulfoxide compound. The method according to claim 3 or 4, wherein the aryl compound is an optionally substituted diaryl sulfide compound. The method according to claim 3, wherein the acid is sulfuric acid or sulfonic acid. The method according to claim 1, wherein the second sulfonium salt is produced by reacting a halide containing the halide ions with the first sulfonium salt. The method according to any one of claims 1 to 7, wherein the third sulfonium salt is produced by reacting a metal salt containing a second anion with a second sulfonium salt. The method according to any one of claims 1 to 8, wherein the second anion contains at least one fluorine atom. The second anion includes CF ₃ SO ₃ ⁻ , CF ₃ CF ₂ CF ₂ CF ₂ SO ₃ ⁻ , AsF ₆ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , BF ₄ ⁻ and B (C ₆ F ₅ ) ₄ ^−. The method according to any one of claims 1 to 9, wherein the method is one selected from the group consisting of: