JP5252620B2 - Photoacid generator and resin composition for photolithography - Google Patents

Description

  The present invention relates to a resin composition for photolithography used for semiconductor production and the like, and a photoacid generator (PAG) that is a component thereof, in particular, a photoacid generator that generates acid when irradiated with ultraviolet rays (i-line), And a photolithographic resin composition comprising the photoacid generator.

  Nonionic i-line-compatible photoacid generators are attracting attention because they are relatively compatible with resins and can be used with high-pressure mercury lamps that are inexpensive light sources (for example, Non-Patent Document 1 to Non-Patent Document 1). Reference 5).

  Accordingly, the inventors have developed an imide-type photoacid generator N-trifluoromethanesulfonyloxy-7-methylthianthrene-2,3-dicarboxylic acid imide (hereinafter referred to as Me-THITf) having a thianthrene having an absorption at 290 nm as a chromophore. And N-pentafluorobenzenesulfonyloxy-7-methylthianthrene-2,3-dicarboxylic imide (hereinafter abbreviated as Me-THIPS) have been developed (Non-Patent Document 5). See).

Me-THITf and Me-THIPS generate trifluoromethanesulfonic acid, which is a super strong acid when irradiated with light, and catalyze the crosslinking and insolubilization of the resin. The molar absorption coefficient at these i-line (wavelength 365 nm) is located respectively 1570M ^-1 cm ^-1 and 1640M ^-1 cm ^-1, which is commercially available products of the photoacid generator N- trifluoromethane sulfonyl b carboxymethyl -1 , 8-naphthylimide (hereinafter abbreviated as NITf).

  However, although Me-THITf and Me-THIPS are excellent photoacid generators, the solubility in a solvent was not so good and the compatibility with the resin was insufficient. In addition, synthesis of these photoacid generators requires a process of protection and deprotection, so it takes a lot of labor and a long reaction time to reach the final products, Me-THITf and Me-THIPS. Needed.

  Accordingly, the inventors have a short reaction time, a high solubility in a solvent, and a sufficiently high compatibility with a resin, N-trifluoromethanesulfonyloxy-7-tert-butylthianthrene-2 , 3-Dicarboxylic acid imide (hereinafter abbreviated as tert-THITf), N-pentafluorobenzenesulfonyloxy-7-tert-butylthianthrene-2,3-dicarboxylic acid imide (hereinafter abbreviated as tert-THIPS) )) And other non-ionic photoacid generators are being developed.

These tert-THITf and tert-THIPS have a t-butyl group instead of the methyl group of Me-THITf and Me-THIPS, so they have high solubility in solvents and compatibility with resins, but they are thermally stable. Sex was insufficient. Therefore, when a resist film is formed on a silicon wafer using a photolithographic resin composition containing these photoacid generators, the resist film must be dried at a low temperature for a long time, thereby reducing the productivity of the semiconductor. It was an obstacle to pulling up.
T. Asakura, H. Yamato, M. Ohwa, J. Photopolym. Sci. Technol., 13, 223 (2000). H. Okamura, Y. Watanabe, M. Tsunooka, M. Shirai, T. Fujiki, S. Kawasaki, M. Yamada, J. Photopolym. Sci. Technol., 15, 145 (2002). H. Okamura, K. Sakai, M. Tsunooka, M. Shirai, J. Photopolym. Sci. Technol., 16, 87 (2003). C. Iwashima, G. Imai, H. Okamura, M. Tsunooka, M. Shirai, J. Photopolym. Sci. Technol., 16, 91 (2003). H. Okamura, R. Matsumori, M. Shirai, J. Photopolym. Sci. Technol., 17,131, (2004).

  Therefore, an object of the present invention is to provide a photoacid generator that generates an acid by i-ray irradiation, has high solubility in a solvent, high compatibility with a resin, and excellent thermal stability.

  As a result of intensive studies on the structure of the photoacid generator, the inventors have generated an acid by i-ray irradiation, and have high solubility in a solvent, compatibility with a resin, and excellent thermal stability. A photolithographic composition comprising the generator and the photoacid generator has been developed.

（式中、R₁は低級アルキル基であり、R₂は低級アルキル基である。また、R₃は水素、低級アルキル基、フェニル基、ベンジル基のうちの何れか一つである。さらに、X^-はCF₃SO₃ ^-、PF₆ ^-、SbF₆ ^-、BF₄ ^-、C₄F₉SO₃ ^-のうちの何れか一つである。）で示される化合物からなる群れより選ばれた少なくとも一種の化合物を含む含むものである。なお、低級アルキル基とは炭素数１〜６の鎖状又は環状のアルキル基のことである。 That is, the photoacid generator according to claim 1 is:
Formula (I) and Formula (II)

(In the formula, R ₁ is a lower alkyl group, R ₂ is a lower alkyl group, and R ₃ is any one of hydrogen, a lower alkyl group , a phenyl group, and a benzyl group . X ⁻ is any one of CF ₃ SO ₃ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , BF ₄ ⁻ and C ₄ F ₉ SO ₃ ⁻ ). It contains at least one compound. The lower alkyl group is a chain or cyclic alkyl group having 1 to 6 carbon atoms.

The photoacid generator according to claim 2 is the photoacid generator according to claim 1, wherein R ₁ is a methyl group or a butyl group in the formulas (I) and (II).

The photoacid generator according to claim 3 is the photoacid generator according to claim 1 or claim 2, wherein R ₂ is a t-butyl group or a methyl group in formulas (I) and (II). It is a basic one.

The photoacid generator according to claim 4 is the photoacid generator according to any one of claims 1 to 3, wherein in the formula (I) and the formula (II), R ₃ Is one of hydrogen, a phenyl group, and a benzyl group.

The photoacid generator according to claim 5 is the photoacid generator according to any one of claims 1 to 4, wherein in formula (I) and formula (II), X ⁻ Is any one of CF ₃ SO ₃ ⁻ , PF ₆ ⁻ and C ₄ F ₉ SO ₃ ⁻ .

  The resin composition for photolithography according to claim 6 contains the photoacid generator according to any one of claims 1 to 5.

  This resin composition for photolithography contains, in addition to a photoacid generator, a resin that is cross-linked and insolubilized by an acid generated from the photoacid generator, and, if necessary, a solvent for improving known coating properties. In addition, various additives may be included.

  Examples of the resin include polymers, oligomers, and polyfunctional monomers having an epoxy group, an oxetane group, and a vinyl ether group in the side chain. Among these, an oligomer having an epoxy group is preferable from the viewpoint of high reactivity, versatility, and properties of a cured product. In addition, you may use these resin individually or in combination of 2 or more types.

  Examples of the solvent include organic solvents such as N, N′-dimethylformamide, tetrahydrofuran, toluene, dimethoxyethane, acetonitrile, diethylene glycol dimethyl ether, cyclohexanone, and propylene glycol methyl ether acetate. Among these, cyclohexanone is preferable because of its high solubility in the compound and its appropriate boiling point. In addition, you may use these solvents individually or in combination of 2 or more types.

  Examples of the additive include dyes, pigments, thickeners, antifoaming agents, leveling agents, and dispersing agents.

  The photoacid generator according to claim 1 generates an acid upon irradiation with i-rays, has high solubility in a solvent, compatibility with a resin, and high thermal stability. Therefore, a uniform photolithography composition excellent in thermal stability can be obtained.

In the photoacid generator of claim 2, since R ₁ is a methyl group or a butyl group, the solubility in a solvent and the compatibility with a resin can be further increased. The solubility can also be improved by introducing linear, branched and cyclic alkyl groups other than methyl and butyl groups.

In the photoacid generator of claim 3, since R ₂ is a t-butyl group or a methyl group, the solubility in a solvent and the compatibility with a resin can be further increased. Among them, the introduction of a t-butyl group can improve the solubility and is advantageous for production.

In the photoacid generator according to the fourth aspect, since R ₃ is any one of hydrogen, a phenyl group, and a benzyl group, solubility and photoreactivity can be controlled. In view of solubility and photoreactivity, it is preferable to introduce a benzyl group.

The photoacid generator according to claim 5 can be used as an initiator for photocationic polymerization because X ⁻ is CF ₃ SO ₃ ⁻ , PF ₆ ⁻ , or C ₄ F ₉ SO ₃ ⁻ . X ⁻ is not limited to the above-mentioned negative ions, and can be selected from various negative ions.

  According to the resin composition for photolithography of claim 6, a more uniform resin layer (film) can be more easily and efficiently formed on a substrate made of Si or the like, which contributes to improvement of semiconductor productivity.

  Hereinafter, the present invention will be described by way of examples. However, the scope of the claims of the present invention is not limited by the following examples in any way.

1. Synthesis and Evaluation of Photoacid Generator A plurality of ionic acid photogenerators were synthesized according to the synthesis routes shown in FIGS. 1 and 2, and their physical properties and the like were evaluated. The details will be described below. In addition, in order to clarify the relationship between FIG. 1 and FIG. 2 and the following description, the same number is assigned to the same compound.

(1) Reagent
As tert-butylbenzene (hereinafter abbreviated as Compound 1) and 4,5-dichlorophthalimide (hereinafter abbreviated as Compound 3), those purchased from Aldrich were used as they were. Disulfur dichloride, anisole, phosphorous pentoxide, and methanesulfonic acid were purchased from Wako Pure Chemicals. Potassium trifluoromethanesulfonate, potassium perfluoro-1-butanesulfonate, and potassium hexafluorophosphate were used as they were purchased from Tokyo Chemical Industry. Zinc purchased from Kishida Chemical was used as it was. NITf used as it was purchased from Midori Chemical. The formamide purchased from Nacalai Tesque was used as it was. N, N′-dimethylformamide (DMF), toluene, acetonitrile, and cyclohexanone were distilled from CaH ₂ . The tert-THITf used was synthesized according to the method already developed by the inventors.

(2) Measuring device
¹ H NMR spectrum was measured with an FT-NMR spectrometer (JEOL, GX-270). The IR spectrum was measured with an FT-IR spectrometer (JASCO, FT / IR-410). Mass spectrometry was performed with a mass spectrometer (GCMS QP2010plus, manufactured by Shimadzu Corporation). The UV-Vis spectrum was measured with a UV-Vis spectrometer (Shimadzu Corporation, UV2400PC). The decomposition point (T _d ) was measured with a thermogravimetric analyzer (Shimadzu Corporation, TGA-50).

(3) Synthesis of photoacid generator shown in FIG. 1 (i) Synthesis of 4-tert-butylbenzene-1,2-dithiol Synthesis was performed according to Japanese Patent Application Laid-Open No. 07-173130. Compound 1 (91.0 g, 679 mmol), iodine (107 g, 423 mmol), disulfur dichloride (84.9 ml) and chloroform (257 ml) were placed in a four-necked flask and reacted at 42 ° C. for 24 hours while refluxing. The reaction system was returned to room temperature, zinc (164 g, 2.51 mol) and 35% hydrochloric acid (780 ml, 1.06 mol) were added, and the mixture was reacted for 2 hours while refluxing at 60 ° C.

  After completion of the reaction, the reaction system was returned to room temperature, the product was extracted four times with chloroform (500 ml), the organic phase was dried over anhydrous magnesium sulfate, and then the solvent was distilled off. Finally, the residue was distilled under reduced pressure (1.33 hPa, 110 ° C.) to give 4-tert-butylbenzene-1,2-dithiol (hereinafter abbreviated as Compound 2), which is a colorless and transparent liquid. Obtained (yield 17.2 g, yield 12%). In addition, this compound 2 was identified from the analysis result shown below.

¹ H NMR (CDCl ₃ ): δ 7.35 (1H, s, aromatic), 7.25 (1H, d, aromatic), 7.05 (1H, d, aromatic), 3.72 (1H, s, SH), 3.54 (1H, s, SH), 1.21 (9H, s, -C (CH ₃ ) ₃ ).

(Ii) Synthesis of 7-tert-butylthianthrene-2,3-dicarboxylic acid imide Under nitrogen, compound 2 (0.500 g, 2.52 mmol), potassium hydroxide (0.480 g, 8.58 mmol), DMF (12.0 ml) and A mixed solution of toluene (5.00 ml) was put into a flask and a Dean-Stark apparatus was assembled. Then, the contents of the flask were stirred at 130 ° C. for 18 hours to be reacted. At that time, water generated from the reaction system was discharged together with toluene as needed. The reaction system was cooled to 60 ° C., compound 3 (1.00 g, 4.65 mmol) was added, and the mixture was stirred at 90 ° C. for 18 hours.

  The reaction system was returned to room temperature, extracted four times with chloroform and water, the organic layer was dried over anhydrous magnesium sulfate, and then the solvent was distilled off. As a result, 7-tert-butylthianthrene-2,3-dicarboxylic imide (hereinafter abbreviated as compound 4) was obtained as a yellow solid (yield 0.920 g, yield 58%). In addition, this compound 4 was identified from the analysis result shown below.

mp: 218-220 ° C. ¹ H NMR (CDCl ₃ ): δ 7.88 (2H, d, aromatic), 7.48 (1H, d, aromatic), 7.39 (1H, s, aromatic), 7.32 (1H, d, aromatic), 1.28 (9H, s, -C (CH ₃ ) ₃ ) .IR (KBr): 3257cm ^-1 (NH), 1714cm ^-1 (C = O) .Anal.Calcd for C ₁₈ H ₁₅ NO ₂ S ₂ : C, 63.32; H, 4.43; N, 4.10.Found: C, 63.35; H, 4.16; N, 3.64.MS (EI): 341 (M ⁺ , 100).

(Iii) Synthesis of 7-tert-butylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide Compound 4 (5.67 g, 15.9 mmol) and acetic acid (80 ml) were placed in a four-necked flask, While stirring, 1M nitric acid (6.0 ml) was slowly added dropwise. After completion of the dropwise addition, the mixture was refluxed at 125 ° C. for 20 minutes. The reaction solution was returned to room temperature and poured into ice water (400 ml). The precipitated solid was washed 4 times with ion exchange water. The washed product is vacuum-dried to obtain 7-tert-butylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide (hereinafter abbreviated as Compound 5) which is a pale yellow solid. Obtained (5.23 g, yield 88%). In addition, this compound 5 was identified from the analysis result shown below.

mp: 234-237 ° C. ¹ H NMR (CDCl ₃ ): δ7.52 (1H, d, aromatic), 7.64 (1H, d, aromatic), 7.67 (1H, s, aromatic), 8.10 (2H, d, aromatic), 1.33 (9H, s, -C (CH ₃ ) ₃ ); δ7.67 (1H, d, aromatic), 7.87 (1H, d, aromatic), 7.95 (1H, s, aromatic), 8.45 (2H , d, aromatic), 1.33 (9H, s, -C (CH ₃ ) ₃ ) .IR (KBr): 3492cm ^-1 (NH), 1727cm ^-1 (C = O) .Anal.Calcd for C ₁₈ H ₁₅ NO ₃ S ₂ : C, 60.48; H, 4.23; N, 3.92; found: C, 60.09; H, 3.96; N, 3.75.MS (EI): 357 (M ⁺ , 20), 294 (M ⁺ -63,100 ).

(Iv) Synthesis of thiantrenium-2,3-dicarboxylic acid imide salt (a) 7-tert-butyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic acid imide trifluoro Synthesis of Lomethanesulfonate Diphosphorus pentoxide (1.14 g, 4.02 mmol) and methanesulfonic acid (14.5 ml, 164 mmol) were placed in an eggplant flask and stirred until dissolved. Compound 5 (4.99 g, 14.0 mmol) and anisole (0.77 ml, 14.3 mmol) were placed in a two-necked flask and dissolved by stirring. Using a Pasteur pipette, a solution of diphosphorus pentoxide and methanesulfonic acid was slowly added dropwise to a two-necked flask cooled in an ice bath. After the completion of the dropwise addition, the mixture was reacted in a hot water bath (30 ° C.) for 2 hours and left at room temperature overnight. The obtained liquid reaction product was slowly added dropwise to ice water, potassium trifluoromethanesulfonate (2.98 g, 15.8 mmol) was added thereto, and the mixture was stirred with a glass rod to precipitate a pearl yellow solid.

  The precipitate was filtered through a glass filter and dried. The dried product was applied to a medium pressure column (eluent: chloroform) to remove impurities, and the eluent was changed to methanol and collected. After drying the methanol solution and extracting the residue with boiling pure water, the water is distilled off and dried to give a pale yellowish white solid, 7-tert-butyl- (5 or 10)-(4-methoxyphenyl). ) Thiantrenium-2,3-dicarboxylic acid imide trifluoromethanesulfonate (hereinafter abbreviated as compound 6a) was obtained (yield 1.13 g, yield 19%). In addition, this compound 6a was identified from the analysis result shown below.

mp: 158-162 ° C. ¹ H NMR (CDCl ₃ ): δ7.82 (2H, s, aromatic), 8.14 (1H, s, aromatic), 8.50 (1H, s, aromatic), 8.92 (1H, s, aromatic), 7.23 (2H, d, aromatic), 6.92 (2H, d, aromatic), 3.68 (3H, s, -CH ₃ ), 1.35 (9H, s, -C (CH ₃ ) ₃ ) .IR (KBr ): 1737cm ^-1 (C = O), 1162cm ^-1 (S (= O) ₂ ), 1263cm ^-1 (-CF ₃ ), 1029cm ^-1 (COC) .UV (acetonitrile): ε ₃₆₅ = 3460L / mol・ Cm, ε ₂₅₄ = 24800L / mol ・ cm.T _d : 317 ℃

(B) Synthesis of 7-tert-butyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic imide hexafluorophosphate diphosphorus pentoxide (1.04 g, 365 mmol) and Methanesulfonic acid (7.00 ml, 79.2 mmol) was placed in an eggplant flask and stirred until dissolved. Compound 5 (2.50 g, 7.00 mmol) and anisole (0.77 ml, 14.3 mmol) were placed in a two-necked flask and dissolved by stirring. Using a Pasteur pipette, a solution of diphosphorus pentoxide and methanesulfonic acid was slowly added dropwise to a two-necked flask cooled in an ice bath. After completion of the dropwise addition, the mixture was reacted in a hot water bath (30 ° C.) for 2 hours and reacted overnight at room temperature. The obtained liquid reaction product was slowly dropped into ice water, potassium hexafluorophosphate (1.32 g, 7.17 mmol) was added thereto, and the mixture was stirred with a glass rod to precipitate a pearl yellow solid.

  The precipitate was filtered through a glass filter and dried. The dried product was applied to a medium pressure column (eluent: chloroform) to remove impurities, and the eluent was changed to methanol and collected. 7-tert-butyl- (5 or 10)-(4-methoxyphenyl), a pale yellowish white solid, is obtained by drying the methanol solution and extracting it with boiling pure water. Thianthrenium-2,3-dicarboxylic imide hexafluorophosphate (hereinafter abbreviated as compound 6b) was obtained (yield 0.34 g, yield 8%). In addition, this compound 6b was identified from the analysis result shown below.

mp: 164-167 ° C. ¹ H NMR (CDCl ₃ ): δ7.75 (2H, s, aromatic), 7.99 (1H, s, aromatic), 8.54 (1H, s, aromatic), 8.90 (1H, s, aromatic), 7.28 (2H, d, aromatic), 6.87 (2H, d, aromatic), 365 (3H, s, -CH ₃ ), 1.32 (9H, s, -C (CH ₃ ) ₃ ) .IR (KBr ): 1732cm ^-1 (C = O), 842cm ^-1 (PF), 1073cm ^-1 (COC) .UV (acetonitrile): ε365 = 2750L / mol ⁴ cm, ε254 = 22100L / mol ⁴ cm.T

(C) Synthesis of 7-tert-butyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic acid perfluorobutanesulfonate diphosphorus pentoxide (0.56 g, 196 mmol) And methanesulfonic acid (9.00 ml, 101 mmol) were placed in an eggplant flask and stirred until dissolved. Further, compound 5 (1.32 g, 3.70 mmol) and anisole (1.00 ml, 18.6 mmol) were placed in a two-necked flask and dissolved by stirring. While cooling the two-necked flask with an ice bath, a solution of diphosphorus pentoxide and methanesulfonic acid was slowly dropped from the eggplant flask into the two-necked flask using a Pasteur pipette. After completion of the dropwise addition, the reaction was allowed to proceed in a hot water bath (30 ° C.) for 2 hours, and the liquid reaction product was left at room temperature overnight. The reaction product was slowly added dropwise to ice water, potassium perfluoro-1-butanesulfonate (2.06 g, 6.10 mmol) was added thereto, and the mixture was stirred with a glass rod to precipitate a pearl yellow solid.

  The precipitate was filtered through a glass filter and dried. The dried product was applied to a medium pressure column (eluent: chloroform) to drain impurities, and the eluent was changed to methanol and collected. The recovered methanol solution is dried and then extracted with boiling pure water.The water is distilled off and dried to give a pale yellow solid, 7-tert-butyl- (5 or 10)-(4-methoxyphenyl). ) Thiantrenium-2,3-dicarboxylic acid imide perfluorobutanesulfonate (hereinafter abbreviated as compound 6c) was obtained (yield 0.50 g, yield 18%). In addition, this compound 6c was identified from the analysis result shown below.

mp: 142-143.5 ° C. ¹ H NMR (CDCl ₃ ): δ8.99 (2H, s, aromatic), 8.49 (1H, s, aromatic), 8.05 (1H, s, aromatic), 7.74 (1H, s, aromatic), 7.28 (2H, d, aromatic), 6.87 (2H, d, aromatic), 3.64 (3H, s, -OCH ₃ ), 1.29,0.87 (9H, s, s, -C (CH ₃ ) ₃ ) IR (KBr): 3448 cm ^-1 (NH), 1733 cm ^-1 (C = O), 1261 cm ^-1 (-CF ₃ ), 1054 cm ^-1 (COC) UV (acetonitrile): ε ₃₆₅ = 3340 L / mol ・cm, ε ₂₅₄ = 26800L / mol ・ cm.T _d : 312 ° C.

(D) Synthesis of 7-tert-butyl- (5 or 10)-[4- (1-butoxy) phenyl] thiantrenium-2,3-dicarboxylic imide trifluoromethanesulfonate diphosphorus pentoxide (0.48 g 170 mmol) and methanesulfonic acid (2.80 ml, 31.6 mmol) were placed in an eggplant flask and stirred until dissolved. Compound 5 (1.00 g, 2.80 mmol) and n-butylphenyl ether (0.841 g, 5.6 mmol) were placed in a two-necked flask and dissolved by stirring. While cooling the two-necked flask in an ice bath, the solution of diphosphorus pentoxide and methanesulfonic acid in the eggplant flask was slowly dropped into the two-necked flask using a Pasteur pipette. After completion of the dropwise addition, the reaction was allowed to proceed in a hot water bath (30 ° C.) for 2 hours, and the liquid reaction product was left at room temperature overnight. The reaction product was slowly added dropwise to ice water, potassium trifluoromethanesulfonate (0.60 g, 3.2 mmol) was added thereto, and the mixture was stirred with a glass rod to precipitate a pale yellow solid.

  The precipitate was filtered through a glass filter and dried. The dried product was applied to a medium pressure column (eluent: chloroform) to drain impurities, and the eluent was changed to ethyl acetate and collected. The collected ethyl acetate solution was concentrated, and the concentrated solution was added dropwise to hexane to precipitate a pale yellow solid. This solid was filtered and dried to obtain a light yellow solid 7-tert-butyl- (5 or 10)-[4- (1-butoxy) phenyl] thiantrenium-2,3-dicarboxylic acid imide trifluoromethane A sulfonate (hereinafter abbreviated as compound 7) was obtained (yield 0.65 g, yield 36%). In addition, this compound 7 was identified from the analysis result shown below.

mp: 207-213 ° C. ¹ H NMR (CDCl ₃ ): δ 9.96 (1H, s, NH), 9.05 (1H, m, aromatic), 8.50 (1H, m, aromatic), 8.17 (1H, s, aromatic), 7.80 (2H, m, aromatic), 7.36 (2H, d, aromatic), 6.92 (2H, d, aromatic), 3.87 (3H, s, -OCH _2- ), 1.63 (3H, m, -CH _2- ), 1.36 (12H, m, -C (CH ₃ ) ₃ , -CH _2- ), 0.87 (3H, t, -CH ₃ ) .UV (acetonitrile): ε ₃₆₅ = 5000 L / mol ・ cm.ε ₂₅₄ = 28400L / mol ・ cm.Td:295℃.

(4) Synthesis of photoacid generator shown in Fig. 2 (i) Synthesis of dichlorophthalimide (a) Synthesis of 4,5-dichlorophthalimide
4,5-dichlorophthalic anhydride (21.0 g, 96.8 mmol) and formamide (84.0 g, 1.86 mmol) were placed in a four-necked flask and aged at 100 ° C. for 25 hours. The reaction solution was purged with cold water (5 ° C. or lower, 525 ml) and filtered under reduced pressure, and then dried under reduced pressure at 40 ° C. to give 4,5-dichlorophthalimide (hereinafter abbreviated as Compound 9a) as a white solid. Obtained (yield 20.2 g, yield 96%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 99.5 Area%.

(B) Synthesis of N-phenyl-4,5-dichlorophthalimide
4,5-dichlorophthalic anhydride (10.0 g, 46 mmol), acetic acid (69.3 g), and DMF (54.2 g) were placed in a four-necked flask and stirred. Aniline (4.29 g, 46 mmol) was added, washed with DMF (13.3 g) and aged at 100 ° C. for 5 hours. The reaction solution was filtered under reduced pressure and dried at 40 ° C. under reduced pressure to obtain N-phenyl-4,5-dichlorophthalimide (hereinafter abbreviated as compound 9b) as a white solid (yield 11.1 g, yield). Rate 83%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 100 Area%.

(C) Synthesis of N-benzyl-4,5-dichlorophthalimide
Add 4,5-dichlorophthalic anhydride (15.2 g, 70 mmol), acetic acid (105.3 g) and DMF (82.3 g) into a four-necked flask and stir, then add benzylamine (7.43 g, 70 mmol). Then, it was washed with DMF (20.2 g) and aged at 100 ° C. for 3 hours. The reaction solution was filtered under reduced pressure and dried at 40 ° C. under reduced pressure to obtain N-benzyl-4,5-dichlorophthalimide (hereinafter abbreviated as Compound 9c) as a white solid (yield 17.9 g, Yield 84%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 100 Area%.

(Ii) Synthesis of methylthianthrene-2,3-dicarboxylic acid imide (a) Synthesis of 7-methylthianthrene-2,3-dicarboxylic acid imide Toluene-3,4-dithiol (hereinafter abbreviated as compound 8). 12.5 g, 80 mmol), DMF (347.8 g) and potassium-t-butoxide (22.4 g, 200 mmol) were placed in a four-necked flask and heated at 95 ° C. for 2 hours for potassium chloride. Compound 9a (16.4 g, 76 mmol) was added to the reaction solution and aged at 65 ° C. for 6 hours. The reaction solution was added with 100 ml of water and 100 ml of methanol, cooled to 0 ° C. or lower, filtered under reduced pressure, and dried under reduced pressure at 40 ° C. to give 7-methylthianthrene-2,3-dicarboxylic acid imide as a yellow solid. (Hereinafter abbreviated as Compound 10a) was obtained (yield 18.8 g, yield 83%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 98.5 Area%.

(B) Synthesis of N-phenyl-7-methylthianthrene-2,3-dicarboxylic acid imide Compound 8 (2.81 g, 18 mmol), DMF (73.9 g), potassium-t-butoxide (5.05 g, 45 mmol) It put into the necked flask, and it heated at 95 degreeC for 2 hours, and potassium-chlorinated. Compound 9b (4.97 g, 17 mmol) was added to the reaction solution and aged at 65 ° C. for 20 hours. The reaction solution was added with 24 ml of water and 240 ml of methanol, cooled to 0 ° C. or lower, filtered under reduced pressure, and dried under reduced pressure at 40 ° C., so that N-phenyl-7-methylthianthrene-2,3 as a yellow solid was obtained. Dicarboxylic acid imide (hereinafter abbreviated as compound 10b) was obtained (yield 5.48 g, yield 85%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 99.7 Area%.

(C) Synthesis of N-benzyl-7-methylthianthrene-2,3-dicarboxylic imide Compound 8 (8.75 g, 56 mmol), DMF (233.0 g), potassium-t-butoxide (15.7 g, 140 mmol) It put into the necked flask, and it heated at 95 degreeC for 2 hours, and potassium-chlorinated. Compound 9c (16.3 g, 53 mmol) was added to the reaction solution and aged at 65 ° C. for 2 hours. 70 ml of water and 70 ml of methanol were added to the reaction solution, cooled to 0 ° C. or lower, filtered under reduced pressure, and dried under reduced pressure at 40 ° C. to give N-benzyl-7-methylthianthrene-2,3 which is a yellow solid. Dicarboxylic acid imide (hereinafter abbreviated as compound 10c) was obtained (yield 17.1 g, yield 82%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 96.8 Area%.

(Iii) Synthesis of methylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide (a) Synthesis of 7-methylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide Compound 10a (4.79 g, 16 mmol) and acetic acid (83.9 g) were placed in a four-necked flask and stirred. 1M nitric acid (20 ml) was added to the reaction solution and aged at 100 ° C. for 11 hours. The reaction solution was purged with cold water (below 5 ° C., 400 ml), filtered under reduced pressure, and then dried under reduced pressure at 40 ° C. to give 7-methylthianthrene- (5 or 10) -oxide-2, which is a pale yellow solid. 3-Dicarboxylic imide (hereinafter abbreviated as compound 11a) was obtained (yield 3.74 g, yield 74%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 95.7 Area%.

(B) Synthesis of N-phenyl-7-methylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide Compound 10b (4.51 g, 12 mmol) and acetic acid (62.9 g) were added to a four-necked flask. Stir in. 1M nitric acid (9.2 ml) was added to the reaction solution and aged at 100 ° C. for 4 hours. The reaction solution was purged with cold water (5 ° C or lower, 300 ml), filtered under reduced pressure, and then dried under reduced pressure at 40 ° C. As a pale yellow solid, N-phenyl-7-methylthianthrene- (5 or 10) -oxide- 2,3-dicarboxylic imide (hereinafter abbreviated as compound 11b) was obtained (yield 3.46 g, yield 73%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 86.7 Area%.

(C) Synthesis of N-benzyl-7-methylthianthrene- (5 or 10) -oxide-2,3-dicarboxylic imide Compound 10c (5.06 g, 13 mmol) and acetic acid (68.2 g) were added to a four-necked flask. Stir in. 1M nitric acid (7.8 ml) was added to the reaction solution and aged at 100 ° C. for 5 hours. The reaction solution was purged with cold water (5 ° C or lower, 330 ml), filtered under reduced pressure, dried under reduced pressure at 40 ° C, and a light yellow solid N-benzyl-7-methylthianthrene- (5 or 10) -oxide- 2,3-dicarboxylic acid imide (hereinafter abbreviated as compound 11c) was obtained (yield 4.46 g, yield 85%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 97.4 Area%.

(Iv) Synthesis of thiantrenium-2,3-dicarboxylic imide trifluoromethanesulfonate (a) 7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic acid Synthesis of imido trifluoromethanesulfonate Methanesulfonic acid (7.60 g), anisole (0.56 g) and compound 11a (1.58 g, 5.00 mmol) were placed in a four-necked flask and stirred. To the reaction solution, a diphosphorus pentoxide (0.2 g) / methanesulfonic acid (7.60 g) solution was slowly added dropwise and aged at 30 ° C. for 22 hours. After 14.4 g of the reaction solution was purged with cold water (5 ° C. or lower, 150 ml) and filtered under reduced pressure, potassium trifluoromethanesulfonate (2.30 g) was added to the filtrate and stirred to perform anion exchange.

  The precipitated solid was filtered under reduced pressure and then dried under reduced pressure at 40 ° C., so that 7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic imide trifluoride, which is a yellow solid, was obtained. Lomomethanesulfonate (hereinafter abbreviated as compound 12a) was obtained (yield 1.56 g, yield 69%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 97.0 Area%. Moreover, this compound 12a was identified from the analysis result shown below.

mp: 144-147 ° C. ¹ H NMR (DMSO-d ₆ ): δ 11.90 (1H, s, NH), 8.98 (1H, d, aromatic), 8.47-8.37 (2H, m, aromatic), 7.98 ( 1H, m, aromatic), 7.77-7.68 (1H, m, aromatic), 7.28 (2H, m, aromatic), 7.09 (2H, m, aromatic), 3.76 (3H, s, -CH ₃ ), 2.49 (3H , s, -CH ₃ ) .UV (acetonitrile): ε ₃₆₅ = 4870 L / mol ・ cm.T _d : 313 ° C.

(B) Synthesis of N-phenyl-7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic imide trifluoromethanesulfonate Methanesulfonic acid (6.09 g), anisole (0.44 g) and compound 12b (1.57 g, 4.0 mmol) were placed in a four-necked flask and stirred. A diphosphorus pentoxide (0.16 g) / methanesulfonic acid (6.09 g) solution was slowly added dropwise to the reaction solution, and the mixture was aged at 30 ° C. for 44 hours. After purging 12.0 g of the reaction solution into water (180 ml) and filtering under reduced pressure, potassium trifluoromethanesulfonate (2.26 g) was added to the filtrate, followed by stirring and anion exchange.

  The precipitated solid was filtered under reduced pressure and dried at 40 ° C. to give a yellow solid N-phenyl-7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic acid Acid imide trifluoromethanesulfonate (hereinafter abbreviated as compound 12b) was obtained (yield 1.28 g, yield 51%). The purity measured by HPLC and an absorptiometer (UV: 254 nm) was 89.4 Area%. Moreover, this compound 12b was identified from the analysis result shown below.

mp: 145-148 ° C. ¹ H NMR (CDCl ₃ ): δ8.98 (1H, d, aromatic), 8.16 (2H, m, aromatic), 7.70-7.20 (8H, m, aromatic), 6.87 (2H, d, aromatic), 3.69 (3H, d, -OCH ₃ ), 2.44 (3H, d, -CH ₃ ) .UV (acetonitrile): ε ₃₆₅ = 4470 L / mol-cm.T _d : 321 ° C.

(C) Synthesis of N-benzyl-7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3-dicarboxylic acid trifluoromethanesulfonate Methanesulfonic acid (8.99 g), anisole (0.89 g) and Compound 11c (3.24 g, 8.0 mmol) were placed in a four-necked flask and stirred. To the reaction solution, a diphosphorus pentoxide (0.3 g) / methanesulfonic acid (8.99 g) solution was slowly added dropwise and aged at 30 ° C. for 19 hours. After purging 11.1 g of the reaction solution into cold water (5 ° C. or lower, 225 ml) and filtering under reduced pressure, potassium trifluoromethanesulfonate (0.85 g) was added to the filtrate, followed by stirring and anion exchange.

  The precipitated solid was filtered under reduced pressure and then dried under reduced pressure at 40 ° C., so that N-benzyl-7-methyl- (5 or 10)-(4-methoxyphenyl) thiantrenium-2,3- Dicarboxylic acid imide trifluoromethanesulfonate (hereinafter abbreviated as compound 12c) was obtained (yield 2.00 g, yield 78%). The purity measured by HPLC and absorptiometer (UV: 254 nm) was 96.9 Area%. Moreover, this compound 12c was identified from the analysis result shown below.

mp: 124-126 ° C. ¹ H NMR (CDCl ₃ ): δ8.87 (1H, d, aromatic), 8.36 (1H, t, aromatic), 8.13 (1H, s, aromatic), 7.75-7.55 (2H, m, aromatic), 7.35-7.21 (8H, m, aromatic), 6.93 (2H, m, aromatic), 4.81 (2H, s, -CH ₂ -Ph), 3.76 (3H, d, -OCH ₃ ), 2.51 (3H, s, -CH ₃ ) .UV (acetonitrile): ε ₃₆₅ = 5060 L / mol ・ cm.T _d : 312 ° C.

(5) Physical properties of photoacid generator (i) Measurement of UV-Vis spectrum UV-Vis spectrum was measured in acetonitrile of synthesized compounds 6a and 6b. The result is shown in FIG. From the UV-Vis spectrum of FIG. 3, it was confirmed that the two kinds of synthesized photoacid generators had absorption at i-line (365 nm). The measured concentration of Compound 6a was 1.55 × 10 ⁻⁵ M, and the concentration of Compound 6b was 1.52 × 10 ⁻⁵ M.

In addition, the molar extinction coefficient (ε ₃₆₅ ) of compound 6a and compound 6b was calculated from this spectrum. The results are listed in Table 1. For comparison, the molar extinction coefficients (ε ₃₆₅ ) of tert-THITf and NITf are also shown.

As shown in Table 1, respectively compound 6a, the molar extinction coefficient of the compound 6b 3460M ^-1 cm ^-1, a 2750M ^-1 cm ^-1, are conventional ^{tert-THITf (1950M -1 cm -1} ), NITf It was larger than (330M ^-1 cm ^-1 ). This suggests that the compound 6a and the compound 6b may be decomposed more efficiently than tert-THITf and NITf when irradiated with 365 nm light.

(Ii) Measurement of decomposition point The decomposition points (T _d ) of the compounds 6a and 6b were measured by a thermogravimetric method in a nitrogen atmosphere at a heating rate of 10 ° C / min. The resulting TGA curve is shown in FIG. The measured decomposition points (T _d ) are shown in Table 1. For comparison, the decomposition points (T _d ) of tert-THITf and NITf are also shown.

As shown in Table 1, the decomposition points (T _d ) of the compounds 6a and 6b were 317 ° C. and 268 ° C., respectively, which were higher than the conventional tert-THITf (156 ° C.) and NITf (225 ° C.). . This suggests that compound 6a and compound 6b are superior in thermal stability to conventional photoacid generators and are theoretically stable in the temperature range of use as a photoacid generator. In addition, the difference in the counter anion can be considered as a cause of the large difference between the decomposition points (T _d ) of the compound 6a and the compound 6b.

(iii) Change in absorption spectrum due to photolysis Generally, a photodegradable compound is decomposed by absorbing light, causing a change in absorbance of the UV-Vis spectrum. Therefore, compound 6a and compound 6b were irradiated with light (wavelength 365 nm) in acetonitrile for photolysis, and the change in the UV-Vis spectrum was measured. The result is shown in FIG. The measured concentration of Compound 6a was 1.74 × 10 ⁻⁵ M, and that of 6b was 1.55 × 10 ⁻⁵ M.

  As shown in FIG. 5, it was found that the absorption at around 250 nm and 360 nm decreased for compound 6a and compound 6b by light irradiation, while the absorption near 290 nm increased. This indicates that both compounds absorb 365 nm light and photodegrade.

  Further, in order to examine the effect of the difference in counter anion on the photodegradation rate, the decomposition rate was calculated from the increase in the peak at 290 nm of compound 6a and compound 6b. The result is shown in FIG.

As shown in FIG. 6, when the decomposition rates of both were compared, the decomposition rate of compound 6a was slightly faster than the decomposition rate of compound 6b, and the decomposition rates of both were almost the same. Further, although the compound 6a had a larger value of ε ₃₆₅ than the compound 6b, there was almost no difference between the decomposition rates of the two. The reason may be that the quantum yield of compound 6a is smaller than that of compound 6b.

The molar extinction coefficient (ε ₃₆₅ ) and photodecomposition rate (k) of the photoacid generators 6c, 7, 12a-12 are measured, and the molar extinction coefficient (ε ₃₆₅ ), photodecomposition rate (k) and photodecomposition rate (k) based on 6a The relative photolysis quantum yield (φ _d ^rel ) was calculated. The results are shown in Table 2. From this table, it was found that all photoacid generators except 12b had a high photoreaction rate and a relative photodecomposition quantum yield, and exhibited good photodegradability.

The photodegradation rate in Table 2 is the rate of decrease when the acetonitrile solution of each photoacid generator (1.0 to 3.0 × 10 ⁻⁵ M) is put in a quartz cell and irradiated with 365 nm light in the air. Was measured and calculated by the following formula (I).

2. Production of Film and Its Evaluation A resin composition for photolithography containing the photoacid generator synthesized in Example 1 was prepared, and this was photopolymerized to produce a film, and the properties of this film were evaluated. Polyglycidyl methacrylate (hereinafter abbreviated as PGMA) was used as the resin component of the resin composition for photolithography.

(1) Reagent Glycidyl methacrylate (hereinafter abbreviated as GMA) was used by distilling one purchased from Tokyo Kasei. Further, 2,2′-azobisisobutyronitrile (hereinafter abbreviated as AIBN) was purchased from Nacalai Tesque and recrystallized (solvent: chloroform). Further, NITf and tert-THITf obtained and synthesized in the same manner as in Example 1 were used.

(2) Measuring equipment, etc.
M _n and M _w of PGMA the pump (JASCO, 880-PU), a detector (JASCO, RI-1530,870-UV ), degasser (JASCO, DG-980-53), a thermostat (chromatographic Science, CS -600H) and a column (TOSOH, GMH _HR -N, GMH _HR -H) were used, and measurement was performed by the GCP method. Note that THF was used as the eluent, and the flow rate was set to 0.8 ml / min. Polystyrene (Tosoh) was used as the molecular weight standard substance.

  Photopolymerization was performed by extracting and irradiating only 365 nm light from the light generated by a high-pressure mercury lamp (USHIO, UM-102) with an interference filter (Asahi Spectroscopy, MZ0365). The light intensity was measured with an ultraviolet illuminometer (Oak Seisakusho, UV-MO2).

Further, a spin coater (Mikasa spin coater, 1H-D ₃ type) was used for the production of the film, and a film thickness measuring device (Nanometrics Japan, Nanospec M3000) was used for the film thickness measurement.

(3) Production of film (i) Synthesis of polyglycidyl methacrylate (PGMA) First, a mixture of GMA (4.26 g, 66.4 mmol), AIBN (244 mg, 1.49 mmol), isopropylbenzene (23.2 ml), DMF (21 ml) After bubbling with argon and replacing with argon, polymerization was carried out at 60 ° C. for 2 hours. Next, the reaction solution was added dropwise to methanol, and the resulting precipitate was filtered off. Finally, reprecipitation purification was performed 3 times in a THF / methanol system. As a result, PGMA was obtained as a white powder (yield 2.20 g, yield 26%). It was confirmed by ¹ H NMR that no monomer remained. The molecular weight determined by the GPC method was M _n = 34000, M _w = 55800, M _w / M _n = 1.64 in terms of polystyrene.

(Ii) Production of PGMA film First, about 1 mol% of each photoacid generator (compound 6a: 0.69 mg, compound 6b 0.69 mg, tert-THITf: 0.688 mg, NITf: 0.480 mg) with respect to PGMA (20.0 mg) This was dissolved in 218 mg of cyclohexanone and applied onto a Si plate by a spin coater. Next, the film was obtained by pre-baking to remove the residual solvent.

(4) Measurement of insolubilization rate The effect of the difference in the photoacid generator on the insolubilization rate of the film was examined. Specifically, the prepared film was irradiated with light having a wavelength of 365 nm with different irradiation light amounts, and then immersed in THF, and the insolubilization rate was determined from the film thickness ratio before and after the immersion. FIG. 7 shows a mechanism in which an acid is generated from the photoacid generator by light irradiation, and the epoxy group of the PGMA side chain is crosslinked and insolubilized by this acid.

(I) Effect of photoacid generator that generates trifluoromethanesulfonic acid on insolubilization rate Compound 6a, tert-THITf, NITf, which is a photoacid generator that generates trifluoromethanesulfonic acid by photolysis, is used to generate light. The effect of the difference in acid generator on the insolubilization rate of the film was investigated. The result is shown in FIG. Note that the pre-baking temperature when producing the film was 80 ° C., the pre-baking time was 5 minutes, and the thickness of the produced film was 0.3 μm. The immersion time in THF was 10 minutes.

  As shown in FIG. 8, when the acid catalytic ability of compound 6a, tert-THITf, and NITf were compared by insolubilization of PGMA, it was found that compound 6a had excellent acid catalytic ability. In general, it has been found that insolubilization of a PGMA film by a photoacid generator depends on the quantum yield of acid generation and the strength of the acid generated. Here, since the intensity | strength of the acid to generate | occur | produce is the same, it can be considered that the difference in an acid catalyst ability originates in the quantum yield of the acid generation of the compound 6a being excellent.

The reason why the quantum efficiency of the compound 6a is excellent may be that ε ₃₆₅ is increased by introducing an anisole moiety into the thianthrene skeleton. That is, it is considered that the increase in ε ₃₆₅ effectively absorbs and decomposes 365 nm light and can generate acid efficiently.

  In addition, as shown in FIG. 8, the molecular weight of PGMA used by the photo-acid generator differs. In general, it is known that as the molecular weight of PGMA increases, insolubilization easily occurs. In consideration of these, it can be seen that the compound 6a which showed a high insolubilization rate despite the use of PGMA having a small molecular weight has an excellent acid catalytic ability.

(Ii) Effect of ionic photoacid generator on insolubilization rate Effect of photoacid generator difference on film insolubilization rate using the same ionic photoacid generators Compound 6a, Compound 6b and NITf I investigated. The result is shown in FIG. In addition, the prebaking temperature at the time of producing a film was 90 ° C., the prebaking time was 5 minutes, and the thickness of the produced film was 0.4 to 0.5 μm. The immersion time in THF was 5 minutes.

  As shown in FIG. 9, when the acid catalytic ability of compound 6a, compound 6b, and NITf is compared by insolubilization of PGMA, compound 6a and compound 6b are superior to NITf, and compound 6a is slightly superior to compound 6b. Although yes, there was no significant difference.

In general, it has been found that insolubilization of a PGMA film by a photoacid generator depends on the strength of the generated acid. Further, comparing the pKa of the acids CF ₃ SO ₃ H and HPF ₆ produced by irradiating compound 6a and compound 6b with light, CF ₃ SO ₃ H is larger than HPF ₆ and compound 6b is stronger. It is thought to produce acid. Therefore, although it is predicted that there is a large difference in the acid catalyst between compound 6a and compound 6b, this was not the case.

  This is probably because even if a large amount of strong acid is generated, the crosslinking reaction rate is slow at room temperature and is not reflected in the insolubilization rate of the PGMA film in the time scale of this measurement. The reason for the slow crosslinking reaction at room temperature is that the segmental motion of the PGMA side chain is insufficient, so that acid diffusion and crosslinking reaction are limited.

It is a figure which shows the synthetic pathway of the manufacturing method of the photo-acid generator of this invention. It is a figure which shows the synthetic pathway of the manufacturing method of the other photo-acid generator of this invention. It is a figure which shows the result of having measured the UV-Vis spectrum of the compound 6a and the compound 6b in acetonitrile. It is a figure which shows the result of having measured the decomposition point of the compound 6a and the compound 6b by the thermogravimetry. It is a figure which shows the result of having irradiated the light of wavelength 365nm to the compound 6a and the compound 6b in acetonitrile, and measuring the change of the UV-Vis spectrum. It is a figure which shows the result of having irradiated the light of wavelength 365nm to the compound 6a and the compound 6b in acetonitrile, and having calculated the decomposition rate. It is a figure which shows the mechanism in which the epoxy group of a PGMA side chain bridge | crosslinks and insolubilizes. It is a figure which shows the result of having investigated the influence which the difference in a photo-acid generator exerts on the insolubilization rate by forming a film using the resin composition for photolithography containing the photo-acid generator which generate | occur | produces a trifluoromethanesulfonic acid. It is a figure which shows the result of having formed a film using the resin composition for photolithography containing an ionic photoacid generator, and having investigated the influence which the difference in a photoacid generator has on the insolubilization rate.

Claims (6)

Formula (I) and Formula (II)

(In the formula, R ₁ is a lower alkyl group, R ₂ is a lower alkyl group, and R ₃ is any one of hydrogen, a lower alkyl group , a phenyl group, and a benzyl group . X ⁻ is any one of CF ₃ SO ₃ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , BF ₄ ⁻ and C ₄ F ₉ SO ₃ ⁻ ). A photoacid generator comprising at least one compound.
The photoacid generator according to claim ₁ , wherein R ₁ in formula (I) and formula (II) is a methyl group or a butyl group. The photoacid generator according to claim 1 or ₂ , wherein in formula (I) and formula (II), R ₂ is a t-butyl group or a methyl group. The photoacid generator according to any one of claims 1 to ₃ , wherein in formula (I) and formula (II), R ₃ is any one of hydrogen, a phenyl group, and a benzyl group. Agent. The formula (I) and the formula (II), wherein X ⁻ is any one of CF ₃ SO ₃ ⁻ , PF ₆ ⁻ , and C ₄ F ₉ SO ₃ ⁻ . The photoacid generator according to one claim.   A resin composition for photolithography, comprising the photoacid generator according to any one of claims 1 to 5.

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