JP5115043B2 - Silicone copolymer having sulfur functional group and method for producing the same - Google Patents

Description

  The present invention relates to a novel silicone copolymer having a sulfur functional group useful as an electronic material or a material for fine processing.

  In recent years, with the progress of miniaturization of semiconductor elements, further miniaturization of a lithography process used for manufacturing the semiconductor element has been demanded. The background of rapid progress in miniaturization includes higher NA of projection lenses, improved resist performance, and shorter wavelengths.

  In particular, the shortening of the exposure wavelength has brought about a great change, but the demand for further miniaturization is great, and the shortening of the wavelength from KrF (248 nm) exposure to ArF (193 nm) exposure is progressing.

  The ArF immersion process developed in semiconductor microfabrication is a process in which a layer of water is provided between the lens of the light source and the resist, and ArF exposure (n = 1.44) is used to make ArF exposure ( This is a process for creating a finer pattern by apparently setting the wavelength of 193 nm to a wavelength of 134 nm.

  Thus, at present, there are attempts to create a fine pattern by shortening the exposure wavelength and research to create a fine pattern by increasing the numerical aperture of the lens used. However, when the refractive index of the resin is low, if the numerical aperture of the lens used increases, there is a problem that the light to be exposed is totally reflected at the resin interface and the light is not transmitted into the resin. Thus, there is a problem that it cannot be applied to a process for creating a fine pattern (see Patent Document 1). Therefore, for use in electronic materials, particularly in microfabrication processes, it is necessary to increase the refractive index of the resin to prevent total reflection of light at the resin interface.

  On the other hand, a three-layer resist process in which an intermediate layer is provided has been devised in order to cope with miniaturization, and an example of a silicone polymer having a phenolic hydroxyl group as the intermediate layer has been reported (see Patent Document 2). However, since these polymers have a phenol skeleton, there is a problem that the resin itself absorbs a large amount at a far ultraviolet exposure wavelength such as ArF (193 nm) used in microfabrication and does not transmit light.

For this reason, there has been a demand for a novel silicone polymer having a high refractive index, which is a silicone polymer that can be used in electronic materials, particularly in fine processing.
JP 2006-227632 A JP 2003-149822 A

  The present inventor has found that the silicone copolymer having a sulfur functional group improves the refractive index at a wavelength of 220 nm or less as a result of various studies on the material that improves the refractive index at the far ultraviolet exposure wavelength. The present invention has been made based on the findings.

That is, the present invention has the following general formula:

(In the formula, R represents a cyclic sulfide group, A represents a hydrocarbon group having an aromatic ring, B represents a hydrocarbon group not containing an aromatic group, a, b and c represent mol%, and a represents 1 to 50) Mol%, b is 1 to 50 mol%, c is 20 to 98 %, provided that b + c is 21 or more and a + b + c = 100)
And having a weight average molecular weight (polystyrene conversion) of 500 to 10,000.

  The silicone copolymer having a sulfur functional group of the present invention is a material suitable for use in the far ultraviolet region because of its good transparency at a short exposure wavelength in the far ultraviolet region and a high refractive index. Since the silicone copolymer of the present invention can be easily cured by applying heat of 200 ° C. or higher, it can be introduced into a microfabrication process because it functions as an antireflection film.

  Further, the silicone copolymer of the present invention can be applied not only in the field of electronic materials but also in a wide range of fields such as paints and adhesives.

The silicone copolymer of the present invention has the following general formula:

(In the formula, R represents a hydrocarbon group containing a sulfur functional group)
And the following general formula

(Wherein X represents a hydrocarbon group)
It is a silicone copolymer containing the repeating unit shown by these.

  The following skeleton of the silicone copolymer of the present invention

Represents a silsesquioxane skeleton, wherein each silicon atom is bonded to three oxygen atoms, and each oxygen atom is bonded to two silicon atoms. The silsesquioxane skeleton has, for example, the following general formula

It can be shown by the structural formula shown in

  Moreover, the silicone copolymer of the present invention has, for example, the following general formula:

The ladder type silicone copolymer shown by these may be sufficient.

The cyclic sulfide group represented by R in the silicone copolymer of the present invention represents a hydrocarbon group having a sulfur atom in the cyclic skeleton .

The cyclic sulfide group represented by R has the following general formula

Are preferred .

  The silicone copolymer of the present invention has the following general formula:

(In the formula, R represents a cyclic sulfide group, A represents a hydrocarbon group having an aromatic ring, B represents a hydrocarbon group not containing an aromatic group, a, b and c represent mol%, and a represents 1 to 50) Mol%, b is 1 to 50 mol%, c is 20 to 98 %, provided that b + c is 21 or more and a + b + c = 100)
It is a silicone copolymer shown by these.

  A represents a hydrocarbon group having an aromatic ring, and is a site for adjusting optical characteristics at a typical far ultraviolet exposure wavelength indicated at 193 nm. That is, all light is transmitted when the aromatic ring is not included at a far ultraviolet exposure wavelength of 200 nm or less. In order to make the resin easy to use, by introducing a hydrocarbon group having an aromatic ring, it may be possible to adjust the optical characteristics by giving absorption to the resin itself.

  The hydrocarbon group having an aromatic ring is preferably a hydrocarbon group having a benzene ring such as a phenyl group, a phenylmethyl group, or a phenylethyl group, and more preferably a phenyl group from the viewpoint of obtaining raw materials. Moreover, condensed polycyclic hydrocarbons, such as 1-naphthyl group, 2-naphthyl group, 9-anthracenyl group, and 9-phenanthrenyl group, are also preferable, and 1-naphthyl group and 2-naphthyl group are more preferable from the viewpoint of obtaining raw materials. A hydrocarbon group having a benzene ring such as a 4-methylphenyl group, a 3-methylphenyl group, a 2-methylphenyl group, and a 4-ethylphenyl group having a substituent bonded to an aromatic ring, a 2-methyl-1-naphthyl group , A substituted polycyclic hydrocarbon group such as a 5-methyl-1-naphthyl group or the like may be used.

  B represents a hydrocarbon group having no aromatic ring, and is preferably a hydrocarbon group having high transparency at a far ultraviolet exposure wavelength of 200 nm or less. The hydrocarbon group is preferably a linear, branched or cyclic monovalent hydrocarbon group having 1 to 20 carbon atoms, and may be a crosslinked hydrocarbon group. As a preferable example of the hydrocarbon group having no aromatic ring, the linear hydrocarbon group having 1 to 20 carbon atoms is a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, n -Hydrocarbons such as hexyl groups. Preferable branched hydrocarbon groups include hydrocarbon groups such as isopropyl group and isobutyl group. Preferred cyclic hydrocarbon groups include cyclic hydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group. A hydrocarbon group may be bonded to the cyclic hydrocarbon group. In addition, preferred examples of the crosslinked hydrocarbon group include a crosslinked hydrocarbon group having the following structural formula.

A hydrocarbon group may be bonded to the crosslinked hydrocarbon group. Methyl group, ethyl group, n-propyl group, cyclohexyl group and norbornanyl group are more preferable because of easy availability of raw materials, and the use of sterically small hydrocarbon groups increases the abundance ratio of Si-O in the resin. Therefore, a methyl group is most preferable.

The silicone copolymer of the present invention has the following general formula:

(In the formula, R represents a cyclic sulfide group, A represents an aromatic hydrocarbon group, B represents a hydrocarbon group not containing an aromatic group, a, b, and c represent mol%, a represents 1 to 50 mol%, b is 1 to 50 mol%, c is 20 to 98 %, provided that b + c is 21 or more and a + b + c = 100)
It is a silicone copolymer shown by these.

Here, a component shows the silicone copolymer site | part which has cyclic sulfide .

The component a is 1 to 50 mol% .

b component shows the silicone copolymer site | part which has an aromatic hydrocarbon group. b component is 1 mol% or more and 50 mol% or less. When the b component is 1 mol% or more and 50 mol% or less, there is no problem that light is not transmitted at an exposure wavelength in the far ultraviolet region of 200 nm or less used in the semiconductor field.

c component shows the silicone copolymer site | part which has the hydrocarbon group which does not contain an aromatic. When a substituent having a small carbon number such as a methyl group or an ethyl group is introduced, the proportion of Si—O in the silicone copolymer increases. If the proportion of Si-O is increased, for example, resistance to etching used in the semiconductor field is improved, which may be a very good material . c component is 2 0 mol% or more.

Silicone copolymers of the present invention, the weight average molecular weight (polystyrene equivalent), area by near-5 00 10,000.

The dispersity of the silicone copolymer of the present invention is preferably in the range of 1.0 to 10.0, and most preferably in the range of 1.0 to 2.0.
Silicone copolymer of the present invention

Preferably, the following general formula

(Wherein R represents a cyclic sulfide group, and X represents a chlorine or alkoxy group)
And the following general formula

(In the formula, A represents an aromatic hydrocarbon group, and X represents a chlorine or alkoxy group)
And the following general formula

(In the formula, B represents a hydrocarbon group not containing an aromatic group, and X represents a chlorine or alkoxy group)
In the presence of water and a catalyst in the reaction solvent.

  Here, X represents chlorine or an alkoxy group. Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propyloxy group, an n-butyloxy group, and an isopropyloxy group. Group and ethoxy group are preferred.

  As the reaction solvent, alcohol solvents such as methanol, ethanol, isopropanol, n-butanol and t-butanol, water-insoluble hydrocarbon solvents such as toluene and xylene, and water-soluble hydrocarbon solvents such as acetonitrile and tetrahydrofuran can be used. However, since water is used in the hydrolysis reaction, alcohol solvents such as methanol, ethanol and isopropanol are preferred.

  The amount of water used in the hydrolysis is preferably 3.0 to 50.0 equivalents, more preferably 3.0 to 10.0 equivalents, based on the total number of moles of raw material monomers.

  As the catalyst used in the hydrolysis and condensation polymerization, either an acidic catalyst or a basic catalyst can be used. However, the basic catalyst is preferably an acidic catalyst because the condensation polymerization proceeds and the molecular weight increases. Examples of acidic catalysts include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, carboxylic acids such as oxalic acid, trifluoroacetic acid, malonic acid, succinic acid and citric acid, and sulfonyl compounds such as p-toluenesulfonic acid and methanesulfonic acid. Strong acids are preferred.

  When a basic catalyst is used, it is preferable to use an ammonium salt such as tetramethylammonium hydride or tetraethylammonium hydride.

Silicone copolymer of the present invention is the weight average molecular weight (polystyrene equivalent) of low molecular weight which is from 5 00 to the range of 10,000. Further, the dispersity is preferably in the range of 1.0 to 10.0, and most preferably in the range of 1.0 to 2.0. The silicone copolymer obtained is particularly preferable under strongly acidic conditions because it has a low molecular weight and low dispersion.

  Extract the reaction solution obtained by hydrolysis and condensation polymerization with an aprotic solvent such as toluene or ethyl acetate, wash with water, and then evaporate the solvent in the oil layer to synthesize the desired silicone copolymer. can do.

In the present invention , the following general formula

(In the formula, R represents a cyclic sulfide group, A represents an aromatic hydrocarbon group, B represents a hydrocarbon group not containing an aromatic group, a, b, and c represent mol%, a represents 1 to 50 mol%, b is 1 to 50 mol%, c is 20 to 98 %, provided that b + c is 21 or more and a + b + c = 100)
In the case of producing the silicone copolymer represented by, for example, it can be synthesized by the synthesis method shown below.

(In the formula, R represents a cyclic sulfide group, A represents an aromatic hydrocarbon group, B represents a hydrocarbon group not containing an aromatic group, a, b, and c represent mol%, a represents 1 to 50 mol%, b is 1 to 50 mol%, c is 20 to 98 %, but b + c is 21 or more and a + b + c = 100, X is chlorine or an alkoxy group, methoxy group, ethoxy group, n-propyl group, isopropyl group is selected. Show)
Here, X represents chlorine or an alkoxy group, and examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propyloxy group, an n-butyloxy group, and an isopropyloxy group. A methoxy group and an ethoxy group are preferable.

  Thus, a silicone copolymer having a sulfur functional group can be synthesized, and a novel silicone copolymer having a sulfur functional group having an improved refractive index at an exposure wavelength of 200 nm or less is provided. Moreover, since the silicone copolymer of this invention has a sulfur functional group and can form a siloxane film by making it react with a hardening | curing agent, it can expand | deploy to a coating material and an adhesive agent use.

  Hereinafter, the present invention will be specifically described with reference to examples.

  In the following examples, the following apparatus was used for the measurement, and a general reagent purchased from a reagent manufacturer was used as a raw material.

measuring device
NMR measurement: JEOL 400MHz NMR measuring instrument
IR measurement ・ ・ ・ IR Prestige-21 made by Shimadzu
GPC measurement: Tosoh HLC-8220
Refractive index measurement ・ ・ ・ JAWOOLLAM Refractive index measuring device Wvase 32
Reference example 1
Synthesis of 3-mercaptopropylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 20:10:70) with stirrer, reflux condenser, dropping funnel and thermometer A 1 L four-necked flask was charged with 47.8 g of water and 4.4 g of 35% hydrochloric acid, and 16.3 g (0.083 mol) of 3-mercaptopropyltrimethoxysilane and 5.7 g of phenyltrimethoxysilane (0.042 mol). ) And 39.7 g (0.291 mol) of methyltrimethoxysilane in 252.2 g of toluene were added dropwise at a reaction temperature of 10 to 20 ° C. over 2 hours. After completion of the dropwise addition, after aging for 2 hours at the same temperature, it was confirmed by GC analysis of the reaction solution that all the raw materials were gone. Next, liquid separation was performed after standing, and an oil layer was recovered. Subsequently, it was washed with a 5% aqueous sodium hydrogen carbonate solution, further washed with water, and finally a toluene oil layer was recovered.

  The solvent was removed from the obtained oil layer with an evaporator, and 3-mercaptopropylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 20:10:70) was a white powder. Of 33.8 g was obtained. As a result of GPC analysis of the obtained copolymer, it was weight average molecular weight (Mw: polystyrene conversion) 1,230 and dispersity (Mw / Mn: polystyrene conversion) 1.4.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
2840 cm ^-1 (-SH), 1030-1120 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: DMSO-d6)
0.565-1.021 ppm (bs), 1.183-2.505 ppm (bs), 7.550-8.615 ppm (bs).

Reference example 2
Synthesis of 3-mercaptopropylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) Equipped with stirrer, reflux condenser, dropping funnel and thermometer In addition, 47.8 g of water and 4.4 g of 35% hydrochloric acid were charged into a 1 L four-necked flask, and 32.7 g (0.166 mol) of 3-mercaptopropyltrimethoxysilane and 5.7 g of phenyltrimethoxysilane (0.042 mol) were added. And a solution of 28.3 g (0.208 mol) of methyltrimethoxysilane in 252.2 g of toluene at a reaction temperature of 10 to 20 ° C. were added dropwise over 2 hours and extracted by the method described in Reference Example 1 to recover a toluene oil layer.

  The solvent was removed from the obtained oil layer with an evaporator, and 3-mercaptopropylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) was a white powder. 42.7g of was obtained. As a result of GPC analysis of the obtained copolymer, the weight average molecular weight (Mw: polystyrene conversion) was 1,210, and the dispersity (Mw / Mn: polystyrene conversion) was 1.4.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
2840 cm ^-1 (-SH), 1026-1111 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: DMSO-d6)
0.560-1.035ppm (bs), 1.181-2.550ppm (bs), 7.021-8.252ppm (b).

Reference example 3
Synthesis of mercaptomethylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) 200 mL 4 equipped with stirrer, reflux condenser, dropping funnel and thermometer A 1-neck flask was charged with 15.7 g of water and 1.47 g of 35% hydrochloric acid, 9.50 g (0.056 mol) of mercaptomethyltrimethoxysilane, 2.80 g (0.014 mol) of phenyltrimethoxysilane and methyltrimethylsilane. A solution of 9.61 g (0.071 mol) of methoxysilane in 32.9 g of toluene was added dropwise at a reaction temperature of 10 to 20 ° C. over 2 hours, followed by extraction by the method described in Reference Example 1 to recover a toluene oil layer.

  The solvent was removed from the obtained oil layer with an evaporator, and a 3-mercaptomethylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) was a colorless viscous liquid. 11.7 g) was obtained. As a result of GPC analysis of the obtained copolymer, it was 1,190 in weight average molecular weight (Mw: polystyrene conversion) and dispersity (Mw / Mn: polystyrene conversion) 1.4.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
2565 cm ^-1 (-SH), 1042-1271 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: DMSO-d6)
0.561 ppm (bs), 7.545-8.610 ppm (bs).

Example 1
Synthesis of 2-thienylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) equipped with stirrer, reflux condenser, dropping funnel and thermometer A 200 mL four-necked flask was charged with 10.8 g of water and 1.01 g of 35% hydrochloric acid, and 9.76 g (0.039 mol) of 2-thienyltriethoxysilane and 1.92 g (0.010 mol) of phenyltrimethoxysilane, A solution of methyltrimethoxysilane (6.57 g, 0.048 mol) in toluene (27.0 g) was added dropwise at a reaction temperature of 10 to 20 ° C. over 2 hours, followed by extraction by the method described in Reference Example 1 to recover a toluene oil layer.

  The solvent was removed from the obtained oil layer with an evaporator, and a 3-mercaptomethylsilsesquioxane / phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 40:10:50) was a colorless viscous liquid. ) Was obtained. As a result of GPC analysis of the obtained copolymer, the weight average molecular weight (Mw: converted to polystyrene) was 1,100, and the dispersity (Mw / Mn: converted to polystyrene) was 1.2.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
1026-1269 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: DMSO-d6)
0.175 ppm (bs), 6.975-7.1282 ppm (bs), 7.551-8.612 ppm (bs).

Comparative Example 1
Synthesis of phenylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 10:90) Into a 1 L four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer, 57.8 g of water And 5.2 g of 35% hydrochloric acid aqueous solution were charged, and 107.8 g of toluene of 10.0 g (0.050 mol) of phenyltrimethoxysilane and 61.8 g (0.454 mol) of methyltrimethoxysilane was added at a reaction temperature of 10-20. It was dropped at 0 ° C. and extracted by the method described in Example 1, and a toluene oil layer was recovered.

  The solvent was removed from the obtained oil layer with an evaporator to obtain 35.7 g of 1-naphthylsilsesquioxane / methylsilsesquioxane copolymer as white powder. As a result of GPC analysis, the weight average molecular weight (Mw: converted to polystyrene) was 1,900, and the dispersity (Mw / Mn: converted to polystyrene) was 2.0.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
1018-1196cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: CDCl ₃ )
0.135 ppm (bs), 7.210-8.194 ppm (b).

Example 1 The silicone copolymer synthesized in Reference Examples 1 to 3 and Comparative Example 1 was dissolved in PGMEA (propylene glycol monoethyl ether acetate) to form a 20% solution. Next, it was applied to a silicon wafer with a spin coater and heated to 250 ° C. in an oven to form a 0.5 micron cured film. The results of measuring the refractive index of the film at a wavelength of 193 nm are shown in Table 1. This is a typical wavelength of 193 nm deep ultraviolet light. The refractive index can be improved by introducing sulfur atoms into the silicone copolymer.

From Table 1, the refractive index of the silicone copolymer containing no sulfur atom in Comparative Example 1 was 1.69, whereas in Example 1 and Reference Examples 1 to 3 in which a sulfur atom was introduced, the refractive index was 1. It improved to 1.75 or more.

Reference example 4
3-mercaptopropylsilsesquioxane / 1-naphthylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 20:50:30)
A 1 L four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel and a thermometer was charged with 22.8 g of water and 2.1 g of 35% hydrochloric acid, and 7.8 g of 3-mercaptopropyltrimethoxysilane (0.040 g). Mol), 24.6 g (0.099 mol) of 1-naphthyltrimethoxysilane and 8.1 g (0.059 mol) of methyltrimethoxysilane in a solution of 61.3 g of toluene at a reaction temperature of 10 to 20 ° C. over 2 hours. The toluene oil layer was recovered by dropping and extracting by the method described in Reference Example 1.

  The solvent was removed from the obtained oil layer with an evaporator, and 3-mercaptopropylsilsesquioxane / 1-naphthylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio 20:50: white powder) was obtained. 30) 30.3g was obtained. As a result of GPC analysis of the obtained copolymer, the weight average molecular weight (Mw: polystyrene conversion) was 750, and the dispersity (Mw / Mn: polystyrene conversion) was 1.2.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
2845 cm ^-1 (-SH), 3055, 1504 cm ^-1 (naphthalene), 1028-1115 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: DMSO-d6)
0.561-1.025ppm (bs), 1.183-2.500ppm (bs), 6.697-8.315ppm (bs).

Comparative Example 2
Synthesis of 1-naphthylsilsesquioxane / methylsilsesquioxane copolymer (molar composition ratio: 50:50) 8 g and 24.9 g of 35% hydrochloric acid aqueous solution were charged, and a solution of 299.9 g (1.196 mol) of 1-naphthyltrimethoxysilane and 682.9 g of toluene of 162.9 g (1.196 mol) of methyltrimethoxysilane was reacted. It dripped at the temperature of 10-20 degreeC, and extracted by the method of Example 1, and collect | recovered toluene oil layers.

  The solvent was removed from the obtained oil layer with an evaporator to obtain 320.0 g of 1-naphthylsilsesquioxane / methylsilsesquioxane copolymer as white powder. As a result of GPC analysis, it was a weight average molecular weight (Mw: converted to polystyrene) 820 and a dispersity (Mw / Mn: converted to polystyrene) 1.2.

  The spectrum data of the obtained copolymer is shown below.

Infrared absorption spectrum (IR) data
3055, 1504 cm ^-1 (naphthalene), 1026-1111 cm ^-1 (Si-O)
Nuclear magnetic resonance spectrum (NMR) data ( ¹ H-NMR solvent: CDCl ₃ )
0.182ppm (bs), 7.021-8.252ppm (b)
The silicone copolymer having a naphthalene skeleton synthesized in Example 5 and Comparative Example 2 was dissolved in PGMEA (propylene glycol monoethyl ether acetate) to form a 20% solution. Next, it was applied to a silicon wafer with a spin coater and heated to 250 ° C. in an oven to form a 0.5 micron cured film. The results of measuring the refractive index of the film at a wavelength of 193 nm are shown in Table 2. This is a typical wavelength of 193 nm deep ultraviolet light.

The silicone copolymer having a naphthalene skeleton of Comparative Example 2 had a refractive index of 1.50, whereas the silicone copolymer of Reference Example 4 into which sulfur atoms were introduced improved the refractive index to 1.57. . The refractive index can be improved by introducing sulfur atoms into the silicone copolymer.

Claims (6)

The following general formula

(In the formula, R represents a cyclic sulfide group, A represents a hydrocarbon group having an aromatic ring, B represents a hydrocarbon group not containing an aromatic group, a, b and c represent mol%, and a represents 1 to 50) Mol%, b is 1 to 50 mol%, c is 20 to 98 %, provided that b + c is 21 or more and a + b + c = 100)
A silicone copolymer having a weight average molecular weight (in terms of polystyrene) of 500 to 10,000. R is

The silicone copolymer according to claim 1, which is any one of the following. The silicone copolymer according to claim 1 or 2, wherein A is a phenyl group. B is a methyl group, The silicone copolymer in any one of Claims 1-3. Manufactured by hydrolyzing a silicon monomer having a substituent R (R is a cyclic sulfide group), A (A is an aromatic hydrocarbon group), B (B is a hydrocarbon group not containing an aromatic group) under acidic conditions The method for producing a silicone copolymer according to claim 1. Cyclic sulfide group

The method for producing a silicone copolymer according to claim 5, wherein: