JP2000016820A - Silica glass granule and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain granular silica causing no foams in a silica glass product in processing the silica glass product, consequently having neither a problem of giving rise to crystal defects of silica in the use of it as a crucible for pulling up, for example, single crystal silicon nor a defect of deformation at a high temperature and a method for producing the granular silica. SOLUTION: This silica glass granule has an OH group content based on an infrared absorption spectrum of <=100 weight ppm (a value obtained by calculating a beta coefficient from a transmission infrared absorption spectrum after melt vitrification at 2.6 μm and 2.73 wavelength) and the ratio of the number of four-membered rings/the number of many-membered rings based on a laser Raman spectrum of >=0.0470 by its area ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silica glass powder and a method for producing the same, and more particularly, to a crucible for pulling single crystal silicon, a diffusion tube for impurity doping, and a semiconductor. The present invention relates to a silica glass powder useful as a jig and as a raw material for producing a glass substrate for a photomask for pattern transfer of a large-scale integrated circuit, a fiber for optical communication, an optical material, and a method for producing the same.

[0002]

2. Description of the Related Art Crucibles used for pulling high-purity silicon single crystals for semiconductors, quartz glass jigs used for semiconductor devices, diffusion tubes, etc. are conventionally made of natural quartz purified by acid washing or the like. Was used. However, with the increasing integration of devices, the miniaturization of defects on silicon wafers and the reduction of the possibility of contamination with impurity elements have become more demanding, and the raw material for silica glass has changed from natural quartz to synthetic silica. It is getting.

[0003] Methods for producing synthetic silica are roughly classified into two types, one using silicon tetrachloride or an alkyl silicate as a raw material. In the method using silicon tetrachloride as a raw material, highly corrosive hydrogen chloride is produced as a by-product during flame hydrolysis in an oxyhydrogen flame, and a small amount of chlorine may remain in the synthesized silica. On the other hand, the method using an alkyl silicate as a raw material is more advantageous in that hydrogen chloride is not produced as a by-product and a synthetic silica containing no chlorine can be obtained. Therefore, the latter method is used in the production of high-purity silica.

Silica made of alkyl silicate as a raw material has about several hundred ppm of silanol groups (Si-OH) generated by hydrolysis in quartz glass products even after a long-term calcination treatment at a high temperature of 1000 ° C. or more. Will remain. When used as a crucible, the silanol groups create fine bubbles in the crucible. This bubble may burst when the single crystal is pulled up, causing a crystal defect in the silicon single crystal. When used as a jig or tube, the remaining silanol groups cause softening at high temperatures.
Therefore, jigs and tubes exposed to high temperatures for a long time in the device manufacturing process are easily deformed.

Attempts to reduce silanol groups have been
Some are known so far. JP-A-2-2-2894
No. 16 discloses a method of producing low silanol silica by heating amorphous silica in an atmosphere having a low steam partial pressure in two stages. According to this method, internal silanol can be reduced to 120 ppm or less. The silanol group concentration in this method is calculated using an absorbance value of infrared absorption by a diffuse reflection method as an index. However, this method is not a method of measuring the silanol group concentration in accordance with actual use, but it is necessary to actually carry out melt vitrification and measure infrared absorption absorbance by a transmission method. Therefore, in practice, the reduction of silanol groups has not been sufficient, and the above-mentioned drawbacks have not been solved.

JP-A-8-26742 discloses that a synthetic quartz glass powder contains 1 × 10 ^-1 to 1 × 10 ^-4 ppm of boron, and has an internal silanol group concentration of 150 ppm or less.
A synthetic quartz glass powder having an isolated silanol group of 5 ppm or less is disclosed. However, the boron content must be within a predetermined range, which complicates the production process, and the synthetic quartz glass powder itself is expensive and impractical. Further, there is a problem that the method for measuring the concentration of silanol groups is not practical, and the reduction of silanol groups is not yet sufficient.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a method for producing a silica glass product, which does not generate bubbles in the silica glass product, and thus, for example, when used as a crucible for pulling single crystal silicon, crystal defects of the silica. The present invention provides a particulate silica and a method for producing the same, which do not have a problem of causing deformation of the silica at high temperatures.

[0008]

SUMMARY OF THE INVENTION The present inventors have found that bubbles are generated in a silica glass product, which may cause crystal defects of silica when used as a crucible for pulling single-crystal silicon, for example. Various investigations were made on how the silanol group can be removed. As a result, it was surprisingly found that the use of the following prescribed method makes it possible to easily reduce silanol groups in a manner that would not be considered in conventional methods. The novel silica glass powder produced by the method has excellent properties different from conventional products, that is,
After processing into a product, it was found that no bubbles were generated in the product, and therefore, it did not cause crystal defects or the like of silica at the time of use and did not deform at a high temperature. is there.

That is, according to the present invention, (1) the OH group content based on the infrared absorption spectrum is not more than 100 ppm by weight based on the weight of the silica glass powder (the transmission infrared absorption spectrum after melt vitrification). Is a value obtained by calculating the beta coefficient from the transmittance at wavelengths of 2.6 μm and 2.73 μm), and the ratio of the number of 4-membered rings / multi-membered rings based on the laser Raman spectrum is the area ratio. Is not less than 0.0470.

In a preferred embodiment, (2) the silica gel is produced by hydrolyzing the organic silicate in a dispersed state, and then the silica gel is separated and calcined to produce silica glass powder. In the method, the organic silicate is hydrolyzed at a temperature of 50 ° C. to a reflux temperature or lower in the presence of a basic catalyst, and then the separated silica powder gel is heat-treated with hot water or steam. (3) the method for producing a silica glass powder according to the above (1), (3) the method according to the above (2), wherein the basic catalyst is ammonia,
(4) The method according to the above (2) or (3), wherein the organic silicate is hydrolyzed at a temperature of 50 to 70 ° C., (5) an organic solvent substantially incompatible with water for the hydrolysis, and In an organic solvent having a boiling point higher than the boiling point of the alcohol by-produced with the hydrolysis of the organic silicate, at a temperature equal to or higher than the boiling point of the alcohol and lower than the boiling point of the organic solvent,
The method according to any one of the above (2) to (4), wherein the reaction is carried out while continuously distilling and removing the by-product alcohol.
(6) The method according to the above (5), wherein the organic silicate is one or more alkyl silicates selected from the group consisting of methyl silicate, ethyl silicate and propyl silicate, (7) the organic silicate is methyl silicate, ethyl silicate The method according to the above (5), which is one or more alkyl silicates selected from the group consisting of silicates and isopropyl silicates, may be mentioned.

As described above, in an organic solvent which is substantially incompatible with water and which has a boiling point higher than that of alcohol by-produced by hydrolysis of the organic silicate, When the hydrolysis is carried out at a temperature equal to or higher than the boiling point and lower than the boiling point of the organic solvent while continuously distilling and removing the by-produced alcohol, water and the organic solvent due to the by-produced alcohol accompanying the hydrolysis are removed. Does not occur. Therefore, there is an advantage that the operability is not deteriorated due to the generation of a soft and difficult-to-handle gel, and the particle shape and particle size distribution of the generated silica can be easily controlled.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the silica glass powder has an OH group content of 100 ppm by weight or less based on the weight of the silica glass powder. When the OH group content exceeds the above upper limit, bubbles are generated in the product when the product is processed into a silica glass product, and thus, when used as a crucible for pulling single crystal silicon, for example, crystal defects of silica are caused. At high temperatures.

Here, the OH group content in the silica glass powder is determined to be 2.6 μm and 2.73 in the infrared absorption spectrum.
This is a value obtained by calculating a beta coefficient from the transmittance at a wavelength of μm. The sample subjected to measurement by the infrared absorption spectrum was formed by forming a synthetic silica layer composed of silica glass particles on the inner surface of a natural quartz crucible by an arc melting method, and then cutting out the silica layer as a thin plate of 1 to 2 mm. It was prepared by

In the silica glass powder of the present invention, the number of 4-membered rings is 0.0470 or more in terms of the area ratio of 4-membered rings / multi-membered rings in the laser Raman spectrum. The 4-membered ring number is
If it is less than the above lower limit, there is a disadvantage that it is deformed at a high temperature.
The sample used for the measurement was prepared by the same method as the measurement by the infrared absorption spectrum.

The silica of the present invention can be produced by the following method.

That is, in a method for producing silica glass particles by hydrolyzing an organic silicate in a dispersed state to form silica powder particles, and then separating and firing the silica powder particles, The method comprises hydrolyzing an organic silicate at a temperature of 50 ° C. to a reflux temperature or lower in the presence of a neutral catalyst, and then subjecting the separated silica powder gel to heat treatment with hot water or steam.

The basic catalyst used in the method includes, for example, ammonia, methylamine, monoethanolamine, ammonium carbonate and the like. Of these, ammonia is particularly preferably used. The amount of catalyst added depends on its strength, hydrolyzability of the organic silicate used,
The amount may be determined by the reaction temperature or the like, and may be a conventional amount for such a hydrolysis reaction. The use of the basic catalyst makes it possible to increase the pore diameter of the resulting silica powder gel much more than that using an acid catalyst.
When firing the silica powder gel by this,
In the case of using an acid catalyst, the pores disappear at a firing temperature of about 1100 ° C, whereas in the case of using a basic catalyst, the pores are maintained up to about 1200 ° C. Accordingly, it is possible to sufficiently secure an escape route of water generated by the condensation between silanol and silanol by heating in the above-mentioned calcination, whereby the silanol groups present in the gel can be sufficiently removed, and the amount of OH groups can be reduced. The reduction can be achieved.

The temperature at which the organic silicate is hydrolyzed is 5
The temperature is from 0 ° C to the reflux temperature or lower, preferably 50 to 70 ° C. By keeping the temperature within the above range, the pore size of the generated silica powder gel can be made larger. If the temperature is lower than the above-mentioned temperature, the pore diameter of the generated silica powder gel becomes small, and the pores are crushed when the silica powder gel is calcined, so that the effects of the present invention cannot be achieved.

After the formation, there is no particular limitation on the method of subjecting the separated silica powder gel to heat treatment with hot water or steam.
Heat treatment with hot water or steam is preferably 150 ° C.
As described above, particularly preferably, the silica powder gel is exposed to hot water or steam kept at 200 ° C. or higher, and the temperature of the silica powder gel is adjusted to the above hot water while checking the temperature rise of the silica powder gel. Or, it ends when the temperature rises to near the steam temperature.

There is no particular limitation on the method for producing silica powder granules by hydrolyzing an organic silicate to form silica powder granules, then separating and firing the silica powder granules to produce silica glass powder granules. A method can be used.

In particular, Japanese Patent Application No. 8-1754 of the applicant of the present invention.
It is preferable to use the method described in No. 63. That is,
Hydrolysis, in an organic solvent that is substantially incompatible with water, and in an organic solvent having a boiling point higher than the boiling point of the alcohol by-produced with the hydrolysis of the organic silicate, the boiling point of the alcohol or higher and the In this method, the by-product alcohol is continuously distilled off at a temperature lower than the boiling point of the organic solvent.

In the above method, the organic silicate may be a linear or branched lower alkyl silicate, for example, methyl silicate, ethyl silicate, propyl silicate (n-propyl silicate and isopropyl silicate), a mixture thereof or a condensation thereof. Products (dimers, oligomers, etc.) and the like can be used. Alternatively, a mixed ester having two or more alkoxy groups (for example, methyl ethyl ester: Si (OMe) ₂ (OEt) ₂ or the like) may be used. Although an organic silicate in which the OR group is an alkoxy group having 4 or more carbon atoms can be used, the boiling point of the by-produced alcohol becomes higher than that of water. Is slow, and the amount of silica produced per unit weight of the raw material is reduced, so it is not economical.
Alkyl silicates selected from ethyl silicate and propyl silicate (particularly isopropyl silicate) are preferred.

The method is characterized in that the hydrolysis reaction is carried out in a solvent substantially incompatible with water, and at that time, alcohol by-produced in the reaction is continuously distilled off. It is. Therefore, the organic solvent used needs to have a boiling point higher than that of the by-produced alcohol, in addition to being substantially incompatible with water. Specific examples of solvents that can be used include aromatic hydrocarbon solvents such as benzene (boiling point of about 80 ° C.) and toluene (boiling point of about 111 ° C.).
℃), xylene (boiling point about 138.4 ℃ (o-), 139.1 ℃ (m-),
144.4 ° C (p-)), dodecylbenzene (boiling point about 180 ° C)
Etc .; aliphatic hydrocarbon solvents such as n-hexane (boiling point of about
68.7 ° C), decane (boiling point approx. 174 ° C), dodecane (boiling point approx.
216 ° C.); halogen-based hydrophobic solvents such as tricrene (boiling point: about 87 ° C.), tetrachloroethylene (boiling point: about 121 ° C.)
° C) and the like; non-polar ether solvents such as anisole (boiling point: about 153.8 ° C) and dibutyl ether (boiling point: about 142.4 ° C). Preferably, among these solvents, a solvent having a boiling point higher than that of the alcohol by-produced from the organic silicate to be used is selected. The amount of solvent depends on the amount of water used. Usually, an equivalent (volume) or more solvent of water is used.

The amount of water added for the hydrolysis is preferably at least 1 equivalent to 1 equivalent of OR group (alkoxy group in the case of alkyl silicate) of the organic silicate. If it is less than 1 equivalent, the yield will decrease. The upper limit of the amount of water is not particularly limited, but is practically 4 equivalents or less per 1 equivalent of the OR group of the organic silicate.

The hydrolysis reaction is carried out by mixing the above-mentioned organic solvent, organic silicate, water and a catalyst. However, since these components are separated into an aqueous phase and an organic phase as they are, they are forcibly stirred, for example, to be in a dispersed state. The water and the organic silicate are brought into contact at the interface of the generated water droplets to cause hydrolysis. As described above, since the reaction proceeds in water droplets dispersed in the organic solvent, the size of the water droplets is adjusted by changing the stirring intensity and the stirring method, and the particle size of the silica glass powder particles is controlled. it can. Also, by changing the charge ratio of water and organic solvent,
Particle size can be controlled. For example, when the amount of the organic solvent is 2 to 6 times (volume) the amount of water, the particle diameter of most of the particles (finally obtained silica glass powder) is in the range of 10 to 500 μm. You can do so.

The particle shape can be controlled to be spherical or crushed by changing the mixing ratio of water and the solvent and the stirring speed. The compounding ratio varies depending on the solvent used, but generally when the proportion of the solvent is large, it tends to be spherical, and when the proportion of water is large, it tends to be crushed. The higher the stirring speed, the easier it is to be spherical.

In order to continuously distill and remove the alcohol by-produced as the hydrolysis reaction proceeds, the above-mentioned hydrolysis reaction is heated to a temperature above the boiling point of the alcohol by-produced and below the boiling point of the organic solvent. Do it. However, when the boiling point of the organic solvent is 100 ° C or higher, the heating temperature should be lower than 100 ° C in order to avoid evaporation of water. If the heating temperature (that is, the reaction temperature) is lower than the boiling point of the by-produced alcohol, the by-produced alcohol is not removed. Therefore, the presence of the alcohol, which is a hydrophilic organic solvent, promotes the compatibilization between the aqueous phase and the organic phase. As a result, the suspension is destroyed. As a result, the whole reaction solution is gelled, so-called agar-like gel is formed, and a powder-like gel cannot be obtained. If the heating temperature is equal to or higher than the boiling point of the organic solvent, the organic solvent is also distilled off, so that a good suspension state of water and the organic solvent cannot be obtained and an agar gel is easily formed. As described above, by continuously distilling and removing the by-produced alcohol, the hydrolysis reaction proceeds while maintaining the suspension state, and the hard gel is obtained in the state of powder and granules.

The obtained silica powder gel is a hard gel and easy to handle, so that it can be easily separated from the reaction mixture by a conventional method, for example, by filtration. It is preferable that the separated powder gel is sufficiently washed with water to remove an organic solvent and impurity ions. By sufficiently washing, carbonization during subsequent firing can be prevented, and water-soluble metal ions and the like are removed, so that high-purity silica glass particles can be obtained.

Next, the silica powder gel is fired according to a conventional method to obtain silica glass powder. The calcination is preferably performed at a high temperature of 1000 ° C. or more for several hours, particularly preferably at a high temperature of 1100 ° C. or more for 10 hours or more to remove silanol. In order to remove silanol, it is preferable that the firing temperature is higher.However, if the temperature is too high, fusion of particles may be caused, or the material of the container during firing may not withstand silica itself, and there is a risk of impurity contamination. Occurs. Therefore, the firing temperature is particularly preferably about 1100 to 1300 ° C. Note that it is preferable to perform the drying step before the firing step, because the bulk of the powder gel can be significantly reduced and the load of the subsequent firing step can be reduced. Drying is usually 150 ~
Perform at 200 DEG C. for 1-2 hours.

In the above method, alcohol produced as a by-product of the hydrolysis is continuously removed, so that the hydrolysis of the organic silicate proceeds and the polycondensation of the produced SiO ₂ proceeds, and the silica glass particles The yield is improved.
Moreover, since almost no by-product alcohol remains after the reaction, the obtained silica gel is hard and easy to handle and separate. For example, JP-A-58-1
In the method described in Japanese Patent No. 76136, a soft gel-like material is produced, and therefore, in the embodiment, the temperature is low at a low temperature for a long time (for example, 90 ° C.).
Drying process for 20 hours), which caused deformation and cracking of the particles due to prolonged compression. The above method does not cause such a disadvantage.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0032]

EXAMPLES Each characteristic value in the following examples and comparative examples was measured as follows. <OH group content> An infrared spectrophotometer was used. The beta coefficient was calculated from the transmittance at wavelengths of 2.6 μm and 2.73 μm in the infrared absorption spectrum. <4-membered ring number> A laser Raman spectrophotometer was used. <Heat resistance (bending test)> Length 50 mm x width 5
A test piece having a size of 2 mm x 2 mm was prepared. Fig. 1
The temperature was raised from room temperature to 1400 ° C. in 1.5 hours in an electric furnace in 1.5 hours, and Δh after holding at that temperature for 2 hours was measured and evaluated.

[0033]

Example 1 A reactor equipped with a stirrer, a thermometer and a heating device was charged with 1200 parts by weight of methanol, 1200 parts by weight of water,
0.2 parts by weight of 8% aqueous ammonia and 1200 parts by weight of tetramethyl orthosilicate were charged. Next, the reaction mixture was stirred to be uniform, and then the stirring was stopped, followed by heating to 60 ° C. to hydrolyze tetramethyl orthosilicate to form a silica powder gel. After completion of the hydrolysis, the gel was taken out of the reactor, transferred into a pressure vessel, and then subjected to heat treatment with 200 ° C steam until the temperature of the silica powder gel reached 180 ° C.

After the completion of the heat treatment, the resulting silica powder gel was filtered off, washed with water, and then reduced under reduced pressure using an electric dryer.
Dried at 200 ° C. for 1 hour. The dried silica powder granules are placed in an electric furnace at a rate of 30 ° C./hour at a rate of 1200 ° C.
C., and kept at this temperature for 20 hours to obtain silica glass powder.

The obtained silica glass powder was sprayed on the inner surface of a quartz crucible made of natural quartz at a high temperature by an arc melting method to form a synthetic silica layer having a thickness of about 3 mm. Next, a part of the crucible was cut out and observed with an optical microscope. As a result, it was found that the synthetic silica layer had almost no air bubbles. Furthermore, quantification of OH groups, measurement of the number of 4-membered rings, and measurement of heat resistance were performed using the sample.

As a result, the OH group content was 95.6 weight p.
pm, the number of 4-membered rings (area ratio of 4-membered rings / multi-membered rings) is 0.0498, and the heat resistance (Δh) is 39.3 m.
m.

[0037]

Example 2 152 parts by weight of distilled and purified tetramethyl orthosilicate was placed in a four-neck glass flask, and 300 parts by weight of distilled and purified xylene and 90 parts of distilled water were placed therein.
Parts by weight and 0.025 parts by weight of 28% aqueous ammonia were added. Then, the flask was stirred while heating (speed
300 rpm). After 15 minutes, when the temperature of the reaction solution reached 64 ° C., methanol began to be distilled off. After heating was continued for a further 30 minutes until the liquid temperature reached 95 ° C. and the distillation of methanol was continued, stirring was stopped and the mixture was allowed to cool to room temperature. The resulting silica powder gel was separated by filtration, transferred into a pressure vessel, and then subjected to heat treatment with 200 ° C steam until the temperature of the silica powder gel reached 180 ° C.

After the completion of the heat treatment, the obtained silica powder gel was filtered off, washed with water, and then dried at 200 ° C. for 1 hour by an electric drier. Then, the temperature was raised to 1200 ° C. at a rate of 200 ° C./hour in an electric furnace, and the temperature was maintained for 20 hours to obtain spherical silica glass particles.

The obtained silica glass powder was used in the same manner as in Example 1 and observed with an optical microscope, and further, quantification of OH groups, measurement of the number of 4-membered rings, and measurement of heat resistance were performed. As a result of observation with an optical microscope, it was found that there were almost no bubbles inside the synthetic silica layer.

The OH group content, the number of 4-membered rings and the heat resistance were almost the same as in Example 1, and were good.

[0041]

[Comparative Example 1] (In the case of using glacial acetic acid) The same procedures as in Example 1 were carried out except for using 1.2 parts by weight of glacial acetic acid instead of 0.2 parts by weight of 28% ammonia water, and Was measured. As a result of observation with an optical microscope, many bubbles were observed inside the synthetic silica layer. OH group content is 145.0 weight pp
m was significantly higher than that of Example 1, and the 4-membered ring number was 0.0458, which was significantly lower than that of Example 1. Also, the heat resistance was extremely poor.

[0042]

Comparative Example 2 (When the reaction temperature is low)
Each property was measured in the same manner as in Example 1 except for the above. As a result of observation with an optical microscope, many bubbles were observed inside the synthetic silica layer. The OH group content was 180.0 ppm by weight, which was significantly higher than that of Example 1. Also, 4
The number of ring members was extremely low, and the heat resistance was extremely poor.

[0043]

Comparative Example 3 (In the case where steam treatment was not performed) The same operation as in Example 1 was performed except that the heat treatment with steam was not performed, and each property was measured. As a result of observation with an optical microscope, many bubbles were observed inside the synthetic silica layer.

[0044]

Comparative Example 4 (Using acetic acid) Each property was measured in the same manner as in Example 2, except that 1.5 g of acetic acid was used instead of 0.025 parts by weight of 28% aqueous ammonia.
As a result of observation with an optical microscope, many bubbles were observed inside the synthetic silica layer. The OH group content was extremely high, the number of 4-membered rings was extremely low, and the heat resistance was extremely poor.

[0045]

Comparative Example 5 A silica glass powder was obtained by the method described in JP-A-8-26742. Then, the silica glass powder was observed in the same manner as in Example 1 by an optical microscope, and further, quantification of OH groups, measurement of the number of 4-membered rings, and measurement of heat resistance were performed. As a result of observation with an optical microscope, more air bubbles were observed inside the synthetic silica layer than in Example 1. The OH group content was 124.0 wt ppm, which was significantly higher than that of Example 1, and the heat resistance was 42.3 m.
m was worse than that of Example 1.

[0046]

Reference Example 1 Using natural quartz IOTA-6 (manufactured by Unimin Corporation, USA), the same operation as in Example 1 was carried out, and each property was measured.

As a result of observation with an optical microscope, it was found that the silica layer had almost no air bubbles. Also,
The OH group content was 94.1 ppm by weight, the number of 4-membered rings (area ratio of 4-membered ring / multi-membered ring) was 0.0462, and the heat resistance was 25.5 mm.

From the above results, it was found that the silica glass powder of the present invention has an OH group content almost equal to that of natural quartz and has heat resistance closer to that of natural quartz.

[0049]

According to the present invention, when processed into a silica glass product, no bubbles are generated in the silica glass product, and therefore, for example, crystal defects of silica are caused when used as a crucible for pulling single crystal silicon. The present invention provides a particulate silica and a method for producing the same, which do not have the problems described above and do not have the disadvantage of deforming at high temperatures.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a heat resistance measuring device (bending test device).

[Explanation of symbols]

 1: Test piece (before heating) 2: Test piece (after heating)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuru Eguchi 1-5 Nagatanocho, Fukuchiyama-shi, Kyoto Prefecture Fuso Siltec Co., Ltd. (72) Inventor Kazuaki Higuchi 1-5 Nagatano-cho, Fukuchiyama City, Kyoto Fuso Siltec Co., Ltd. (72) Inventor Masatoshi Sakai 1-5 Nagatano-cho, Fukuchiyama-shi, Kyoto F-term in Fuso Siltec Co., Ltd. 4G014 AH04 4G062 AA10 BB02 CC05 MM02 MM27 MM40

Claims (4)

[Claims] 1. An OH group content based on an infrared absorption spectrum is 100 ppm by weight based on the weight of silica glass powder.
The following is a value obtained by calculating the beta coefficient from the transmittance at wavelengths of 2.6 μm and 2.73 μm in the transmission infrared absorption spectrum after melt vitrification, and a 4-membered value based on the laser Raman spectrum. A silica glass powder characterized in that the ratio of the number of rings / the number of multi-membered rings is 0.0470 or more in terms of the area ratio. 2. A method for producing a silica glass powder by hydrolyzing an organic silicate in a dispersed state to form a silica powder gel, and then separating and firing the silica powder gel. Hydrolyzing the organosilicate in the presence of a neutral catalyst at a temperature of from 50 ° C. to a reflux temperature,
2. The method for producing silica glass particles according to claim 1, wherein the separated silica particle gel is heat-treated with hot water or steam. 3. The method according to claim 2, wherein the basic catalyst is ammonia.
The described method. 4. The method according to claim 1, wherein the hydrolysis is carried out in an organic solvent which is substantially incompatible with water and which has a boiling point higher than that of the alcohol by-produced with the hydrolysis of the organic silicate. 4. The method according to claim 2, wherein the by-product alcohol is continuously distilled off at a temperature equal to or higher than the boiling point of the organic solvent and lower than the boiling point of the organic solvent.