JP3457010B2 - Method for producing cristobalite quartz glass powder - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing quartz glass powder. More specifically, the present invention relates to a method for producing a quartz glass powder which can be suitably used for various applications such as a quartz glass product for semiconductor industry and a multi-component glass raw material for optical communication.

[0002]

2. Description of the Related Art With the increase in the purity of semiconductors, synthetic quartz powder has come to be used in place of natural quartz powder raw material containing many impurities. However, with these synthetic quartz powders, a large amount of silanol remains even after firing, and a silanol content of 100 ppm or less cannot be obtained. It is generally known that when a synthetic quartz powder is used as a raw material to manufacture a quartz member for the semiconductor industry, for example, a quartz crucible for pulling a single crystal, the crucible is deformed at a high temperature.

As described above, there is a background in which it is required to reduce the silanol content of the synthetic quartz powder. In recent years, a special treatment such as chlorine treatment is generally performed on the synthetic quartz powder to reduce the silanol content. However, when a crucible for pulling a silicon single crystal is made from a synthetic quartz powder that has been subjected to these chlorine treatments as a raw material, chlorine impurities of about several ppm are usually contained. When a silicon single crystal is pulled up using such a crucible, impurities in the crucible migrate into the single crystal, so that there is a problem that a high-purity silicon crystal cannot be obtained.

As described above, there is an ever-increasing demand for low silanol in quartz glass powder which is a raw material for quartz glass products for the semiconductor industry and multi-component glass for optical communication. Further, in recent years, the demand for high-purity silicon single crystals has increased with the high integration of semiconductor elements, and high viscosity of crucibles for manufacturing thereof at high temperatures has been required.

[0005]

In order to reduce the silanol content, it is considered that quartz powder should be crystallized. For the purpose of crystallization only, it is generally known that firing at a temperature higher than 1350 ° C. results in cristobalite formation, but in such high temperature firing, impurities such as aluminum from the furnace material and the firing sheath are used. The migration of metal impurities is unavoidable. Further, there is a problem that the obtained quartz powder is sintered and becomes a large lump. On the other hand, in order to avoid these impurities, 135
When firing is performed at a temperature of 0 ° C. or lower, the obtained quartz powder has an amorphous crystal form and a silanol content of 200.
It is extremely high, from ppm to several hundreds of ppm, and is not suitable for quartz members for the semiconductor industry. Therefore, there is a need for a technique for avoiding impurities from the furnace material and the fired pod and reducing the silanol content of the obtained fired quartz powder.

The object of the present invention is to solve the problems of the conventional synthetic quartz powder and to meet the industrial demand, and to produce cristobalite crystallized silica powder and dry silica gel having a particle size in the range of 50 to 100 microns. A method for producing a high-purity quartz glass using, which provides a high-purity quartz glass having a low silanol content by a single firing at a lower temperature than before, and a method for producing a quartz glass powder.

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to solve the above problems, and as a result, added a specific amount of cristobalite crystallized silica powder to a dry silica gel powder as a raw material and mixed them. And then 1000 ℃ to 13
By performing the firing in the temperature range of 50 ° C., the obtained quartz glass powder is completely converted into cristobalite, and silica glass powder having a silanol content of 100 ppm or less, which can be suitably used for semiconductor industrial materials, can be obtained. After finding out that, the present invention has been completed.

The method for producing the cristobaliteized quartz glass powder of the present invention has a particle size of 50 with the dry silica gel powder.
It is characterized in that a mixture of cristobalite crystallized silica powder in the range of up to 100 microns is fired. The firing temperature is preferably in the range of 1000 ° C to 1350 ° C, and the weight of the cristobalite crystallized silica powder having a particle size in the range of 50 to 100 microns is 0.5 to 50% by weight based on the dry silica gel powder. It is preferable.

The manufacturing method of the present invention will be described in detail below. The dry silica gel powder used in the production method of the present invention preferably has high purity, and dry silica gel powder obtained by a general sol-gel method is preferably used. The surface area and particle size are not particularly limited. Further, the water content contained in the dried silica gel powder is not particularly limited, but in consideration of the influence on the firing furnace and the like, it is preferably 0 to 20%.

The cristobalite crystallized silica powder used in the production method of the present invention is 0.5% by weight, preferably 20% by weight of the amount of quartz powder obtained from the silicate ester. From the viewpoint of dispersibility, the smaller the particle size, the better.
It is micron.

The method of mixing the dry silica gel powder and the cristobalite crystallized silica powder in the production method of the present invention is carried out after firing unless the cristobalite crystallized silica powder and the amorphous silica powder to be seed crystals are sufficiently mixed. Crystallization of the obtained silica powder is not sufficiently promoted, resulting in a high silanol content,
Special attention must be paid to these mixtures. The specific method will be described below. In the case of mixing a relatively small amount, it is preferable to use a mixer in which a cylindrical container made of polyethylene, polypropylene or nylon and containing balls made of the same material as the container or made of silicon are rotated. Further, industrially, a horizontal cylindrical mixer with internal blades, a double cone mixer, a ball mill and the like are preferably used. Specifically, dry silica gel and crystalline silica powder, together with silicon balls, are placed in a polyethylene cylindrical wide-mouthed bottle, the lid is placed, and the bottle is placed between two parallel rollers for 10 to 30 minutes. 60-1 per minute
Mix 20 times.

The firing temperature in the production method of the present invention is 1000 ° C. as in the so-called sol-gel method.
The above is sufficient, and it is preferably 1000 to 1350 ° C. At a firing temperature of less than 1000 ° C., the silica glass powder obtained after firing has a large specific surface area and cannot be suitably used for the semiconductor industry. When the temperature is higher than 1350 ° C., impurities such as metal impurities such as aluminum are transferred from the furnace material and the sinter, which is not preferable. The firing time is usually 1 hour or more.

The crystal form of the synthetic quartz glass powder obtained as described above is cristobalite, and the silanol content is 100 ppm or less, and it is suitable for use as a quartz glass product for semiconductor industry, especially as a raw material for quartz crucible. be able to. Further, because of its high purity, it can be used as a raw material for multi-component glass for optical communication.

[0014]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The silanol contents of Examples and Comparative Examples were calculated by the following formula.

[0015]

[Equation 1]

As the dried silica gel powder of the examples, those obtained by the sol-gel method by hydrolysis and dehydration condensation of methyl orthosilicate were used. As the cristobalite crystallized silica powder, dry silica gel powder obtained by the sol-gel method was fired at 1550 ° C. for 6 hours using an electric furnace, and cristobalite crystallization was confirmed by an X-ray diffraction method. After that, it was crushed in an agate mortar and used to have a particle size of about 50 μm.

(Example 1) 60 g of dried silica gel powder and 12 g of cristobalite crystallized silica powder corresponding to 20% by weight of the dried silica gel powder were placed in a polyethylene container having an internal volume of 500 ml, and 10 silicon balls of 15 mmφ were further added. Close the lid. This container was placed between two rollers and rotated at 60 rpm for 30 minutes to obtain a mixed silica gel. A part of this mixed silica gel was crushed in an agate mortar and subjected to X-ray diffraction, and the result is shown in FIG. From this figure, it was found that the mixed silica gel was a mixture of cristobalite crystallized silica and amorphous silica. This mixed silica gel is put in a baking pod made of high-purity alumina having an internal capacity of 200 ml, and the lid made of the same material as the pod is put into an electric furnace to set the baking conditions (heating rate 2.2 ° C / min, baking temperature 1350 ° C, baking). (Time: 4 hours, cooling rate: 2.2 ° C / min)
Was fired at. Firing gave 67 g of quartz glass powder. The weight loss due to calcination was 7.0% with respect to the amount of mixed silica gel. This quartz glass powder was crushed in an agate mortar and subjected to X-ray diffraction. The result is shown in FIG. 1 (b). Compared to the diffraction peaks of the cristobalite crystals in the mixed silica gel, the crystallinity of the quartz glass powder after firing is clearly higher. The true specific gravity of this quartz glass powder was 2.32, which was almost perfect cristobalite. The measurement results of this quartz glass powder by a Fourier transform infrared spectrophotometer (hereinafter abbreviated as FT-IR) are shown in FIG. No silanol peak was observed, indicating that silanol was not contained at all.

Example 2 A quartz glass powder was obtained in the same manner as in Example 1 except that the amount of cristobalite crystallized silica powder was 0.3 g (0.5% by weight of dry silica gel powder). . The crystal form of the obtained quartz glass powder was confirmed to be cristobalite by X-ray diffraction. The true specific gravity was 2.25. Also, FT-IR
In the measurement, a peak showing a slight amount of silanol was observed, and the silanol content determined from the height of the peak was 66 p.
It was pm and 100 ppm or less.

Comparative Example 1 The procedure of Example 1 was repeated except that the crystallized silica powder of cristobalite was replaced with amorphous silica glass powder. The X-ray diffraction pattern of the obtained quartz glass powder is shown in FIG. No peak indicating cristobalite was observed, and it was completely amorphous. Also, FT-IR
The result of the measurement is shown in FIG. A peak indicating silanol was recognized and the silanol content was 176 ppm.

(Comparative Example 2) The operation of mixing dry silica gel powder and cristobalite crystallized silica powder was not carried out at all, and when these were put into the baking pod, first, the raw material dry silica powder was put to make the upper surface uniform. After smoothing, the cristobaliteized silica powder was gently added.
Others were the same as in Example 1. In the X-ray diffraction pattern of the obtained quartz glass powder, a low peak of cristobalite was confirmed in the non-crystal, and it was found to be a mixture of crystalline and non-crystalline. In the FT-IR measurement, the height of the peak showing silanol changes with each measurement,
The silanol value was between 88 and 335 ppm.

Table 1 shows the mixing conditions and silanol content of these examples and comparative examples.

[Table 1]

[0022]

EFFECTS OF THE INVENTION The method for producing quartz glass powder of the present invention is (1) simple and does not require special treatment such as chlorine treatment which has been conventionally performed on synthetic quartz glass powder having a high silanol content. With a simple operation, silica glass powder having a low silanol content, which is useful as a quartz member for the semiconductor industry, is obtained. (2) By adding cristobalite crystallized silica powder to dry silica gel powder, complete crystallization can be achieved even at a relatively low firing temperature at which crystallization is not normally caused.
This avoids the migration of impurities from the furnace material and the fired pod that occur during high temperature firing. (3) Since a simple method of mixing the dry silica gel powder and the cristobalite crystallized silica powder with each other is used, impurities such as impurities due to the operation are less mixed and the relatively simple device is used. Enables industrialization.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of (a) mixed silica gel and (b) quartz glass powder obtained in Example 1.

2 is an FT-I of the silica glass powder obtained in Example 1. FIG.
It is an R measurement result. The arrow in the figure indicates the position of the peak of silanol.

FIG. 3 is an X-ray diffraction diagram of (c) mixed silica gel and (b) quartz glass powder obtained in Comparative Examples.

FIG. 4 is an FT-IR of the quartz glass powder obtained in a comparative example.
It is a measurement result. The arrow in the figure indicates the position of the peak of silanol.

FIG. 5 shows a manufacturing process flow of the quartz glass powder of the present invention.

Claims (3)

(57) [Claims] 1. Dry silica gel powder and particle size 50 to 10
A method for producing cristobaliteized quartz glass powder, which is obtained by firing a mixture of cristobalite crystallized silica powder having a range of 0 micron. 2. The method for producing a cristobaliteized quartz glass powder according to claim 1, wherein the firing is carried out in a temperature range of 1000 ° C. to 1350 ° C. 3. The weight of the cristobalite crystallized silica powder having a particle size in the range of 50 to 100 microns is 0.5 to 50% by weight based on the dry silica gel powder.
A method for producing the cristobaliteized quartz glass powder described.