JP5344767B2 - Method for producing quartz glass crucible for pulling silicon single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a quartz glass crucible for pulling up silicon single crystals in which silica powder released from the outermost layer in which unmelted or semi-melted silica powder is unevenly distributed in a crucible is properly controlled without grinding, on the other hand, the crystalline part in the outermost layer is largely left, heat resistance at high temperature is maintained, and silicon single crystals can be produced at a high yield. <P>SOLUTION: The method for producing a quartz glass crucible for pulling up silicon single crystals is characterized in that raw material powder is fed into a rotating die, so as to form a crucible-shaped raw material powder layer, from the inside thereof, arc discharge heating is performed, and melting is caused so as to produce a quartz glass crucible having a smooth inner surface, an opaque or translucent external layer and the outermost layer in which unmelted or semi-melted silica powder is unevenly distributed at the outside thereof, solid silica powder is sprayed on the outer surface thereof under the spraying pressure of 0.1 to 5 MPa, thereafter, high pressure water is sprayed under the spraying pressure of 24 to 40 MPa, and next, hydrofluoric acid aqueous solution treatment is performed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a silica glass crucible used for pulling a silicon single crystal, and more specifically, by optimally controlling the release powder of unmelted or semi-melted silica powder in the outermost layer of the silica glass crucible, The present invention relates to a method for producing a quartz glass crucible that can produce a single crystal at a high yield and is excellent in heat resistance at high temperatures.

  A so-called Czochralski method (CZ method) is widely used for the production of silicon single crystals. In this production method, a quartz glass crucible is generally used. This quartz glass crucible for pulling up a silicon single crystal is manufactured by a method in which raw material powder is supplied into a rotating mold to form a crucible-like raw material powder layer, and arc discharge is heated from the inside to melt it. It has an inner surface, an opaque or translucent outer layer, and an outermost layer in which unmelted or semi-molten quartz powder is unevenly distributed. When pulling up the silicon single crystal using the quartz glass crucible, the unmelted or semi-melted quartz powder of the outermost layer is detached when the silicon single crystal is pulled up, mixed into the silicon melt, and remains undissolved in the silicon. There was a drawback that the yield of the single crystal was lowered.

In order to solve this drawback, Patent Document 1 proposes a method of grinding the outermost layer to remove unmelted or semi-molten quartz powder. However, this method has a drawback that the crystalline part of the crucible is completely removed and the heat resistance at high temperature is lowered.
Japanese Patent No. 2962976

  In view of such a current situation, the present inventors have continued intensive research, and as a result, the raw material powder is supplied into a rotating mold to form a crucible-like raw material powder layer, which is heated and melted by arc discharge from the inside thereof. After producing a silica glass crucible having an inner surface, an opaque or translucent outer layer, and an outermost layer in which unmelted or semi-melted silica powder is unevenly distributed on the outer surface, and spraying solid silica powder on the outer surface, high pressure water , Followed by hydrofluoric acid aqueous solution treatment to reduce the dislocation silica powder from mixing into the silicon melt and reduce crystal dislocations, leaving a large amount of crystalline part in the outermost layer, and using this as the core for the outer surface It has been found that a quartz glass crucible can be produced which can be easily crystallized as a whole, maintains heat resistance at high temperatures, and can stably produce silicon single crystals with high yield. That is,

  In the present invention, the silica powder separated from the outermost layer in which the unmelted or semi-melted silica powder of the crucible is unevenly distributed without grinding is suppressed, and the crystalline part of the outermost layer remains, and the heat resistance at high temperature is maintained. It is an object of the present invention to provide a method for producing a quartz glass crucible for pulling a silicon single crystal that can produce a silicon single crystal with a high yield.

  The present invention that achieves the above object is to supply raw material powder into a rotating mold to form a crucible-like raw material powder layer, and then arc discharge heat from the inside to melt and smooth inner surface and opaque or translucent After producing a quartz glass crucible having an outer layer and an outermost layer in which unmelted or semi-molten silica powder is unevenly distributed on the outer side, and spraying solid silica powder on its outer surface at a pressure of 0.1 to 5 MPa, The present invention relates to a method for producing a quartz glass crucible for pulling a silicon single crystal, characterized by spraying high-pressure water at a spray pressure of 24 to 40 MPa and then performing a hydrofluoric acid aqueous solution treatment.

As described above, the silica glass crucible for pulling a silicon single crystal obtained by the production method of the present invention has a smooth inner surface, an opaque or translucent outer layer, and an unmelted or semi-molten silica powder unevenly distributed on the outer side. A quartz glass crucible for pulling a silicon single crystal having an outermost layer, wherein there is no separation silica powder on the inner surface of the crucible, and at least the silica powder separated from the outermost layer in the straight body portion is 0.1 to 1. It is a quartz glass crucible of 0 pieces / cm ² . Usually, quartz glass crucibles are covered with a sheet-like lid on the crucible opening to prevent foreign matter from entering, and are further packed in a bag. When setting the crucible into a carbon mold, etc., the silica powder is detached from the outer surface of the crucible and enters the inside of the crucible and adheres to the silicon single crystal when the silicon single crystal is pulled up, causing crystal dislocation and causing the silicon single crystal. Although the productivity of the crystal may be reduced, if the silica powder to be detached is within the above range, the silica powder separated from the outermost layer is prevented from being mixed into the silicon melt, and the crystal dislocation is reduced and the silicon single crystal Can be manufactured at a high yield. When the number of silica powders separated from the outermost layer is 0.1 to 1.0 / cm ² , the detached silica powder from the outermost layer is hardly mixed into the silicon melt, and the yield of the silicon single crystal is further increased. As it improves, the crystalline part remains, so it has excellent heat resistance at high temperatures. If the silica powder released from the outermost layer is less than 0.1 pieces / cm ² , the crystalline part is insufficient and the heat resistance of the quartz glass crucible at a high temperature is lowered. It is. On the other hand, if the number of silica powders separated from the outermost layer exceeds 1.5 / cm ² , the detached silica powder is likely to be mixed into the crucible, and the yield of the silicon single crystal is remarkably reduced. The adhesive tape method used in the present invention is an adhesive tape (trade name: Million Vinyl Tape Black, manufactured by Kyowa Co., Ltd.) attached to the outer surface of a quartz glass crucible manufactured by a rotational mold method, and adheres to the adhesive tape. This is a method in which the number of quartz powders is counted and measured visually.

In the above method for producing a silica glass crucible, a part which forms a rotating mold and at least a straight body part of the crucible supplies raw material powder into a stainless steel mold to form a crucible-like raw material powder layer, Solid silica powder is sprayed at a spraying pressure of 0.1 to 5 MPa on the outer surface of a quartz glass crucible manufactured by a so-called rotary mold method in which arc discharge is heated and melted from the inside, and then high-pressure water of 24 to 40 MPa is applied to the crucible. And controlling the hydrofluoric acid aqueous solution treatment so that the inner surface etching amount is 1 to 50 μm and the outer surface etching amount is 1 to 10 μm. It is manufactured by rinsing with pure water and drying. By the treatment, the detached silica powder on the inner surface of the crucible is sufficiently removed, and the detached silica powder from the outermost layer is 0.1 to 1.0 / cm ² by the adhesive tape method. If the spray pressure of the solid silica powder is less than 0.1 MPa, the removal of unmelted or semi-melted silica powder is not sufficient, and the detached silica powder tends to accumulate in the wastewater after treatment with high-pressure water or hydrofluoric acid aqueous solution. There is concern about a decrease in workability, and when it exceeds 5 MPa, the semi-molten crystalline part of the outer surface is scraped and the heat resistance at high temperatures is reduced. As the solid silica powder to be used, natural silica powder, synthetic silica powder or a mixed silica powder thereof is used. Further, when the pressure of the high-pressure water is less than 24 MPa, the detached silica powder is not sufficiently removed, and when it exceeds 40 MPa, the crystalline portion is removed and the heat resistance of the crucible at a high temperature is lowered.

  In the hydrofluoric acid aqueous solution treatment, the hydrofluoric acid aqueous solution may be sprayed on the inner and outer surfaces of the crucible, or the crucible may be immersed in the hydrofluoric acid aqueous solution, but the inner surface etching amount is 1 to 50 μm, and the outer surface etching amount is It is important that the thickness is 1 to 10 μm. If the etching amount on the inner surface is less than 1 μm, the removal of surface impurities and detached silica powder is not sufficient, and if the etching amount exceeds 50 μm, the inner surface becomes rough and the crystallization rate of the silicon single crystal decreases. Furthermore, when the etching amount of the outermost layer is less than 1 μm, the removal of surface impurities and detached silica powder is not sufficient, and when the etching amount exceeds 10 μm, the semi-molten portion of the outer surface is easily peeled off and the detached silica powder increases. . If the etching process is further carried out from this state to remove all of the semi-molten portion, the detached silica powder can be reduced. However, in this case, the crystalline portion on the outer surface is removed and the heat resistance at high temperature is lowered.

  In the manufacturing method described above, at least the portion of the rotating mold that forms the straight body portion is made of stainless steel, so that the outermost layer of unmelted or semi-molten silica powder is formed in a preferred range. When the carbon mold is used, the layer of unmelted or semi-melted silica powder becomes thin and the heat resistance tends to decrease. Similarly, the thickness of the raw material powder remaining between the rotating mold and the outermost layer of the fused quartz glass crucible is set to 3 to 7 mm at least in the straight body portion, so that the unmelted or semi-melted silica powder is similarly obtained. The layers are optimized. If the amount is less than the above range, the number of unmelted or semi-melted silica powder layers is reduced.

  The present invention provides a simple method of spraying solid silica powder on the outer surface of the crucible obtained by the rotational mold method, spraying high-pressure water, and applying the inner and outer surfaces by hydrofluoric acid aqueous solution treatment. In addition, there is no silica powder separating from the outermost layer, and there is little silica powder separating from the outermost layer, which suppresses crystal dislocation due to mixing of the separated silica powder into the silicon melt, and in addition, the crystalline portion of the outermost layer is left at a high temperature. High heat resistance can be maintained and silicon single crystals can be manufactured with high yield.

  EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto.

The purified high purity natural silica powder is put into a rotating stainless steel mold, a crucible shaped body is formed by centrifugal force, an arc electrode is inserted therein, and the opening is covered with a plate-shaped lid. Covering and making the inside cavity into a high-temperature gas atmosphere with an arc electrode, forming a molten glass to make an opaque outer layer, then supplying synthetic silica powder from the silica powder supply means at 100 g / min, and melting it from the synthetic quartz glass An inner layer was formed to produce a 24-inch quartz glass crucible. After spraying solid silica powder onto the outer surface of the quartz glass crucible at a spraying pressure of 1 MPa, high-pressure water is sprayed at a spraying pressure of 30 MPa and the distance between the crucible and the high-pressure water spray nozzle is kept at 50 mm, and then 25% by mass A quartz glass crucible is manufactured by spraying a hydrofluoric acid aqueous solution for 40 minutes on the inner surface and 10 minutes on the outer surface, rinsing the inner surface to 20 μm, etching the outer surface to 5 μm, rinsing with pure water for 20 minutes, and drying. did. The number of detached silica powders on the outer surface of the straight body portion of the obtained quartz glass crucible was measured by an adhesive tape method and found to be 0.5 / cm2. When this quartz glass crucible was filled with polycrystalline silicon, melted and the single crystal was pulled by the CZ method, the silicon single crystal could be pulled up without disturbance.
(Comparative Example 1)

In Example 1, a quartz glass crucible was produced in the same manner as in Example 1 except that the outer surface was treated with a hydrofluoric acid aqueous solution for the same 40 minutes as the inner surface, and the number of detached silica powder in the outermost layer was determined as an adhesive tape. It was 2.3 pieces / cm3 when measured by the method. When the silicon single crystal was pulled up using this quartz glass crucible, dislocations occurred several times and the pulling was continued and the pulling was continued, but the final yield was 75% of the setting.
(Comparative Example 2)

  A quartz glass crucible was produced in the same manner as in Example 1 except that the outer surface of the quartz glass crucible produced in the same manner as in Example 1 was ground. The number of quartz powder detached from the obtained quartz glass crucible was measured by the adhesive tape method and found to be 0.02 particles / cm 3. When the silicon single crystal was pulled up using this quartz glass crucible, the crucible was deformed during the pulling, and the pulling of the single crystal had to be stopped.

INDUSTRIAL APPLICABILITY The present invention is a production method that can produce a silicon single crystal with a high yield and is useful in the field of pulling a silicon single crystal.

Claims (2)

Feeding raw material powder into a mold with at least a straight body that rotates is made of stainless steel to form a crucible-like raw material powder layer, and then arc discharge heating from the inside to melt and smooth inner surface and opaque or translucent A silica glass crucible having an outer layer and an outermost layer in which unmelted or semi-melted silica powder is unevenly distributed on the outside, and spraying solid silica powder on the outer surface at a spraying pressure of 0.1 to 5 MPa, in high-pressure water spraying pressure 24～40M Pa, and sprayed while maintaining a distance between the crucible and the high-pressure water jet nozzles 10 to 60 mm, then facilities hydrofluoric acid aqueous solution treatment, the etching amount of the inner surface 1 to 50 [mu] m, A method for producing a quartz glass crucible for pulling a silicon single crystal , wherein the etching amount of the outer surface is 1 to 10 μm . The thickness of the raw material powder remaining between the outermost layer of the melt and the mold rotating quartz glass crucible, a silicon single crystal for pulling quartz according to claim 1, characterized in that the 3~7mm at least in the straight body portion A method for producing a glass crucible.