JPH02188489A - Method for regenerating quartz crucible for pulling up silicon single crystal - Google Patents

Abstract

PURPOSE:To improve the yield of the quartz crucible for pulling up a silicon single crystal with respect to its fabrication by removing the protrusions on the inner surface of the crucible or the foreign matter in the region to a specified depth from the inner surface to smooth the surface. CONSTITUTION:The protrusions on the inner surface of the quartz crucible for pulling up a silicon single crystal or the foreign matter other than vitreous silica in the region to a depth of <=1mm from the inner surface are removed by mechanical grinding or chemical etching, and the periphery of the ground part or etched part is heat-treated and smoothed. In this method, the periphery of the ground or etched recess is melted after drying by an arc flame by a graphite electrode (<5ppm ash) or an oxyhydrogen flame, vitrified, and smoothed. When a silicon single crystal is pulled up with a crucible with the periphery of the ground recess not smoothed, the periphery is easily released, and the released pieces of quartz are mixed into the produced silicon single crystal to cause defect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for repairing and reproducing a defective quartz crucible for pulling silicon single crystals.

[Conventional technology and problems]

Semiconductor silicon single crystals are currently produced mainly using the Czochralski method (
C2 method). In the CZ method, polycrystalline silicon is filled into a quartz crucible, heated and melted at about 1450° C., and a silicon single crystal is pulled from the molten silicon.

The quartz glass crucible used here is usually manufactured by melting quartz powder with an arc flame, but SiO volatilized during melting
etc. may oxidize on the way and fall onto the inner surface of the crucible again, or protrusions may be formed due to the generation of air bubbles, or impurities such as metal powder or other substances may adhere to the inner surface of the crucible, causing contamination. When silicon single crystals are manufactured using a quartz crucible that contains protrusions and foreign substances that are formed on the inner surface of the crucible due to these various causes, it is difficult to pull the single crystal. At that time, the protrusions and foreign substances are peeled off from the crucible and mixed into the single crystal, causing crystal defects, thereby reducing the single crystallization yield (the yield of single crystals obtained from polycrystals).

For this reason, conventionally, quartz crucibles containing such protrusions or foreign matter on the inner surface area were considered defective and were not used for pulling single crystals, resulting in lower yields in quartz crucible production and higher crucible costs. .

(Findings related to problem solving) As a result of various studies for the purpose of improving the manufacturing yield of the above-mentioned quartz crucible, the present inventors found that the protrusions on the inner surface of the crucible and/or We have discovered a method for removing foreign substances present in this area, and have found that by doing so, quartz crucibles, which could not be used in the past, can be fully used for pulling silicon single crystals.

(Structure of the Invention) The present invention is capable of removing foreign matter other than glassy silica contained in a region having a thickness of at least lll11 from the inner surface of a quartz crucible for pulling silicon single crystals. Provided is a method for regenerating a quartz crucible for pulling a silicon single crystal, characterized in that after mechanically grinding or chemical etching, the peripheral edge of the grinding mark or etching mark is heat treated to make it smooth.

The present invention removes protrusions and foreign matter contained in the inner surface of a quartz crucible for pulling silicon single crystals and a region within a thickness of at least 1 mm from the surface, thereby making the quartz crucible, which has been considered to be unusable as a defective product, The present invention provides a method for recycling a crucible into a crucible that can be used for pulling silicon single crystals.

In the present invention, the protrusions on the inner surface of the quartz crucible are as follows. Quartz crucibles for producing silicon single crystals are generally produced by a rotational molding method. In this method, quartz powder formed into the shape of a crucible is heated and melted from the inside with an arc flame to form a crucible, but SiO, etc. generated during melting volatilizes and condenses on the inner wall of the arc furnace, causing it to fall. Silica protrusions or protrusions originating from gases such as nitrogen adhering to the raw quartz powder may also occur. Further, fine metal powder and other impurities other than silica may adhere to the vicinity of the inner surface of the crucible to form foreign matter.

Such protrusions or foreign matter may be removed by mechanical grinding or chemical etching. Mechanical grinding mainly uses diamond tools to completely remove protrusions and foreign objects.

Chemical etching is suitable for removing foreign matter near the surface, and fluoro-nitric acid is mainly used. After grinding, wash with water, then wash with pure water and dry. It is desirable that drying be carried out in an atmosphere as clean as possible. Grinding marks may be treated with hydrofluoric acid.

In the present invention, after drying, it is necessary to apply an arc flame or an oxyhydrogen flame using a high-purity (ash content <5 ppm) graphite electrode to the periphery of the recess formed by grinding or etching to melt it and smooth it into a glass state. be. If the crucible is used to pull a silicon single crystal without smoothing the periphery of the ground concavity, the periphery will tend to peel off during pulling, and peeled quartz pieces will get mixed into the manufactured silicon single crystal, resulting in defects. easy.

Some attempts have been made to fill and melt quartz powder into the recesses created by grinding or etching, but this is time consuming and impractical. According to the present invention, if the traces of grinding or etching are clean and the peripheral edges are smooth, the presence of the recesses has the effect of improving the stirring effect of the molten silicon and making the temperature of the molten silicon uniform.

Remove foreign substances other than glassy silica from the inner surface of the quartz crucible with a thickness of at least 1 mm by mechanical grinding or chemical etching. 1. When pulling a silicon single crystal using a quartz crucible, the inner surface of the crucible is removed. Since a region with a thickness of 0.5 to 0.7 mm from the surface is eroded by the molten silicon, if the foreign matter in the region lll11 is removed, it will not be incorporated into the manufactured silicon single crystal. Therefore, when pulling 2 to 3 silicon single crystals in one quartz crucible, it is necessary to pull 2.5 to 2.5 m
It is necessary to remove foreign bodies in an area with a thickness of 3 mm.

This allows the quartz crucible to be used repeatedly.

〔Effect of the invention〕

The silicon single crystal pulled using a quartz crucible obtained by the method of the present invention shows the same single crystallization yield as the silicon single crystal pulled using a quartz crucible, which is conventionally considered to be a good product, and is extremely suitable for recycling so-called defective products. It is valid. Therefore, the overall yield of quartz crucibles is significantly improved.

[Examples and comparative examples]

Example 1 A quartz crucible manufactured by the rotary molding method that was found to be defective was polished to remove foreign matter contained in the protrusions on the inner surface and in an area with a thickness of 11 mm from the inner surface using a diamond tool, washed, and dried. High purity (
Ash content <5 pp■) The peripheral edge of the scraped area was melted and smoothed using the arc flame of a graphite electrode, and used for pulling a silicon single crystal. As a result, as shown in the following table, a single crystallization yield equivalent to that of a silicon single crystal pulled in a good quality quartz crucible was obtained.

Comparative Examples 1 to 3 Among the quartz crucibles manufactured by the rotary molding method, a defective quartz crucible and a defective quartz crucible whose inner surface was only ground were used to pull silicon single crystals and determine the single crystallization rate. Ta. The results are shown in the table as a comparative example together with the results of Example 1.

table

Claims (1)

[Claims] Protrusions existing on the inner surface of a quartz crucible for pulling silicon single crystals and/or at least 1 mm from the inner surface
After mechanically grinding or chemically etching foreign substances other than glassy silica contained in a region with a thickness of A method for regenerating a quartz crucible for pulling silicon single crystals.