JPH0653634B2 - Regeneration method of quartz crucible for pulling silicon single crystal - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for repairing and remanufacturing a defective quartz crucible for pulling a silicon single crystal.

[Conventional technology and problems]

Semiconductor silicon single crystals are currently manufactured mainly by the Czochralski method (CZ method). In the CZ method, polycrystalline silicon is filled in a quartz crucible and melted by heating at about 1450 ° C. to pull up a silicon single crystal from the molten silicon. The quartz glass crucible used here is usually manufactured by melting quartz powder with an arc flame.Since volatilized SiO, etc. is oxidized during the process, it falls onto the inner surface of the crucible again or bubbles are generated. Etc., a protrusion is formed, and metal powder such as impurities and substances other than silica adhere to the inner surface of the crucible,
In many cases, it becomes foreign matter when mixed. Hereinafter, substances other than glassy silica contained in such a crucible wall are referred to as foreign substances.

When a silicon single crystal is manufactured using a quartz crucible containing protrusions and mixed foreign matter formed on the inner surface of the crucible due to these various causes, the protrusions and foreign matter are separated from the crucible when the single crystal is pulled up. Then, they are mixed in the single crystal, and the yield of the single crystal (the yield of the single crystal obtained from the polycrystal) is reduced. Therefore, conventionally, a quartz crucible containing such protrusions or foreign matters in the area of the inner surface is not used for pulling a single crystal as a defective product, and the yield in manufacturing the quartz crucible is reduced to increase the cost of the crucible. .

(Knowledge on Problem Solving) The inventors of the present invention have conducted extensive studies to improve the production yield of quartz crucibles, and also for defective quartz crucibles, remove protrusions on the inner surface of the quartz crucible and foreign substances contained in the crucible. We obtained the knowledge that it can be recycled as a good product. However, in this case, it is not possible to obtain a quartz crucible with a high single crystallization rate when pulling silicon by simply grinding the protrusions and foreign substances, and it is necessary to heat and melt the grinding trace to smooth it. Found out.

[Structure of Invention]

According to the present invention, a protrusion existing on the inner surface of a quartz crucible for pulling a silicon single crystal and / or a foreign substance contained in a portion having a thickness of at least 1 mm from the inner surface is mechanically ground, and then the grinding mark is formed. There is provided a method for reclaiming a quartz crucible for pulling a silicon single crystal, which comprises heat-treating and smoothing.

In the reclaiming method of the present invention, first, the protrusions present on the inner surface of the quartz single crystal pulling crucible and the foreign matter contained in the region having a thickness of at least 1 mm from the inner surface are mechanically ground and removed.

In the present invention, the protrusions on the inner surface of the quartz crucible are as follows. A quartz crucible for manufacturing a silicon single crystal is generally manufactured by a rotary molding method. In this method, quartz powder molded in the shape of a crucible is heated and melted from the inside by an arc flame to form a crucible, but SiO and the like generated during melting are volatilized and condensed on the inner wall of the arc furnace, etc.
This may fall and become a silica protrusion, or a protrusion derived from a gas such as nitrogen attached to the raw quartz powder may be generated. In addition, fine metal powder or other impurities other than silica may adhere to the vicinity of the inner surface of the crucible to form foreign matter.

According to the present invention, such protrusions and foreign matters that are visually recognized are grasped by visual observation or optical detection means and are removed by mechanical grinding. Although it can be removed by optical etching, when locally removing the inner surface of the crucible, there is an advantage that mechanical grinding does not require pretreatment and can be easily performed. In mechanical grinding, for example, a tool such as a diamond tool is used to scrape off the corresponding portion. After grinding, wash with pure water and dry. It is preferable to dry in an atmosphere as clean as possible. The grinding trace may be treated with hydrofluoric acid.

In the recycling method of the present invention, it is necessary to mechanically grind the protrusions and the foreign matter, and then melt the grinding marks by an arc flame or an oxyhydrogen flame to obtain a glassy smooth state. It is preferable to use a high-purity graphite electrode having an ash content of less than 5 ppm for generating an arc flame. If a silicon single crystal is pulled up using the crucible without smoothing the peripheral edge of the ground recess, the peripheral edge is easily peeled off during pulling, and quartz peeled pieces are mixed into the manufactured silicon single crystal, resulting in defects. easy.

There is an attempt to fill the recesses formed by grinding with quartz powder and melt it for repair, but it is time-consuming and not practical. According to the present invention, if the trace of grinding is clean and the peripheral portion is smooth, the presence of the concave portion rather improves the stirring effect of the molten silicon and has the effect of making the temperature of the molten silicon uniform.

By the above mechanical grinding, foreign matters other than glassy silica existing in an area having a thickness of at least 1 mm from the inner surface of the quartz crucible are removed. When pulling a silicon single crystal using a quartz crucible, a region of 0.5 to 0.7 mm in thickness from the inner surface of the crucible is eroded by molten silicon, so if a foreign substance in a region of 1 mm is removed, silicon produced It is never incorporated into a single crystal. Therefore, with one quartz crucible, 2-3
When pulling individual silicon single crystals, it is necessary to remove foreign matter deeper from the inner surface to a region having a thickness of 2.5 to 3 mm.

This allows the quartz crucible to be used repeatedly.

〔The invention's effect〕

The silicon single crystal pulled by using the quartz crucible obtained by the method of the present invention shows a single crystallization yield equivalent to that of the silicon single crystal pulled by the quartz crucible which has been conventionally regarded as a good product, and is extremely useful for reproducing a so-called defective product. It is valid. Therefore, the yield of the integrated quartz crucible is significantly improved.

[Examples and Comparative Examples]

Example 1 Among the quartz crucibles manufactured by the rotary molding method, which were regarded as defective, the protrusions on the inner surface and the foreign matter contained in the region having a thickness of 1 mm from the inner surface were ground and removed by a diamond tool, and after washing and drying. High purity (ash <
(5 ppm) The peripheral edge of the scraped trace was melted and smoothed by the arc flame of the graphite electrode and used for pulling a silicon single crystal. As a result, as shown in the following table, a yield of single crystallization equivalent to that of a silicon single crystal pulled by a good 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 quartz crucible in which only the inner surface of the defective crucible was only ground were used to pull up a silicon single crystal to obtain a single crystallization rate. It was This result is shown in the table together with the result of Example 1 as a comparative example.

Claims (1)

[Claims] 1. A method for mechanically grinding a protrusion existing on the inner surface of a quartz crucible for pulling a silicon single crystal and / or a foreign substance contained in a portion having a thickness of at least 1 mm from the inner surface, and thereafter, the grinding trace is formed. A method for reclaiming a quartz crucible for pulling a silicon single crystal, characterized by smoothing by heating and melting.