JPH0952791A - Crucible for pulling up silicon single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a long-life crucible which is suppressed in inside surface corrosion at the time of pulling up a silicon single crystal. SOLUTION: This crucible for pulling up the silicon single crystal is formed of a quartz material which is obtd. by melting high-purity quartz at >=1,750 deg.C, solidifying the melt and converting into 100% cristobalite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crucible for pulling a silicon single crystal, and more particularly to a crucible capable of preventing deterioration and extending its life.

[0002]

2. Description of the Related Art A quartz crucible is generally used as a crucible for pulling a silicon single crystal. The quartz crucible also has a transparent quartz glass crucible and a semitransparent quartz glass crucible depending on the manufacturing method. Practically, a semitransparent quartz glass crucible is widely used from the viewpoint of strength, but this semitransparent quartz glass crucible is also regarded as a problem due to the effect of bubbles contained therein. One of them is the effect of rough skin on the inner surface of the crucible due to melting of the crucible. The bubble portions generate fine projections as the crucible melts, and these become crystal nuclei to form speckled cristobalite. It is known that the cristobalite thus formed is desorbed from the crucible and falls into the molten silicon to adversely affect the growth of the pulled single crystal.

On the other hand, in Japanese Unexamined Patent Publication (Kokai) No. 6-72793, it is stated that the dissolution of bubbles contained in the vicinity of the inner surface of the silica glass crucible into silicon causes crystal defects (dislocation) due to crystal dislocations. A device having a controlled bubble content rate has been devised. Further, in JP-A-6-92779, the inner layer of a double-structured crucible made of quartz glass is made substantially bubble-free and the surface layer is made smooth, and the outer layer is controlled in the diameter of semitransparent bubbles and the presence density of bubbles. However, they do not essentially solve various inconveniences associated with melting in the crucible and formation of cristobalite crystals.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a crucible having a long service life in which internal disadvantages such as melting of the crucible and formation of cristobalite crystals at the time of pulling a silicon single crystal are eliminated, and inner surface corrosion is suppressed. The purpose is to

[0005]

A crucible for pulling a silicon single crystal according to the present invention for attaining this object is a 100% cristobalite obtained by melting and solidifying high-purity quartz at a temperature of 1750 ° C. or higher. It is characterized in that it is made of quartized quartz material.

From the purpose of use of silicon crystals, the inclusion of impurities must be avoided as much as possible. Therefore, the crucible used for the production is necessarily quartz. As will be described later, at the pulling temperature of silicon crystal (about 1500 ° C.), it is inevitable that the crucible material is dissolved in silicon and cristobalite, which is a crystalline material, is generated. Various inconveniences that occur during the pulling of a silicon single crystal are due to the inclusion of impurities that accompany the melting of the crucible material and the fact that the generated cristobalite is fine crystals that peel off from the crucible surface. Therefore, adopting the configuration of the present invention prevents the crucible material from being dissolved in silicon and the infusible material from being mixed into silicon, thereby solving these problems.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention focuses on the fact that the conventional problems that occur when pulling a silicon single crystal are due to the melting of the crucible and the formation of a crystalline substance (cristobalite), and the melting of the crucible is controlled. By doing so, the conventional inconvenience is eliminated. That is, the surface roughness caused by the corrosion phenomenon of the crucible is due to the formation of a crystalline substance (cristobalite) generated on the crucible surface as the crucible is melted. Since this substance has a melting point of 1720 ° C, once it is formed, the silicon single crystal growth temperature (about 1500 ° C)
Does not dissolve in. On the other hand, as can be seen from the thermal equilibrium diagram of quartz, this temperature range is a cristobalite generation region, so that it is not uncommon for quartz to undergo cristobalite crystals due to thermal transformation. It is said that the reason for the crystallization is a trace amount of impurities contained in quartz and bubbles present in the semitransparent glass. In fact, the corrosion of natural quartz, which is rich in impurities, is several times greater than that of synthetic quartz of high purity. However, even high-purity artificial quartz is corroded if it is immersed in silicon at the temperature for a long time. If there is no formation of cristobalite microcrystals at the time of this corrosion, and only dissolution causes little damage to single crystal growth, the formation of cristobalite may be unavoidable in view of the conditions for imparting silicon crystal characteristics.

Therefore, the present invention provides a crucible material that does not change even at such a high temperature. That is, focusing on the fact that cristobalite does not dissolve in silicon in the silicon single crystal growth temperature range, a crucible material 100% cristobalite was devised. Further, this cristobalite also has a risk of peeling in the case of aggregation of microcrystals, and thus needs to be fused. At this time, the fusion with quartz glass causes 100% of the present invention because that portion is melted into silicon and the surface of the crucible is roughened.
The manufacturing method of cristobalite crucible material is based on the scientific manufacturing method considering the thermal equilibrium state of quartz. That is, high-purity quartz is once melted at 1750 ° C. under an inert gas, and cristobalite is precipitated in the temperature lowering process. Therefore, the raw material used at this time is glassy or crystalline (tridymite, cristobalite) or a mixture,
Either is fine.

[0009]

【Example】

(Example 1) 99.999% artificial quartz was put into an alumina crucible, sufficiently melted at 1750 ° C in an argon atmosphere, and slowly cooled to obtain a lump made of crystals. As a result of X-ray diffraction analysis, this lump was found to be cristobalite. This lump is cut into 30 × 30 × 5 mm, and fused into an artificial quartz glass crucible for pulling a silicon single crystal, about 15
The silicon single crystal was pulled up at 00 ° C. After about 72 hours, when observing the inner surface of the crucible, a small amount of fine cristobalite and a brown ring were formed in the surrounding artificial quartz glass part, but no brown ring was generated in that part, and dissolution etc. No signs of corrosion were observed.

Comparative Example 1 Using the same natural quartz glass test piece as in Example 1, a pulling test of a silicon single crystal was conducted under the same conditions. As a result, the surface of the natural quartz glass part was found to have many fine cristobalite formations and brown rings as compared with the surrounding artificial quartz glass part, and the dissolution corrosion phenomenon was confirmed.

Comparative Example 2 Using the same artificial quartz glass test piece as in Example 1, a silicon single crystal pulling test was conducted under the same conditions. As a result, a small amount of fine cristobalite was formed and a brown ring was generated on the surface of the test piece as in the peripheral portion, and the dissolution corrosion phenomenon was confirmed.

(Comparative Example 3) 50% crystalline and 50 glassy
% 99.999% artificial quartz was mixed well, put in an alumina crucible, melted at 1400 ° C. in an argon atmosphere, and slowly cooled to obtain a lump. As a result of analysis by X-ray diffraction, this lump was a coexisting substance of cristobalite and glass although the amount of cristobalite was larger than that of the raw material mixture. This was used as a test piece similar to that of Example 1, and a silicon single crystal pulling test was conducted under the same conditions. As a result, a large brownish brown ring was generated around the cristobalite on the surface of the test piece, fine cristobalite was formed similarly to the peripheral portion, and a brownish brown ring was generated, and a partial dissolution corrosion phenomenon was confirmed.

[0013]

Industrial Applicability As described above, the present invention can be said to be an industrially very advantageous technique as a crucible for pulling a silicon single crystal with almost no corrosion and no impurities or infusible substances are mixed.

Claims (1)

[Claims] 1. A crucible for pulling a silicon single crystal, which is made of a 100% cristobalite-made quartz material obtained by melting and solidifying high-purity quartz at a temperature of 1750 ° C. or higher.