JPS58156595A - Graphite crucible for silicon single crystal pulling apparatus - Google Patents

Abstract

PURPOSE:To prevent the shortening of the life of the titled graphite crucible caused by the warpage of the crucible, by using a graphite material having a specific thermal expansion coefficient and a specific average pore diameter. CONSTITUTION:A graphite crucible for the rotary pulling of a silicon single crystal is prepared by using a graphite material having a thermal expansion coefficient of 4.8-6.0X10<-6>/ deg.C between room temperature and 1,000 deg.C and an average pore diameter of 15,000Angstrom determined by mercury pressing method. The intrusion of silicon carbide generated by the reaction of silicon monoxide with the graphite crucible through the surface of the graphite can be prevented, and the life of the graphite crucible can be made more than twice the life of the conventional crucible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a crucible used in a V recon single crystal pulling apparatus using a rotational pulling method called the Czochralski method.

In general, a silicon single crystal pulling apparatus used for refining silicon polycrystals into single crystals mainly consists of a graphite crucible containing a quartz crucible for melting silicon polycrystals. However, the graphite crucible during silicon single crystal pulling is heated to a high temperature of approximately 1500°C.

When melting the VQcon polycrystal, it will be heated to about 1600"C. As a result, the quartz crucible and graphite will react with each other, producing silicon oxide and carbon monoxide. As a result of the silicon oxide reacting with the graphite crucible, the surface layer portion of the graphite crucible is converted into silicon carbide.

And as graphite V-fupo was used many times, l!
The drawback is that the inside of the crucible is converted to silicon carbide, eventually causing internal strain and resulting in extreme warping, shortening the durability life6.Normally, the durability life of a graphite crucible varies depending on the graphite material used5. ~15 days. On the other hand, the reaction between the graphite crucible and silicon monoxide gas is
Because the reaction is carried out at a low temperature of 1600°C, it is not possible to completely convert each graphite particle that makes up the graphite crucible into silicon carbide, and in fact, the surface of the pores that exist between the graphite particles and the graphite Boundary portions connecting particles are selectively converted into silicon carbide.

This conversion reaction process is I! To explain in detail: - One of the two carbon atoms that reacted with silicon oxide dissipates as carbon monoxide and becomes K, and the reaction is repeated in which a silicon atom with a larger atomic radius than the carbon atom intervenes in its place. Due to the trapping, the number of times the graphite crucible itself is used increases, and microcracks occur due to physical non-uniformity. As a result, the graphite crucible warps, which is thought to shorten the lifespan of the graphite crucible during use.

In view of the above points, the present inventors researched the causes of warpage in graphite crucibles and found that the coefficient of thermal expansion of graphite material (from room temperature to 1000°C) was compared with that of silicon carbide (from room temperature to 1000°C). ) and further reduce the average diameter of pores contained in the graphite material (obtained by mercury intrusion method), it is possible to prevent life deterioration due to warping that occurs in conventional methods. I found out. Examples of the present invention will be described below.The graphite crucible of the present invention has an outer diameter of 33QInl and an inner diameter of 3051FII, and this graphite crucible is divided into two parts.
Table 1 shows the results of the comparison with comparative examples for examples in which this was used to pull silicon single crystals.

Table 1 The coefficient of thermal expansion of silicon carbide is 4.6 x 10 /C in the range from room temperature to 1000"C, and by making the coefficient of thermal expansion of the graphite material used in the graphite crucible higher than that of silicon carbide. It has been found that warping that occurs during use of a graphite crucible can be prevented.

In this case, the coefficient of thermal expansion in any direction within the graphite material must be higher than that of silicon carbide.

At the same time, the reaction between the graphite crucible and silicon monoxide penetrates deeper into the graphite material as the average diameter of the pores in the ink lead material increases, making it durable enough for use! In the present invention, the average pore diameter of the graphite material must be 15,000 A or less because it has a positive effect on life. The above reason is that in a graphite crucible using a graphite material whose thermal expansion coefficient is higher than that of silicon carbide,
It is presumed that silicon carbide, which has been converted to a graphite surface at the operating temperature of , always maintains compressive internal stress during repeated cooling cycles, which reduces the occurrence of warping. However, if the coefficient of thermal expansion of the graphite material is too high, the compressive internal stress 4 during cooling increases with repeated use, and the silicon carbide layer converted to the graphite surface grows thicker than 9. As a result of stress concentration, the durability life of the graphite crucible is reduced.In the case of a single call, the coefficient of thermal expansion of the graphite material used is 4.8 to 6.0X.
Black at 0 shot is optimal within the range of 10/C!
) The durability of the crucible is not due to the occurrence of warping; rather, as it is repeatedly used, silicon carbide, which is a conversion product of silicon monoxide and the graphite crucible, gradually penetrates deeper from the graphite surface, and the graphite crucible itself. strength gradually deteriorates. When the strength becomes weaker than the internal stress of the graphite crucible caused by the converted silicon carbide, the graphite crucible breaks and reaches the end of its durable life. -The penetration of silicon oxide varies greatly depending on the average pore diameter of the graphite material. As is clear from the results of the examples of the present invention, it can be seen that as the average pore diameter becomes larger, the penetration of silicon monoxide becomes deeper and the durability life becomes shorter.

・ Therefore, in the graphite crucible of the present invention, 1500
It is optimal to use a graphite material with an average pore size of 0A or less.

1. As is clear from the above explanation, the graphite crucible used for pulling silicon single crystal according to the present invention is different from the conventional graphite crucible.
The cost of silicon single crystals is about twice as high, so the effect of reducing the cost of silicon single crystals is extremely large.

Patent registration applicant Ibigawa Electric Industry Co., Ltd. Representative Jun Taga

Claims (1)

[Claims] Thermal expansion coefficient is 4.8-6. A graphite crucible for a V 13 con single crystal pulling device, which is made of black ship material which is OX 10 /C and has an average pore diameter of 15.00 OA.