JP2000159593A - Production of silica glass crucible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silica glass crucible which can be served for a long period of time, enables the quality of silicon single crystal pulled up to be improved and enable the time of producing such single crystal to be shortened as well. SOLUTION: This method for producing a silica glass crucible comprises the following practice: a rotary carbonaceous mold 1 with a crystallization promoter layer 2 formed at least on the inner surface is charged with high-purity quartz powder to form a quartz powder-packed layer which, in turn, is subjected to arc melting to form a green crucible body 4 made up of a semi-molten layer 5, a molten opaque layer 6 with a crystallized thin-layer portion 6a adjacent to the semi-molten layer, and a molten transparent layer 7; wherein a crystallization is advanced successively from the outside; subsequently, the semi-molten layer of the resultant green crucible body is ground and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a quartz glass crucible used for pulling a silicon single crystal.

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a quartz glass crucible has been disclosed in Japanese Patent Application Laid-Open Publication No. H11-27139 in order to prevent the quartz glass crucible from being exposed to a high temperature near a softening point during pulling of a silicon single crystal and being bent inward. As described in JP-A-6-219768 and JP-B-7-91160,
Manufacturing methods for strengthening quartz glass crucibles are known.
In the former method, a high purity quartz raw material powder containing 1 ppm or less of an alkali metal mainly composed of Na, K and Li, and each metal impurity content of 10 ppm or less is added to Al, Y
And mixed at least one of a nitrate or sulfate-containing solution of a metal atom component selected from the group consisting of La and La as a nucleating agent, followed by heat treatment to remove the acid component. Is formed by vitrification. On the other hand, the latter method crushes and purifies quartz raw materials,
After reducing the total content of metal impurities to 30 ppm or less, the molten metal is held for 12 hours or more to scatter alkali metals. Then, after forming into a crucible shape, by heating for a long time at a high temperature, a cristobalite layer is formed at least on the outer surface.

[0003]

However, in the former method of the conventional method of manufacturing a quartz glass crucible, Al, Y or La having a low diffusibility, which serves as a nucleus for forming cristobalite, is added to the raw material, so that it can be obtained. Although the viscosity of the quartz glass crucible is increased and thermal deformation is reduced even during long-term use, metal atom components can diffuse inward during long-term use, completely preventing contamination of the silicon melt. This is difficult and may cause defects in the silicon single crystal to be grown. On the other hand, the latter requires a long time to generate the cristobalite layer, and thus has a problem that the manufacturing time is long. Therefore, the present invention provides a method for manufacturing a quartz glass crucible that can be used for a long time, can improve the quality of a silicon single crystal pulled by using the obtained product, and can shorten the manufacturing time. The purpose is to:

[0004]

In order to solve the above-mentioned problems, a method for producing a quartz glass crucible according to the present invention comprises a rotating carbon mold having a crystallization accelerator layer formed on at least an inner surface thereof. A powder is charged to form a quartz powder-filled layer, and the quartz powder-filled layer is arc-melted to form a semi-molten layer in which crystallization proceeds in order from the outside, and a thin layered portion adjacent to the semi-molten layer is crystallized. After forming the crucible body composed of the opaque layer and the molten transparent layer, the semi-molten layer of the crucible body is ground and removed. The thickness of the crystallization accelerator layer is preferably 0.5 mm or more from the inner surface of the carbon mold.

[0005] The crystallization of the semi-molten layer in the crucible body is
The crystallization is carried out with the crystallization accelerator applied to the inner surface of the carbon mold as the nucleus.After that, the crystallized part becomes a nucleus, crystallization proceeds, and the opaque layer adjacent to the semi-molten layer It leads to a thin layered part. Therefore, no crystallization promoter exists in the thin layered portion of the molten opaque layer. As crystallization promoters, Be, Mg, C
group IIa elements such as a, Sr and Ba, or B, Al, Ga,
Group IIIb elements such as In are used. The crystallization accelerator layer is formed by applying a solution obtained by dissolving the crystallization accelerator in water and / or alcohol and applying or dipping by brushing or spraying. As carbon type, CIP
A material made of a material or a carbon composite material is used. If the thickness of the crystallization promoter layer formed on at least the inner surface of the carbon mold is less than 0.5 mm from the inner surface, homogenization of the crystallized portion formed on the quartz glass crucible cannot be achieved. It is desirable that the crystallization accelerator layer has a uniform thickness over the whole as much as possible. The thickness of the crystallized thin layer portion of the molten opaque layer is 0.01 to 0.5 mm.
Desirably, it is 3 mm. The thickness is 0.01m
If it is less than m, the viscous vitrification of the quartz glass due to the presence of the same portion is not sufficiently achieved, the deformation of the quartz glass crucible is not suppressed, and the crystallization yield of the silicon single crystal is reduced, and the crystallization is reduced. When the thickness exceeds 0.3 mm, the crystallized layer is peeled off, and the effect is lost.

[0006]

Embodiments of the present invention will be described below with reference to specific examples and comparative examples. Example 1 First, as shown in FIG. 1, a carbon mold 1 for a 24-inch diameter quartz glass crucible (inner diameter 660 mm, depth 450 m)
m) A 0.5M solution of barium hydroxide was applied on the inner surface by brushing, and then dried at a temperature of 120 ° C. for 1 hour to form a crystallization accelerator layer 2 having a thickness of 1 mm on the inner surface. . Next, while setting and rotating the carbon mold 1 in a crucible melting machine (not shown), a high-purity quartz powder such as a purified quartz powder is charged to form a quartz powder filling layer having a required thickness. A crucible body 4 was obtained by arc melting between the plurality of electrode rods 3 and the carbon mold 1 by arc discharge. As shown in FIG. 2, the obtained crucible element 4 has a semi-molten layer 5 in which crystallization has progressed sequentially from the outside, and a thin layered portion (0.01 to 0.3 mm) 6 a adjacent to the semi-molten layer 5 a Consisted of a crystallized molten opaque layer 6 and a molten transparent layer 7. Next, the semi-molten layer 5 of the crucible element 4 was removed by grinding to obtain a quartz glass crucible. The obtained quartz glass crucible is set in a single crystal pulling apparatus, and a silicon single crystal is pulled up three times, and a gap between the innermost portion of the quartz glass crucible and the innermost part of the straight body portion in each pulling (average of 10 pieces). Is measured, and the number of defects (number of BMDs) of a wafer cut out from the pulled silicon single crystal
(Average of 10 sheets) was measured, and the results were as shown in Table 1, which also shows those of a normal quartz glass crucible and a quartz glass crucible in which a nucleating agent was uniformly dispersed.

[0007]

[Table 1]

As can be seen from Table 1, the quartz glass crucible of the embodiment has a maximum gap of 2.
As small as 2 mm and the number of defects on the wafer is up to 55 × 1
0 while ⁴ / cm ² and was low, the conventional quartz glass crucible, while a maximum gap is as large as 6.5 mm, the quartz glass crucible using nuclear molding agent, the maximum gap is 2.5m
m, but the number of wafer defects is up to 110 × 10 ⁴
Pieces / cm ² .

The time required for manufacturing the quartz glass crucible of the embodiment was 90% of that of the quartz glass crucible having the cristobalite layer formed on the outer surface.

In the above-described embodiment, the case where barium is used as a crystallization accelerator has been described. However, the present invention is not limited to this, and the same applies when another group IIa element or group IIIb element is used. The effect was obtained.

[0011]

As described above, according to the method for manufacturing a quartz glass crucible of the present invention, a thin layered portion on the outer surface is crystallized, and the portion is formed at the time of melting and molding the crucible. Therefore, it is possible to use for a long time, to improve the quality of the silicon single crystal pulled by using the obtained one, and to shorten the manufacturing time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an arc fusion forming step of an embodiment of a method for manufacturing a quartz glass crucible according to the present invention.

FIG. 2 is a partial cross-sectional view of a crucible body obtained by the arc fusion forming step of FIG.

[Explanation of symbols]

 Reference Signs List 1 carbon type 2 crystallization accelerator layer 3 electrode rod 4 crucible body 5 semi-molten layer 6 molten opaque layer 6a thin layered part 7 molten transparent layer

Claims (2)

[Claims] 1. A high-purity quartz powder is charged into a rotating carbon mold having a crystallization accelerator layer formed on at least an inner surface thereof to form a quartz powder-filled layer. After forming a crucible body consisting of a semi-molten layer in which crystallization has progressed sequentially from the outside, a molten opaque layer in which a thin layered portion adjacent to the semi-molten layer has crystallized, and a molten transparent layer,
A method for producing a quartz glass crucible, wherein a semi-molten layer of a crucible body is ground and removed. 2. The method for producing a quartz glass crucible according to claim 1, wherein the thickness of the crystallization accelerator layer is 0.5 mm or more from the inner surface of the carbon mold.