JP2000247781A - Graphite crucible - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a graphite crucible so designed that the cylindrical portion thereof is constructed of longitudinally plurally divided members and both the upper part and lower part of the cylindrical portion are respectively fitted with such rings of carbon fiber-reinforced carbonaceous material that each of their inner diameters becomes nearly equal to the outer diameter of the cylindrical portion when a stock is melted to enable a quartz crucible disposed inside the cylindrical portion to be used repeatedly. SOLUTION: This graphite crucible 1 so designed as to hold a quartz crucible 6 inside which a stock is to be melted and also designed to be supported externally is made up of a cylindrical portion 2 and the bottom 3, wherein the cylindrical portion 2 is constructed of longitudinally divided cylindrical members 2a, 2b in two or three portions. Both the upper and lower parts of the cylindrical portion 2 are respectively fitted with rings 4, 5 of carbon fiber-reinforced carbonaceous material equal in thermal expansion coefficient to quartz so that the outer diameter of the cylindrical portion 2 becomes nearly equal to each of the inner diameters of the rings 4, 5 when a stock in the quartz crucible 6 is melted. Besides, the outer diameter of the cylindrical portion 2 at a site above that fitted with the lower part ring 5 is made smaller than that at the site fitted with the ring 5 so as to facilitate the attachment/detachment of the crucible 1 after cooled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a graphite crucible,
In particular, it relates to a graphite crucible composed of a cylindrical portion and a bottom.

[0002]

2. Description of the Related Art Conventionally, dissolving silicon has been described with reference to FIG.
As shown in FIG. 1A, a quartz crucible 16 for dissolving silicon therein and a graphite crucible 11 for accommodating the silicon and supporting it from the outside are used. The quartz crucible 16 is heated to a high temperature during the melting of the silicon and is softened and receives the weight of the silicon melt, so that the outer surface thereof is in close contact with the inner surface of the graphite crucible 11. When cooled in this state, graphite has a thermal expansion coefficient about 10 times larger than that of quartz, so that a large tensile stress is generated in the graphite crucible 11, and the graphite crucible 11 is broken.

To cope with this problem, as shown in FIG. 3B, the graphite crucible 11 is usually divided into two or three vertically (for example, Japanese Utility Model Laid-Open Publication No. 7-31855 and Japanese Unexamined Patent Publication No. 345587). Since the dividing surface 12 opens during cooling, the graphite crucible 11 does not break.

As another technique, there is a method of using a crucible made of carbon fiber reinforced carbon material instead of the graphite crucible 11 (for example, see Japanese Utility Model Publication No. 3-43250). Since the coefficient of thermal expansion of the carbon fiber reinforced carbon material is similar to that of quartz, the carbon fiber reinforced carbon material does not break like a graphite crucible even with an integral type.

[0005]

In the prior art, after cooling, as shown in FIG. 3 (b), the dividing surface 12 is in an open state, and when the quartz crucible 16 is taken out from this, the graphite crucible 11 Return to the original closed state. However, quartz crucible 1
6 cannot be put back into the closed graphite crucible 11 because the outer diameter is larger than before use, and cannot be used repeatedly.

As described above, the prior art has a disadvantage that the quartz crucible 16 cannot be used repeatedly once it is cooled after melting. When a crucible made of carbon fiber reinforced carbon material is used, a quartz crucible can be used repeatedly, but there is a disadvantage that the crucible is extremely expensive.

The present invention has been made in view of such problems of the conventional apparatus, and a graphite crucible which solves the problem of the conventional apparatus in which the quartz crucible disposed inside cannot be used repeatedly. The purpose is to provide.

[0008]

In order to achieve the above object, in a graphite crucible according to the present invention, in a graphite crucible comprising a cylindrical portion and a bottom portion, the cylindrical portion is vertically divided into a plurality of members. And a ring made of a carbon fiber reinforced carbon material having an outer diameter substantially equal to the inner diameter when the raw material is melted was mounted on the upper and lower portions of the cylindrical portion.

In the above graphite crucible, it is desirable that the outer diameter of the cylindrical portion above the portion where the lower ring is mounted is smaller than the outer diameter of the portion where the ring is mounted.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing one embodiment of a graphite crucible according to the present invention, wherein 1 is a graphite crucible, 2 is a cylindrical portion, 3 is a bottom portion, and 4 and 5 are rings.

The graphite crucible 1 is divided into a cylindrical part 2 and a bottom part 3, and the cylindrical part 2 is further divided vertically into two or three parts, and is constituted by a plurality of cylindrical members 2a and 2b.

The present invention relates to a cylindrical portion 2 of the graphite crucible 1.
Is characterized in that rings 4 and 5 are fitted on the upper and lower portions of the outer periphery of the. The rings 4 and 5 are made of carbon fiber reinforced carbon material. The reason for using carbon fiber reinforced carbon material for the rings 4 and 5 is that the thermal expansion coefficient is equivalent to that of quartz, that it has sufficient strength even when heated to a high temperature by a melting heater, and that the quality of silicon is high. For example, it is not necessary to generate impurities that lower the concentration. . The inner diameter of the rings 4 and 5 is set to be substantially equal to the outer diameter when the raw material in the quartz crucible 6 is melted, for example, when silicon is melted, when the graphite crucible is heated to 1500 ° C. The outer diameter of the graphite crucible 1 where the lower ring 5 is to be fitted is made equal to the inner diameter of the ring 5 when the raw material is melted. The outer diameter of the portion 5a above the lower ring 5 is made slightly smaller than the outer diameter of the portion where the ring 5 is fitted, as shown in FIG. By doing so, the ring 5 can be easily removed from the graphite crucible 1 after cooling. Although the upper ring 4 is mounted near the upper edge of the cylindrical portion 2, when it is mounted further downward, the outer diameter above the part where the upper ring 4 is mounted is further reduced. do it.

By mounting such rings 4 and 5, the quartz crucible 6 can be used repeatedly. The reason that the quartz crucible 6 can be used repeatedly is as follows.
FIG. 2 shows a horizontal section of the melting crucible. The inner diameter of the ring 4 (5) is equal to the outer diameter of the graphite crucible 1 closed when the raw material is melted (for example, 1500 ° C.). Since the coefficient of thermal expansion of graphite is as large as about 10 times that of carbon fiber reinforced carbon material, the outer diameter of the graphite crucible 1 is smaller than the inner diameter of the ring 4 (5) at normal temperature, and the ring 4 (5) and the graphite crucible 1 There is a little gap between them. Since the outer diameter of the unused quartz crucible 6 is slightly smaller than the inner diameter of the graphite crucible 1, there is a slight gap between the quartz crucible 6 and the graphite crucible 1. This state is shown before the dissolution in FIG. During melting, the temperature of the graphite crucible 1 becomes the temperature of the melt (for example, about 1500 ° C.),
The gap with (5) is eliminated. Since the quartz crucible 6 receives the weight of the melt (silicon melt) in a softened state, its outer surface is in close contact with the inner surface of the graphite crucible 1. This state is shown in FIG. 2B during melting. After the melting is completed and the crucible 6 is emptied, the graphite crucible 1 contracts when cooled. Although both the ring 4 (5) and the quartz crucible 6 shrink, the thermal expansion coefficient of both the carbon fiber reinforced carbon material and quartz is about 1/10 that of graphite, so that the shrinkage can be ignored in practical use. This state is shown after the cooling in FIG.
As shown in FIG. 2C, a small gap x is formed in the divided surface of the graphite crucible 1, and the ring 4 (5), the graphite crucible 1, and the quartz crucible 6 are integrated. When the melting is performed again by using the melting crucible, the graphite crucible 1 expands to eliminate the gap x between the divided surfaces, and returns to the melting state in FIG. 2B. Then, after cooling, the state returns to the state after cooling in FIG. Thus, the quartz crucible 6 can be used repeatedly.

An example of casting a silicon ingot using the melting crucible of the present invention is as follows. In this case, there is a spout at the top of the quartz crucible 6,
Tilt the melting crucible and tap. Set the melting crucible. The silicon material is charged into the melting crucible. The vacuum vessel is closed and the inside of the vacuum vessel is evacuated. By heating with a heater, the silicon raw material is completely dissolved. Tilt the melting crucible and pour it into the mold. The silicon melt is solidified in the mold. The melting crucible is cooled. Remove the mold. When dissolving is continued, the above is repeated.

[0015]

As described above, in the graphite crucible according to the present invention, the cylindrical portion is formed of a plurality of members divided in the vertical direction, and when the raw material is dissolved, the outer diameter of the cylindrical portion is changed to the inner diameter. Since the ring made of carbon fiber reinforced carbon material, which is almost the same as the above, was attached to the upper and lower parts of the cylindrical portion, even if the melting crucible was cooled after melting, the quartz crucible could be used repeatedly and the carbon fiber It is cheaper than a crucible made of reinforced carbon material.

If the outer diameter of the cylindrical portion above the portion where the lower ring is mounted is made smaller than the outer diameter of the portion where the lower ring is mounted, the ring can be easily removed, so that the quartz crucible can be used. Can be easily removed from the graphite crucible.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a graphite crucible according to the present invention.

FIG. 2 is a view showing a state of thermal expansion and thermal contraction of a cylindrical member and a ring of a graphite crucible according to the present invention, wherein (a) shows a state before melting, and (b) shows a state during melting. Figure showing
(C) is a diagram showing a state after cooling.

3A and 3B are diagrams illustrating a conventional graphite crucible, in which FIG. 3A illustrates a state during melting, and FIG. 3B illustrates a state after cooling.

[Explanation of symbols]

1 {graphite crucible, 2} cylindrical part, 2a, 2b}
‥‥ Cylindrical member, 3 ‥‥‥ Bottom member, 4 ‥‥‥ Top ring, 5 ‥‥‥ Bottom ring

Claims (2)

[Claims] 1. A graphite crucible comprising a cylindrical portion and a bottom portion, wherein the cylindrical portion is made of a member divided into a plurality of members in a vertical direction, and the outer diameter of the cylindrical portion is changed to the inner diameter when a raw material is dissolved. A graphite crucible characterized in that rings made of a carbon fiber reinforced carbon material substantially equal to the above are mounted on the upper and lower portions of the cylindrical portion. 2. An outer diameter of the cylindrical portion above a portion where the lower ring is mounted is smaller than an outer diameter of a portion where the lower ring is mounted. The graphite crucible described in the above.