JP3012299U - Graphite crucible for pulling silicon single crystal - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a graphite crucible for pulling a silicon single crystal by the Czochralski method, and an object thereof is to provide a long-life graphite crucible in which cracking does not easily occur. The present invention is made of a carbon fiber reinforced carbon composite material in which a straight body portion 2 of a crucible and an R portion 3 continuous from the straight body portion are integrated, and is constructed in combination with a bottom portion 4 of the crucible. It is a graphite crucible 1 for pulling a silicon single crystal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a graphite crucible for pulling a silicon single crystal by the Czochralski method.

[0002]

[Prior art]

 The crucible used in the Czochralski method has a double structure of a quartz crucible for melting silicon and a graphite crucible for containing the same. In recent years, large-sized single crystals have been manufactured in order to obtain silicon single crystals with high yield. Along with this, a large graphite crucible is needed. However, as the capacity of the graphite crucible increases, so does the thermal strain due to the difference in the coefficient of thermal expansion between the quartz crucible and the graphite crucible, and the straight body, especially its upper edge, and the continuous R from the straight body. Stress concentrates on the part, and cracks in the graphite crucible easily occur. Conventionally, as measures against this, a graphite crucible is divided into a plurality of parts, a portion where stress is concentrated is made thicker, and a graphite material having a low coefficient of thermal expansion is developed.

[0003]

[Problems to be solved by the device]

 However, when the graphite crucible is divided into a plurality of pieces, the stress is temporarily absorbed and there is some effect, but the straight body part and the R part are not yet sufficiently effective. In addition, making the stress-concentrated portion thick increases the size of the crucible, which in turn increases the size of the entire lifting device. In addition, a graphite crucible is required to have a high density, which is contrary to the characteristics required to achieve a low coefficient of thermal expansion. Therefore, an object of the present invention is to provide a graphite crucible having a novel structure capable of solving these problems.

[0004]

[Means for Solving the Problems]

 This problem can be solved by using a carbon fiber reinforced carbon composite material (hereinafter also referred to as C / C composite material) in at least the stress concentration portion of the graphite crucible to increase the strength of this portion. That is, the graphite crucible for pulling a silicon single crystal according to the present invention is composed of a carbon fiber reinforced carbon composite material in which a straight body portion of the crucible and an R portion continuous from the straight body portion are integrated, and a crucible bottom portion is formed. It is configured by combining them.

The C / C composite material used in the present invention is obtained by impregnating a continuous fiber (filament) of carbon fiber with a thermosetting resin such as a phenol resin and winding it around a crucible-shaped mandrel. Those which have been heat-cured, baked, and optionally impregnated with pitch or resin for densification, and then repeated baking, final heat treatment, and further highly purified are used. With such a manufacturing method, the straight body portion and the R portion are made of an integral C / C composite material. The bottom of the crucible can be manufactured as a single piece, but since the bottom of the crucible does not generate much stress, it does not require much strength and is extremely difficult to mold (wrap). It is not necessary for Lu to make a bo.

The coefficient of thermal expansion of the particularly preferred C / C composite material is 1.0 × 10 ⁻⁶ / K (room temperature to 1,000 ° C.) or less. Since the C / C composite material having a low coefficient of thermal expansion is close to the coefficient of thermal expansion (0.5 × 10 ⁻⁶ / K) of the quartz crucible, the stress generated can be further reduced. Further, the bulk density of the C / C composite material is particularly preferably 1.5 g / cm ³ or more, and it is possible to suppress the silicidation by the silica crucible or the SiO gas generated from the molten silicon, and to suppress the graphite crucible by the silicification reaction. Cracking can be suppressed particularly effectively.

The bottom of the crucible is usually made of a so-called isotropic or anisotropic graphite material that has been conventionally used as a material for a graphite crucible. Optimally, it is composed of a C / C composite material having a thermal expansion coefficient similar to that of the used C / C composite material, for example, a 2D-C / C composite material. Further, a convex portion may be provided at the center of the crucible tray, and the convex portion may be configured as the crucible bottom portion.

[0008]

[Operation] The main point of interest of the present invention is to replace the conventional graphite material with a C / C composite material for the stress concentrating portion, and by doing so, the stress concentrating portion can be made stronger. When the stress concentration part is a C / C composite material, the straight body part and the R part must be integrated. The reason is that when only the straight body part or only the upper edge part is made of C / C composite material, the combination of C / C composite material and normal graphite material is effective against cracking during cooling. This is because there is a step due to the difference in the coefficient of thermal expansion. On the other hand, if the straight body portion and the R portion are integrated with the C / C composite material as in the present invention, problems such as cracks and steps during cooling do not occur.

The C / C material for the straight body portion and the R portion and the graphite crucible for pulling a silicon single crystal have a coefficient of thermal expansion close to that of a quartz crucible and have a large mechanical strength, so that some thermal stress occurs. However, the crucible does not crack.

[0010]

【Example】

 An embodiment of a graphite crucible according to the present invention will be described with reference to FIGS.

A schematic cross-sectional view of one embodiment of the graphite crucible according to the present invention is shown in FIG. The straight body portion 2 of the graphite crucible 1 and the R portion 3 continuous from the straight body portion are made of an integrated C / C composite material, and can be easily attached to and detached from the crucible bottom portion 4 made of an isotropic graphite material. The graphite crucible 1 is formed by fitting as much as possible. An adhesive such as carbon cement may be applied to this fitting surface and the both may be bonded to form a graphite crucible. Further, the crucible bottom part 4 is not limited to isotropic graphite, and may be made of an anisotropic graphite material or a C / C composite material.

A schematic cross-sectional view of another embodiment of the graphite crucible according to the present invention is shown in FIG. Similar to FIG. 1, 2 indicates a straight body portion, 3 indicates an R portion, and both are integrally made of a C / C composite material. The crucible bottom portion 4 is also made of a C / C composite material, and its screw portion 4a is screwed to the R portion 3 to form a graphite crucible. An adhesive such as carbon cement may be applied to this joint surface and the two may be adhered together to form a graphite crucible. Further, for the crucible bottom portion 4, of the C / C composite materials, a 2D-C / C composite material is particularly preferable in terms of the coefficient of thermal expansion.

FIG. 3 is a schematic sectional view of yet another embodiment of the graphite crucible according to the present invention. Similar to FIG. 1, 2 indicates a straight body portion, 3 indicates an R portion, and both are integrally made of a C / C composite material. The crucible bottom portion 4 is also made of a C / C composite material, and its screw portion 4a is screwed to the R portion 3 to form a graphite crucible. An adhesive agent such as carbon cement may be applied to this joint surface, and both may be adhered to form a graphite crucible. Further, as in the case of FIG. 1, the crucible bottom 4 is preferably a 2D-C / C composite material among C / C composite materials in terms of the coefficient of thermal expansion.

Here, the portion made of the C / C composite material is manufactured as follows. A carbon fiber filament impregnated with a phenol resin was wound on a crucible-shaped mandrel in parallel and helical windings so that slippage did not occur in the R part, and molding and hardening were performed. After sufficient curing, firing and graphitization were performed in an inert atmosphere, and then pitch impregnation and firing were repeated, followed by graphitization and purification. By this process, a C / C composite material having a straight body portion 2 and an R portion 3 integrated without a crucible bottom portion was produced.

[0015]

[Effect of device]

 As described above, in the graphite crucible for pulling a silicon single crystal according to the present invention, the straight body portion including the upper edge portion where the stress is concentrated and the R portion continuous from the straight body portion are integrated. Since it is made of C / C composite material, the strength of the portion where stress is concentrated becomes extremely high. Further, the C / C composite material has a lower coefficient of thermal expansion than the ordinary graphite material, and is close to the coefficient of thermal expansion of an English crucible, so that the generated stress can be reduced. Due to these synergistic effects, it can be used as a long-life graphite crucible.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of a graphite crucible for pulling a silicon single crystal according to the present invention.

FIG. 2 is a schematic cross-sectional view of another embodiment of a graphite crucible for pulling a silicon single crystal according to the present invention.

FIG. 3 is a schematic cross-sectional view of yet another embodiment of a graphite crucible for pulling a silicon single crystal according to the present invention.

[Explanation of symbols]

 1 Graphite Crucible 2 Straight Body 2a Upper Edge 3 R Part 4 Bottom 4a Screw Part

Claims (1)

[Scope of utility model registration request] 1. A silicon single crystal pulling-up, which comprises a carbon fiber reinforced carbon composite material in which a straight body portion of a crucible and an R portion continuous from the straight body portion are integrated, and which is configured in combination with a bottom portion of the crucible. Graphite crucible.