JPH05279169A - Graphite crucible for pulling single crystal - Google Patents

Abstract

PURPOSE:To prevent Si from depositing on the outer surface of a graphite crucible by forming projections and/or depressions on the outer surface and inhibit the graphite crucible from sticking to the receiver at the fitting face. CONSTITUTION:On the outer surface of a graphite crucible 30 which can be divided in halves at the dividing faces 11, are formed projections 12 and/or depressions 12 of shapes 1mm wide longer in the circumference directions than in the height direction. Thus, the graphite crucible can be prevented from sticking on the dividing surface and inhibited from being damaged due to the difference in thermal expansion between the graphite and quartz crucibles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite crucible for pulling a single crystal, and more particularly to a graphite crucible for pulling a single crystal used for producing a single crystal of a semiconductor material such as silicon.

[0002]

2. Description of the Related Art Conventionally, a rotation pulling method called Czochralski method (hereinafter, referred to as CZ method) has been widely used for manufacturing a semiconductor material, particularly silicon (hereinafter, referred to as Si) single crystal. .. FIG. 2 is a schematic cross-sectional view of a general crystal device used in the CZ method, and 10 in the figure shows a cylindrical graphite crucible with a bottom. The graphite crucible 10 is supported by a support shaft 15 that rotates at a predetermined speed in the direction of the arrow in the figure, and a heater 18 is concentrically arranged outside the graphite crucible 10. A quartz crucible 16 having a bottomed cylindrical shape is fitted inside the graphite crucible 10.
The quartz crucible 16 is filled with the melt 17 of the Si raw material for crystal melted by the heater 18. Further, on the central axis of the quartz crucible 16, a pull-up shaft 19 such as a wire which is coaxial with the support shaft 15 and rotates at a predetermined speed in the same direction or the opposite direction is arranged. Then, the seed crystal 20 attached to the tip of the pulling shaft 19 is melted 17
A single crystal 21 formed by solidifying the melt 17 by bringing the pulling shaft 19 into contact with the surface of the
Grow.

By the way, in recent years, the size of the single crystal 21 has been increased in order to obtain a single crystal with a good yield, and the capacity of the quartz crucible 16 filled with the melt 17 has been increased. Therefore, the graphite crucible 10 has also become large. However, the tensile stress on the inner surface of the graphite crucible 10 caused by the difference in the coefficient of thermal expansion between the fitted quartz crucible 16 and the graphite crucible 10 is increased, and deformation, cracks, defects, etc. Defects (referred to as breakage) are likely to occur, and the number of times the graphite crucible can be used is reduced.

FIG. 3 is a cross-sectional view schematically showing a graphite crucible which has been subjected to a treatment for suppressing the breakage of the graphite crucible. In FIG. 3, 10 is a graphite crucible divided into two by a dividing surface 11. Shows. A quartz crucible (not shown) is fitted to the inner surface of the graphite crucible 10, and a lower portion of the graphite crucible 10 is fitted to a pedestal 14 supported by a support shaft 15. By this fitting, two pieces are formed. The divided graphite crucible 10 is held in close contact with the dividing surface 11. When a tensile stress is applied to the graphite crucible 10 thus configured, the fitting surface 22 and the dividing surface 11 between the graphite crucible 10 and the pedestal 14 are divided.
Is opened and internal stress is released, so that damage to the graphite crucible is suppressed.

[0005]

When pulling a single crystal, Si solution that is scattered by bumping, Si vapor that is generated when Si is pulled, and droplets of Si produced by the reaction of SiO gas are graphite. It tends to adhere to the outer peripheral surface of the crucible 10. Further, the attached droplet-like Si is a graphite crucible 1
0 along the outer peripheral surface of the graphite crucible 10 and the cradle 1
4 and / or the split surface 11 of the graphite crucible 10 easily enters. Therefore, when the molten Si is solidified during cooling, the graphite crucible 10 is fixed to the pedestal 14 and / or the dividing surface 11 of the graphite crucible 10, the release of the internal stress is suppressed, and the graphite crucible 10 is easily damaged. There was a risk of it getting lost.

The present invention has been made in view of the above problems, and reduces adhesion of Si to the outer peripheral surface of the graphite crucible,
An object of the present invention is to provide a graphite crucible for pulling a single crystal capable of suppressing sticking between the fitting surface of the graphite crucible and the pedestal and / or the dividing surface of the graphite crucible.

[0007]

In order to achieve the above object, the graphite crucible for pulling a single crystal according to the present invention is characterized in that projections and / or depressions are formed on the outer peripheral surface of the graphite crucible.

The graphite crucible for pulling a single crystal is characterized in that the shape of the protrusion and / or the depression is longer in the crucible circumferential direction than in the crucible height direction.

[0009]

[Function] As a result of an investigation by the present inventor about a situation in which droplet-like Si attached to the outer peripheral surface of the graphite crucible drops while traveling along the outer peripheral surface of the graphite crucible, when a protrusion and / or a depression is formed on the outer peripheral surface, It has been found that the droplet-like Si is likely to stay because the course is obstructed and the dropping speed is reduced (hereinafter, referred to as a dropping suppressing action). Further, it has been found that the above-mentioned drip suppressing effect is effective when the size of the projection and / or the depression is 1 mm or more in diameter and the shape is longer in the circumferential direction than in the height direction of the graphite crucible.

Further, it has been found that when the protrusions and / or the depressions are formed, the outer peripheral area of the graphite crucible increases and the protrusions are closer to the heater, so that the evaporation of the droplet-like Si is promoted. In this case, the size of the protrusion and / or the depression formed on the outer peripheral surface may be small,
It was found that even when the maximum diameter is 100 μm or less, the evaporation of Si attached to the outer peripheral surface of the crucible is promoted.

Further, it has been found that when a relatively large projection and / or depression and a small projection and / or depression are formed in combination, it is more useful for preventing the deposition of droplet-like Si and dropping.

According to the graphite crucible for pulling a single crystal according to the present invention, since protrusions and / or depressions are formed on the outer peripheral surface of the graphite crucible, adhesion and dropping of droplet-like Si on the outer peripheral surface of the graphite crucible is suppressed. Will be done.
Further, when the shape of the above-mentioned projections and / or depressions is longer in the crucible circumferential direction than in the crucible height direction, it is possible to further suppress the adhesion and dropping of droplet-like Si on the outer peripheral surface of the graphite crucible. Become.

[0013]

EXAMPLES Examples and comparative examples of the graphite crucible for pulling a single crystal according to the present invention will be described below with reference to the drawings.
It should be noted that components having the same functions as those of the conventional example are designated by the same reference numerals.

1A and 1B schematically show a graphite crucible for pulling a single crystal according to an embodiment. FIG. 1A is a perspective view and FIG. 1B is a developed view. In the figure, reference numeral 30 denotes a graphite crucible having a diameter of 12 inches, which is divided into two. The outer peripheral surface of the graphite crucible 30 has a circumferential length of 50 mm and a width of 5 mm.
A large number of protrusions 12 having a shape of mm and a thickness of 2 mm are formed, and the intervals between the protrusions 12 are set to 20 mm in the circumferential direction of the graphite crucible 30 and 25 mm in the height direction of the graphite crucible 30. Further, on the outer peripheral surface of the graphite crucible 30, recesses 13 having a diameter of about 0.2 mm and a depth of about 0.3 mm are formed at a rate of about 30 per 1 cm ² of the outer peripheral surface area of the graphite crucible 30. ..

When the single crystal pulling graphite crucible configured as described above is used, the graphite crucible 30 is fitted into the receiving base 14 as in the conventional case (FIG. 3), and the receiving base 1 is used.
4 is supported by a support shaft 15 which rotates at a predetermined speed, a cylindrical quartz crucible (not shown) having a bottom is fitted inside the graphite crucible 30, and a crystal raw material is melted inside the quartz crucible. The liquid is filled.

Next, the results of testing the service life of the graphite crucible 30 for pulling a single crystal according to the embodiment will be described.
In this test, the operation of heating and melting Si to a constant temperature without pulling a single crystal and then cooling and solidifying to a constant temperature was repeated, and the number of times the graphite crucible 30 was used (fitting between the graphite crucible 30 and the pedestal 14) was repeated. Face 22 and /
Alternatively, the number of repetitions of the above operation until the graphite crucible 30 was cracked due to the fixation of the divided surfaces 11 of the graphite crucible 30 was investigated.

As a comparative example, a conventional segmented graphite crucible 10 having no projections 12 and / or depressions 13 was repeatedly used to melt and solidify Si in the same manner as above. The reason for repeating the melting and solidifying operation of Si is that Si expands when it solidifies, so this repeating operation is more severe than ordinary pulling of a single crystal, and the number of times of service in a short time is compared. To get it.

The results are shown in Table 1 below.

[0019]

[Table 1]

In the embodiment, a graphite crucible 30 is used.
There is little formation of SiC on the mating surface 22 between the pedestal 14 and the pedestal 14, and there is no formation of SiC on the outer peripheral surface of the graphite crucible 30. It was double.

As is clear from these results, in the graphite crucible 30 for pulling a single crystal according to the embodiment, the fitting surface 22 between the graphite crucible 30 and the pedestal 14 and the graphite crucible 30 are different from the conventional graphite crucible 10. The amount of Si deposited on the outer peripheral surface is reduced, and the life of the graphite crucible 30 is extended. As described above, a large number of protrusions 12 having a shape with a circumferential length of 50 mm, a width of 5 mm, and a thickness of 2 mm are formed on the outer peripheral surface of the graphite crucible 30, and the diameter thereof is approximately 0.2.
By forming a large number of dents 13 having a shape of mm and a depth of approximately 0.3 mm, it is possible to suppress adhesion and dripping of Si on the outer peripheral surface of the graphite crucible 30 and permeation into the fitting surface 22 and the dividing surface 11. It was confirmed that the fitting surface 22 between the graphite crucible 30 and the pedestal 14 and / or the division surface 11 of the graphite crucible 30 can be prevented from sticking to prolong the life.

[0022]

As described above in detail, in the graphite crucible for pulling a single crystal according to the present invention, since the protrusion and / or the depression is formed on the outer peripheral surface of the graphite crucible, Si
It is possible to suppress the adhesion and dripping of the graphite crucible on the outer peripheral surface and the permeation and sticking to the fitting surface between the graphite crucible and the pedestal and / or the divided surface of the graphite crucible, and the thermal expansion of the graphite crucible and the quartz crucible. It is possible to suppress breakage of the graphite crucible due to the difference in the rate.

[Brief description of drawings]

FIG. 1 schematically shows an embodiment of a graphite crucible for pulling a single crystal according to the present invention, in which (a) is a perspective view,
(B) is a development view.

FIG. 2 is a schematic sectional view showing a crystal growth apparatus used in a conventional CZ method.

FIG. 3 is a schematic cross-sectional view showing a conventional split crucible.

[Explanation of symbols]

 30 Graphite crucible 12 Protrusion 13 Dimple

Claims (2)

[Claims] 1. A graphite crucible for pulling a single crystal, wherein protrusions and / or depressions are formed on the outer peripheral surface of the graphite crucible. 2. The graphite crucible for pulling a single crystal according to claim 1, wherein the shape of the protrusion and / or the depression is longer in the crucible circumferential direction than in the crucible height direction.