JP2741164B2 - Graphite member for semiconductor single crystal pulling device and semiconductor single crystal pulling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphite member for a semiconductor single crystal pulling apparatus, and more particularly to a silicon carbide or silicon nitride used for pulling a single crystal such as silicon, gallium arsenide, indium phosphide by the Czochralski method. Alternatively, the present invention relates to a graphite member coated with a ceramic containing the same and a single crystal pulling apparatus provided with the graphite member.

[0002]

2. Description of the Related Art One of the most typical silicon single crystal pulling methods for semiconductors is pulling a silicon single crystal by the Czochralski method. In this method, for example, using a vacuum apparatus as shown in FIG. 1, polycrystalline silicon 14 is housed in a quartz crucible 13 housed in a graphite crucible 12 on a support base 11, and the inside of the apparatus is kept under an inert gas atmosphere. After doing
The polycrystalline silicon 14 is melted by a graphite heating element 15 arranged on the outer periphery of the graphite crucible 12, a silicon seed crystal 16 is immersed in the silicon melt, and is lifted upward while rotating, so that a single crystal is formed at the lower end of the seed crystal 16. Crystalline silicon 17 is manufactured.

In a silicon single crystal pulling apparatus, various graphite members are used as materials capable of withstanding a high-temperature atmosphere. However, since graphite members generally used in pulling devices are porous, graphite powder generated during processing remains in pores on the surface, and the graphite powder is easily detached from the graphite member, and silicon powder is removed. Mix into the melt. Graphite powder mixed into the silicon melt not only induces crystal defects in the silicon single crystal, but also significantly changes the electrical characteristics of semiconductors because graphite powder contains trace amounts of various metals. Will be.

Recently, the diameter of a silicon single crystal to be pulled has been remarkably increased, and the amount of polycrystalline silicon to be filled in a quartz crucible at one time has increased. It is necessary to increase the calorific value of the steel and raise the heat generation temperature. For this reason, the temperature of the graphite member increases, and the graphite member having a high temperature easily reacts with silicon monoxide evaporating from the silicon melt, so that there is a problem in that the graphite member is greatly consumed and deteriorated, and the number of uses thereof is reduced.

Therefore, in order to protect the surface of the graphite member, the graphite member is coated with silicon carbide or silicon nitride or a ceramic containing these by a chemical vapor deposition method or a silicidation reaction.

[0006]

However, when a graphite member coated with silicon carbide or silicon nitride or a ceramic containing them is used in a pulling apparatus, the life of the graphite member can be extended and a high-quality silicon single crystal can be obtained. On the other hand, at the time of evacuation in the pulling apparatus, there is a problem that the time required to reach a vacuum in the apparatus becomes longer, and the production efficiency of single crystals is reduced. In pursuit of the cause, the present inventors have conducted intensive studies and found that the reason why the vacuum arrival time becomes longer is not that the gas adsorbed on the silicon carbide coating layer etc. gradually desorbs, but the silicon carbide coating layer. It has been found that the gas absorbed by the graphite substrate after passing through the above is gradually desorbed over a long period of time.

[0007]

The inventors of the present invention have found that the problem of the longer vacuum arrival time is that the silicon carbide or silicon nitride coating the graphite member or the ceramic layer containing them is partially removed. , The graphite base is provided in a predetermined ratio, that is, 0.03 cm ² or more per 1 cm ^{3 of the} graphite member.
It was found that the problem was solved by exposing at a rate of 96 cm ² or less, and the present invention was completed. The exposed area of the graphite substrate can be applied irrespective of the difference in shape and size of the graphite member. That is, by securing an exposed surface at a predetermined ratio or more per unit volume of the graphite substrate that absorbs the gas, the occluded gas is released at once at the time of evacuation in the silicon single crystal pulling apparatus, and the time to reach vacuum is carbonized. It can be made substantially equivalent to a graphite member not covered with silicon or the like. The above-mentioned problem that it takes a long time to reach the vacuum is caused by suppressing the release of the occluded gas by making the silicon carbide coating layer or the like thick, for example, 80 μm or more, and completely covering the graphite substrate over the entire surface. However, since the cost of the silicon carbide coating and the like increases and the occluded gas of the graphite substrate is not released, the internal pressure inside the coating of the silicon carbide or the like increases as the temperature of the graphite substrate increases, and Because of the possibility of peeling or breakage of the silicon coating layer or the like, it is not practically advantageous to provide the above-mentioned exposed surface. In addition, by setting the exposed area of the graphite substrate used in the silicon single crystal pulling apparatus to an exposed surface of a predetermined ratio or less per unit volume of the graphite substrate, carbon mixing from the graphite substrate into the melt is reduced, and the silicon pulled up The impurity concentration in the single crystal can be made substantially equal to the impurity concentration in the silicon single crystal when a graphite member whose entire surface is covered with silicon carbide or the like is used. The thickness of the coating layer such as silicon carbide is preferably 20 to 200 μm, and more preferably 40 to 150 μm. 20μ thickness
m, the effect of the coating becomes insufficient,
If it exceeds 300, further improvement of the covering effect cannot be expected, and the cost will increase.

[0008] The ceramic containing silicon carbide or silicon nitride used in the present invention refers to a mixture containing a raw material or a by-product of a synthesis reaction of silicon carbide or silicon nitride,
It means a ceramic containing silicon carbide or silicon nitride as a main component, such as a mixture in which a simple substance of a metal, a metal oxide or the like is positively added.

[0009]

According to the present invention, for example, a crucible 12, a heat insulating member 1 is provided.
8, heat insulation member, heat shielding member 19, crucible support member 11,
The present invention can be applied to any graphite member for a silicon single crystal pulling apparatus such as a spacer, a fastening member, and a gas sealing member 21, and it is more preferable to apply the present invention to a graphite member located above a crucible. According to the present invention, at the time of evacuation in the pulling device, the gas occluded in the graphite substrate is released at a stretch, and the vacuum arrival time is almost the same as when a graphite member not coated with silicon carbide or the like is used. Therefore, the production efficiency of silicon single crystal can be increased. In addition, it is possible to extend the life of the graphite member and obtain a high-quality silicon single crystal.

[0010]

EXAMPLE A high purity isotropic graphite member manufactured through cold isostatic pressing was coated with silicon carbide by a chemical vapor deposition method, as shown in FIG. When various graphite members for a silicon single crystal pulling device such as the shielding member 19 and the gas sealing member 21 are actually used in the silicon single crystal pulling device (pulling device volume: 4
Table 1 shows the results of the vacuum arrival time of 00 liter, the degree of vacuum: 133.3 Pa, the evacuation efficiency: 3000 liter / minute, the temperature in the pulling apparatus: room temperature, and the results of the number of service life of each graphite member. 2 is shown.

[0011]

[Table 1]

[0012]

[Table 2]

It is clear from Table 1 that when a graphite member coated with silicon carbide and partially exposing the graphite substrate is used, the same level of vacuum arrival time as a graphite member not coated with silicon carbide can be obtained. From Table 2, it can be seen that the service life of the graphite member of the present invention is at the same level as that of a graphite member coated entirely with silicon carbide.

FIG. 2 is a graph showing the results of measuring the impurity concentration in a silicon single crystal when the exposure ratio of a graphite substrate coated with silicon carbide having a thickness of 40 μm was variously changed.
As is clear from this figure, the exposure ratio is 0.96 cm ² / cm ³
It can be seen that when the concentration exceeds 1, the carbon concentration in the obtained silicon single crystal increases remarkably, and the concentration of heavy metal impurities also increases.

As described above, the ratio of the exposed area of the graphite substrate specified in the present invention is 0.03 cm ² / cm ³ or more and 0.9% or less.
The reason why it is 6 cm ² / cm ³ or less is that if it is smaller than 0.03 cm ² / cm ³ , the vacuum reaching time in the silicon single crystal pulling apparatus becomes longer and the production efficiency of the silicon single crystal is lowered, so that 0.96 cm ² / cm ^{3. If} it exceeds ² / cm ³ , the quality of the obtained silicon single crystal is adversely affected.

The same experiment was performed on a graphite member coated with silicon nitride, and a single crystal equivalent to that of silicon carbide was obtained.

[0017]

According to the present invention, in a graphite member for a silicon single crystal pulling apparatus in which a graphite base is coated with silicon carbide or the like, the graphite base is exposed in a predetermined ratio of area, thereby making the inside of the pulling apparatus. At the time of evacuation, the gas occluded in the graphite substrate is released at a stretch, and the vacuum arrival time can be made substantially the same as when a graphite member not coated with silicon carbide or the like is used. Can increase the production efficiency. In addition, it is possible to extend the life of the graphite member and obtain a high-quality silicon single crystal.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a silicon single crystal pulling apparatus.

FIG. 2 is a graph showing measurement results of an impurity concentration in a silicon single crystal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Crucible support 12 Graphite crucible 13 Quartz crucible 14 Polycrystalline silicon 15 Graphite heating element 16 Seed crystal 17 Single crystal silicon 18 Heat insulation member 19 Heat shielding member 20 Rotation axis 21 Gas sealing member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Setsuo Okamoto 1 at Higashihama-cho, Amagasaki-shi, Hyogo Prefecture, Sumitomo Citizens Co., Ltd. Inventor Hiroyuki Hirano, 212-11-2 Nakahime, Onohara-cho, Mitoyo-gun, Kagawa Prefecture

Claims (4)

(57) [Claims] 1. A graphite member for a semiconductor single crystal pulling apparatus comprising a graphite substrate coated with silicon carbide or silicon nitride or a ceramic containing the same, wherein the member
cm ³ per 0.03 cm ² or more, wherein the graphite substrate is exposed at a rate of 0.96 cm ² or less semiconductor single crystal pulling apparatus for a graphite member. 2. A coated graphite substrate with a ceramic containing silicon carbide or silicon nitride, or these, 1 cm ³
A semiconductor single crystal pulling apparatus characterized in that a graphite member having a graphite substrate exposed at a rate of 0.03 cm ² or more and 0.96 cm ² or less is disposed inside the semiconductor single crystal pulling apparatus. 3. The graphite member for a semiconductor single crystal pulling apparatus according to claim 1, wherein the semiconductor single crystal is a silicon single crystal. 4. The semiconductor single crystal pulling apparatus according to claim 2, wherein said semiconductor single crystal is a silicon single crystal.