JPH07257987A - Graphite member for semiconductor single crystal pulling up device and semiconductor single crystal pulling up device - Google Patents

Abstract

PURPOSE:To reduce the evacuating time of a silicon single crystal pulling up device and enhance the single crystal production efficiency by removing a part of the coating layer of a graphite member formed by coating a graphite substrate with IL ceramics such as silicon carbide to expose the graphite substrate. CONSTITUTION:A graphite substrate is coated with silicon carbide or silicon nitride or a ceramics contg. silicon carbide and silicon nitride to form the graphite member for a semiconductor single crystal pulling up device, and the substrate is exposed at the rate of 0.03-0.96cm<2> per cm<3> of the member. The member can be applied to all the graphite members such as a crucible 12, heat insulating member 18, heat shielding member 19, crucible supporting member 11 and gas sealing member 21, and the means is more preferably applied to the graphite member positioned above the crucible.

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 specifically to silicon carbide or silicon nitride used for pulling a single crystal of silicon, gallium arsenide, indium phosphide, etc. by the Czochralski method. Alternatively, the present invention relates to a graphite member coated with a ceramic containing these and a single crystal pulling apparatus provided with the graphite member.

[0002]

2. Description of the Related Art One of the most typical methods for pulling a silicon single crystal for semiconductors is pulling a silicon single crystal by the Czochralski method. In this method, for example, a vacuum device as shown in FIG. 1 is used, polycrystalline silicon 14 is housed in a quartz crucible 13 housed in a graphite crucible 12 on a support 11, and an inert gas atmosphere is created inside the device. After doing
The graphite heating element 15 arranged on the outer periphery of the graphite crucible 12 melts the polycrystalline silicon 14, soaks the silicon seed crystal 16 in the silicon melt, and pulls the silicon seed crystal 16 upward while rotating it to form a single crystal at the lower end of the seed crystal 16. Crystalline silicon 17 is manufactured.

In the silicon single crystal pulling apparatus, various graphite members are used as materials capable of withstanding a high temperature atmosphere. However, since the graphite member used in the pulling device is generally porous, graphite powder generated during processing remains in the pores on the surface, and this graphite powder easily separates from the graphite member and Mix in the melt. The graphite powder mixed in the silicon melt not only induces crystal defects in the silicon single crystal, but also contains a small amount of various metals in the graphite powder, which greatly changes the electrical characteristics of the semiconductor. It will be.

Further, recently, the diameter of the pulled silicon single crystal has been remarkably increased, and accordingly, the amount of polycrystalline silicon to be filled in a quartz crucible at one time has increased, and a large amount of electric power is required for melting. It is necessary to increase the calorific value of and to raise the exothermic temperature. Therefore, the temperature of the graphite member becomes high, and the graphite member which has been heated to a high temperature easily reacts with silicon monoxide evaporated from the silicon melt, resulting in severe wear and deterioration, and there is a problem that the number of times of use thereof is shortened.

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 them 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 these is used in a pulling apparatus, the life of the graphite member is extended and a high-quality silicon single crystal is obtained. On the other hand, when the inside of the pulling apparatus is evacuated, there is a problem that the time required for the inside of the apparatus to reach a vacuum becomes long and the production efficiency of the single crystal is reduced. As a result of intensive investigations by the present inventors to investigate the cause, the reason why the vacuum arrival time is long is not due to the gradual desorption of the gas adsorbed to the silicon carbide coating layer or the like, but to the silicon carbide coating layer. It was found that the gas occluded by the graphite substrate after permeating through the above was gradually desorbed over a long period of time.

[0007]

SUMMARY OF THE INVENTION Therefore, the inventors of the present invention have a problem that this vacuum reaching time becomes long because a part of the silicon carbide or silicon nitride coating the graphite member or the ceramic layer containing them is removed. , A predetermined ratio of the graphite substrate, that is, 0.03 cm ² or more per 1 cm ^{3 of the} graphite member,
The inventors have found that the problem can be solved by exposing at a ratio of 96 cm ² or less, and completed the present invention. The exposed area of the graphite substrate can be applied regardless of the difference in shape and size of the graphite member. That is, by ensuring an exposed surface of a predetermined volume or more per unit volume of a graphite substrate that is occluding gas, the occluded gas is released all at once when the silicon single crystal pulling device is evacuated, and the vacuum arrival time is carbonized. It can be made almost equivalent to a graphite member not covered with silicon or the like. The problem that it takes a long time to reach the vacuum is that the silicon carbide coating layer or the like is thickened to, for example, 80 μm or more, and the graphite substrate is completely covered over the entire surface to suppress the release of the occluded gas. However, since the cost of coating silicon carbide increases and the stored gas in the graphite substrate is not released, the internal pressure inside the coating of silicon carbide rises as the temperature of the graphite substrate rises. Since the silicon coating layer or the like may be peeled off or damaged, it is practically less advantageous than providing the exposed surface. Further, by setting the exposed area of the graphite base used in the silicon single crystal pulling apparatus to an exposed surface of a predetermined ratio or less per unit volume of the graphite base, carbon incorporation from the graphite base into the melt is reduced, and the silicon to be pulled up is reduced. The impurity concentration in the single crystal can be made almost equal to the impurity concentration in the silicon single crystal when a graphite member whose entire surface is coated with silicon carbide or the like is used. The thickness of the coating layer of silicon carbide or the like is preferably 20 to 200 μm, more preferably 40 to 150 μm. 20μ thick
If it is less than m, the effect of coating becomes insufficient, and 200 μm
If it exceeds, it is not possible to expect further improvement of the covering effect and the cost becomes high.

The ceramic containing silicon carbide or silicon nitride used in the present invention is a mixture containing raw materials or by-products of the synthesis reaction of silicon carbide or silicon nitride,
It refers to a ceramic containing silicon carbide or silicon nitride as a main component, such as a simple metal or a mixture in which a metal oxide is positively added.

[0009]

In the present invention, for example, the crucible 12 and the heat insulating member 1 are provided.
8, heat insulating member, heat shield member 19, crucible support member 11,
The present invention can be applied to any graphite member for a silicon single crystal pulling device 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, the gas occluded in the graphite substrate is released all at once during the evacuation of the pulling device, and the vacuum arrival time is almost the same as when the graphite member not coated with silicon carbide or the like is used. They can be made equivalent, and the production efficiency of silicon single crystals can be improved. Moreover, 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, a crucible 12, a support 11, a heat retaining member 18, and a heat insulating member 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 liters, vacuum reachability: 133.3 Pa, evacuation efficiency: 3000 liters / minute, and temperature inside the pulling device: room temperature. Table 1 shows the results of the service life times of each graphite member. Shown in 2.

[0011]

[Table 1]

[0012]

[Table 2]

It is clear from Table 1 that when a graphite member coated with silicon carbide and a part of the graphite substrate is exposed, a vacuum arrival time of the same level as that of the graphite member not coated with silicon carbide can be obtained. Therefore, it can be seen from Table 2 that the service life of the graphite member of the present invention is at a level equivalent to that of the graphite member having the entire surface coated with silicon carbide.

The graph of FIG. 2 is the result of measuring the impurity concentration in the silicon single crystal when the exposure ratio of the 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 it exceeds, the carbon concentration in the obtained silicon single crystal remarkably increases and the concentration of heavy metal impurities also increases.

Thus, 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
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 long and the production efficiency of the silicon single crystal is lowered. ^This is because if it exceeds ² / cm ³ , the quality of the obtained silicon single crystal is adversely affected.

When a graphite member coated with silicon nitride was subjected to the same experiment, a single crystal equivalent to the case of silicon carbide was obtained.

[0017]

According to the present invention, in a graphite member for a silicon single crystal pulling apparatus, which is obtained by coating a graphite base with silicon carbide or the like, by exposing the graphite base in a predetermined area, The gas occluded in the graphite substrate is released at once at the time of evacuation, and the time to reach the vacuum can be made almost the same as when using a graphite member not coated with silicon carbide or the like. Can improve the production efficiency. Moreover, it is possible to extend the life of the graphite member and obtain a high-quality silicon single crystal.

[Brief description of 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 impurity concentration in a silicon single crystal.

[Explanation 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 Rotating Shaft 21 Gas Sealing Member

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Shingo Kizaki Inventor Shingo Kizaki 1 Higashihama-cho, Amagasaki City, Hyogo Sumitomo Cix Co., Ltd. Person Osamu Yoshimoto 2181-2 Nakahime, Onohara Town, Mitoyo-gun, Kagawa Prefecture

Claims (4)

[Claims] 1. A graphite member for a semiconductor single crystal pulling apparatus, comprising a graphite substrate coated with silicon carbide, silicon nitride, or a ceramic containing them.
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 graphite substrate is coated with silicon carbide or silicon nitride or a ceramic containing them, and 1 cm ³
A semiconductor single crystal pulling apparatus, wherein 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 the semiconductor single crystal is a silicon single crystal.