JPS63117906A - Member for production apparatus of polycrystalline silicon - Google Patents

Abstract

PURPOSE:To prolong the service life of members and to prevent deterioration of the purity of polycrystalline silicon by providing gas-impermeable silicon nitride film on an internal surface of a base material which forms a fluidized reaction tube member for production apparatus of polycrystalline silicon is formed. CONSTITUTION:The gas-impermeable silicon nitride film with >=10mum thickness is provided on the internal surface of the base material. Silicon carbide, silicon - silicon carbide, silicon nitride, silicon nitride - silicon carbide, quartz glass, carbon, zirconia and alumina are exemplified as the base material. The above- mentioned silicon nitride film is formed by a chemical vapor deposition from a mixed gas of silicon tetrachloride - ammonia - hydrogen or a mixed gas of silicon tetrachloride - nitrogen - hydrogen.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a member for polycrystalline silicon manufacturing equipment, particularly for use in thermal decomposition and hydrogen reduction of 1-lichlorosilane in a fluidized bed reactor. The present invention relates to a member for a polycrystalline silicon manufacturing apparatus that is suitable as a reactor for producing polycrystalline silicon.

(Prior Art) Semiconductor polycrystalline silicon is usually manufactured by thermal decomposition of trichlorosilane (S j , HCQa) and epitaxial growth by hydrogen reduction.

In this method, a high-purity polycrystalline silicon plate is placed inside a quartz glass Pelger, and it is heated to 1,000 m
-1. ．． The process was carried out by heating to 200°C, flowing a mixed gas of trichlorosilane and hydrogen gas, and depositing silicon produced by thermal decomposition and hydrogen reduction on a silicon rod according to the following formula (% formula (1)). This method has the advantage that polycrystalline silicon of relatively high purity can be obtained because the silicon substrate and the silicon attached to it are not in contact with the reaction vessel, but this method also It has the disadvantages of slow speed and, because it is a batch process, low productivity and therefore high cost.

Therefore, for the production of polycrystalline silicon, a continuous production method using a fluidized bed reactor is being developed. For example, as shown in FIG. 1, a polycrystalline silicon seed crystal is grown from a seed crystal tank 3 at the top of a vertical reaction tube 1 which is heated to 1,000 to 1,200°C by an external heating source 2. At the same time, a mixed gas of trichlorosilane and hydrogen gas is fed into the reaction tube from the gas inlet 4 at the bottom of the reaction tube to keep the seed crystals in a fluid state inside the reaction tube, and the exhaust gas is released from the gas outlet 5 to the outside. According to this method, the seed crystals, which have become larger and heavier due to the precipitation of silicon obtained by thermal decomposition and reduction of trichlorosilane, turn into polycrystalline silicon particles and form polycrystalline silicon grains at the bottom of the reaction tube. Since it falls into the crystalline silicon tank 6, polycrystalline silicon can be easily obtained by collecting it. This method can be made continuous by simply feeding seed crystals continuously, and the silicon precipitation rate is fast, so polycrystalline silicon can be obtained at low cost, but this method requires a reaction temperature. Because of the high heat resistance, quartz glass cannot be used for this reaction tube because it causes devitrification and cracks, so silicon carbide tubes, which have excellent heat resistance, are used. This method has the disadvantage that trace amounts of silicon carbide are mixed into the polycrystalline silicon due to friction when the seed crystal comes into contact with the tube wall during flow, reducing the purity of the desired polycrystalline silicon.

(Structure of the Invention) The present invention relates to a part H for a polycrystalline silicon manufacturing apparatus that solves the above-mentioned disadvantages. It is characterized by providing the following.

That is, as a result of various studies on reaction tube materials used for fluidized-bed production of high-purity polycrystalline silicon, the present inventors prepared gas-impermeable materials on the surface of an appropriate base material with a controlled amount of impurities. We discovered that if a silicon nitride film is provided, the purity will not decrease even if silicon nitride mixes into the target polycrystalline silicon, and we have discussed the allowable amount of impurities in this silicon nitride film. The present invention was completed by conducting research on the following.

The base material for forming the fluidized bed reaction tube as a member for the polycrystalline silicon manufacturing apparatus of the present invention is silicon carbide, silicon-
Examples include silicon carbide, silicon nitride, silicon nitride-silicon carbide, quartz glass, carbon, zirconia, alumina, etc., but when making this selection, it is necessary to consider the usage conditions, purity, thermal expansion, etc. There is. Among these, silicon carbide, silicon-silicon carbide, silicon nitride, silicon nitride-silicon carbide, and quartz glass are preferred from the viewpoint of heat resistance, purity, and coefficient of thermal expansion. This base material is provided with a silicon nitride film using the method described below, and in order to make this silicon nitride film highly pure, it is necessary to prevent contamination from the base material, so this base material is also Since it is necessary to have a high purity, carbonaceous materials are purified using hydrogen chloride or hydrogen fluoride gas at around 1,800°C. , silicon nitride, and silicon nitride-silicon carbide are also preferably treated with hydrochloric acid at about 1,200°C. However, zirconia and alumina have the disadvantage of being difficult to achieve high purity, and those produced by the sol-gel method are expensive.

This substrate then needs to be coated with a silicon nitride film on its surface, and since this silicon nitride film comes into contact with the seed crystal flowing in the fluidized bed reaction tube, it is possible to obtain high purity. It is necessary to make it a thing. Therefore, for this silicon nitride, it is necessary to use a raw material that has been sufficiently purified by distillation, etc., but this material contains less than 110 PP of iron and copper, and is
- Contains lithium, potassium, and lithium” 1 (: is 1.P
It is preferable to set it to below Pm. In addition, since this silicon nitride film comes into contact with the flowing seed crystal, it needs to have a certain thickness or more, and this should be at least O/111, but it should be at least 50 O/111. It is better to

This silicon nitride film may be formed by any method, but generally known chemical vapor deposition (hereinafter abbreviated as CVD) may be used. Silicon nitride can be produced by this CVD method using a gas system containing silicon and nitrogen, but usually a mixed gas of silicon tetrachloride-ammonia-hydrogen system or silicon tetrachloride-nitrogen-hydrogen system is used. 1,20 ml under reduced pressure
0-1, 4. It may be heated to 00°C. In order to form this silicon nitride film by the CVD method, as shown in FIG. The silicon carbide tube 13 is installed, and a high frequency is applied to the high frequency coil 12 to heat the graphite heating element 14 to heat the inside of the furnace.
After heating to about 0°C and reducing the pressure inside the furnace to about 10 torr by sucking the air inside the furnace using a pressure reducing device from the gas outlet 15, silicon tetrachloride-ammonia is added from the gas inlet 16. - The above-mentioned base material obtained in this way can be made by introducing a hydrogen mixed gas and CVDing the silicon nitride produced by this chemical reaction as a film on the surface of the silicon carbide tube 13. When the member for polycrystalline silicon manufacturing equipment of the present invention is provided with a silicon nitride film on its surface, when it is used as a reaction tube in a fluidized bed type polycrystalline silicon manufacturing equipment, the silicon nitride film becomes hard and has excellent heat resistance. This product has a lifespan of more than 2,000 hours because it is a product.
It has the advantage that it can be operated continuously for a long time because it still shows durability of 1 minute even after 2 hours. In addition, the polycrystalline silicon grains made with this device have several PPs due to contact with the silicon nitride film in the fluidized bed.
This silicon nitride contains silicon nitride of order b, but as mentioned above, this silicon nitride contains a small amount of impurities, and this is a compound of silicon and nitrogen, and this nitrogen is molten silicon (polycrystalline silicon). ) When single-crystal silicon is pulled up, it is volatilized into the atmosphere, so it is not a problem at all for single-crystal silicon.In fact, this nitrogen is vaporized into the atmosphere when pulling single-crystal silicon from a quartz glass crucible. 7- It acts as an anti-slip agent with the licon melt, has the effect of suppressing the elution of quartz glass, and has the effect of stabilizing the pulling of single crystals, and has the advantage of being preferred from this point of view as well. It is.

Next, examples of the present invention will be given.

Example: Diameter: 230++wn x Thickness: 10mm
A silicon carbide tube with a length of 2,000III11 was placed in the CVD furnace shown in Figure 2, and the temperature was raised to 1,350°C using high-frequency heating, and the pressure inside the furnace was reduced to 10 Torr using a pressure reducing device. After that, silicon tetrachloride 20 c, c/min and hydrogen gas 2 Q/min were flowed into the tube and reacted for 5 hours, resulting in a silicon nitride film with a thickness of 50 cm on the surface of the silicon carbide tube. A uniformly distributed product was obtained.

Next, the silicon carbide tube provided with this silicon nitride film was used as a reaction tube of the fluidized bed type polycrystalline silicon production apparatus shown in Fig. 1, and the temperature inside the furnace was set to 1,150°C, and 2.77 kg of trichlorosilane was injected from the bottom of the tube. /hour, hydrogen gas],,07Nrn
'/hour flows in, and the particle size is 0.3~0.5w from the top.
Seed silicon with n and o.

By dropping it at a rate of 0.8 kg/hour and flowing it with the gas flow described in 1., polycrystalline silicon grains with a grain size of 1 to 2 nwn due to the growth of seed crystals could be obtained at a rate of iokg/hour. The reaction remained normal even after 2,000 hours, so the reaction was stopped.

Next, when the polycrystalline silicon was made into single crystal silicon by the pulling method, the yield was 95%, the same result as the conventional method, and the purity of this silicon was
I checked the resistivity.

This impurity μ is B O,21+)llb, P O,0
5PPb, A Q O,, OiP'Pb, A s
O,01PPb, C<0.05P yen), and the specific resistance value was PI, 500Ω・G. Comparative Examples The silicon carbide tubes used in the examples, which had been pretreated with acid at high temperature, were heated to a fluidized bed polycrystalline tube. When polycrystalline silicon was made using the reaction tube of a silicon manufacturing device under the same conditions as in the example, the grain size was 1 to 1.
We were able to obtain polycrystalline silicon grains of 211111 at a rate of 10 kg/hour, and this reaction continued for 2,000 hours. As a result, the yield is 5
When we measured the purity and specific resistance of this silicon, we found that this impurity amount was B5.9PPb, Po
.

40PPb, A Q 3.7PPb, A s <0
．． 04PPb, CO, 50PPb, and the specific resistance value was P35Ω・σ・

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of a continuous polycrystalline silicon production apparatus using a fluidized bed reactor, and Fig. 2 is a longitudinal cross-section of a reaction apparatus for producing the polycrystalline silicon production apparatus components of the present invention by the CVD method. This shows a top view.

Claims (1)

[Scope of Claims] 1. A member for a polycrystalline silicon manufacturing apparatus, characterized in that a gas-impermeable silicon nitride film having a film thickness of 10 μm or more is provided on the inner surface of a base material. 2. Claim 1, wherein the base material is made of silicon carbide, silicon-silicon carbide, silicon nitride, silicon nitride-silicon carbide, quartz glass, carbon, zirconia, or alumina. The member for polycrystalline silicon manufacturing equipment described above. 3. Polycrystalline silicon production according to claim 1, wherein the silicon nitride film is produced by chemical vapor deposition from a silicon tetrachloride-ammonia-hydrogen gas mixture or a silicon tetrachloride-nitrogen-hydrogen gas mixture. Equipment parts.