JPS59107917A - Apparatus for manufacturing polycrystalline silicon - Google Patents

Abstract

PURPOSE:To deposit efficiently polycrystalline Si on the surface of seed Si by feeding gaseous H2 as a reducing agent to a fluidized bed reactor from the porous inner wall when an inorg. silane compound and gaseous H2 are fed to the reactor to deposit polycrystalline Si on the surface of seed Si. CONSTITUTION:An inorg. silane compound such as silicon tetrachloride, trichlorosilane, dischlorosilane, monochlorosilane or monosilane is fed to a fluidized bed reactor 1 from an inlet 6 for introducing a gaseous starting material. Gaseous H2 as a reducing agent is fed to the space between the outer wall 9 of the reactor 1 and the porous inner wall 10 from inlets 8 for introducing H2, and it is spouted from many pores in the wall 10 and reacted with the silane compound. The silane compound is reduced and deposited as polycrystalline Si of high purity on the surface of polycrystalline seed Si charged into the reactor 1 from a charging inlet 3. Since the reaction is an endothermic reaction, polycrystalline Si is liable to deposit on the inner wall 10 adjacent to a heater 2. Gaseous H2 spouted from the pores in the wall 10 prevents deposition on the wall 10, so polycryltalline Si is deposited on the surface of seed Si in a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for producing polycrystalline silicon, and more particularly to an improvement in a fluidized bed reactor for producing polycrystalline silicon from an inorganic silane compound.

Conventionally, a mixed gas of high purity silicon tetrachloride, inorganic silane compounds such as trichlorosilane, dichlorosilane, monochlorosilane, monosilane, etc. and hydrogen and a particle size of 50 as seeds are used.
~1000μ of high purity silicon is supplied to a fluidized bed reactor and operated at a temperature of 400~1200℃ and a pressure of 1~3 atm to precipitate and grow polycrystalline silicon on the surface of high purity silicon seed particles. The manufacturing method is known.

The reactions in this case are shown below (1) (2) (S) (
It is said that the reaction proceeds according to the reaction formulas 4) and (5).

Si (J4 +2H2→ st + 4aci
(1) SiH(J3 + H2→ Sl +
RoH(J (2) SiHCl2
→ st + 2H(J (S)SiH3
(J → si+ ncz+H2(4)SiH, →
s1+ 2H2 (5) This method of manufacturing polycrystalline silicon using a fluidized bed provides a large reaction surface area, so the rate of silicon precipitation is fast, high productivity can be expected with a small reactor capacity, and continuous operation is possible. This is also a preferred method because it is easy.

Since the reaction between the inorganic silane compound and hydrogen is endothermic in the reactor used in this method, heat must be applied from the outside during the reaction, so a heating source is usually installed on the side of the fluidized bed reactor to heat it. It has become. Therefore, the temperature of the reactor wall is necessarily higher than that of the surface of the certain silicon particles in a fluidized state.

Therefore, as the reaction progresses, silicon is deposited on the surface of the seed silicon particles, and at the same time, silicon is also deposited on the inside of the wall of the reactor (hereinafter referred to as the outer wall), and the rate of silicon deposition per unit area is The outer wall of the reactor becomes larger than the surface of the seed silicon particles.As a result, as the reaction progresses, the thickness of the silicon layer deposited on the inside of the reactor outer wall increases, reducing the functionality of the fluidized bed reactor. However, the operation of the fluidized bed reactor must be periodically stopped to remove the silicon deposited on the inner surface of the outer wall, resulting in a decrease in productivity.

In addition, when quartz, silicon carbide, silicon nitride, etc. are used as the reactor material, there is a large difference between the coefficient of thermal expansion of the reactor material and the thermal expansion coefficient of the precipitated silicon. Another fatal drawback was that the reactor was damaged when the temperature was lowered.

The present invention is a fluidized bed reactor used for producing polycrystalline silicon from an inorganic silane compound that solves these drawbacks, and includes a porous inner wall provided inside the side outer wall of the fluidized bed reactor.
By configuring hydrogen gas to be supplied from small holes in the porous inner wall to the reaction section in the fluidized bed from the gap force between the outer wall and the inner wall, polycrystalline silicon does not adhere to the wall surface of the reactor. It is an object of the present invention to provide a high-purity polycrystalline silicon manufacturing apparatus that can prevent the above problems and can operate steadily and continuously for a long period of time.

That is, the present invention provides a fluidized bed reactor for producing polycrystalline silicon from an inorganic silane compound, in which a porous inner wall is provided inside the side outer wall of the reactor, and hydrogen gas is passed between the inner wall and the outer wall. It is characterized in that it is configured to have a passageway, and hydrogen gas is supplied from the passageway to the reaction section of the fluidized bed through small holes in the inner wall.

The present invention will be explained in detail below with reference to the drawings. The drawing is a cross-sectional view of a device according to an embodiment of the invention. The reactor 1 is provided with a heater 2 on its side, a seed silicon inlet 3 and a gas outlet 4 in its upper part, and a silicon outlet 5, a raw material gas inlet 6, and a hydrogen gas inlet 8 in its lower part.

In addition, the raw material gas is introduced into the reaction section through the raw material gas inlet 6 and the perforated plate 7, and the hydrogen gas is introduced from the hydrogen gas inlet 8 into the outer wall 9 and the porous inner wall of the reactor. Hydrogen gas is supplied to the reaction section 60 of the fluidized bed from small holes in the inner wall 10 of the porous material.

The reactor of the present invention is made of materials such as quartz, silicon nitride, silicon carbide, carbon stainless steel, Inconel, and No. 1 steroid, and the porous inner wall material can also be made of the same materials. The porous inner wall is preferably a screen formed from the above-mentioned material having fine mesh pores, but is not limited thereto.

Next, a method for producing polycrystalline silicon from an inorganic silane compound using the reactor of the present invention will be described. Reactor 1
Seed silicon with an average particle size of 50 to 1 DOOp is added to the reactor, the temperature inside the reactor is heated to 400 to 1200'C, and hydrogen gas, silicon tetrachloride, trichlorosilane, dichlorosilane,
A mixed gas with at least one type of inorganic silane compound selected from monochlorosilane, monosilane, etc. is introduced into the reactor 1 through a perforated plate 7 from a raw material gas inlet 6 provided at the bottom of the reactor 1.
to be introduced within. Further, hydrogen gas introduced from the hydrogen gas inlet 8) passes through a hydrogen gas passage between the outer wall 9 and the inner wall 10 of the reactor, and is introduced into the fluidized bed through small holes in the porous inner wall 10. Hydrogen introduced from the hydrogen gas passage does not clog the small pores in the inner wall.1 Under such conditions, for example, under pz pressure slightly higher than the pressure of the fluidized bed, hydrogen is introduced from the small pores in the porous inner wall into the fluidized bed. It is preferable to make it blow out.

As the reaction progresses and silicon precipitates and grows on top of the seed silicon, the heavier 91132 particles move downward in the fluidized bed and are continuously drained from the silicon outlet 5 provided at the bottom of the reactor. It will be collected.

Hydrogen chloride, silicon fine powder, unreacted gas, etc. produced as a result of the reaction are led out of the reactor through the exhaust port 4 at the top of the reactor and sent to the exhaust gas treatment system.

As explained above, the present invention provides a fluidized bed reactor for producing polycrystalline silicon from an inorganic silane compound, in which a porous inner wall is provided inside the side outer wall of the reactor, and hydrogen gas is passed between the inner wall and the outer wall. According to the present invention, there is provided a polycrystalline silicon production apparatus characterized in that the polycrystalline silicon manufacturing apparatus is configured such that hydrogen is supplied to a reaction section in a fluidized bed through small holes in an inner wall. Unlike a fluidized bed reactor, silicon does not adhere to the walls of the reactor, making long-term continuous operation possible and improving productivity.

In addition, since hydrogen gas can be introduced from the hydrogen gas passage in the reactor, the amount of hydrogen supplied can be sufficiently adjusted, making it possible to prevent sudden reactions from occurring.

EXAMPLES The present invention will be explained in more detail below with reference to Examples.

Inner diameter 11oI +++++1 height 1oo as shown in the example drawings
The inside diameter of the stainless steel fluidized bed reactor 1 is made of porous silicon carbide with many small holes of 7 μm.

A fluidized bed reactor 1 provided with a thick inner wall 1o was used.

A mixed gas containing 20 mol % of trichlorosilane and 80 mol % of hydrogen was supplied from the raw material gas inlet 6 at a rate of 8.4 l/min. Inject 2-8 liters of hydrogen gas from hydrogen gas inlet 8.
The hydrogen gas was supplied at a rate of 0.06 cmZSec to the fluidized bed through small holes in the porous inner wall 10 at a rate of 0.06 cmZSec.

Also, from the upper seed silicon inlet 4 of the fluidized bed reactor, particle size 2
00μ high purity polycrystalline silicon was supplied at a rate of 2 jj /hr. The fluidized bed was heated by the heater 2 on the side of the reactor, and the reaction temperature in the fluidized bed was set to 900°C and 300°C.
As a result of continuous operation for hours, polycrystalline silicon was obtained at an average rate of 22.9 g/hr.

When the fluidized bed reactor was dismantled after the operation was completed, no polycrystalline silicon was found to be attached to the inner or outer walls of the fluidized bed reactor.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of a device according to an embodiment of the invention. Attached amount 1... Fluidized bed reactor, 2... Heater, 3... Seed silicon inlet, 4... Gas outlet, 5... Silicon outlet, 6... Raw material gas introduction lower. ...eye plate,
8...Hydrogen gas inlet, 9...Outer wall of the reactor,
10... Porous inner wall.

Claims (1)

[Claims] In a fluidized bed reactor for producing polycrystalline silicon from an inorganic silane compound, a porous inner wall is provided inside the side outer wall of the reactor, and small pores in the inner wall are used as hydrogen gas passages between the inner wall and the outer wall. An apparatus for producing polycrystalline silicon, characterized in that it is configured to supply hydrogen to a reaction part in a fluidized bed through