JPS58213624A - Preparation of high purity silicon - Google Patents

Abstract

PURPOSE:To prepare high purity silicon, in high efficiency, preventing the deposition of silicon to the inner wall of the reaction tube of a fluidized bed apparatus, by ionizing and charging high purity silicon particles, and contacting with a silicon- containing gas to precipitate silicon. CONSTITUTION:A gaseous mixture of trichlorosilane and hydrogen at a molar ratio of 1:1 is introduced through the feed line 4 to the reaction tube 1. Silicon seed particles 8 are introduced through the line 3 into the ionization chamber 5, electrically charged by the exposure to arc discharge generated by the DC source 6, and introduced into the reaction tube 1. The reaction tube 1 is heated at about 1,000 deg.C by the electrical furnace 7, and the silicon seed particle 8 is grown during the descending motion in the tube 1. Since the temperature of the reaction tube is relatively low, the deposition of silicon to the inner wall 2 of the reaction tube can be suppressed, and since the seed particle is activated by arc discharge, a sufficiently high rate of reaction and uniform silicon particles can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high purity silicon by depositing silicon on silicon particles using a fluidized bed method.

With the rapid development of semiconductor devices, the demand for semiconductor-grade single crystal silicon is increasing. Conventionally, single-crystal silicon has been manufactured using the Czochralski method, but the increasing demand for single-crystal silicon has led to a shortage of supply or an increase in the price of polycrystalline silicon, which is its raw material. especially,
In the case of solar cells, silicon raw materials account for a high proportion of the cost, and there is a strong need for technological development to reduce costs.

Conventionally, polycrystalline silicon has been produced by depositing it on a silicon rod through a hydrogen reduction reaction of tetrasilane gas. In this method, trichlorosilane or dichlorosilane is reduced with hydrogen, and silicon is deposited on a silicon rod heated by electricity. The silicon rod is heated to about 1100~1200 by resistance heating.
The quartz glass bell jar type reaction vessel is kept at about 300C to prevent silicon from depositing on its inner wall. However, this method has the disadvantage that the deposition area is small, so the amount of silicon deposited per hour is small, and the energy consumption required for production is large.

In order to overcome these drawbacks of the current technology, methods have been proposed in which silicon is deposited on fluidized fine silicon particles having a substantially large deposition area. However, in this fluidized bed method, while the silicon particles are flowing down the reaction vessel,
This method utilizes a reaction in which silicon is deposited on the surface of particles, and a large portion of the reaction gas was discarded unreacted as waste gas. Furthermore, since the reaction tube wall also has the same reactivity as silicon particles, silicon precipitates on the reaction tube inner wall, which not only cannot be recovered but also causes the container to break.

The purpose of the present invention is to overcome the drawbacks of the fluidized bed method and to propose a method with higher precipitation efficiency.

This problem can be solved by improving the reactivity of the silicon particles with the reactive gas and by preventing the particles from increasing in size due to contact with each other.

For this purpose, the particles are ionized and reacted in an active state before being brought into contact with the reaction gas trichlorosilane or dichlorosilane. Silicon particles have either a positive or negative charge, which increases their reactivity with the reactive gas, and the particles repel each other, making it difficult for them to come into contact with each other, making it difficult to achieve uniform silicon growth on the particles. Ta.

EXAMPLE A mixed gas consisting of trichlorosilane and hydrogen in a molar ratio of 1:1 is fed through the supply pipe 4 and enters the reaction tube 1. The flow rate of the mixed gas was 50 t/min. Silicon seed particles 8 having a size of 0.1 to 0.5 particles were introduced through the supply pipe 3. Silicon seed particles 8 are introduced into the ionization chamber 5 before entering the reaction tube 1. Here, arc discharge was performed using the DC power supply 6 to charge the silicon seed particles 8, which were then introduced into the reaction tube 1. The reaction tube 1 was heated to xoooc by an electric furnace 7, and the silicon seed particles 8 grew while descending therein. Since the reaction tube temperature was relatively low, there was little silicon precipitation on the reaction tube inner wall 2, and the seed particles were activated by arc discharge, a sufficient reaction rate was obtained. As a result, silicon particles of 4Kf could be formed in a continuous reaction for 20 hours.

Note that the discharge method of the present invention is not limited to arc discharge, and similar effects were obtained with corona discharge or glow discharge under low pressure.

[Brief explanation of drawings]

The figure is a longitudinal sectional view of an apparatus implementing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Reaction tube, 2... Reaction tube inner wall, 3... Silicon particle supply pipe, 4... Reaction gas supply pipe, 5... Ionization chamber, ゛''1≦2;1 Plaster knee 1α 1, C9) Connaught 4: -1 ↑ H5jXs+H1 -

Claims (1)

[Claims] 1. In a high-purity silicon production method in which silicon is deposited from a silicon-containing gas on high-purity silicon particles using a fluidized bed reactor, the high-purity silicon particles are ionized, charged, and brought into contact with the silicon-containing gas. A method for producing high-purity silicon, characterized by precipitating silicon.