SU950676A1 - Process for producing material from silicon dioxide - Google Patents

Description

D54) METHOD FOR PRODUCING ILTERILLA FROM SILICON DIOXIDE

This invention relates to the production of silica materials that can be used in the manufacture of quartz crucibles used in semiconductor manufacturing.

A known method for producing silicon dioxide blanks on a rotating and / or axially moving mandrel by high-temperature steam hydrolysis of volatile silicon halide in a flame of an oxygen-hydrogen burner fij.

When transporting the reaction gas mixture from the evaporator to the flame of the oxygen-hydrogen burner, the temperature of the mixture due to heat loss decreases. The condensation of liquid chlorides from the vapor-gas mixture on the inner surface takes place; - feed equipment. Because of this, the composition of the vapor-gas mixture entering the burner varies, which leads to a decrease in the silicon dioxide deposition rate and the density of the workpiece material.

The closest technical solution to the present invention is a method for obtaining a material from silicon dioxide by high-temperature steam hydrolysis of halides preheated to 50-275 ° C.

with oxygen in the stream of low-temperature reaction plasma1T1. The preheating of the reaction gas-vapor mixture is carried out with a high resistance heating tape,

However, in this process, the percentage recovery of silica from the reaction products is low. Because of this, the required rate of material acquisition is not provided. In addition, the density of the material obtained is insufficient to ensure high quality products, such as crucibles, obtained from the material after its further sintering.

The purpose of the invention is to increase the rate of precipitation of silica and increase the density of the material. ,

The goal is achieved by the fact that according to the method of obtaining a material from silicon dioxide by high-temperature steam hydrolysis of previously heated silicon halide compounds with oxygen in a low-temperature reaction stream

Plasma preheating of silicon halide compounds with oxygen is carried out up to 300-50 ° C.

The heating of the reaction gas-vapor 30 mixture of silicon halide compounds

with oxygen up to ZOO-ZOO C, the osuadest is a preliminary interaction of the components of the gas-vapor mixture with the formation of intermediate reaction products, resulting in high-temperature. Peroral hydrolysis occurs. The degree of conversion of the starting products to silicon dioxide increases.

It has been established experimentally that this increases the Cs rate of obtaining silica material on the mandrel. The density of the silica material also increases.

The obtained experimental data are given in the table.

When the reaction gas vapor mixture is preheated to a temperature below 300 ° C, the components of the mixture do not preliminarily interact, and the percentage of extraction of dioxide from the reaction products remains low, and the rate of production of the material is insufficient at the same time as low density.

When the reaction gas-vapor mixture is preheated to a temperature above. Before being fed into the burner, the material of the apparatus feeding the mixture is chlorinated. Due to the corrosion of the material, impurities, mainly iron and nickel, get into the reaction gas-vapor mixture and, therefore, contaminate the resulting material. This reduces the quality of products and is unacceptable for technical requirements.

As can be seen from the table, when the reaction gas vapor mixture is preheated below the rate. The precipitation of silicon dioxide and the percentage of its extraction from the reaction products remain low. With an increase in the preheating temperature, these indices improve, reaching the maximal values during the preliminary heating.

Example. A pair of silicon tetrachloride is fed from the vaporizer in the oxygen carrier gas stream. The temperature of the mixture at the outlet of the evaporator is 30 ° C. Then, the reaction gas-vapor mixture of silicon tetrachloride with oxygen is fed through channels laid in the zone of thermal radiation of the hydrogen plasma torch. In this case, the heating of the reaction gas-vapor mixture proceeds to temperatures of, respectively, .250, 300, 350, 400, 450, 500, For each test series. The mixture thus heated is fed into the combustion zone of a torch of a hydrogen plasma heater of a known type for carrying out high-temperature steam hydrolysis.

SiCl4 - 0, j + H, 2 -9 SiOa +

The temperature of the hydrolysis of 1100-1500 ° C, the consumption of silicon tetrachloride 3 kg / h and oxygen b kg / h for each series of tests was the same. The duration of the process for the preparation of the workpiece was kept constant for 2 hours.

Accordingly, each series of tests was obtained j seven batches of material. In each batch, the rate of precipitation of silicon dioxide, the percentage of extraction, the density and the content of iron in it are the main indicators determining the efficiency of the process and the quality of the product.

The data presented in the table.

Heat of the reaction gas mixture to 400-g500s. A further decrease in the rate of precipitation of silicon dioxide and the percentage of its extraction from the reaction products with an increase in the preheating temperature is due to the fact that side reactions begin to occur with the formation of radicals of chloride compounds -

silicon, which, interacting with one another, hinders decomposition with the formation of silicon dioxide.

The required values of the material density are achieved by preheating to ZOO-ZBO C. However, at preheating temperatures above 500 ° C, burner corrosion occurs and the content of iron impurities in the material exceeds the permissible value under technical conditions.

The use of the proposed method of obtaining material from silicon dioxide as compared to the known method provides an increase in the rate of silicon dioxide deposition on the mandrel and the density of the material obtained, due to the use in the method of a new temperature mode — preheating the reaction gas mixture to 300-500 ° C. The use of such a temperature regime provides an increase in the degree of hydrolysis of silicon tetrachloride by 20-25%. The deposition rate of silicon dioxide increases 1.3-1.9 times. Material density

increases by 15-29%, which significantly increases the quality of products obtained from blanks.

Claims (2)

1. The UK patent 989467, cl. C 1 A, 1965. 2. US patent number 3806570, cl. 264-66, 1974.