SU1597341A1 - Method of separating trichlorosilane and silicon tetrachloride from mixture of chlorosilanes - Google Patents

Abstract

The invention relates to methods for separating trichlorosilane and silicon tetrachloride from a mixture of chlorosilanes, can be used in the manufacture of semiconductor silicon, and can improve the purity of products and their yield. The mixture of chlorosilanes is subjected to a three-stage rectification with feeding into the cube of the column of the second stage water vapor at 40-106 ° C to form oxygenated silanes in an amount that provides a mass ratio in the cube of the second stage trichlorosilane: oxygen-containing silanes, equal to (12.2-20): 1. The formed oxygen-containing silanes are simultaneously sent to the separation of polysilane chlorides and to the third stage of the rectification of a mixture of chlorosilanes with a mass ratio (98-75): 1, respectively. The bottoms product together with oxygenated silanes purified from polysilane chlorides is sent to the first stage of a two-stage rectification for separation of SICL ₄ at a weight ratio of (5-16): 1, respectively. At the same time, in the first stage of the rectification of a mixture of chlorosilanes, an additional distillate is used, separated from the reflux condenser at a weight ratio (10-19): 1, respectively. 1 ill., 1 tab.

Description

The invention relates to methods for separating trichlorosilane and silicon tetrachloride from a mixture of chlorosilanes and can be used in the manufacture of semiconductor silicon.

The purpose of the invention is to increase the purity of the products, as well as increase the productivity of the process.

Example. The initial mixture of chlorosilanes (82 wt.% CXCl3, 0.2 wt.% Polysilane chlorides (PSC), the rest is SiCl) is subjected to rectification in three stages. In the first stage in the column with 6 sieve plates 01200 mm, the initial mixture is fed to the upper part

columns. Chlorosilanes containing oxygen-containing silanes are also fed there from the first stage of the cycle for the isolation and purification of silicon tetrachloride at a mass ratio of 10: 1, respectively.

. From the cube of the column of the first stage, the vapor phase is taken, it is condensed in a refrigerator located at the upper mark, and a stream of liquid chlorosilanes containing trichloro silane (TCS) from the refrigerator is fed to the second stage of rectification into the cube of the column. In the second stage, two parallel working columns with b plates, p 600 mm, are used.

cl

with

with

Into the cubes of the column a stream of inert ase is also supplied; water vapor at the temperature of the vapor phase in the contact zone of lorsilanes and water vapor 106 C, in an oxygen-like manner, forms oxygen-containing chlorosilanes.

The mass ratio of trichlorosylan:: oxygen-containing silanes support in a cube equal to 20: 1,

From the bottom of the column of the second stage, the liquid phase containing oxygen-containing chlorosilanes is taken and fed in the amount of 230-600 kg / h to the column

J 600 mm with 6 plates for polysilane chloride cleaning step j.

The distillate from the reflux condenser of the 2nd stage distillation of chlorosilanes, also containing oxygen-containing chlorosilanes, is fed into the lower part of the third stage of the distillation in an amount that provides the mass ratio of oxygen-containing silanes sent to the purification stage and the third stage of the rectification, equal to 25

75: 1.

In the third stage, in a 1200 mm column with 64 plates, the selection of a ready-made, trichlorosilane product from a reflux condenser is 1950 kg / h. Q

The bottoms residue of the 3rd stage of rectification of the mixture of chlorosilanes is fed to the upper part of the 1st stage of the column 2-stage distillation together with the distillate of the column of the separation of polysilane chlorides containing oxygen-35 silanes, with a weight ratio of bottoms: oxygen-containing silanes equal to 16: one. The column of the 1st stage of the selection of silicon tetrachloride has 01200 mm-with 64 plates. From the cube of this column, the product is fed to the neutralization stage, and from the reflux condenser to the 1st stage of removal of trichlorosilane in the amount of 80-150 kg / h together with the initial mixture of chlorosilanes.

The vapor phase from the bottom of the column of the first stage of separation and purification of silicon tetrachloride (TK) is directed to a condenser located at the upper mark, where the vapors condense, and the condensate is directed to the lower part of the second column 01200 mm

40

With b plates for the isolation and purification of silicon tetrachloride. The bottom of the column is supplied to the polysilane chloride neutralization stage, and

.55

Q

Q 5

Q

35 -

40

55

pure silicon tetrachloride is taken from the reflux condenser.

The obtained target product - trichlorosilane contains not more than 0.1 wt. other chlorosilanes and not more than 2

x10 in wt.% boron. The maximum amount of trichlorosilane produced is 1970 kg / h. Silicon tetrachloride, resulting from a two-stage isolation and purification, contains not more than 0.01 wt. other chlorosilanes (trichlorosilane and polysilane chlorides in total).

The results of the other experiments and known data are presented in the table.

To assess the quality of the TCS obtained, the proportion of polycrystals with a resistance of more than 500 from donors grown from a certain amount of trichlorosilane is determined from the phosphorus content.

one

Thus, the proposed method allows to increase the yield of products and its purity according to B, A1. and R.

Claims (1)

Invention Formula The method of separation of trichlorosilane and silicon tetrachloride from a mixture of chlorosilanes, including a three-stage rectification of this mixture, contacting the hydrogen-containing reagent with the second stage bottom residue containing trichlorosylan, separation of trichlorosilane from the third-column reflux condenser, separation of the tetrachloride silicon from the bottom residue; in order to increase the purity of the products and the productivity of the process, the extraction of silicon tetrachloride is carried out by two-stage distillation of the bottom the third stage of the rectification of the mixture of chlorosilanes, and water vapor is used as the hydrogen-containing reagent, the contact is carried out at 40-1Ob C to form oxygen-containing silanes in an amount that ensures the cubic mass ratio of trichlorosilane: oxygen-containing silanes equal to (10-20) : 1, then the resulting oxygen-containing silanes are sent simultaneously to the separation of the polysilane chlorides and to the third stage of the rectification of a mixture of chlorosilanes with mass 51 the ratio (98-75): 1, respectively, after the separation of the polysilane chlorides, oxygen-containing silanes were sent to the first stage of the two-stage rectification in an amount that ensures the mass ratio of the bottom residue of the third rectification stage: oxygen containing silanes, equal to. (5-T57: 1, and at the first stage of rectification of chlorosilanes an additional dis- tyl is taken, separated from the reflux condenser of the column of the first stage of two-stage rectification at a mass ratio of (10-19): respectively. eight Table continuation Worse than in the known method. It is not allowed by TU i 8-it-l80-77 (content B 2-3-10 May .%)