Process for preparation of polycrystalline silicon

• US 7,033,561 B2
• Filed: 05/23/2002
• Issued: 04/25/2006
• Est. Priority Date: 06/08/2001
• Status: Expired due to Term

• Current Assignee: Dow, Inc.
• Original Assignee: Dow, Inc.
• Inventors: Zalar, Michael Matthew, McQuiston, Todd Michael, Kendig, James Edward, Landis, David Russell
• Primary Examiner(s): Johnson, Edward M.
• Application Number:
  US10/472,683
• Publication Number:
  US 20040131528A1
• Time in Patent Office: 1,433 Days
• Field of Search: 423/342, 423/341, 423/343, 423/347, 423/349
• US Class Current: 423/349
• CPC Class Codes: C01B 33/03 by decomposition of silicon halides or halosilanes or reduction thereof with hydrogen as the only reducing agent
• CPC Class Codes: C01B 33/035 by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
• CPC Class Codes: C01B 33/04 Hydrides of silicon
• CPC Class Codes: C01B 33/1071 Tetrachloride, trichlorosilane or silicochloroform, dichlorosilane, monochlorosilane or mixtures thereof

Abstract

A process for preparing polycrystalline silicon comprising the steps of (A) reacting trichlorosilane with hydrogen thereby forming silicon and an effluent mixture comprising tetrachlorosilane and disilane described by formula HnCl6—nSi2 where n is a value of 0 to 6 and (B) co-feeding the effluent mixture and hydrogen to a reactor at a temperature within a range of about 600° C. to 1200° C. thereby effecting hydrogenation of the tetrachlorosilane and conversion of the disilane to monosilanes.

Claims

1. A process for preparing polycrystalline silicon comprising the steps of

(A) reacting trichlorosilane with hydrogen thereby forming silicon and an effluent mixture comprising tetrachlorosilane and disilane described by formula H_nCl_6-nSi₂ where n is a value of 0 to 6 and

(B) co-feeding the effluent mixture, hydrogen, and HCl to a reactor at a temperature of abut 400°

C. to about 600°

C. and at a pressure of about 100 to about 600 psig thereby effecting hydrogenation of the tetrachlorosilane to trichlorosilane and conversion of the disilane to monosilanes.

2. A process according to claim 1 further comprising (C) recovering trichlorosilane formed in step (B) and recycling to step (A).

3. A process for preparing polycrystalline silicon comprising the steps of

(A) depositing silicon on a heated element by the reaction of trichlorosilane with hydrogen thereby forming an effluent mixture comprising trichlorosilane, tetrachlorosilane, disilane described by formula H_nCl_6-nSi₂ where n is a value of 0 to 6, and particulate silicon,

(B) separating the effluent mixture into a fraction comprising trichlorosilane and a high-boiling fraction comprising the tetrachlorosilane, disilane, and particulate silicon, where the trichlorosilane is recycled to step (A),

(C) removing the particulate silicon from the high-boiling fraction,

(D) co-feeding the high-boiling fraction from step (C), hydrogen, and HCl to a reactor at a temperature of about 400°

C. to about 600°

C. and a pressure of about 100 to about 600 psig thereby effecting hydrogenation of the tetrachlorosilane to trichlorosilane and conversion of the disilane to monosilanes, and

(E) recovering trichlorosilane formed in step (D) and recycling to step (A).

4. A process for preparing polycrystalline silicon comprising the steps of

(A) reacting trichlorosilane with hydrogen thereby forming silicon and an effluent mixture comprising tetrachlorosilane and disilane described by formula H_nCl_6-nSi₂ where n is a value of 0 to 6 and

(B) co-feeding the effluent mixture and hydrogen to a reactor at a temperature within a rage of about 600°

C. to 1200°

C. thereby effecting hydrogenation of the tetrachlorosilane to trichlorosilane and conversion of the disilane to monosilanes.

5. A process according to claim 4 further comprising (C) recovering trichlorosilane formed in step (B) and recycling to step (A).

6. A process according to claim 4, were the disilane is a mixture of hexachlorodisilane, pentachlorodisilane, and tetrachlorodisilane.

7. A process according to claim 4, where the effluent mixture of step (A) is processed through one or more separation steps to isolate a mixture comprising primarily tetrachlorosilane and disilane prior to the conduct of step (B).

8. A process according to claim 4, where the effluent mixture fed to step (B) comprises greater than about 90 mol % tetrachlorosilane and 0.01 to about 10 mol % disilane.

9. A process according to claim 4, where the effluent mixture fed to step (B) comprises greater than 90 mol % tetrachlorosilane and about 0.01 to about 1 mol % disilane.

10. A process according to claim 4, where the reactor temperature in step (B) is about 900°

C. to 1100°

C. and the molar ratio of tetrachlorosilane to H₂ is within a range of 1;

1.5 to 1;

15.

11. A process for preparing polycrystalline silicon comprising the steps of

(A) depositing silicon on a heated element by the reaction of trichlorosilane with hydrogen thereby forming an effluent mixture comprising trichlorosilane, tetrachlorosilane, disilane described by formula H_nCl_6-nSi₂ where n is a value of 0 to 6, and particulate silicon,

(B) separating the effluent mixture into a fraction comprising trichlorosilane and a high-boiling fraction comprising the tetrachlorosilane, disilane, and particulate silicon, where the trichlorosilane is recycled to step (A),

(C) removing the particulate silicon from the high-boiling fraction,

(D) co-feeding the high-boiling fraction from step (C) and hydrogen to a reactor at a temperature within a range of about 600°

C. to 1200°

C. thereby effecting hydrogenation of the tetrachlorosilane to trichlorosilane and conversion of the disilane to monosilanes, and

(E) recovering trichlorosilane formed in step (D) and recycling to step (A).

12. A process according to claim 11, were the disilane is a mixture of hexachlorodisilane, pentachlorodisilane, and tetrachlorodisilane.

13. A process according to claim 11, where the effluent mixture fed to step (B) comprises greater than about 90 mol % tetrachlorosilane and 0.01 to about 10 mol % disilane.

14. A process according to claim 11, where the effluent mixture fed to step (B) comprises greater than about 90 mol % tetrachlorosilane and 0.01 to about 1 mol % disilane.

15. A process according to claim 11, where the reactor temperature in step (B) is about 900°

C. to 1100°

C. and the molar ratio of tetrachlorosilane to H₂ is within a range of 1;

1.5 to 1;

15.

16. A process for preparing chlorosilanes comprising co-feeding a mixture comprising tetrachlorosilane, disilane described by formula H_nCl_6-nSi₂ where n is a value of 0 to 6, and hydrogen to a reactor at a temperature within a range of about 600°

C. to 1200°

C. to effect hydrogenation of the tetrachlorosilane and conversion of the disilane to monosilanes.