Method of purifying metallurgical grade silicon employing reduced presure atmospheric control

US4172883A · kind A · utility

Inventors

• Robert A. Administrator of the National Aeronautics and Space Frosch · La Cañada Flintridge, US
• William M. Ingle · Phoenix, US
• Stephen W. Thompson · Oneida, US
• Robert E. Chaney · Scottsdale, US

Key dates

• Filing date: Jun 23, 1978
• Grant date: Oct 30, 1979
• Expiry date: Jun 23, 1998

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01B33/037
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A method wherein a quartz tube is charged with chunks of metallurgical grade silicon and/or a mixture of such chunks and high purity quartz sand, and impurities from a class including aluminum, boron, and the like, as well as certain transition metals including nickel, iron, manganese and the like. The tube is then evacuated and heated to a temperature within a range of 800.degree. C. to 1400.degree. C., whereupon a stream of gas comprising a reactant, such as silicon tetrafluoride, continuously is delivered at low pressures through the charge for causing a metathetical reaction of impurities of the silicon and the reactant to occur for forming a volatile halide and leaving a residue of silicon of an improved purity. Additionally, the reactant may include carbon monoxide gas, whereby impurites such as iron and nickel react therewith to form volatile carbonyls.