The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 29, 1980
Filed:
Jul. 18, 1978
H Ming Liaw, Scottsdale, AZ (US);
Charles J Varker, Scottsdale, AZ (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A combined method for purifying silicon and growing single crystals. A multiple step process is disclosed by which metallurgical grade silicon is purified and converted into a high quality monocrystalline silicon ingot. Each of the steps in the process is designed to remove specific impurities and thus improve the electrical quality of the silicon material. First, the insoluble slag and high segregation coefficient impurities are removed. Soluble impurities are then removed by a reactive gas step, and by a liquid-liquid extraction step using reactive metallic oxides or an oxide solvent. The remaining impurities are removed by segregation during freezing by pulling an ingot from a portion of the molten metallurgical grade silicon. The ingot so formed is then used to charge a second crystal puller. One or more of the previous purifying steps can then be repeated for the charge of the second crystal puller and an ingot of improved purity can be pulled from the melt of the second puller. In like manner, third and successive reiterations of the process can be used to obtain silicon of the desired purity and crystal quality.