Metal treatment – Process of modifying or maintaining internal physical... – Chemical-heat removing or burning of metal
Patent
1974-09-19
1976-07-13
Rutledge, L. Dewayne
Metal treatment
Process of modifying or maintaining internal physical...
Chemical-heat removing or burning of metal
29572, 118 48, 136 89, 148175, 156613, 357 20, 357 30, 357 59, 357 65, 427 86, 427113, 427248, H01L 21205, H01L 2184, H01L 3100
Patent
active
039691632
ABSTRACT:
The disclosure relates to a method of upgrading metallurgical grade silicon to semiconductor grade for making low cost silicon devices and particularly solar cells. This is accomplished by passing conductive fibers such as graphite or the like which are compatible with the later processing steps through an area which is cooled below 700.degree. C and which contains silicon difluoride and a proper N-type dopant. At these temperatures, the silicon difluoride gas will break down into pure silicon which will deposit onto the fiber with the formation of silicon tetrafluoride gas which is then recycled into a further chamber. In the further chamber, the gaseous silicon tetrafluoride is mixed with the impure metallurgical grade silicon at temperatures above 700.degree. C to form the silicon difluoride gas which is then fed into the former chamber for deposition of pure silicon onto the continuously moving fibers of graphite or the like. A p-type layer can then be formed over the n-type layer in any standard manner, such as by then passing the coated fibers through a further reaction chamber wherein p-type dopant is diffused into the top surface of the n-type layer that has been formed. The dopants alternatively could be added in the gas stream of SiF.sub.4 or the p-layer formed by ion implantation. In this way, relatively inexpensive p-n junction devices are formed without the requirement of purifying, cutting and polishing a silicon slice in the standard manner.
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Comfort James T.
Honeycutt Gary C.
Levine Harold
Rutledge L. Dewayne
Saba W. G.
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