Establishment of the feasibility of a process capable of low cost, high volume production of silane (Phase I), and the pyrolysis of silane to semiconductor-grade silicon (Phase II). Low Cost Silicon Solar Array Project, Task I. Quarterly progress report, April--June 1977

The purpose of this program is to establish the practicality of a process for the high volume, low cost production of silane and its subsequent pyrolysis into a semi-conductive grade silicon metal. A small process develop unit for producing silane from dichlorosilane (DCS) using a tertiary amine functional ion exchange resin as a catalyst for a redistribution reaction has been operated successfully on what is now a routine basis. High quality silane has been produced in good yield and limiting equipment size has been identified. The silane gas product is essentially free of foreign compounds (to 5 ppM detection limit) and produces a silicon epitaxial film with a resistivity of 20 ohm cm and very strong ''N'' type character. Epi film quality was very good. The overall yield of silane was 92% of theory. The production rate, limited by the 2.66 cm diameter distillation column, was 112 g/hr. Design of a silicon tetrachloride (STC) hydrogenation reactor used to convert co-product STC to trichlorosilane has been completed and fabrication and installation are underway, as is a modification of the silane unit to permit use of trichlorosilane as feed, producing STC and silane. The production of silicon by the pyrolysis of silane is currently being accomplished in a free space reactor. The free space reactor product is a very fine powder which is then consolidated by melting. The melt is cast into rods. Analysis of the product from earlier experiments indicated that metal or graphite liners in the reaction chamber region resulted in product contamination. A quartz liner is currently being evaluated in the reaction chamber. Other identified contamination sources are air borne particles and contamination during melting and/or casting.