Low-Cost Solar-Array Project. Quarterly progress report, April-June 1980

The overall objective of the LSA Silicon Material Task is to establish a chemical process for producing silicon at a rate and price commensurate with the production goals of the LSA project for solar-cell modules. As part of the overall Silicon Material Task, Union Carbide developed the silane-silicon process and advanced the technology to the point where it has a definite potential for providing high-purity polysilicon on a commercial scale at a price of $14/kg by 1986 (1980 dollars). This work, completed under Phases I and II of the contract, provided a firm base for the Phase III Program (initiated in April 1979) aimed at establishing the practicality of the process by pursuing the following specific objectives: (1) design, fabricate, install, and operate an Experimental Process System Development Unit (EPSDU) sized for 100 MT/yr to obtain extensive performance data to establish the data base for the design of commercial facilities; (2) perform support research and development to provide an information base usable for the EPSDU and for technological design and economic analysis for potential scale-up of the process; and (3) perform iterative economic analyses of the estimated product cost for the production of semiconductor-grade silicon in a facility capable of producing 1000 MT/yr. This process for preparing semiconductor-grade silicon in the EPSDU from metallurgical-grade (M-G) silicon is based on a well-integrated arrangement of purification steps that provides a cost-effective process system. The three basic steps entail converting M-G silicon to trichlorosilane, redistributing the trichlorosilane to produce silane, and thermally decomposing the silane to form amorphous silicon powder. The powder is then melted and the molten silicon is cast to polycrystalline for subsequent use in fabricating solar cells. Progress is reported in detail. (WHK