Production of elemental silicon from impure silane feed

Details Production of elemental silicon from impure silane feed Production of elemental silicon from impure silane feed

C - Chemistry, Metallurgy

01

B

23/326, 23/389

C01B 33/02 (2006.01) B01D 53/02 (2006.01) C01B 33/029 (2006.01) C01B 33/04 (2006.01)

Patent

CA 1195478

-1- Abstract Elemental silicon is produced by a process and apparatus wherein relatively impure silane (SiH4) is purified in the gaseous state, while mixed with an inert carrier gas, to an impurity content no higher than that of "electronic grade" silicon, then is thermally decomposed to form elemental silicon of electronic grade purity, without need for purifica- tion of the elemental silicon itself. The purifi- cation is carried out by injecting the impure silane gas as a series of timed, spaced pulses into a carrier gas stream which transports the silane pulses to a gas chromatographic column, through which the pulses flow in sequence. The components of each pulse are differentially retarded by the packing so that they move through the column at different rates, as a result of which they exit at different but precisely spaced time intervals in relation to pulse input time. The emergence from the column of the silane "peak" or portion of the respective pulse is detected individually or is timed from the pulse input. When detected or timed, the eluent silane peak and admixed carrier gas are valved to a receiver separately from the other components, which exit before and after that peak. The silane gas fraction of the peak is then thermally decomposed, to form elemental silicon which is of electronic purity, or it may be -2- collected and pressurized before thermal decomposition. The admixed carrier gas is not decomposed, remains a gas, and thereby is separated from the silicon. Depending on the extent to which the gas purification is carried, the product silicon may have a measured resistivity of about 1500 ohms cm. or better, and can be used in fabrication of solar cells or semiconductor devices without further purification.

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