Patent GB-809250-A (GB)
Title: Improvements in or relating to processes and apparatus for the production of ultra-pure substances
IPC: C22B41/00
Filed: 1955-05-17
Abstract: High purity silicon or other semi-conductor substance such as gallium phosphide or gallium nitride is produced by decomposition or reduction of a gaseous compound of the substance or gaseous compounds of the components of the substance and deposition along the length of a carrier body formed of the substance or of a component thereof, the carrier body being heated by an electric current flowing through it. The body produced may be subjected to heat treatment, e.g. by heating to incandescence or by zone-melting, to homogenize it or to convert it into a mono-crystal.  Donor or acceptor impurities may be added during the deposition and distributed as required by a zone-melting process.  The initial carrier body, which may be in the form of rod, wire or strip, is supported at its ends by supports to which it may be secured by clamping, welding, soldering or sinerting. Additional heat may be supplied by high-frequency induction or by radiation and the carrier body may be rotated about its longitudinal axis while the deposition is in progress.  Heating of the carrier should be controlled during deposition to maintain a constant surface temperature.  The production of silicon by reduction of silicochloroform with hydrogen is referred to.  The starting material, e.g. a halide of the substance, is preferably subjected to a purification process prior to decomposition.  For this purpose the halide may be heated to a temperature just below, or even just above, its decomposition temperature or reduction temperature for such a time that impurity compounds are decomposed with only minor decomposition of the halide itself.  The halide may be passed in contact with purifying agents to effect removal of impurities, e.g. silicochloroform may pass over heated silicon grains or rods. Organic impurities may be removed by oxidation using oxygen or an oxygen-containing gas.  Partial hydrolysis may also be used, impurities being eliminated by addition of small quantities of water, e.g. as hydrates such as calcium chloride or filter paper or cellulose powder saturated with steam.  The products of hydrolysis may be separated by decanting or filtration.  Specification 795,191 is referred to.ALSO:High purity germanium or other semi-conductor substance is produced by decomposition or reduction of a gaseous compound of the substance and precipitation of the substance along the length of a carrier body formed of the said substance, the carrier body being heated by an electric current flowing through it. The carrier body is preferably of at least the purity required of the product.  Semi-conductor alloys of the 3rd and 5th or 2nd and 6th or 1st and 7th Groups of the Periodic system may also be prepared by simultaneous or successive deposition from corresponding compounds or from a coupler compound containing both constituents on to a carrier containing one or more of the components of the alloy.  Reference is also made to the production of silicon-germanium alloys.  The body produced may be subjected to heat treatment, e.g. by heating to incandescence or by a zone-melting process, to homogenize it or to convert it into a mono-crystal.  Donor or acceptor impurities may be added during the deposition and distributed as required by a zone-melting process.  The initial carrier body, which may be in the form of a rod, wire or strip, is supported at its ends by supports to which may be secured by welding, soldering, sintering or clamping. Additional heat may be supplied by high frequency induction or by p radiation and the carrier may be rotated about its longitudinal axis while the deposition is in progress.  Heating of the carrier should be controlled during the deposition to maintain a constant surface temperature.  Specification 795,191 is referred to.