Patent GB-960893-A (GB)
Title: The production of semiconductor elements and the purification of wholly or partially halogenated hydrides of such elements
IPC: C30B25/08
Filed: 1961-06-21
Abstract: <PICT:0960893/C1/1> A semi-conductor element, e.g. Si, is made by decomposing thermally or by electric discharge a wholly or partially halogenated hydride of the semi-conductor element in the gaseous state by adding to the liquid halogen compound, e.g. SiCl4, SiHCl3, an hydrolysable halogen compound of Ti or Al which hydrolyses more readily than the halogen compound and is soluble therein, the Ti or Al halide is hydrolysed to the hydrated metal oxide together with optionally some of the halogen compound, the halogen compound is evaporated and the gas passed over a carrier of the element, and the halogen compound is decomposed thermally or by electric discharge to deposit the semi-conductor element on the surface of the carrier. The hydrolysable halogen compound of Ti or Al may be AlBr3, TiCl4, or AlCl3. The decompositio may be carried out at a temperature not more than 200 DEG  C. above the m.p. of the Si. The liquid mixture, e.g. containing 10 mol. per cent TiCl4 or AlBr3, may be contacted, e.g. for 10 minutes, with a stream of moist inert gas and any solid matter formed, e.g. including AlBr3. POCl3, TiCl4. PCl3, TiCl4. SCl4 or Li AlBr4, separated, e.g. by decanting, and the liquid added at a dilution of 1 in 1000-10,000 to further liquid halogenide as a source of the metal compound. In an example a Si halide is purified by mixing with 10-2-10-1 mol. per cent TiCl4 or AlBr3, moist compressed air, N2 or H2 is passed through the liquid for 10 minutes through a porous disc of glass or quartz, the hydrated oxide is allowed to settle and the purified Si halide is separated, e.g. by decanting, and/or evaporated for use in the production of a semi-conductor. Apparatus of quartz or glass consists of reaction vessel 1 with carrier 2 between electrodes 3 and 31 of C coated with Si. A D.C. source 4 passes current through 2 via an adjustable resistor 5. SiHCl3 is fed to evaporation vessel 7 from storage 9. TiCl4 or AlBr3 is placed in 7, in constant temperature bath 7a, dissolved in the SiHCl3 and hydrolized by passing moist H2 via pipe 10 to perforated plate 11.  Carrier 1 is heated and fed with dry H2, from part 12, which is also fed via pipe 8 to 7 and via pipe 6 to 1 where Si is deposited on 2. The deposition is interrupted to feed more Si HCl3 to 7 and hydrolysis is repeated by adding further metal halide and passing more moist H2 through pipe 10. An electric discharge may be used to deposit Si on the ends of the electrodes which are gradually drawn apart.  The Si rods produced may be molten zone refined, four times, without a crucible and in a vacuum.ALSO:A semi-conductor element, e.g. Ge, is made by decomposing thermally or by electric discharge a wholly or partially halogenated hydride of the semi-conductor element in the gaseous state by adding to the liquid halogen compound, a hydrolysable halogen compound of Ti or Al which hydrolyses more readily than the halogen compound and is soluble therein, the Ti or Al halide is hydrolysed to the hydrated metal oxide together with optionally some of the halogen compound, the halogen compound is evaporated and the gas passed over a carrier of the element, and the halogen compound is decomposed thermally or by electric discharge to deposit the semi-conductor element on the surface of the carrier. The hydrolysable halogen compound of Ti or Al may be AlBr3, TiCl4 or AlCl3.  The decompositio may be carried out at a temperature not more than 200  DEG C. above the melting point of the Ge.ALSO:A molten zone is passed four times in a vacuum and without a crucible through a rod of silicon having a specific resistance of 1,000 ohm.cm. to produce a product having a specific resistance of 2,000-4,000 ohm.cm. and a carrier life of 400-600 m sec.