| 摘要 |
In the deposition of silicon from a gaseous or vaporous compound thereof on to an electrically heated body thereof, the compound is initially brought into contact with the body under such conditions that erosion instead of deposition is effected so as to purify the surface of the body. Similar conditions may be used to interrupt deposition so as to remove an undesirable polycrystalline deposit from a monocrystalline body and/or at the end of deposition to purify the surface of the final deposit. The axis of a body in the form of a silicon rod is preferably the (111) crystal axis. In the deposition of silicon from a mixture of silicon tetrachloride and hydrogen, relationships between the ratio SiCl4/H2 and temperature for deposition and erosion are given <PICT:0914042/III/1> in Fig. 2 (not shown). Similar conditions apply using a mixture of silicochloroform and hydrogen except that the minimum ratio of silicon compound to hydrogen for erosion is about 0,5 instead of about 0,3 and hydrogen chloride is preferably present in addition to hydrogen. The hydrogen chloride may be produced by the addition of steam. As shown, metered streams of hydrogen from line 22 and a mixture of hydrogen and silicon tetrachloride from line 21 are mixed in a line 23 and then injected into a glass or quartz vessel 13 surrounded by a reflector 38 and containing a pair of silicon rods 28 and 29 connected by a current-conducting bridge 30 of silicon, carbon, or graphite and having terminals 26 and 27 respectively of carbon or graphite pressed into silver in a hollow water-cooled silver base 24, terminal 27 being insulated from the base 24. The bridge 30 is freely slidable on at least one of the rods. Alternating current of adjustable strength is passed through the rods. The rods may be initially heated by means of two resistance heating elements 40. Specifications 853,729 and 861,135 are referred to. |
