A method and an apparatus for transferring elemental carbon impurities present in a silicon rod to an end of the rod

摘要

1,148,706. Treating silicon. SIEMENS A.G. 11 March, 1968 [11 March, 1967], No. 11832/68. Heading B1S A rod of silicon containing elemental carbon is zone-melted in a continuously evacuated chamber, carbon-containing compounds being continuously removed from the gas being withdrawn from the chamber. The carbon is thereby concentrated in one end of the rod and the carbon content of the main portion of the rod may be reduced from 38 to 11 pmm. Gas withdrawn from a chamber 2 may be passed over a condensing baffle 14 and through a diffusion pump 3, absorption trap 17 and a further pump 5. Alternatively (Fig. 2), the withdrawn gas may be passed through a gettering pump (21), using liquid titanium, and absorption pump (22), and a final pump. Movement within the chamber is effected by means of shafts passing through bushings 11- 13 lubricated with silicone grease, molybdenum disulphide, tungsten diselenide, or graphite.