GB1321204A - Production of semiconductor monocrystals - Google Patents

Abstract

1321204 Zone melting SIEMENS AG 10 Jan 1972 [25 Feb 1971] 1032/72 Heading B1S A semiconductor monocrystalline rod of diameter more than 25 mms is made by non- crucible zone melting of a rod of semiconductor material supported vertically and melted by a single-winding induction coil with an earthed centre tap in an argon atmosphere slightly above atmospheric pressure by (1) melting a seed crystal of considerably smaller diameter than the rod onto one end of the rod, (ii) reducing the cross-sectional area of the rod at its junction by periodically moving the ends of the rod away from each other at a speed of at most 30 mm/min whilst rotating the rod at a rotational speed of 10-40 r.p.m. and (iii) increasing the diameter of the rod from the molten zone by laterally displacing the rod relative to the heating coil by 1/10 to 1/12 of the diameter of the starting rod. As shown, in container 1, a molten zone 4 is produced by coil 3, in a silicon rod mounted vertically between supports 8 and 9 which are driven by shafts 12 and 13 respectively. To the lower end of 2 is attached, by melting, seed crystal 5 which has been drawn into a necklike construction 6. The lower part of the rod is increased in thickness by displacing rotating support 8 relative to the heating coil 3. At the commencement of the drawing process argon is fed from a cylinder 14 via a line 15 into the container 1. A pressure-reducing valve 16, a stop-valve 17 and a pressure-gauge 18 are located in line 15.