Verfahren zum Herstellen von einkristallinen Halbleiterstaeben

摘要

A monocrystalline rod of silicon having a diameter of at least 25 mm. is pulled from a molten zone produced by induction heating of the upper end of a rod of larger diameter. The ratio of the diameters of the thicker and thinner rods is preferably greater than 1.4. The molten zone may be initially produced by induction heating or electron bombardment. The larger diameter rod may be preheated by resistance or induction heating or by being surrounded by a silver heat reflector in the form of a cylinder having a vertical slit to prevent coupling. Pulling may be in a vacuum or protective gas atmosphere. The crystal being pulled may be rotated at 10-150 rpm. The melt may be replenished by adding powdered or liquid material or by further melting the rod. In the latter case, the thicker rod may be raised or the induction coil lowered as pulling proceeds. According to Fig. 3, (not shown) a rod 23 is pulled from a melt 21 maintained molten by an induction coil 22 in a cup-like depression in a larger diameter rod 20, molten material being supplied to the molten zone through a slip 24 by melting of a rod 26 by an induction coil 25. According to Fig. 4 (not shown) the melt is replenished by melting the rim of the cup-like depression by an induction coil 34.