GB838848A - Improvements in or relating to methods of manufacturing crystalline material - Google Patents

Abstract

<PICT:0838848/III/1> In a method of manufacturing crystalline semi-conductor material in which a fractional portion of a molten mass of semi-conductor material containing impurities is cooled to initiate crystallization, and additional increments of the molten mass are progressively cooled at the interface between the crystallized portion and the molten mass to crystallize the material by continued accretion to the crystallized portion, the molten mass in the region adjacent to the interface is progressively increasingly agitated to maintain the impurity content of the crystallized material constant throughout its length. Semi-conductor material 13 (Fig. 1), such as germanium or silicon, containing a donor or acceptor impurity, is placed in a crucible 10, and is melted by an inductive heating coil 11. A seed crystal 14 is brought into contact with the melt and is slowly withdrawn in direction Y to grow a continuous crystal, the crystal holder 15 being rotated by gears 18 and 19 and a motor 17. The melt adjacent the interface 16 is progressively increasingly agitated as the crystal is grown, either by increasing the angular velocity of the seed crystal 14, or by vibrating the crystal by means of a transducer 20 mechanically connected to holder 15 and electrically coupled to a signal generator 21, the frequency of the driving signal from generator 21 or the amplitude of vibration being progressively increased. In another method semi-conductor material containing a small amount of impurity is placed in a boat 30 (Fig. 3) and melted by an induction heating coil 31. The boat 30 is slowly withdrawn in the direction M to permit the melt to cool and crystallize. A transducer 33 connected to a source of ultrasonic-frequency electrical energy 35 is placed in contact with the crystallized portion 34, and agitation of the melt in the region of the interface 36 is increased as the crystal is grown.