Manufacture of pure silicon

摘要

A crystalline body is produced by drawing a seed crystal 18 (Fig. 3) from a melt 21 obtained by melting a limited portion of material at the top of a rod-like mass 17. The seed 18 is supported by a rod 16 and the mass 17 is supported on a rod 15, the rods 16 and 15 being raised at such respective rates that the melt 21 is maintained at a constant level. The material is melted by a single-turn coil 1 consisting of a water-cooled copper box of annular form but divided by a narrow slot which is connected to a source of high-frequency current. The inside edge of the coil 1 is tapered so that the electromagnetic field applies lifting forces to the melt to assist the surface tension in holding the melt in position. In a modification the mass 17 is surrounded by a water-cooled copper sleeve which distorts the electromagnetic field so that the lifting forces are changed so that a larger volume of melt can be maintained, so that a crystal of larger diameter can be grown. The material may be a semi-conductor, such as silicon or germanium, and significant impurities may be added to the melt. Specifications 826,575 and 829,421 are referred to.