Single crystal prepn. by zone melting - using plasma jet to effect melting, with acid pickle operation between two melting steps

摘要

The parent patent described a method of preparing crystals esp. Si by zone melting in which a polycrystalline ingot is placed in a boat, fused by a plasma jet and then the boat is displaced w.r.t. the plasma. In this addition, the ingot is pickled in acid between two such plasma fusion treatments. The heat necessary to fuse the zone is provided with a plasma jet at 10000-15000 K. The temp. distribution inside the molten zone is rotated about the axis of the plasma jet with max. at the surface and a min. at the lower part which is in contact with the boat. Improved purificn. is achieved.