A process for melting a rod of polycrystalline material zone-by-zone

摘要

A thin crystalline seed is joined to the tapered end of a thick polycrystalline rod of silicon by means of a pancake induction coil and a molten zone is passed through the rod from the joint by means of a cylindrical induction coil. The rod is maintained vertical with the tapered end at the top or bottom during the process. The pancake coil may be removed before commencement of zone-melting or kept stationary and open-circuited or connected in parallel with one or more condensers. An incandescent zone may be passed through the rod during return of the cylindrical coil. One or more further molten zones may be passed through the rod, the zones being formed by the cylindrical and/or pancake coils. The diameter of the seed and rod may be 6 and 40 mm respectively.