batch still for framstellning of crystalline silicon with a jernhalt as less a 1 / 20 of jernhalten in mother liquor

摘要

A process for producing crystalline silicon having an iron concentration less than about one-twentieth of the iron concentration of the mother liquor. Iron contaminated silicon is introduced into a mold and the mold walls are maintained at a temperature sufficient to cause silicon crystalline growth. The mother liquor is agitated to wash the exposed surfaces of the growing silicon crystals and to prevent the freezing of the top surface of the mother liquor. A hollow crystalline silicon ingot is formed and both the inner zone centrally of the crystalline ingot and the outer zone adjacent to the mold wall are removed leaving an inner zone having an iron concentration less than one-twentieth of the iron concentration of the original mother liquor.