Cover flux and method for silicon purification

摘要

Cover flux devices and methods are shown. Methods and devices are shown such that, as a solidification front moves from a cooling surface of a mold towards a surface of molten silicon substantially opposite the cooling surface, impurities are driven out of the solid silicon and into the liquid to react with a flux layer on the silicon.

主权项

1. A method, comprising:
pouring molten silicon into a mold; forming a solid layer of silicon on a top surface of the silicon, and placing flux material on the solid layer; placing a top heater over the mold to melt the solid layer of silicon, wherein the flux material remains floating on the molten silicon; directionally solidifying the molten silicon, from a bottom of the mold towards the top surface of the silicon; and reacting the flux with impurities at the interface between the top surface of the silicon and the flux.