PROCESS FOR PRODUCING POLYCRYSTALLINE SILICON INGOT

摘要

A process in which a polycrystalline silicon ingot improved in life time characteristics, which are correlated with the conversion efficiency of solar wafers, is inexpensively produced by the ordinary-pressure hydrogen-atmosphere melt method. In the process, the generation of oxygen and impurities in the silicon melt is inhibited and light-element impurities are removed through reaction or crystallization. Fine crystal grains can be grown at a high rate, and a high-purity polycrystalline silicon ingot having a crystal structure reduced in crystal defect can be grown. A silicon raw material is melted in an atmosphere of 100% hydrogen at ordinary pressure or an elevated pressure to prepare a silicon melt and simultaneously dissolve hydrogen in the silicon melt. The silicon melt containing hydrogen dissolved therein is solidified. Thereafter, the solid is held at a high temperature around the solidification temperature to grow silicon crystal grains in the solid phase and thereby obtain a polycrystalline silicon ingot.