Purified Si film formation from metallurgical-grade Si by hydrogen plasma induced chemical transport

Purified Si film is prepared directly from metallurgical-grade Si (MG-Si) by using hydrogen plasma induced chemical transport at subatmospheric pressure. The purification mechanism is based on the different hydrogenation behaviors of the various impurity elements in MG-Si. The prepared Si films clearly had fewer typical metal impurities (Fe, Al, Ti, Cr, Mn, etc.) than those in the MG-Si. In particular, the Fe concentration was drastically reduced from 6900 mass ppm to less than 0.1 mass ppm by one time chemical transport. Furthermore, metal impurity concentrations were further reduced by repeating chemical transport deposition.