Purification of metallurgical-grade silicon up to solar grade

An estimate has been made of the feasibility of a metallurgical purificatio n process, the NEDO (New Energy and Industrial Technology Development Organ ization) melt-purification process, for manufacturing solar-grade silicon f rom metallurgical-grade silicon. Equipment has been developed to pilot manu facturing plant scale. The system comprises an electron-beam furnace for ph osphorus removal and a plasma furnace for boron removal. Each furnace has a mold for directional solidification to remove metallic impurities. The con centration of each impurity in the silicon ingot purified through the whole process satisfied the solar-grade level, The Solar-grade silicon produced showed p-type polarity and resistivity within the range 0.5-1.5 Omega cm. C opyright (C) 2001 John Wiley & Sons, Ltd.