Purification of metallurgical‐grade silicon up to solar grade

Abstract An estimate has been made of the feasibility of a metallurgical purification process, the NEDO (New Energy and Industrial Technology Development Organization) melt‐purification process, for manufacturing solar‐grade silicon from metallurgical‐grade silicon. Equipment has been developed to pilot manufacturing plant scale. The system comprises an electron‐beam furnace for phosphorus removal and a plasma furnace for boron removal. Each furnace has a mold for directional solidification to remove metallic impurities. The concentration 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 Ω cm. Copyright © 2001 John Wiley & Sons, Ltd.