Polysilicon manufacturing implementing the reduction of silicon tetrachloride with zinc vapor: 
A very uncommon approach from Chisso

Masatsugu Yamaguchi, 
Research group leader at Japan Solar Silicon, Inc., Japan

Dr. Masatsugu Yamaguchi holds a Master of Engineering, Chemistry, from the Muroran Institute of Technology, Japan. He received his PhD from Hokkaido University, Japan, in 1996. From 2002 to 2006 he was the research group leader at the Minamata Research Center at Chisso Corporation, Japan. Since February 2007 he has held the same position at Japan Solar Silicon Co., Ltd. a joint venture established by Chisso to commercialize the silicon production process.

Within the scope of a research program from New Energy and Industrial Technology Development Organization (NEDO), Chisso Corporation has been developing a highly productive and potentially very cost-effective manufacturing technology for solar grade silicon. This technology consists of three basic processes. First: the reduction of silicon tetrachloride (SiCl4) with zinc vapor to get high purity multicrystalline silicon. Second: electrolysis of zinc chloride into high purity zinc metal and chlorine gas. And last: reaction of metallurgical silicon with chlorine out of the electrolysis.

PV cells produced with multicrystalline silicon produced using the Chisso process show the same performance as cells produced with silicon from traditional processes. Chisso has completed the first stage of development in the laboratory and is currently performing pre-commercial manufacturing at a pilot scale plant. In 2007, Chisso Corporation, Nippon Mining Holdings, Inc. and Toho Titanium Co., Ltd established Japan Solar Silicon Co., Ltd., a joint venture for the further development of this technology.

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