Purification of Si using Catalytic CVD

  • Jo, Chul-Gi (Energy Materials & Surface Science Laboratory, School of Chemical Engineering and School of Semiconductor and Chemical Engineering & Solar Energy Research Center, Chonbuk National University) ;
  • Lee, Kyeong-Seop (Energy Materials & Surface Science Laboratory, School of Chemical Engineering and School of Semiconductor and Chemical Engineering & Solar Energy Research Center, Chonbuk National University) ;
  • Song, Min-Wu (Energy Materials & Surface Science Laboratory, School of Chemical Engineering and School of Semiconductor and Chemical Engineering & Solar Energy Research Center, Chonbuk National University) ;
  • Kim, Young-Soon (Energy Materials & Surface Science Laboratory, School of Chemical Engineering and School of Semiconductor and Chemical Engineering & Solar Energy Research Center, Chonbuk National University) ;
  • Shin, Hyung-Shik (Energy Materials & Surface Science Laboratory, School of Chemical Engineering and School of Semiconductor and Chemical Engineering & Solar Energy Research Center, Chonbuk National University)
  • Published : 2009.11.25

Abstract

Silicon is commercially prepared by the reaction of high-purity silica with wood, charcoal, and coal, in an electric arc furnace using carbon electrodes, so called the metallurgical refining process, which produces ~98% pure Si (MG-Si). This can be further purified to solar grade silicon (SoG-Si) by various techniques. The most problematic impurity elements are B and P because of their high segregation coefficients. In this study, we explored the possibility of the using Cat-CVD for Si purification. The existing hot-wire CVD was modified to accommodate the catalyzer and the heating source. Mo boat (1.5 cm ${\times}$ 1 cm ${\times}$ 0.2 cm) was used as a heating source. Commercially available Si was purchased from Nilaco corporation (~99% pure). This powder was kept in the Mo-boat and heated to the purification temperature. In addition to the purification by cat-CVD technique, other methods such as thermal CVD, plasma enhanced CVD, vacuum annealing was also tried. It is found that the impurities are reduced to a great extent when treated with cat-CVD method.

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