Removal of SiC particles from solar grade silicon melts by imposition of high frequency magnetic field
(1. Department of Materials Science and Engineering, Norwegian University of Science and Technology (NTNU),
P.O. Box 7491, Trondheim, Norway;
2. SINTEF Materials and Chemistry, Flow Technology Group, P.O. Box 7465, Trondheim, Norway)
P.O. Box 7491, Trondheim, Norway;
2. SINTEF Materials and Chemistry, Flow Technology Group, P.O. Box 7465, Trondheim, Norway)
Abstract: Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon (MG-Si) was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics (CFD) were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.
Key words: SiC particle; electromagnetic separation; solar grade silicon (SoG-Si); photovoltaic cells; computational fluid dynamics (CFD); non-metallic particles; metallic impurities