Effect of alternating magnetic field on the removal of metal impurities in silicon ingot by directional solidification

• Silicon ingots with and without magnetic field under industrial system are obtained.
• The concentration of impurities are decreased due to addition of magnetic field.
• The thickness of the diffusion layer is reduced by the alternating magnetic field.
• The effective segregation coefficient are also reduced.

Multicrystalline silicon ingots without and with alternating magnetic field during directional solidification process under industrial system were obtained from metallurgical grade silicon (MG-Si). The concentrations and normalized concentrations of metal impurities in the two silicon ingots were studied. The result shows that the concentrations and normalized concentrations in high-purity area of the silicon with alternating magnetic field are lower than those of the ingot without alternating magnetic field. The transport mechanism for metal atoms in the diffusion layer area has been changed due to the alternating magnetic field. Alternating magnetic field introduces a convection to reduce the thickness of diffusion layer in the molten silicon, which results in a decreased effective segregation coefficients. Enhancing transport driving force of metal atoms in molten silicon is the effective way to improve the removal rate of metal impurities.