Purification Behavior of Impurity Aluminum in Multicrystalline Silicon by Vacuum Induction Melting and Directional Solidification Method

Purification mechanism of impurity aluminum in multicrystalline silicon ingot made from metallurgical-grade silicon was investigated by composition analysis and theoretical analysis of vacuum induction melting and directional solidification.The results showed that the content of impurity aluminum was significantly decreased due to the obviously evaporation in the stage of thermal insulation (T≥1723 K).The segregation of impurity aluminum plays an important role in the distribution of aluminum in subsequent directional solidification process,but a little amount aluminum evaporation still happened.A new theoretical model including segregation phenomenon and evaporation mechanism was developed to simulate the distribution of aluminum in multicrystaliine silicon.The result of simulation was well consistent with the measured distribution of aluminum in the obtained ingot.