Influence of Unidirectional Solidification Purification on Impurity and Resistivity of Commercial Silicon

Multicrystal silicon (mc-Si) ingot was prepared using 1101 commercial silicon as raw material by vacuum induction melting and unidirectional solidification purification. The chemical composition, microstructure, resistivity and conductive type of the ingot were analyzed by inductive coupled plasma-optical emission spectrometer, scanning electron microscopy, four points resistivity test machine and conductive type tester. The results show that nearly half of the mc-Si ingot was purified to 99.99%, and over 90% of the metal impurities including Fe, Cu and Ni had been removed. The impurities had been redistributed by the segregation effect, which led to the break-up of large columnar crystals growth at 54% height. While the impurity composition and resistivity changed greatly, and the conductive type changed from P type to N type.