Specific features of multicrystalline silicon growth from high-purity commercial silicon

The distribution of impurities in multicrystalline silicon (mc-Si) blocks grown at various velocities from refined commercial silicon by the Stochbarger method have been studied. It is established that the growth velocity $V$ strongly influences the distribution of impurities along the block height. Growth at $V >$ 1 cm/h leads to the breakdown of a crystallization front and the trapping of impurities. The results are explained by the concentration supercooling that arises when the growth velocity is increased above the critical level for a given type of initial material. The optimum rate for the crystallization with simultaneous effective purification of a commercial silicon from impurities has been experimentally determined.