Numerical simulation of impurity transport under the effect of a gas flow guidance device during the growth of multicrystalline silicon ingots by the directional solidification process

A numerical simulation has been performed to determine the concentration of oxygen and carbon in a Si melt during the mc-Si ingot growth process under the influence of a gas guidance device. With the application of this gas guidance device, the gas velocity above the free surface may increase, followed by a decrease in the SiO and CO concentrations flux at the free surface. As a consequence oxygen and carbon concentrations in the melt may decrease. The effectiveness of the gas flow guidance device mainly depends on the gap between it and the free surface. A lower oxygen concentration in the melt may be obtained with a smaller gap. On the other hand, the carbon concentration in the melt also decreases as the gap decreases until the gap reaches a certain small value, after which it increases.