Influence of argon flow rate on melt convection and incorporation of SiC in multicrystalline silicon

The influence of the argon flow rate on the melt convection pattern and precipitate formation has been investigated by global, axisymmetric time-dependent simulations for varied argon flow rates and test crystallisations of G1 sized ingots. The simulations include calculation for the global heat transfer, the gas/melt convection, the melt-crystal interface determination, impurity transport and precipitation. The simulation results have been compared with precipitate distribution and impurity profiles in the test ingots. The ingots were prepared in a laboratory VGF furnace with a modified support crucible system. It can be shown that the argon flow rate has a significant impact on the melt convection pattern and thus the impurity distribution in the solidified ingots. This determines the formation and amount of SiC precipitations especially in the upper part of the ingots