Silicon ingot casting: process development by numerical simulations

Multicrystalline silicon from ingot casting processes has reached a high market share in photovoltaic industry. One reason for this is the increase of the quality of multicrystalline wafers which leads to higher solar cell efficiency. This progress was supported by numerical simulations, namely for the SOLPIN ingot casting process which is used by the Deutsche Solar GmbH for the production of high-quality multicrystalline wafers. In this paper, we give some examples of numerical simulation results, showing the temperature distribution in furnaces and silicon ingots for various process conditions. The influence of lateral and vertical heat flux due to the shape of the liquid–solid phase boundary and the solidification velocity is demonstrated in numerical case studies. As an example for the potential of our process simulations we report about the reduction of the dislocation density in a multicrystalline ingot, which was predicted by simulations and verified by experimental results.