Thermal and mechanical analysis of directionally solidified silicon ingots in silica and silicon nitride crucibles

Silicon nitride is a promising crucible material for directional solidification of multi-crystalline silicon ingots. In contrast to standard quartz crucibles, which can only be used once, crucibles made of silicon nitride have the potential of being used several times and thereby reduce production costs. In a previous study, it was shown that crucible thermal properties have a significant impact on the heat transfer conditions during silicon solidification in a small scale furnace. The aim of the present work is to analyse the effect of the crucible material type on thermally induced stresses and deformations in the ingot and associated material quality. Transient thermal fields calculated using a CFD software, are used in subsequent mechanical calculations. The stress-strain fields in the ingot are calculated using a thermo-elasto-viscoplastic formulation. Results obtained using silica and silicon nitride crucibles are compared.