Dynamic simulation of impurity transport and chemical reactions in a Bridgman furnace for directional solidification of multi-crystalline silicon

Numerical results from a dynamic simulation of impurity transport and reactions in a Bridgman furnace for directional solidification of multi-crystalline silicon are presented and compared to experimental results. The simulation includes the calculation of the thermal field, melt and gas flow velocity field, transport and chemical reactions of oxygen and carbon impurities for the entire process based on heating, melting and solidification phases. Carbon and oxygen distribution in the ingot is analyzed experimentally by means of FT-IR spectroscopy and LECO combustion method, the CO development by means of an μ-GCμ-GC gas analyzer.The simulated impurity distribution in the ingot and the CO development above the free melt surface are in good agreement with the experimental results. Furthermore the results indicate that the carbon solubility limit is already reached at the stage of melting and SiC precipitates are likely to form at the early stage of growth.

► Dynamic simulation of impurity transport and chemical reactions.
► Both, melting and solidification phases are considered.
► Good agreement with experimental results.
► Carbon solubility limit is exceeded during the melting phase.
► Probable SiC formation at the melting stage.