Crystal growth of MCZ silicon with ultralow carbon concentration

摘要

In this study, we investigated the evaporation of carbon monoxide (CO) from silicon melt during crystal growth by evaluating the carbon concentrations in the crystals using photoluminescence (PL) spectro-scopy. In order to achieve greater carrier lifetimes in magnetic-field-induced Czochralski (MCZ) silicon for high-power insulated-gate bipolar transistor (IGBT) devices, we focused on the reduction of carbon impurities in MCZ silicon, that act as heterogeneous nucleation sites for oxygen precipitates. To obtain MCZ silicon with a carbon concentration lower than that of floating-zone (FZ) silicon, it is necessary to prevent the back-diffusion of CO from the hot graphite components into the melt and promote CO evaporation from the melt. By promoting CO evaporation, we managed to grow 6-in. CZ silicon crystals with a carbon concentration lower than 1.0×10~(14) atoms/cm~3 at a solidified fraction of 80%.