Enhancing removal of hydrogen from granular polysilicon by innovating vacuum separation model and method for SoG-Si

Silane process of granular polysilicon has become a promising method for the preparation of polysilicon due to its continuous low temperature, simple process and low energy consumption. However, granular silicon contains more hydrogen than conventional columnar silicon, which can result in the deterioration of single crystal furnace thermal field life and rod stability by the “hydrogen jump” in the process of Czochralski method. Hydrogen removal has become an important problem to be solved in the industry development. Thus, we propose a hydrogen separation model suitable for silicon system based on vacuum experiment and thermodynamic calculation, which can provide a theoretical basis for the research and development of silicon dehydrogenation method. The predicted removal rate of hydrogen at different temperatures and vacuum pressures is in good agreement with the experimental results, reflecting the reasonability of the model. The results show that the hydrogen removal rate increases with the increasing of temperature and the decreasing of pressure, where temperature plays a leading role in the removal of hydrogen in silicon. At less than one atmosphere, the increase in dehydrogenation rate by 1 °C ranges from 0.01% to 0.25% in the temperature range from 1450 to 1800°CAt temperatures below 1800°Cthe maximum dehydrogenation rate is less than 0.001% for each 1pa reduction in pressure from one atmospheric pressure to 1000pa. According to the model calculation results, a hydrogen removal method is designed by using the vacuum electromagnetic induction. The deep removal of trace hydrogen in silicon has been realized, hydrogen in silicon drops rapidly from around 20 ppm to less than 5 ppm.