石墨坩埚厚度对感应加热制备太阳能级多晶硅影响的数值模拟研究

Numerical Simulation of Influence of Graphite Crucible Thickness on Solar-Grade Polysilicon Prepared by Induction Heating

定向凝固法制备的多晶硅是目前主要的光伏原材料,制备过程中热场结构和硅熔体对流形态对于生长高质量的多晶硅极为重要,本文利用专业晶体生长软件CGSim对制备太阳能级多晶硅用真空感应铸锭炉中的石墨坩埚进行改进并进行了数值模拟,分析了不同石墨坩埚厚度的变化对热场、流场、固液界面、硅晶体应力场以及和V/G值的影响。结果表明,当石墨坩埚厚度为20 mm,可获得良好的对流形态、平坦的固液界面、合理的V/G值等,有利于节约多晶硅的生产成本并提高多晶硅的品质,为生产实践中工艺方案优化及缺陷分析等提供重要的理论依据。

Polycrystalline silicon prepared by the directional solidification method is currently the main photovoltaic raw material.During the preparation process,the thermal field structure and the control of the convection morphology of the silicon melt are extremely important for the growth of high-quality polycrystalline silicon.This article uses professional crystal growth software CGSim to prepare solar-grade polycrystalline silicon with vacuum.The graphite crucible in the induction casting furnace was improved and numerical simulation was carried out.The influence of the thickness of different graphite crucibles on the thermal field,flow field,solid-liquid interface,silicon crystal stress field,and V/G value was analyzed.The results show that when the thickness of the graphite crucible is 20 mm,good convection morphology,flat solid-liquid interface,reasonable V/G value,etc.can be obtained,which are beneficial to save the production cost of polysilicon and improve the quality of polysilicon.It provides an important theoretical basis for process optimization and defect aualysis in production practice.