多晶硅真空电磁感应熔炼除磷及其过程研制

Research on removal phosphorus from polysilicon and process development by vacuum induction melting

磷是多晶硅中的主要杂质元素之一,目前采用的酸洗以及定向凝固工艺无法将其含量降低到太阳能级多晶硅所要求的范围之内。采用自行设计的真空电磁感应熔炼炉及定向凝固炉研究了真空度、精炼时间和精炼温度对除磷效果的影响。研究结果表明当炉内压强为5.0×10-1 Pa时,精炼温度和时间分别为1723K和60min时,精炼后硅中磷含量由原来的2.0×10-5(质量分数)降低到1.8×10-6(质量分数);研究推导出了在压强为5×10-1Pa下磷的含量随精炼时间和精炼温度的关系式如下:XP=X0Pexp[(-1.43×10-4-3.1×10-7T)t]同时还对真空感应熔炼除磷过程进行了热力学与动力学分析。

Phosphorus is one of the main impurities in polysilicon.Currently,its content in polysilicon can not be reduced to level required by solar grade silicon（SOG-Si） through acid leaching and directional solidification processes.The effect of the vacuum degree,refining times and refining temperatures on phosphorus removal was investigated by the vacuum melting furnace and directional solidification furnace which were designed by us,respectively.The results showed that phosphorus content in silicon reduced from original 2.0×10-5 to 1.8×10-6 after refinning when the furnace pressure,temperature and time were 5.0×10-1Pa,1723K and 60min,respectively.The relationship of phosphorus content in silicon with refining times and refining temperatures when the furnace pressure was 5.0×10-1Pa was derived as follows： XP=X0Pexp〗 And the thermodynamic and kinetic of phosphorus removal process under vacuum induction melting was also analyzed.