以工业硅为原料,利用介质熔炼、定向凝固和电子束熔炼三种熔体处理技术对工业硅中的B、P和金属杂质进行了去除,制备出了99.9999%级多晶硅材料,其中,杂质B和P的含量分别低于0.20 ppmw(parts per million(weight),百万分之一质量),金属杂质总含量(TM)低于0.23 ppmw.研究发现,介质熔炼去除杂质B的过程中,熔体中发生氧化还原反应可以有效去除大部分的杂质Al和Ca;电子束熔炼过程中,利用饱和蒸气压原理可以有效去除挥发性杂质P、Al、Ca,同时降束诱导多晶硅定向凝固,可将其他金属杂质进一步去除.本研究通过各技术间的耦合除杂,减少了冶金法提纯多晶硅的工序,为连续化、规模化生产提供了技术支撑.
Preparation of 6N grade polycrystalline silicon materials using raw materials of industrial silicon was explored by medium melting, directional solidification and electron beam melting. The contents of impurities B and P in the samples are both lower than 0.20 ppmw, while the total content of metal impurity (TM) is less than 0.23 ppmw. Dur-ing the process of removing B by medium melting, a large proportion of Al and Ca is simultaneously removed through the redox reaction. During the process of electron beam melting, volatile impurities including P, Al and Ca are fur-ther effectively removed by using saturated vapor pressure. Meanwhile, other metal impurities are removed by de-creasing beam power, which induces the occurrence of directional solidification. Coupling of metallurgical methods reduces the purification process of polycrystalline silicon, and provides the technical support for continuous and large-scale production.
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