一种电子束诱导定向凝固除杂的方法

Method for removing impurities through directional solidification with electron beam inducing

Abstract

The invention belongs to the technical field of polysilicon purification, in particular to a method for removing impurities through directional solidification by adopting the technology of electron beam inducing. The method comprises the following steps of selecting, washing and drying metallurgical grade polysilicon with high aluminum content and high calcium content, placing the polysilicon in a crucible, vacuumizing the polysilicon, starting an electron gun to bombard the polysilicon at a beam flow of 400-700 mA till the polysilicon is totally dissolved to form into a molten pool, and continuously smelting the molten pool for 30-60 min; and then reducing the beam flow of the electron beam by adopting a way of logarithmic beam drop, after the beam flow of the electron beam is reduced to 100-150 mA, stopping droping the beam, the melt slowly freezes to form into an ingot, closing the beam flow to obtain a polysilicon ingot with low aluminum and low calcium contents. According to the method provided by the invention, as the evaporation effect and segregation effect of impurities in the silicon are fully utilized, the complementary advantages of two impurity removing ways of electron beam smelting evaporation and directional solidification can be realized; the aluminum and calcium impurities can be ensured to be removed after one step of smelting so as to meet the performance requirements of a solar cell; the process section is reduced, the energy consumption is reduced, and the method can be in favor of the large-scale promotion and application.
本发明属于多晶硅提纯的技术领域,特别涉及一种利用电子束诱导技术进行定向凝固除杂的方法。该方法首先取铝、钙含量高的冶金级多晶硅,将其清洗烘干后置于坩埚内,抽取真空后启动电子枪,以400-700mA的束流轰击多晶硅,至全部熔化,形成熔池,持续熔炼30-60min;然后采用对数降束的方式降低电子束的束流,待电子束束流降低到100-150mA时,停止降束,熔体缓慢凝固形成铸锭,关闭束流,可得到低铝、低钙的多晶硅铸锭。本发明充分利用了杂质在硅中的蒸发效应和分凝效应,实现了电子束熔炼蒸发与定向凝固两种除杂方式的优势互补,保证了一次熔炼后杂质铝和钙可以被去除到满足太阳能电池性能要求的程度,减少了工艺环节,降低了能耗,有利于大规模推广应用。

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    CN-103570024-BJuly 29, 2015青岛隆盛晶硅科技有限公司多晶硅电子束熔炼过程中减少硅液飞溅的方法
    CN-103588208-AFebruary 19, 2014宁夏宁电光伏材料有限公司Method for removing boron and metal impurities for polysilicon melting in electron-beam furnace
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