碳热还原歧化法制备高品质硅的实验研究

【作者】 吕东；

【导师】 马文会；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2009， 硕士

【摘要】 目前正在研究用冶金法制备太阳能级多晶硅的国内外的公司和科研院所较多,其工艺路线不尽相同,但基本原理都是利用硅和硅中杂质之间的物理化学性质,把凝固除杂、真空高温蒸发除杂、氧化除杂、酸浸除杂、造渣除杂、电解还原等方法中的一种或几种有机的组合起来形成一种工艺路线,达到提纯制备太阳能级硅的目的。本研究工艺路线为：采用自行设计的中频感应炉加热,以经过预处理的碳和二氧化硅作为原料,在自行设计的高纯石墨坩埚中发生碳热还原反应,获得高纯度的一氧化硅气体,并在一定温度条件下使一氧化硅气体发生歧化反应获得高纯硅和高纯二氧化硅,分离二氧化硅后再进行真空定向凝固可获得多晶硅。本文利用了X射线衍射仪(XRD)、拉曼光谱仪、扫描电子显微镜(SEM)、电感耦合等离子发射光谱仪(ICP)等设备,研究了歧化生成物的微观结构、生成机理、物相成分、产物的纯度及提纯机理。通过研究获得以下研究结果：(1)实验中的歧化生成物由直径几百纳米的纳米线和纳米球组成,纳米线和纳米球内部为硅,表面附着SiO2,对这些歧化物球磨后,可以采用酸浸的方式分离出歧化生成物中的二氧化硅,获得高纯度的硅；(2)HF酸酸浸可以完全去除歧化生成物中的二氧化硅和B杂质元素,但对纯度较低的P、Fe、Al杂质元素的去除效果不大,分析了B被去除的机理；(3)通过碳热还原歧化法制备的高纯硅中,ICP检测结果表明,B杂质元素含量检测不到,B杂质元素的去除率接近100%,而P、Fe、Al杂质元素的含量和原料相比,降低了一到两个数量级,且原料纯度越高,产物纯度也越高。更多还原

【Abstract】 At present, there are many companies and universities which are researching a new way to get solar grade silicon by metallurgical technology. In spite of these new techniques have many differences, physical or chemical characters of silicon are used in the metallurgy process. Purification aim can be achieved by direction solidification, vacuum distillation at high temperature, oxidizing impurities, carbothermic reduction and so on.Process route in this study is shown as follow. Experimental equipment is self-designed intermediate frequency induction furnace. Pretreated silica wastes and charcoal wastes are used as raw material. High purity SiO gas can be formed by carbothermic reduction at high temperature, and SiO gas will be disproported into high purity silicon and silicon dioxide in the self-designed high purity graphite crucible when temperature go down, then solar grade silicon can be achieved after separating silicon dioxide in HF acid and directional solidification in vacuum.In this paper micromechanism and generation mechanism of the sample prepared by carbothermic reduction and disproportionation method are studied by scanning electron microscope(SEM). Phase composition of the sample is studied by X-Ray diffraction instrument(XRD) and raman spectrum instrument. Purity of the sample are studied by inductive coupled plasma spectrometer(ICP).From the study we can get the following results:(1) Sample prepared by disproportionation method is made up of nanowires and nanospheres whose diameter from 100 nanometer to 600 nanometer, and nanowires and nanospheres are made up of silicon and silicon dioxide which locate on the surface of the silicon, as a result silicon dioxide can be absolutely removed by acid leaching; (2) Silicon dioxide and B element can be absolutely removed by acid leaching,and has bad effect on removing P, Fe,Al element. B element absolutely removing mechanism is analysed;(3) Impurities such as B, P, Fe, Al content in the high purity silicon by carbothermic reduction and disproportionation method is lower than the raw materials, especially B content in the production is close to 0 ppmw. If raw material has high purity, then the production has higher purity.更多还原