定向凝固保温温度对多晶硅定向凝固晶体质量的影响

Influence of Holding Temperature on Crystal Quality of Polycrystalline Silicon during Directional Solidification Process

采用3303#工业硅进行多晶硅真空定向凝固实验,通过实验和数值模拟结合研究了保温温度对多晶硅真空定向凝固过程中铸锭内部的晶体生长取向、杂质去除效果及杂质分布形态的影响。研究表明:下拉速度10μm/s、保温时间0.5 h、保温温度1730 K条件下形成的多晶硅铸锭内部晶体生长取向、除杂效果、杂质分布形态及各项指标最优;当保温温度≥1760 K时,凝固过程中的固态硅料发生重熔,硅锭内部热应力的释放能力减弱,致使晶体内部缺陷明显增加;重熔也会造成最终凝固完成后铸锭内部开裂,固液界面凹凸不平,严重影响大尺寸柱状晶的形成及杂质的去除效果。而保温温度过低会导致挥发性杂质的扩散能力减弱,严重削弱多晶硅铸锭的性能及定向凝固除杂效果。

Vacuum directional solidification experiment of#3303 industrial polycrystalline silicon was carried out with.During the vacuum directional solidification process,the effects of holding temperature on the crystal growth orientation,impurity removal efficiency and ribution pattern of impurities of the polycrystalline silicon were mainly studied by experiments and numerical simulations.Results indicate that when pull-down speed of 10μm/s,holding time of 0.5 h and holding temperature of 1730 K are adopted,growth morphology,impurity removal efficiency and ribution pattern of impurities together with various parameters of the polycrystalline silicon ingot obtained are optimal.However,if holding temperature is higher than 1760 K,silicon ingot will be re-melted during solidification.Additionally,release ability of internal thermal stress is weakened,leading to crack of the ingot.Furthermore,the increasing holding temperature causes the solid-liquid interface sagging,which seriously affects the formation of large-sized column crystals and hinders the removal of impurities.Whereas,as holding temperature is too low,the diffusion ability of volatile impurities is reduced and impurities aggregate where lattice defects occur as a result,reducing the properties of the polycrystalline silicon and hindering the removal of impurities as well.