多晶硅定向凝固反向诱导泉涌效应的研究

项目名称： 多晶硅定向凝固反向诱导泉涌效应的研究

项目编号： No.51304033

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 矿业工程

项目作者： 姜大川

作者单位： 大连理工大学

项目金额： 25万元

中文摘要： 定向凝固是去除多晶硅中金属杂质的主要技术，广泛应用在多晶硅铸锭、冶金法提纯过程中。理论除杂率可达90%以上，但由于凝固后硅锭末端杂质浓度远高于先凝固区域，在浓度差驱动下杂质向已提纯区域扩散，形成反扩散现象，大幅降低了硅锭的良率。如何抑制定向凝固过程中杂质反扩散行为，是一个急需解决的关键共性问题。本项目提出一种全新的研究思路，在凝固达到预期良率、液固共存的状态下，利用硅在凝固时体积发生膨胀的特性，通过改变热场和气氛环境诱导富含杂质的液硅表面首先形核凝固，将石英管从铸锭上方穿过表面插入熔体，通过改变石英管内的压强，使熔体在压力差的作用下涌入石英管，产生泉涌效应，实现熔体与已提纯基体的分离。本项目研究这一过程中的界面控制、熔体流动及凝固提纯等科学问题。本研究是申请人博士工作的延续，也是博士后研究课题，系统研究反向诱导硅熔体泉涌效应的形成机制，将为彻底解决定向凝固的反扩散现象奠定基础。

中文关键词： 多晶硅；定向凝固；泉涌效应；金属杂质；轻质元素

英文摘要： Directional solidification is the main technology to remove metal impurities in multicrystalline silicon, which is widely used in multicrystalline silicon ingot casting and silicon purification by metallurgical route. In theory, the impurity removal efficiency is up to more than 90%. However, the existence of back diffusion phenomenon greatly reduces the yield of the silicon ingot, because the impurity concentration in the end of the ingot is much higher than that in the other area so that impurities diffuse towards purified area under the action of concentration difference. It is an urgent key common problem to restrain the back diffusion behavior during directional solidification process. This project proposes a new method to restrain the back diffusion of the impurities based on the characteristics of volume expansion during silicon solidification. At the end of solidification, the surface of the melt containing a lot of impurities solidifies firstly by changing the thermal field and atmosphere environment. A quartz tube is inserted from the top across the solidification shell into the melt, and then the pressure in the tube will be changed. The silicon melt will gush along the quartz tube under the action of pressure difference, separate from the purified area and solidify rapidly, which is called gushing ef

英文关键词： Silicon；Directional solidification；Fountain effect；Metal impurities；Light elements