电子级多晶硅生产工艺的热力学分析

Thermodynamic Analysis of Production Technology of Electronic Grade Polycrystalline Silicon

基于Gibbs自由能最小原理,对SiHCl3法生产电子级多晶硅闭环工艺的3个反应子系统分别进行了化学反应平衡计算,重点对SiHCl3还原反应子系统进行了热力学分析.对于SiHCl3还原反应子系统,适宜的操作温度为1323～1473K,压力为0.1MPa;温度高于1323K,H2/SiHCl3比大于6.6,低压下有利于SiHCl3还原生产多晶硅.针对传统的SiHCl3还原需要高温下电加热给过程操作带来的诸多不便,提出了用Cl2部分氧化使SiHCl3还原反应体系实现能量耦合的新工艺,即反应过程不需外部加热就可完成,从而节约电耗,同时还发现平衡时体系中加入的Cl2能反应完全,不会影响后序工艺的进行.对于SiCl4转化反应子系统,高压、低H2/SiCl4比有利于生成SiHCl3.

Chemical reaction equilibrium in three reaction subsystems of the closed loop process of electronic grade polycrystalline silicon with SiHCl3 method was computed based on the principle of Gibbs free energy minimization, respectively. Thermodynamic analysis was given emphatically to SiHCl3 reduction subsystem. The suitable operating conditions in SiHCl3 reduction system were 1323-1473 K, 0.1 MPa. It could contribute to producing polycrystaUine silicon through reduction of SiHCl3 under the temperature above 1323 K, the H2/SiHCl3 molar ratio above 6.6：1 and low pressure. Electrical heat under high temperature for traditional SiHCl3 reduction system was difficult for process operation. Based on this, energy coupling achieved by adopting Cl2 partial oxidation in SiHCl3 reduction system was proposed, that is, polycrystaUine silicon production process could be achieved without supplying exterior energy, and electricity consumption could be saved. At the same time it was also found that feed Cl2 could react completely at equilibrium, and subsequent process was not influenced. Increasing pressure and lowering H2/SiCl4 molar ratio were favorable for producing SiHCl3 in SiCl4 conversion system.