多晶硅真空定向凝固过程Marangoni对流对铸锭质量的影响研究

Effect of Marangoni Convection on Ingot Quality During Vacuum Directional Solidification of Polycrystalline Silicon

对于多晶硅垂直布里奇曼真空定向凝固过程,熔体自由表面张力引起的Marangoni对流对晶体生长质量有着明显的影响。本文通过建立多晶硅真空定向凝固过程的热场-流场-应力场多场耦合数学物理模型,采用数值模拟和实验研究了Marangoni对流作用下熔体传热特性、熔体流动行为、铸锭热应力等因素对硅晶体生长质量的影响。结果表明:Marangoni对流会增强硅熔体流场的流动强度,使得硅熔体平均流速增大3倍左右,进而影响硅熔体内部的对流换热能力,使硅熔体和硅固体温度分布更加均匀,硅熔体温度梯度降低4.8%-9.9%,硅固体温度梯度降低2.1%-2.6%,使多晶硅铸锭过程产生更小的热应力和更少缺陷。

Marangoni convection caused by the gradient of melt free surface tension has a significant effect on the growth quality of polycrystalline silicon during vertical Bridgman vacuum directional solidification.In this paper,a multi-field coupled mathematical and physical model of thermal field,flow field,and stress field in the vacuum directional solidification process of polycrystalline silicon was established.Numerical simulations and experiments are used to study the influence of factors such as melt heat transfer characteristics,melt flow behavior,and ingot thermal stress on the growth quality of silicon crystals under Marangoni convection.The results show that Marangoni convection can enhance the flow intensity of silicon melt flow field,make the average velocity of silicon melt increase about three times,and then affect the convective heat transfer capacity of silicon melt,make the temperature distribution of silicon melt and silicon solid more uniform,the temperature gradient of the silicon melt is reduced by 4.8%-9.9%,and the temperature gradient of the silicon solid is reduced by 2.1%-2.6%,which makes the polysilicon ingot process produce smaller thermal stress and fewer defects.