Marangoni效应下下拉速率对多晶硅真空定向凝固晶体质量的影响研究

Effect of Pulling-down Rate on Quality of Multicrystalline Silicon Under Marangoni Effect during Vacuum Directional Solidification Process

通过建立多晶硅真空定向凝固过程中的传热-流动-应力多物理场耦合模型,研究了在熔体表面张力引起的Marangoni效应的作用下,不同下拉速率(5、10、15μm/s)对多晶硅硅锭质量的影响。模拟结果表明:Marangoni效应的存在,使得熔体的流速增大,引起硅料的传热发生较大转变;随着下拉速率的增大,硅料的轴向温度梯度与晶体间的热应力也随之增大;下拉速度为10μm/s时,固液界面形状最为理想。中试的实验结果也证实了10μm/s时的硅锭晶体形貌最好,有着较大尺寸的柱状晶粒,侧面地验证了模拟结果的准确性。

A multi-field coupling model of heat-flow-stress was established to investigate the effect of different pulling-down rates on quality of multicrystalline silicon ingots under the Marangoni effect caused by surface tension of the melt during the vacuum directional solidification process of multicrystalline silicon.The simulation results show that the melt flow rate increases due to the Marangoni effect,which makes the heat transfer of silicon material change greatly.With the increase of the pulling-down rate,the axial temperature gradient of the silicon and the thermal stress of the crystal also increase.When the pulling-down rate is 10 μm/s,the solid/liquid interface is the most ideal.The experimental results also confirm that the silicon ingot crystals at 10 μm/s have the best morphology,and the microstructure is columnar grain with larger size.The accuracy of the simulation results is verified.