氩气流速对400mm大直径磁场直拉单晶硅固液界面、热应力及氧含量的影响

Influence of Argon Flow Rate on the Solid/Liquid Interface,Thermal Stress and Oxygen Concentration in the 400 mm CZ Silicon with a Magnetic Field

大直径化是太阳能光伏用单晶硅发展的趋势之一。由于炉体结构的增大，炉内气体流场的变化对晶硅生长过程产生了一定的影响。本文采用CGSim晶体生长软件，系统分析了氩气进口流速对固液界面，热应力和晶体氧含量的影响。结果表明，随氩气流速的增加，固液界面高度逐渐下降，当氩气流速为中等范围时，固液界面波动最低，有利于提高拉晶过程的稳定性；另一方面，三相交界处热应力最大值随氩气流速的增加而降低，固液界面热应力波动幅度随氩气流速的增加而增加，综合两方面考虑，确定采用中等氩气流速（0．9—1．5m·s-1）工艺可有效避免断晶等缺陷的发生。同时，在中等氩气流速范围内，晶体中心处的氧含量下降至6．55×10^17m／cm3（氩气流速为1．5m·s-1时），与低氩气流速时相比，氧含量降低了18％。

It is a promising research for single crystal silicon with large diameter （above 300 mm） used for photovoltaic materials. Due to the increase of furnace structure, there is an effect on the single crystal silicon growth. The influence of inlet gas flow on the solid-liquid （S/L） interface, thermal stress and oxygen concentration was analysed by the CGSim software. The results show that the height of S/L interface was decreased with increasing the inlet gas flow. The fluctuation of S/L interface was weakest when the gas flow in the medium range, which could improve the stability of silicon growth. On the other hand, the thermal stress value at the tri-phase point was decreased with increasing the gas flow, but the thermal stress fluctuation at the S/L interface was increased. Thus, the optimized inlet gas flow rate was determined in the medium range （ 0. 9-1. 5 m· s- 1 ） to avoid the defect during the silicon growing process. Meanwhile, the oxygen concentration in the silicon was 6.55×10^17 atm/cm3 when the gas flow rate at the 1.5/m· s-1, which was decreased 18% compared with the gas flow rate in the lower range.