退火过程对硅锭热应力与位错影响的数值分析

利用CGSim软件对定向凝固多晶硅从长晶过程开始到退火过程结束进行瞬态数值模拟，研究不同退火温度和退火时间对多晶硅锭内热应力及位错密度的影响。通过软件中热弹性应力非稳态模型（Haasen-Alexander-Sumino模型）计算出位错和Von-Mises应力。结果表明：随着退火温度的升高和退火时间的增加，热应力及位错增殖速率的逐渐减小，在退火1 h后热应力和位错增殖速率大幅减小，退火3 h后减小效果减弱。高温退火时热应力和位错密度低于低温退火，在1250℃下退火3 h是比较合适的方案。

NUMERICAL ANALYSIS OF EFFECT OF ANNEALING PROCESS ON THERMAL STRESSES AND DISLOCATIONS IN SILICON INGOTS

With CGSim software, this study performs transient numerical simulation of the process of directionally solidified polysilicon from the beginning of crystal growth to the end of annealing, and investigates the effects of different annealing temperatures and time on the thermal stress and dislocation density in polysilicon ingots. The dislocation and Von-Mises stress are calculated by using an unsteady model of the thermo-elastic stresses （Haasen-Alexander-Sumino model）. The results of this study demonstrated that with the increase in annealing temperatures and time, the thermal stress and dislocation multiplication rate will reduce gradually, after annealing for 1 h, they will decrease greatly, and after annealing for 1 h, the decrease effect will be greatly weakened. The thermal stress and dislocation density under high-temperature annealing are lower than under low-temperature annealing, and annealing at 1250 ℃ for 3 h is a suitable scheme.