冷心放肩微量提拉法大尺寸蓝宝石单晶生长过程的模拟分析

Simulation Analysis on the SAPMAC Crystal Growth Process of Large Size Sapphire

利用数值模拟方法计算了冷心放肩微量提拉法(SAPMAC)蓝宝石晶体生长过程。结合晶体直径变化、裂纹出现位置与延续方向、晶体透明性等实验现象,通过与提拉法、温梯法、坩埚移动法等相对比,分析了冷心放肩微量提拉法晶体生长各阶段的工艺特点,并根据模拟计算结果对晶体生长系统和晶体生长控制工艺进行了改进。分别利用增大热交换器的散热参数、降低加热温度、改进降温曲线、调节外加轴向和径向温度梯度的方式来实现对晶体生长的引晶、放肩、等径和收尾控制。通过实验比较证明了改进后的晶体生长系统和晶体生长控制工艺能够生长出性能较好的大尺寸蓝宝石晶体。

The SAPMAC （sapphire growth technique with micro-pulling and shoulder at cooled center） process has investigated by numerical simulation method. The characteristics of several different crystal growth stages have been analyzed and compared with Czochralski method, temperature gradient technique and bridgman technique etc. Base on the results of simulation and techniques of different crystal growth stages, the system and control techniques of crystal growth were improved; the conventional SAPMAC furnace was modified with the heat dissipation parameters increased, the heating temperature decreased, the temperature falling curve improved, the additional axial and radial temperature gradient adjusted, so the necking-down, shoulder-extending, iso-diameter and tailing process of the crystal growth can be controlled. The experiment results testified that the grown crystal has better quality and larger size by the improved system of crystal growth and control techniques.