基于有限元分析法的激光剥离技术中GaN材料瞬态温度场研究

Transient Temperature Field Study of GaN Material in Laser Lift-off Technique Based on Finite Element Method

用有限元分析法模拟计算Al2O3/GaN的激光剥离,分析了采用不同能量密度脉冲激光辐照时GaN材料内的瞬态温度场分布。采用波长248 nm的KrF准分子激光器对Al2O3/GaN样品进行激光剥离实验,实验结果与有限元数值模拟结果一致。分析了影响GaN材料温度场分布的因素,在激光光源一定的条件下,温度随时间和深度变化较快。在实现激光剥离时,脉冲激光的能量密度应不低于阈值条件,但为了避免温度过高对器件产生损伤,脉冲激光的能量密度存在上限。多脉冲激光辐照时,脉冲频率是另一关键参量,计算得到了不同能量密度的脉冲激光辐照时频率的选取范围。

Transient temperature field of GaN material irradiated by pulse laser with different energy density was simulated and analyzed for Al2O3/GaN laser lift-off technique using the finite element method （FEM）. Al2O3/GaN lift-off experiment has also been carried out using 248 nm KrF excimer laser. The simulated results using FEM were consistent well with experiment results. It was found that for the certain laser source, the temperature varied quickly with time and depth in GaN material, and the energy density of pulse laser should be no less than the threshold energy density in order to realize lift-off successfully and no more than the maximum value for avoiding damage caused by too high temperature. During multi-pulse laser processing, another key parameter was pulse frequency, whose variation range was calculated as the function of the energy density of laser.