不同延时的组合脉冲激光致硅表面损伤研究

为了研究组合脉冲激光与单晶硅材料的相互作用过程，采用两束脉宽分别为7ns和1ms的脉冲激光复合作用的方式，进行了单束毫秒脉冲激光和组合脉冲激光辐照硅片的实验研究，并结合数值计算对比了两种激光工作模式辐照造成的表面损伤形貌；根据组合脉冲激光延迟时间的不同将损伤形貌分为3类，对熔融深度和表面损伤半径做了进一步的研究。结果表明，组合脉冲激光的损伤效应更为严重，包括解理裂纹、烧蚀和皱褶，表面损伤半径主要取决于入射毫秒脉冲激光的能量密度，而熔融深度随延迟时间的增加而减小；毫秒脉冲激光的预加热以及纳秒脉冲激光造成的表面损伤与后续毫秒脉冲激光的相互作用，使得组合脉冲激光具有更好的损伤效果。该研究结果可为今后组合脉冲激光加工半导体材料提供参考。

Surface damage study of silicon induced by combined millisecond and nanosecond laser with different delays

The laser-silicon interaction process was investigated with the superposed radiation of two pulsed lasers. A pulse duration of 1ms was superposed by 7ns pulses, creating a combined pulse laser (CPL). The experimental study of single millisecond pulse laser and CPL irradiation on silicon wafer was carried out, respectively. Along with numerical calculation, the surface damage morphology caused by the two laser operation modes was compared. It can be divided into three kinds according to different delays of CPL. Further research was done on the melting depth and damage radius. The results show that the damage effect induced by CPL is more severe, including cleavage cracks, ablation and fold. The damage radius on the surface mainly depends on the energy density of incident ms laser, and the melting depth decreases with the increase of delay time. The better damage effect of CPL is ascribed to the pre-heating ms laser and the interaction of the follow-up ms laser with the surface damage formed by the ns laser. The results can be used as a reference for the processing of semiconductor materials by combined pulse laser in the future.