超短激光制备单晶硅光栅结构的热积累效应和实验研究

Research on heat accumulation effects and experiment of fabrication of silicon grating structure with ultrashort laser

针对超短激光辐照单晶硅材料制备光栅结构存在表面裂纹的缺陷,采用双温模型数值模拟出热积累效应,并且实验验证不同加工参数下制备的单晶硅表面光栅结构的表面质量。数值模拟出不同超短激光功率下电子温度和晶格温度的变化规律,通过调节不同的加工参数制备出单晶硅表面光栅结构沟槽,采用超景深三维显微镜对其表面形貌分析。结果表明:当超短激光的输出功率增大时,激光热驰豫时间变大,增大了非平衡状态下激光的烧蚀强度。单晶硅表面的不平整凹坑造成超短激光的反射和散射,从而使得烧蚀后存在凹坑,造成单晶硅表面的损伤溶蚀。当加工速度和加工次数一定时,增大激光的输出功率可以提高超短激光制备光栅结构的加工效率,但过大的激光功率反而造成光栅结构沟槽两侧出现溶蚀凹坑。

Aiming at the defect of surface cracks in grating fabricated by ultrashort laser irradiation of monocrystalline silicon material,the two-temperature model was used to simulate the heat accumulation effect.The surface quality of grating structure on single crystal silicon fabricated under different processing parameters was verified by experiments.The variations of electron temperature and lattice temperature under different ultrashort laser power were numerically simulated.The grating grooves on the surface of monocrystalline silicon were fabricated by adjusting different processing parameters.The surface morphology was analyzed by three-dimensional microscopy.The results show that the thermal relaxation time of the laser increases with the increase of the output power of the ultrashort laser,and the ablation intensity of the laser in the non-equilibrium state increases.The pits on the surface of monocrystalline silicon cause laser reflection and scattering,which results in pits after ablation and damage and corrosion on the surface of monocrystalline silicon.When the processing speed and times are constant,the processing efficiency of grating structure can be improved by increasing the output power of laser.However,excessive laser power results in corrosion pits on both sides of grating grooves.