不同环境中纳秒激光烧蚀单晶硅的物质抛出机理

Investigation on mechanism of material ejection by nanosecond laser ablation of mono-crystalline silicon under different environments

为了探究纳秒激光烧蚀单晶硅过程中熔融物质的喷溅过程,对不同加工环境中纳秒激光烧蚀单晶硅的过程进行了模拟仿真及实验验证。采用Level-Set界面追踪法,通过仿真软件建立有限元模型,对空气、静水和真空加工环境中纳秒激光烧蚀单晶硅时物质抛出过程进行模拟仿真,研究了不同加工环境中温度场、速度场对表面喷溅的影响;采用波长266 nm、脉宽30 ns和频率50 Hz的单脉冲激光烧蚀单晶硅的工艺实验对仿真结果进行验证,通过原子力显微镜和数字显微镜对烧蚀结果进行了表征。结果表明,空气环境中,t=30 ns时熔融物质的喷溅速率达到14.1 m/s,在微孔内部蒸汽压力的作用下,烧蚀区域熔融物质向外喷出;静水环境中,t=30 ns时熔融物质的喷溅速率为1.68 m/s,远低于空气中的喷溅速率,熔融物质快速冷却;真空环境中,材料在短时间内汽化,t=30 ns时熔融物质的喷溅速率最大可达18.4 m/s,较高的喷溅速率有利于物质的抛出。加工环境对纳秒激光烧蚀单晶硅的物质抛出影响较大,这为提高纳秒激光加工单晶硅的加工质量提供了参考。

In order to investigate the process of molten material ejection during nanosecond laser ablation of mono-crystalline silicon,simulation and experimental investigation on nanosecond laser ablation of silicon under different environments were carried out.Simulation on the material ejection during nanosecond laser ablation of silicon under air,water,and vacuum environments with simulation software was carried out based on the Level-Set method.The effects of the temperature field and velocity field on surface sputtering under different environments were investigated.Experiments on laser ablation of mono-crystalline silicon using a wavelength of 266 nm,a pulse width of 30 ns,and a frequency of 50 Hz were done to verify the simulation results.The ablation results were observed by atomic force microscopy and digital microscopy.The results show that the spatter velocity under the air environment is 14.1 m/s at t=30 ns,and the molten material ejectes the ablated holes outwards due to the action of vapor pressure in the ablated area.Under the water environment,the spatter velocity is 1.68 m/s at t=30 ns,much lower than that in air conditions.Under the vacuum environment,the material is vaporized for a short time,and the spatter velocity of the molten material is 18.4 m/s at t=30 ns.The molten materials eject productively due to the high spatter velocity.The adhesion of molten material on the surface is improved.The processing environment has a strong influence on the material ejection during the nanosecond laser ablation of silicon.The investigation provides a reference for improving the quality during nanosecond laser micro-machining.