光电子技术, 2018, 38 (4): 224, 网络出版: 2019-01-15
多脉冲飞秒激光烧蚀硅的热累积效应
Heat Accumulation Effect of Multipulse Femtosecond Laser Ablation of Silicon
飞秒激光 分子动力学 热累积效应 数值模拟 宏观热模型 光滑孔状形貌 硅材料加工 femtosecond laser molecular dynamics thermal incubation effect numerical simulation macrothermal model smooth cavernous appearance silicon processing
摘要
利用分子动力学模型模拟出单个脉冲作用后的热传导过程, 并得到了在下个脉冲辐照前硅材料表面的温度变化情况, 深入探究了非辐射复合及表面浮雕结构对硅表面温度的影响, 并根据分子动力学方程数值模拟了多脉冲飞秒激光烧蚀硅材料的超快热响应, 分析了电子与晶格的瞬态热平衡和硅表面最大温度随俄歇复合的变化。针对硅材料加工领域中高频多脉冲持续扫描硅表面的情况, 建立了宏观加热机制, 以减轻加工过程中的热累积效应。当采用较高重频脉冲时, 宏观热模型计算结果表明多脉冲扫描硅表面时, 温度的热积累不仅与光源本身入射通量和重频有关, 也与扫描速度有关。实验中运用通量为1~2 J/cm2、重频为10 Hz~1 kHz的飞秒激光光源烧蚀硅靶, 发现低频脉冲下表面熔融、氧化等现象不利于产生光滑孔状形貌。
Abstract
The molecular dynamics modeling was used to simulate the heat transferring process when a single pulse arrived, and the temperature change inside the silicon before the next single pulse was set in. The influence of non-radiative recombination and surface relief structure on silicon surface temperature were inquired thoroughly. According to the molecular dynamics equation, the ultrafast thermal response of silicon irradiated by multipulse femtosecond laser was simulated, and transient heat balance between the electron and lattice and silicon surface maximum temperature change with auger recombination were analyzed. Aiming at the situation of continuous high frequency multipulse scanning the silicon surface in the field of silicon material processing, a macro-heating mechanism was established to lessen the thermal accumulation effect during processing. When the high repetition frequency pulse was used, the calculation results of the macroscopic thermal model showed that the thermal accumulation of the temperature was not only related to the incident flux and the repetition frequency of the light source, but also to the scanning speed. In the experiment, the femtosecond laser was used to burn the silicon target while the fluxes was 1 ~ 2 J/cm2 and heavy frequency was 10 Hz ~ 1 kHz. It is found that the surface melting and oxidation of the low-frequency pulse could be adverse to producing a smooth hole shape.
张明鑫, 李志明, 聂劲松, 谢运涛. 多脉冲飞秒激光烧蚀硅的热累积效应[J]. 光电子技术, 2018, 38(4): 224. ZHANG Mingxin, LI Zhiming, NIE Jinsong, XIE Yuntao. Heat Accumulation Effect of Multipulse Femtosecond Laser Ablation of Silicon[J]. Optoelectronic Technology, 2018, 38(4): 224.