飞秒激光多光束干涉光刻硅表面减反微结构

Femtosecond Laser Multi-beam Interference Lithography Anti-reflective Microstructure on Silicon Surface

为了得到均匀分布的硅表面微结构,提出了一种利用多束激光干涉光刻的方法来实现对硅表面微结构分布特征的控制.利用空间光调制器实现飞秒激光多光束干涉,形成分布均匀、周期可控的空间点阵,利用聚焦的空间点阵在单晶硅表面烧蚀得到规则分布的凹坑状结构,并通过改变附加给空间光调制器的相位实现对微结构分布特征及间距的控制.用扫描电子显微镜和分光光度计分别对结构的形貌特征和光学特性进行了测量,结果表明:采用底角为2°的四棱锥镜相位形成四光束干涉,通过10×物镜聚焦,在激光功率25mW、曝光时间30s时,可以形成间距约为3.3μm的密排凹坑微结构,所形成的凹坑结构具有良好的减反效果,在1.2～2μm近红外波段的透过率相对抛光硅平均提高了11.5%.

In order to obtain uniform distribution silicon surface microstructure,a new method was proposed based on multi-beam interference lithography to relaise the controlling of the distribution character of the microstructure.Femtosecond laser multi-beam interference was formed by Spatial Light Modulator(SLM),and the uniform distribution multi-spots with the controllable period were generated.By using these multi-spots,the regular distribution concave structures were fabricated on silicon surface,and the distribution character and period was flexiblly controlled by shift the phase masks on SLM.The morphology and optical character of the microstructure were measured with Scanning Electron Microscopy(SEM) and spectrophotometer.Experimental results show that the close-packed concave structure with the period of about 3.3 μm can be fabricated on the silicon surface under special parameters(10× focusing lens,laser power of 25 mW,exposing time of 30 s) by loading the phase of 4-facet pyramid lens with the base angle of 2°;the formed structure shows good effect of anti-reflection;its transmission at the near infrared band of 1.2~2 μm enhances 11.5% in comparison with the polished silicon.