硅表面抗反射纳米周期阵列结构的纳米压印制备与性能研究

硅表面固有的菲涅耳反射, 使得硅基半导体光电器件(如太阳能电池、红外探测器)表面有30%以上的入射光因反射而损失掉, 严重影响着器件的光电转换效率. 寻找一种方法降低硅基表面的反射率, 进而提高器件的效率成为近年来研究的重点.本文基于纳米压印光刻技术, 在2 英寸单晶硅表面制备出周期530 nm, 高240 nm的二维六角截顶抛面纳米柱阵列结构. 反射率的测试表明, 当入射光角度为8° 时, 有纳米结构的硅片相对于无纳米 结构的硅片来讲, 在400到2500 nm波长范围内的反射率有很明显的降低, 其中, 800到2000 nm波段的反射率都小于10%, 在波长1360 nm附近的反射率由31%降低为零. 结合等效介质理论和严格耦合波理论对结果进行了分析和验证. 关键词： 纳米压印 截顶抛物面阵列 抗反射 等效介质理论

The fabrication of the antireflective periodic nano-arrary structure on Si surface using nanoimprint lithography and the study on its properties

The intrinsic Fresnel reflection of Si surface, which causes more than 30% of the incident light to be reflected back from the surface, seriously influences the photoelectric conversion efficiency of Si-based semiconductor photoelectric device, such as solar cell and infrared detector. Recently, how to find a simple and efficient method, which is also suitable for mass production, aiming to suppress the undesired reflectivity and therefore improving the efficiency of the device, has become a research focus. In this work, we successfully convert a 2D nanopillar array structure into the Si surface via the nanoimprint lithography. The nanopillar has a flat surface and a paraboloid-like side wall profile. The period and the height of the hexagonal array structure are 530 nm and 240 nm, respectively. The cut-paraboloid nanopillar structure generates a relatively smooth gradient of the refractive index in the optical interface, which plays a key role in suppressing the Fresnel reflection in a wide range of wavelength. The reflectivity of the nanopillar arrayed Si surface is tested in a wavelength range from 400 to 2500 nm at an incident angle of 8° during the measurement. Compared with the unstructured Si, the structured Si has a reflectivity that significantly decreases in the test area: in a wavelength range from 400 to 1200 nm, and the reflectivity of the silicon surface is less than 10%. Specifically, the reflectivity is almost zero at a wavelength of about 1360 nm. The results are confirmed with the effective medium and rigorous coupled-wave theory.
Keywords： nanoimprint lithography cut-paraboloid arrays antireflection effective medium theory