基于X射线塔尔博特效应的纳米光栅制作模拟研究

沿纳米多层膜生长方向切割可制成周期只有几纳米而厚度几十微米的切片多层膜光栅. 基于该切片多层膜光栅塔尔博特自成像效应的X射线光刻是一种新型的纳米图样制作方法. 已有学者用该方法完成了百纳米结构光栅的制作. 采用严格耦合波方法, 本文模拟计算了切片多层膜光栅在满足塔尔博特自成像条件下的后表面光场分布, 详细讨论三个影响光栅后表面成像质量的重要参数:光栅厚度、材料厚度所占比例和多层膜周期. 模拟结果表明, 光栅厚度不仅影响X射线透射率, 还会改变像面条纹衬比度. 材料厚度比的大小直接决定像面是否存在清晰条纹, 选取合适的材料厚度比, 得到了前人实验中近场反常成像现象. 计算还表明, 在一定条件下, 采用周期更小的多层膜光栅有望获得更高分辨率的纳米图形, 这说明使用塔尔博特效应制作更加精细的纳米结构图形具有可行性.

Simulation of nano-grating patterning based on X-ray Talbot effect

High aspect ratio gratings can be made by perpendicularly cutting in the growth direction of multilayers. X-ray exposure technique using a sectioned multilayer grating based on Talbot effect is a new type of nano patterning method. Although 300 nanometer gratings through the experiment are completed, some phenomena in the experiments cannot be satisfactorily explained and the factors influencing the nano pattern quality have not been fully understood yet. Here we use a rigorous coupled-wave theory to discuss several important factors, including grating thickness, the fraction of material thickness and multilayer period, which is the first time as far as we know for Talbot self-imaging in X-ray range. Simulation results show that the grating thickness affects both X-ray transmission efficiency and fringe contrast, while the fraction of material thickness determines the quality of fringes. And the position deviation of the best image plane in near field is related to both the thickness of the grating and the multilayer period. Moreover, the multilayer gratings with smaller periods can achieve higher resolution, indicating that the Talbot effect can be used to fabricate a more detailed structure.