Characterization of porosity in periodic 3D nanostructures using spectroscopic scatterometry

Periodic nanostructures have important applications in nanophotonics and nanostructured materials as they provide various properties that are advantageous compared to conventional solid materials. However, there is a lack of metrology techniques that are suitable for large-scale manufacturing, as the traditional tools used in nanotechnology have limited throughput and depth resolution. In this work, we use spectroscopic scatterometry as a fast and low-cost alternative to characterize the porosity of three-dimensional (3D) periodic nanostructures. In this technique, the broadband reflectance of the structure is measured and fitted with physical models to predict the structure porosity. The process is demonstrated using 3D periodic nanostructures fabricated using colloidal phase lithography at various exposure dosages. The measured reflectance data are compared with an optical model based on finite-difference time-domain and transfer-matrix methods, which show qualitative agreement with the structure porosity. We found that this technique has the potential to further develop into an effective method to effectively predict the porosity of 3D nanostructures and can lead to real-time process control in roll-to-roll nanomanufacturing.

周期性纳米结构在纳米光子学和纳米结构材料中具有重要应用，因为它们提供了相较于传统固体材料更具优势的各种特性。然而，缺乏适用于大规模制造的计量技术，因为纳米技术中使用的传统工具在通量和深度分辨率方面存在局限性。在这项工作中，我们使用光谱散射测量法作为一种快速且低成本的替代方法来表征三维（3D）周期性纳米结构的孔隙率。在这种技术中，测量结构的宽带反射率，并与物理模型拟合以预测结构孔隙率。使用通过胶体相光刻在不同曝光剂量下制造的3D周期性纳米结构对该过程进行了演示。将测量的反射率数据与基于时域有限差分和传输矩阵方法的光学模型进行比较，结果显示与结构孔隙率在定性上相符。我们发现该技术有潜力进一步发展成为一种有效预测3D纳米结构孔隙率的方法，并可在卷对卷纳米制造中实现实时过程控制。