Characterization of porosity in periodic 3D nanostructures using spectroscopic scatterometry

Abstract

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.