Optical designs in proximity field nanopatterning for diversification of three-dimensional nanostructures

Abstract

Development of nanopatterning technology has enabled the realization of material properties which are absent in nature. In particular, 3D nanostructures have synergistic effects by unique structural and material properties only emerged in the nano-scale dimension to expand the function and utilization of the material in various fields. To date, 3D nanostructures have been applied to various fields with diverse fabrication methods, but there are not many processes that have sufficient levels for economics efficiency, reliability, and functionality suitable for commercialization. Among the related processes, the proximity field nanopatterning (PnP) realizes 3D nanostructure by a single exposure on phase mask adjacent to photoresist. During this step, 3D interference pattern are printed in the photoresist and the pattern is materialized through a serial lithography process. It is considered that PnP has overall fidelity for commercialization. So far, PnP uses a single-layered phase mask, which realizable 3D nanostructures are limited to the body-centered tetragonal symmetries. In order to fundamentally control the material properties of 3D nanostructures, it is necessary to diversify symmetry of 3D nanostructures. In this Ph.D. study, it is proposed to diversify the realizable 3D nanostructures through optical design of PnP. To accomplish this goal, multilevel phase mask is designed to fabricate diamond-like woodpile structure. The second approach is control of exposure angle for diversification of 3D structures. Final optical study uses algorithm-based inverse design for phase mask pattern, which is capable to generate target 3D nanostructure to maximize the degree of freedom of process.