Flexible Evanescent Wave Interference Lithography System for Sub-half-Wavelength Complex Relief Structures Fabrication

Abstract

Surface microstructures impart various useful properties to objects, for example, improving optical characteristics, wettability, and sliding properties. It is well known that biomimicking relief structures are effective in making such properties arise and have been studied to be applied to various devices. Furthermore, they are expected to be utilized not only for improving a particular property but also for adding more complex functions on a device's surface by fabricating different multi-functional structures on a single surface in the future. However, to begin with, artificially fabricating such biomimicking special functional relief is difficult. One typical feature of biomimicking surfaces is the dual-scale structure, the smaller one of which is less than 200 nm. Moreover, in the case of realizing the more complex devices, it is necessary to fabricate various forms as changing process conditions dynamically. In this study, we proposed and developed a flexible evanescent wave interference lithography system as a novel fabrication method, which allows us to realize the fabrication of sub-half-wavelength complex relief structures. Firstly, we theoretically analyzed the fundamental behavior of the fabricated structure and found that the proposed concept has the potential to realize one of the target complex structures. Secondly, we developed the proposed system with high process flexibility, in which the number of beams, the azimuth angles, and the polarization can be simply manipulated. Finally, we validated the concept of the designed system by some experiments, where we fabricated dual-scale structures with 840-nm and 190-nm fringe patterns simultaneously.