Abstract
Developing a suitable production method for three-dimensional periodic nanostructures with high aspect ratios is a subject of growing interest. For mass production, Talbot lithography offers many advantages. However, one disadvantage is that the minimum period of the light intensity distribution is limited by the period of the diffraction grating used. To enhance the aspect ratio of fabricated nanostructures, in the present study we focus on multiple wave interference between diffracted waves created using the Talbot effect. We propose a unique exposure method to generate multiple wave interference between adjacent diffraction orders by controlling the angle of incidence of an ultraviolet (UV) light source. Using finite-difference time-domain simulations, we obtain fringe patterns with a sub-wavelength period using a one-dimensional periodic grating mask. Moreover, we demonstrate the practical application of this approach by using UV lithography to fabricate sub-wavelength periodic photopolymer-based structures with an aspect ratio of 30 in millimeter-scale areas, indicating its suitability for mass production.
Highlights
The structural properties of high-aspect-ratio periodic nanostructures have drawn considerable interest in recent years due to their applicability to various fields such as medical devices [1], genetic engineering [2,3,4], functional surfaces [5,6,7,8,9], and optical devices [10,11,12,13]
Interference lithography, which is a powerful tool for fabricating periodic nanostructures, has attracted significant attention since the 1970s because it uses a simple lithography process that involves periodic light patterns generated via multi-wave interference, and is well-suited to fabricating periodic structures [14]
In an effort to increase the aspect ratios of structures produced via Talbot lithography, our research focused on the incidence angle flexibility of the ultraviolet (UV) light source based on the notion that by controlling the incidence angle, we could eliminate higher-order diffracted light and generate two-wave interference using diffracted waves with adjacent diffraction orders
Summary
The structural properties of high-aspect-ratio periodic nanostructures have drawn considerable interest in recent years due to their applicability to various fields such as medical devices [1], genetic engineering [2,3,4], functional surfaces [5,6,7,8,9], and optical devices [10,11,12,13]. Since previous investigations have shown that interference lithography requires complex optical setups to maintain high coherence, several more recent studies have focused on optical phenomena in the search for ways to generate interference patterns using simple optical setups These include the near-field holography process, which makes use of 1D periodic gratings to generate fringe patterns with two adjacent order diffracted waves. In this process, which was reported for the first time by Jeon et al in 2004 [24,25], 3D periodic nanostructures can be fabricated over a large area at one time by a process known as “printing periodic light intensity distribution”, which is generated by plane wave transmission via a grating mask [26,27] This Talbot method is disadvantageous in terms of fabrication flexibility because the aspect ratios of fabricated structures are limited by the Talbot effect period. We describe lithography experiments that were performed to experimentally demonstrate the successful fabrication of high-aspect-ratio periodic structures
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