Shrinkage-Considered Mold Design for Improvement of Micro/Nano-Structured Optical Element Performance

Minsu Kim,Eun Song Oh,Moon Kyu Kwak

doi:10.3390/mi11100941

Minsu Kim, Eun Song Oh + Show 1 more

Open Access

https://doi.org/10.3390/mi11100941

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Abstract

Polymer shrinkage in nano-imprint lithography (NIL) is one of the critical issues that must be considered in order to produce a quality product. Especially, this condition should be considered during the manufacture of optical elements, because micro/nano-structured optical elements should be controlled to fit the desired shape in order to achieve the intended optical performance. In this paper, during NIL, we characterized the shrinkage of polymeric resin on micro lens array (MLA), which is one of the representative micro/nano-structured optical elements. The curvature shape and optical performance of MLA were measured to check the shrinkage tendency during the process. The master mold of MLA was generated by the two-photon polymerization (2PP) additive manufacturing method, and the tested samples were replicated from the master mold with NIL. Several types of resin were adjusted to prepare the specimens, and the shrinkage effects in each case were compared. The shrinkage showed different trends based on the NIL materials and MLA shapes. These characterizations can be applied to compensate for the MLA design, and the desired performance of MLA products can be achieved with a corrected master mold.

Highlights

Nano-imprint lithography (NIL) is an advanced lithographic technology for micro/nano devices [1,2,3,4,5]
To achieve the desired field of view (FOV), we considered the shrinkage effect in the design to compensate for the sag data of each lenslet in the micro lens array (MLA)
In this paper, we investigated the problems caused by the shrinkage phenomenon, which may occur in the nano-imprint lithography (NIL) process, which is considered an essential step for the mass production of MLA, a core optical device that has recently been in the spotlight in the industry

Summary

Introduction

Nano-imprint lithography (NIL) is an advanced lithographic technology for micro/nano devices [1,2,3,4,5]. The NIL process can achieve resolutions beyond the limits of light diffraction or scattering because it induces direct contact with the resistance for mechanical deformation of the material. Numerous technologies, such as roll-to-roll NIL, are considered simple and useful for mass production; academia and industries are attempting to actively apply NIL [13,14,15,16,17]. Existing studies on NIL resistance to shrinkage showed that shrinkage can reach up to 20% depending on the mold pattern size [20,21] Such an amount of shrinkage affects the final performance of applications such as optical elements.

Fabrication of Master Mold

Shape Change by Shrinkage

Total Shrinkage

Findings

Conclusions