Post-lithography pattern modification and its application to a tunable wire grid polarizer

Abstract

This study reports a simple and cost-effective post-lithography solution for reducing the characteristic dimensions of structures on the nanometer scale using an external mechanical force without any modification of the existing exposure system. In particular, this study presents a tunable aluminum wire grid polarizer (WGP) made by a laser interference lithography and i-line (365 nm) exposure setup on polyethylene naphthalate. The WGP achieves a 58% maximum linewidth shrinkage of the metal nanowire on the polymer substrate, and further improved the polarization extinction ratio by 83% with a defined operation window and optimized strain. The simulations in this study prove the rise of the extinction ratio with the modulation of the WGP pattern. Physical evidence explains the fall of the extinction ratio for both the increase of the metal crack volume and the delaminated randomly oriented fall-on fragments under extensive operation.

Nano metal crack initiation on polymer and its optical application with tunable metal dimensions

“…This Poisson effect implies dimensional and signal modification in not only the x-direction but also the y-direction. The WGP pattern was prepared by photolithography process and the applied stress was controlled precisely by micropositioner [2]. In order to transfer the stress from the organic substrate (polyethylene naphthalate, PEN, 125 μm) to the metal wires (aluminum (Al), 30 nm) above it, good adhesion between the substrate and the metal wire is expected.…”

“…Since the WGP structure will face an external strain, these differences could cause early bendings or cracks in the structure which could eventually decrease performance of the WGP device. A fundamental study of this problem [2] shows that cracks with a titanium inter-layer appear already with the 8% external strain. Theory of a different Poisson's ratio suggests that crack onset strain (COS) of the structure with non-negligible differences in Poisson's ratios (Ti/Al case) will be far decreased than within the structure that has an insignificant difference in Poisson's ratios (Al single-layer WGP).…”

“…In our previous studies [1][2], wire-grid polarizer (WGP) was used to demonstrate the stress-induced strain and its potential benefits on extinction ratio (ER) modification. These studies focused on the Poisson effect, especially in the direction perpendicular to the stress, and the stress transition from polymeric substrate to inorganic metals above the substrate.…”

“…Here the dimensional change in the z-direction is neglected and the buffer only appears in (a). (a) The structure with limited tunable range of extinction ratio and operation window[2] and (b) the new structure used in this study.…”

Surface plasmon resonance manipulation through application of mechanically generated planar and linear strain

“…In this study, 12.8% strain was generated, at which the PET was plastically deformed without influencing the integrity of the Au nanostructures. 19,20) The SPR response was detected in a dark field (numerical aperture of 0.4) under an optical microscope that was connected to a spectrophotometer. Except in damaged areas [Fig.…”