High-performance wire-grid polarizers using jet and Flash™ imprint lithography

Abstract

Abstract. Extremely large-area roll-to-roll (R2R) manufacturing on flexible substrates is ubiquitous for applications such as paper and plastic processing. It combines the benefits of high speed and inexpensive substrates to deliver a commodity product at low cost. The challenge is to extend this approach to the realm of nanopatterning and realize similar benefits. In order to achieve low-cost nanopatterning, it is imperative to move toward high-speed imprinting, less complex tools, near zero waste of consumables, and low-cost substrates. We have developed a roll-based J-FIL process and applied it to a technology demonstrator tool, the LithoFlex 100, to fabricate large-area flexible bilayer wire-grid polarizers (WGPs) and high-performance WGPs on rigid glass substrates. Extinction ratios of better than 10,000 are obtained for the glass-based WGPs. Two simulation packages are also employed to understand the effects of pitch, aluminum thickness, and pattern defectivity on the optical performance of the WGP devices. It is determined that the WGPs can be influenced by both clear and opaque defects in the gratings; however, the defect densities are relaxed relative to the requirements of a high-density semiconductor device. © The Authors. Published by SPIE under a Creative Commons IntroductionThe ability to pattern materials at the nanoscale can enable a variety of applications ranging from high-density data storage, displays, photonic devices and complementary metaloxide-semiconductor integrated circuits to emerging applications in the biomedical and energy sectors. These applications require varying levels of pattern control, short-and long-range order, and have varying cost tolerances.Roll-to-roll (R2R) printing or web printing involves the patterning of flexible materials such as plastics or metal foils. The flexible material, or web, is unwound from a core, processed, and then returned to a second core at the end of the sequence. R2R processing is in use today by industry and many R2R processes already exist for etch and deposition. Lithographic processes are also established for micron-scale manufacturing and for applications that only require polymer embossing without any subsequent processing.1 Recent work has investigated devices requiring metal etching in conjunction with imprint lithography, but again at a micron scale.2 However, R2R patterning of arbitrary patterns with thin residual layer control (needed for subsequent pattern transfer) at the nanoscale is far more challenging, particularly at a cost structure suited for commodity applications. The challenge is to create a process that is scalable and meets defectivity, throughput, and cost of ownership requirements.The cost of manufacturing is typically driven by speed (or throughput), tool complexity, cost of consumables (materials used, mold or master cost, etc.), substrate cost, and the downstream processing required (annealing, deposition, etching,

Solution‐Processed Aluminum Nanogratings for Wire Grid Polarizers

“…Large discrepancies in the extinction ratio between the experiment and simulation mainly arise from structural imperfections of the Al nanogratings and clear defects that leak light regardless of its polarization (Figure S4, Supporting Information) . In addition to the surface roughness of the Al nanogratings, pores formed inside the Al during the electroless plating are also structural imperfections.…”

“…Therefore, extinction ratio of the fabricated Al WGP is much lower than that from the simulation. Furthermore, nanotrenches unfilled with Al (i.e., clear defects), which can transmit light regardless of its polarization have little effect on the TM transmission; however, the TE transmission significantly increase in proportion and thereby degrade the extinction ratio of the fabricated Al WGP …”

Nanomanufacturing: A Perspective

“…Single-level structures, used in applications such as large-area reflective coatings, 119,120,121 and holographic wrapping paper, 122 do not suffer from these problems. Extending single-level R2R technology to the nanoscale would enable applications such as organic photovoltaics, 123,124 light-management films 125 and wire-grid polarizers for high-contrast displays 126,127,128 anti-reflective coatings, super-hydrophobic (philic) surfaces, as well as those requiring plasmonic activity. 129,130,131 Self-aligned imprint lithography uses a multilevel template that produces pre-aligned structures, avoiding level-to-level alignment problems.…”

40-3: Fabrication of a Wire Grid Polarizer on Liquid Crystal Display Using Nano-imprinting Lithography

“…By using Ewald-Oseen extinction theorem [2], with reflectance and birefringence features of the WGP, the optical efficiency can increase 30~40% in principle. Also, it is widely known that less than 120nm pitch and over 1: 3 aspect ratio of height and width are necessary for the WGP to obtain 10 thousands extinction ratio [3] which is comparable to the absorption type polarizers.…”