(536e) Large-Scale Fabrication of 50nm Nanopore Array in Teflon Using Reactive Ion Etching Technique with Anodized Aluminum Oxide Templates As Etch Masks

Advanced cryogenic systems rely on efficient cooling mechanisms for achieving higher power density and system efficiency. Improving the convective liquid-vapor phase change heat transfer mechanism in cryogenics could lead to substantial energy savings and reduced greenhouse gas emissions. Nanoporous surface textures are known to enhance heat transfer efficiency in the boiling and quenching regimes. Also, studies have reported that Teflon coated surfaces with non-wetting cavities have improved pool boiling heat transfer efficiency. Fabricating Teflon nanopore array surfaces can potentially combine the benefits of both non-wetting and nanotexture surface heat transfer enhancements. Here, we fabricated large-scale Teflon Nanopore array surfaces using highly ordered anodized aluminum oxide (AAO) template as a plasma etch mask. The AAO templates with an average pore diameter of 50nm are fabricated by a two-step anodization process in 0.3M oxalic acid solution. Inductively coupled plasma reactive ion etching technique (ICP-RIE) is used to anisotropically etch the unmasked regions to replicate the nanopore array pattern of AAO on Teflon. In traditional AAO pattern transfer techniques, the AAO barrier layer is removed using dilute phosphoric acid solution and, the polystyrene (spin coated over AAO as a template transfer layer for additional mechanical support) is removed using a single step oxygen plasma etching. Even though straightforward, these techniques are limited to smaller areas of pattern transfer due to incomplete barrier layer pore opening across the template and presence of residual polystyrene inside the pores. In this study, we identified factors that hinder the scale-up process and, we suggested alternative novel techniques to improve the pattern transfer efficiency. It’s imperative to fabricate the Teflon nanopore array over a large surface area to make them commercially viable. By following the alternative novel AAO pattern transfer techniques in this work, we were able to achieve pattern transfer over 90% of the Teflon area that was under the AAO template.