HIGH-ASPECT-RATIO POLYMER MICROSTRUCTURES AND CANTILEVERS FOR BIOMEMSUSING LOW-ENERGY ION-BEAM AND PHOTOLITHOGRAPHY

In this paper, the high etching selectivity of different fluoropolymer s and for the fabrication of high aspect ratio polymer (HARP) microstr uctures is reported. Free standing polymer cantilevers for the develop ment of transparent fluoropolymer-based microfluidic devices are prese nted. Fluoropolymers, such as Teffon(R)-based polymers, are hydrophobi c and inert to most solvents and chemicals. The low surface energy of fluoropolymers makes the fabrication of microstructures from these sub strates most difficult when using conventional silicon microfabricatio n steps. Low energy ion beam methods are used to improve the wetting c haracteristics of photoresists on a family of fluoropolymers including polytetrafluoroethylene (PTFE), Tefzel(R), fluoroethylenepropylene (F EP), and Teflon(R) AF. Satisfactory pattern transfer capability down t o submicron dimensions is achieved through low energy ion beam technol ogy. The optimum selectivity of etch rates between fluoropolymers and photoresists is determined through variations of incident beam angles for multilayer integration. HARP microstructures and cantilever arrays of fluoropolymers are achieved by controlling surface profile with th e high etching selectivity between different polymers and an oblique a ngle of incident beam. These polymer cantilevers have direct applicati ons as biochemically functionalized tips for an atomic force microscop e or as near field probes within integrated microfluidic systems. (C) 1998 Published by Elsevier Science S.A. All rights reserved.