High aspect ratio polymer microstructures and cantilevers for bioMEMS using low energy ion beam and photolithography

Abstract

In this paper, the high etching selectivity of different fluoropolymers and for the fabrication of high aspect ratio polymer (HARP) microstructures is reported. Free standing polymer cantilevers for the development of transparent fluoropolymer-based microfluidic devices are presented. Fluoropolymers, such as Teflon ®-based polymers, are hydrophobic and inert to most solvents and chemicals. The low surface energy of fluoropolymers makes the fabrication of microstructures from these substrates most difficult when using conventional silicon microfabrication steps. Low energy ion beam methods are used to improve the wetting characteristics of photoresists on a family of fluoropolymers including polytetrafluoroethylene (PTFE), Tefzel ®, fluoroethylenepropylene (FEP), and Teflon ® AF. Satisfactory pattern transfer capability down to submicron dimensions is achieved through low energy ion beam technology. 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 the high etching selectivity between different polymers and an oblique angle of incident beam. These polymer cantilevers have direct applications as biochemically functionalized tips for an atomic force microscope or as near field probes within integrated microfluidic systems.