Route to production of suspended perforated membranes

Abstract

The authors report a flexible approach to fabrication of suspended perforated membranes. Interferometric lithography is used to pattern photoresist to create an etch mask on a silicon substrate. Reactive ion etching results in the formation of a matrix of silicon pillars. The interstices of the pillar matrix are then filled with the membrane material. Subsequent removal of the silicon matrix and underlying substrate yields a suspended membrane with perforations where the pillar matrix protruded prior to removal. The method combines interferometric lithography and conventional lithography to provide both periodic and nonperiodic patterns in a seamless process flow. The use of a matrix of sacrificial pillars enables the formation of higher aspect ratio holes than standard liftoff or etched film approaches. Perforated membranes of a siloxane based silica, photocurable polymer, and evaporated Cr are presented, demonstrating the wide process latitude of this approach. Such suspended membranes have application in photonic, metamaterials, DNA translocation, and biological and chemical sensors.