Route to production of suspended perforated membranes

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 ...