Corrugated micromachined membrane structures

Thin film copper membranes on silicon substrates were constructed using microelectronic fabrication techniques. Membranes possessed radial surface corrugation patterns. Membrane sizes ranged from 3.25 mm to 4 mm in diameter. A corrugation height of 10 μm was chosen to maximize membrane flexibility. Two corrugation pitches were used; 200 μm and 120 μm. Double-sided lithography was used to ensure proper alignment between frontside and backside features. Membranes were released using a combination of both KOH and XeF₂ backside etching. Surface corrugations were made using KOH etching on the frontside of the wafer. Thin film copper was deposited using thermal evaporation. Membrane flexibility was studied as a function of diameter and corrugation pitch. Membranes were electrostatically actuated using a high voltage DC supply.