BrF3 dry release technology for large freestanding parylene microstructures and electrostatic actuators

We report here a dry release technology for making large freestanding surface micromachined parylene microstructures and its electrostatic actuators. The technology is a two-step process that combines wet photoresist dissolution with dry silicon etching by bromine trifluoride (BrF3). Large parylene MEMS structures can be fabricated using photoresist as the sacrificial layer that ultimately gets dissolved by acetone. A final dry release in BrF3 vapor helps to free the devices. For example, we have successfully fabricated freestanding 1 mm long cantilevers, 2 mm long bridges, and 2 mm diameter diaphragms. Moreover, electrostatic actuators such as cantilever beams, torsional mirrors and clamped chambers has been successfully fabricated and characterized using this technology. These structures are suitable for fully integrated MEMS devices such as accelerometers, gyros and microphones. [Copyright &y& Elsevier]