Out-of-plane electrostatic actuation of microcantilevers

Abstract

An electrostatic actuation method to generate useful out-of-plane motion of a cantileverstructure is described. The critical design feature is to create an asymmetric electric fieldsuch that an electrostatic force is generated in a direction perpendicular to the wafersurface. The technical application of the actuation method is to large arrays ofmicrofabricated sensors such as cantilevers and in particular to resonator type sensors. Thedesign approach also overcomes several problems associated with exposure ofmicrofabricated cantilever structures to fluid environments, either during processing orduring application of such devices as bio-sensors, e.g. stiction, condensation, squeezedamping, exposure to a biological sample, cleaning and biological activation treatmentsof the cantilever surfaces. The viability of the technique is demonstrated usingmicrofabricated silicon cantilevers utilizing both optical and piezoresistive detection of thecantilever displacement.