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Minimizing impact force during actuation reduces damage to contacting surfaces. An electrostatic actuation method for creating a soft contact between dielectric and semiconductor surfaces is described and applied to cantilevers and clamped beams. The method utilizes a short high-voltage delta-pulse followed by a low dc hold voltage to pull in the cantilever or beams. Removal of the hold voltage releases the beam back to its rest position. The height and the shape of the delta-pulse control the energy transferred to the beams and are shown to be critical in predicting minimum actuation voltages. Actuation pulses with heights even a few tenths of a volt above minimum can lead to stuck devices, whereas minimum pulses do not. The actuation method has been experimentally tested, and a simplified mathematical model has been simulated to confirm the experiment results. In addition, it is observed that a high-voltage actuation pulse applied for a longer time than necessary to actuate, but in phase with the apparent elastic response of the beam, will cause the beam to bounce upward rather than stick during actuation.
Date of Publication: June 2008