Electrostatic testing of simple MEMS structures
Cheng, Kar Mun
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In this thesis, an adapted form of dynamic Electrostatic Force Microscopy is presented as an alternative technique for non-contact dynamic characterization of beam resonators. The actuation of the test resonant beam was accomplished by applying a modulated signal to a probe cantilever that was positioned closely above the resonant beam. The frequency response of the coupled electrostatic interaction between the conductive beams was studied close to the resonance of the test beams. Modulation of the input signal allowed the test resonator to be actuated without requiring on-chip circuitry, and the probing frequency range kept independent of the resonant frequency of the probe cantilever. The resonant response of three test cantilever beams were experimentally characterized using two softer probe cantilevers. A model was constructed to describe the coupled electrostatic interaction and simulations were performed to compare predictions from the model to experimental data. The amplitude response shape, resonant frequency and quality factor from the model fit well with experimental results, showing that the resonant response of a resonator can be characterized using this technique. However, the phase and voltage variation responses were not well characterized, indicating further work to develop the force expressions in the model is needed.