The influence of perforation on electrostatic and damping forces in thick SOI MEMS structures

The influence of perforation on the electrostatic force for thick micro-electromechanical (MEMS) structures is analyzed theoretically and experimentally. A three-dimensional numerical model is provided in order to evaluate the influence of the fringe capacitive field on the electrostatic force. Several configurations of perforated MEMS structures were characterized under ambient air conditions and experimental results demonstrate good consistency with the model prediction. Moreover, a comparative study on the effect of perforation on damping (quality factor) was performed. A quality factor was experimentally determined by analyzing frequency response under electrostatic excitation and time response under pulse loading, and was compared to a few analytical models, which demonstrate reasonable agreement with the measured results. Our study demonstrates that perforation has a significant effect on the quality factor, while its contribution of the electrostatic fringe capacitive field ranges between additional few to few tens of per cents.

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