Parametric Analysis of Electrostatic Comb Drive for Resonant Sensors Operating under Atmospheric Pressure

Abstract

The microelectrostatic comb resonator’s issues with high driving voltage and strong feed-through coupling noise limit its practical use. In earlier studies, the design and structural optimization of microcomb resonators generally focused on lowering beam stiffness and raising electrostatic force density to enhance resonance displacement and lower driving voltage. However, for a microresonator that performs high-speed resonance in the air, it is required to consider the three influencing elements of the electrostatic field, structural mechanics, and fluid mechanics to achieve the best dynamic resonance amplitude. In this paper, the parametric analysis of the comb-driven resonator is carried out. First, the comb-driven electrostatic force and all air-damping terms are investigated using an electrostatic force analytical model considering edge effects, a damping analytical model simplified based on the thin-film damping model, and the finite element model. The analysis results agree with the simulated results. To more accurately quantify the dynamic electrostatic force and damping coefficient, the electrostatic–structure–fluid three-field indirect coupling model was used, and the law of the resonant amplitude of the resonator as a function of the structural parameters was obtained. The results show that, for the electrostatic comb resonator that oscillates at atmospheric pressure, to obtain a high-voltage driving efficiency, a thin polysilicon film can be used to design narrow comb fingers that are dense in the vertical direction and loose in the lateral direction. To validate the accuracy of the model and the results of parameter analysis, an electrostatic comb-drive resonator with shapes optimized from numerical simulations was fabricated. The results show that the driving efficiency is enhanced by 102%, with the chip area increased by 29%, which shows the superiority of parameter optimization.