Development and analysis of microbridge resonators for reduced pull-in voltage and preserved resonant frequency

Abstract. This study presents a novel design methodology for microbridge resonators aimed at reducing pull-in voltage while maintaining resonant frequency. Previous studies have primarily focused on adjusting resonator plate geometry, modifying anchor conditions, or altering material properties to control pull-in voltage. In contrast, this work introduces the ratio of the bottom electrode length to the microbridge length as a critical and tunable design parameter, which has remained unexplored in previous studies. An analytical model is developed to capture the effects of this ratio, and its predictions are validated through finite element analysis. To demonstrate the concept, two microbridges are designed and fabricated with bottom electrode lengths of 42 and 82 µm, corresponding to 35 % and 68 % of the microbridge length, respectively. All other design parameters, such as plate thickness, material properties and cavity height, are kept constant to enable a fair comparison. Electrical characterizations confirm that increasing the bottom electrode-to-microbridge length ratio effectively lowers the pull-in voltage without degrading resonator performance. Results show a 16 % reduction in pull-in voltage when the bottom electrode length is 68 % of the microbridge length, demonstrating the feasibility and advantages of the proposed methodology over existing techniques.