Electrothermal actuation of mems resonator based filters with piezoelectric sensing

摘要

Summary form only given: Microelectromechanical systems (MEMS) resonators have been intensively investigated as an alternative for electronic filter components currently used in communication systems because of their small size and low operating voltages [1]. Electrothermal actuation, compared to other transduction techniques for electrical induction of mechanical vibrations, brings benefits in terms of simple fabrication, impedance matching and low actuation voltages. Electrothermally actuated resonators provide high resonant frequencies, high Q-factors and wide frequency tuning range [2, 3]. Recently, we have demonstrated the piezoelectric sensing of electrothermally actuated double-clamped beam MEMS resonators [3, 4]. Piezoelectric sensing technique, compared to the alternative electrostatic transduction, offers stronger electromechanical coupling, better impedance matching and simpler fabrication process. In addition, it allows active generation of electrical potential under applied mechanical stress, without need for external bias supply. In this work, we investigate on electrothermal actuator design solutions for optimizing frequency tuning range and Q-factor of the devices. Devices of two types were fabricated, with the only difference in the electrothermal actuator layout design, slab and u-shape layout, while other technological parameters and dimensions are the same (Fig. 1). Tested devices were taken from the same die and tested by performing two-port transmission frequency response measurements. The devices operate between 0.75 and 1.2MHz for tuning voltages of 1 to 7 V, and Q-factors up to ~ 400 have been measured in atmospheric conditions. Experimental results have shown that the device actuated with u-shape electrode resonates at lower frequencies with higher Q-factor, and that wider frequency tuning has been obtained under the same actuating conditions. Design, fabrication and measurement setup details will be presented. Moreover, the influence of the electrothermal actuator design on the resonant behavior will be discussed.