Q-enhancement through minimization of acoustic energy radiation in micromachined lateral-mode resonators

This paper describes a technique to increase the quality factor (Q) of lateral-mode piezoelectric resonators by reducing the amount of acoustic energy lost through the support tethers. Trenches are etched in the substrate layer surrounding the resonator at a specific distance from the resonator edge to function as an acoustic reflector. Resonators with optimized reflectors consistently show improved Q´s compared to similar devices lacking the reflectors. The highest measured unloaded Q is 18,000 in vacuum (at ~115 MHz), upwards of 45% improvement over the highest Q recorded from the devices without reflectors.