Q-boosted AlN array-composite resonator with Q>10,000

Quality factors (Q´s) greater than 10,000 and higher than reported for any other sputtered AlN d₃₁-piezoelectric micromechanical resonator have been demonstrated for the first time using an energy sharing mechanical circuit that mechanically couples two electrode-equipped AlN resonators with several electrode-less ones. The key enablers behind the described Q increase are 1) removal of metal electrodes from the inner AlN resonators to remove metal-to-piezoelectric interface losses towards a more than 8× increase in Q; and 2) coupling these higher Q electrode-less resonators to electrode-equipped ones to share energy between the resonators in a way that effectively boosts the Q of the latter with very little increase in motional impedance. By attaining such high Q, this work now proves that the Q of previous AlN resonators was not limited by material inadequacies, and that in fact metal is most responsible for suppressing the Q of previous AlN piezoelectric thin-film devices. The much higher Q´s demonstrated here should greatly decrease both insertion loss in filters and phase noise in oscillators.