Tunable silicon bulk acoustic resonators with multi-face AlN transduction

Abstract

This paper presents tunable width-extensional mode bulk acoustic resonators that are piezoelectrically-actuated and sensed using thin layers of AlN on the sidewalls as well as the top surface. By using both longitudinal and transverse piezoelectric effects of conformally-sputtered AlN layers on sidewalls and top surface of a 20 m thick resonator, a low motional resistance of ~35 Ω was achieved for a 100 MHz silicon resonator operating in air. The motional resistance is improved by at least 10x compared to similar devices with capacitive transduction. Furthermore, it is shown that the resonance frequency of these piezoelectrically-transduced devices can be tuned by varying the electric signal power from 0 to 7 dBm.