Al0.7Sc0.3N butterfly-shaped laterally vibrating resonator with a figure-of-merit (kt2·Qm) over 146

Abstract

This work presents the laterally vibrating Lamb wave resonators (LVRs) based on a 30% aluminum scandium nitride (Al0.7Sc0.3N) thin film with three interdigited transducer pairs operating in the S0 mode. In order to reduce the anchor loss, perfect matched layer-based finite element analysis simulations are utilized to design and optimize the device. Thanks to the high quality AlScN using magnetron sputtering with a single alloy target, vertical etching profile, and designed device structure, 1- μm-thick Al0.7Sc0.3N-based LVRs with high performance are fabricated. The resonator equivalent electric parameters are extracted utilizing the modified Butterworth–Van Dyke model. The best Al0.7Sc0.3N LVR achieves an electromechanical coupling coefficient ( kt2) of 9.7% and a loaded quality factor ( Qr) of 1141.5 operating at approximately 305 MHz. The same resonator shows a motional quality factor ( Qm) of 1507.2, resulting in a high figure-of-merit ( FoM =  kt2 ·  Qm) of 146.2. A 1.8 MHz tuning range is measured for an Al0.7Sc0.3N LVR by applying DC voltage in the range of −40 to 40 V due to the ferroelectric property of high Sc doping in Al0.7Sc0.3N. With the high FoM, Qr, Qm, and low motional resistance ( Rm), the Al0.7Sc0.3N-based LVRs show strong potential in applications of radio frequency communications and piezoelectric transducers.