Lamb Wave Resonators based on Co-sputtered Al0.78Sc0.22N Thin Film

This paper reports the lamb wave resonator based on co-sputtered Al
0.78
Sc
0.22
N thin film. High-quality Al
0.78
Sc
0.22
N thin film with a 1.8° FWHM of (0002) polarization is achieved by magnetron co-sputtering. The process of Inductively Coupled Plasma (ICP) etching is discussed. Optimized ICP etching recipe is characterized to achieve relatively vertical etching profile. The device structure is optimized to improve the quality factor utilizing finite element analysis (FEA) based on perfectly matched layer (PML) in COMSOL Multiphysics®, Al
0.78
Sc
0.22
N lamb wave resonators operating at around 300 MHz are fabricated. A resonator with electromechanical coupling coefficient (
$k_{t}{{}^{2}}$
) over 5% and loaded quality factor (Q) of 1219 is obtained, which exhibits a figure of Merit (FOM) of 63.88.