High Coupling Coefficient Resonance Mode in Al0.68Sc0.32N Surface Acoustic Wave Resonator with AlN Buffer Layer on a Silicon Substrate

We report on a resonance mode with high electro-mechanical coupling coefficient (k
_t
²
) in an Aluminum Scandium Nitride (AlScN) Surface Acoustic Wave (SAW) resonator with an Aluminum Nitride (AlN) buffer layer on a silicon substrate. We demonstrate the influence of electrode material, electrode thickness, AlScN thickness, and device orientation on the k
_t
²
. We utilize the optimized parameters from this study to realize SAW devices in a CMOS compatible fabrication process and measured a k
_t
²
as high as 4.78%, which is a high value for AlScN SAW devices reported on low cost single crystal silicon substrates.