A High Q Value ScAlN/AlN-Based SAW Resonator for Load Sensing

This article presents a high quality factor (
${Q}$
) load sensor based on Sc
_0.2
Al
_0.8
N/aluminum nitride (AlN)-on-silicon surface acoustic wave (SAW) resonator. Finite element method (FEM) analysis is performed to predict the resonance frequency and the wave propagation mode. A high-
${Q}$
of 7200 at the parallel resonance frequency (
${f}_{p}$
) of 447.50 MHz is measured for Sc
_0.2
Al
_0.8
N/AlN configured SAW resonator on a silicon substrate. Experimental values for variation of series resonance frequency (
${\Delta } {f}_{s}$
) and variation of
${f}_{p}$
(
${\Delta } {f}_{p}$
) are found to be −75.3 and −186.8 kHz with variation of applied force
$({\Delta } \textit {F)} = 4.155$
N, operating in the analyzed range. The linear approximation of measured frequency variations under force is
${\Delta } {f}_{s}/{F} = -12.7$
kHz/N and
${\Delta } {f}_{p}/{F} = -46.2$
kHz/N. Moreover, the force sensitivities for this sensor are −28.4 and −103.2 ppm/N for
${f}_{s}$
and
${f}_{p}$
, respectively. This high-
${Q}$
scandium-doped AlN (ScAlN)/AlN-based SAW resonator exhibits high sensitivity, demonstrating that the structure can be used as load sensors in industrial applications such as manufacturing, medical, grocery, and automotive industries.