A High <i>Q</i> 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.