Boosting Performance of SAW Resonator via AlN/ScAlN Composite Films and Dual Reflectors

Surface acoustic wave (SAW) resonators based on aluminum nitride (AlN)/scandium-doped AlN (ScAlN) composite thin films with dual reflection structures demonstrate substantial improvement in acoustic performance. In this work, the factors affecting the final electrical performance of SAW are analyzed from the aspects of piezoelectric thin film, device structure design, and fabrication process. AlN/ScAlN composite films can effectively solve the problem of abnormal grains of ScAlN, improve the crystal orientation, and reduce the intrinsic loss and etching defects. The double acoustic reflection structure of the grating and groove reflector can not only reflect the acoustic wave more thoroughly, but also helps to release the film stress. Both structures are beneficial to obtain a higher Q value. The new stack and design results in large Q_p and figure of merit among SAW devices working at 446.47 MHz on silicon up to 8241 and 18.1, respectively.