A High-Performance NS-SAW Resonator Using 30° YX-Lithium Niobate

With the popularity of 5G technique, large bandwidth devices are urgently needed to meet the enormous transmission requirements. Recently, the shear horizontal (SH) surface acoustic wave (SAW) resonators with large effective coefficient (k² eff) attracted wide attention, however, obtaining a high quality-factor (Q) is still a great challenge due to the bulk acoustic wave radiation into the substrate. In this work, a 30° YX-LiNbO3/SiO2/Si Non-leaky Stack SAW (NS-SAW) resonator with SH mode is proposed. Large velocity difference between the SHSAW wave in LiNbO3 layer and the slow shear bulk acoustic wave in SiO2/Si substrate helps to reduce the bulk wave leakage. Numerical simulations by finite element method (FEM) are implemented to optimize the cut angle of LiNbO3 film and the thickness of each layer. The fabricated NS-SAW resonators yield a k² eff of 24.4% and a Bode-Qmax of 1092. Compared to the reported similar-type SAW resonators, the NS-SAW resonator shows the best level of figure of merit (FoM=266) when k² eff is more than 20%, presenting great potential for designing the wide bandwidth devices in 5G wireless communication.