Simulation and Optimization of Surface Acoustic Wave Devices With High Electromechanical Coupling Factor and Zero Temperature Coupling Coefficient by Pattern Piezoelectric Layer

Recently, a more popular patterned surface acoustic wave (SAW) device with better performance was proposed. This structure has a large electromechanical coupling factor. To make SAW devices easy to be applied to integrated circuit technology, a multilayer structure based on patterned Al/ZnO/Si is designed by using the finite-element method (FEM). First, the dependence of ZnO piezoelectric material on the electromechanical coupling factor is studied systematically. The results show that Al/ZnO/Si structure excites the Rayleigh mode and Sezawa mode with a high electromechanical coupling factor. The patterning of piezoelectric materials could be achieved by etching. The electromechanical coupling factor of the Rayleigh mode is as high as 7.98%, and the electromechanical coupling factor of the Sezawa mode is up to 9.68%. As we all know, the temperature will affect the characteristics of SAW devices. Therefore, the temperature characteristics based on this structure are systematically studied. To achieve zero TCF, SiO2 is used as an intercalation layer for temperature compensation. The structure of the Rayleigh mode and Sezawa mode with the thinner SiO2 layer is easier to achieve zero TCF than that of the conventional structure. Meanwhile, the electromechanical coupling factor of the Sezawa mode based on the patterned Al/ZnO/SiO2/Si structure does not change significantly with increasing SiO2 thickness, with a maximum value of 10.78%, and the minimum value of 10.62%, which is 1.1% larger than that of the structure without SiO2.