Analytically assisted FEM approach for the design and optimization of laterally excited bulk acoustic wave resonators (XBARs) with a high electromechanical coupling.

In this work, laterally excited bulk acoustic wave resonators (XBARs) are designed for high-frequency applications in the 5 GHz range which have applications in MEMS sensors and fifth-generation (5G) mobile networks. XBARs are simulated with 400 nm thick LiNbO3 and narrow fingers of Interdigital transducer (IDT) placed periodically with a pitch of 26 µm to excite the lamb wave resonances at 4.49 GHz with a high electromechanical coupling coefficient (kt2) of 32%. The working of XBARs is investigated by Finite element method (FEM) based COMSOL Multiphysics simulation and analytical model. The XBAR schematic is depicted graphically, together with its deformation, impedance response with corresponding asymmetric displacement modes, and device equivalent MBVD model. The performance of XBARs with different piezoelectric materials was investigated, and it was discovered that XBARs using LiNbO3 as piezoelectric materials and Au electrodes performed best. Following that, Au electrodes are used to create A1 (anti-symmetric lamb) modes with spurious mode mitigation. Furthermore, numerous geometrical aspects such as piezoelectric material thickness, IDT finger width, the pitch of IDT and the ratio of IDT finger width to finger gap were examined in order to enhance kt2 and the Quality factor (Q) of the device. The third and fifth harmonics of XBAR were found at 13.41 and 22.39 GHz, respectively. The modified Butterwort-Van Dyke model (MBVD) is intended to discover the XBAR equivalent circuit model. [ABSTRACT FROM AUTHOR]