Enhanced Performance of ZnO/SiO₂/Al₂O₃ Surface Acoustic Wave Devices with Embedded Electrodes

Abstract

With the advent of the 5G era, surface acoustic wave (SAW) devices with a larger bandwidth and better temperature stability are strongly required, meanwhile the dimensions of devices are continuously scaling down. In this work, a new layout of ZnO/SiO2/Al2O3 SAW devices with embedded electrodes was developed, and with the help of the finite element method (FEM), the propagation characteristics were simulated. Through adopting embedded electrodes, a large electromechanical coupling coefficient (K 2) of 6.6% for the Rayleigh mode can be achieved (5 times larger than that of the conventional ZnO/Al2O3 structure), feasible for wideband SAW devices, and a low acoustic velocity (V p) of 2960 m/s is exhibited simultaneously, which benefits the miniaturization of SAW devices. The dramatic enhancement of K 2 is mainly attributed to the more efficient excitation of SAW in piezoelectric films. Furthermore, a SiO2 overlay is added on the top of the structure to gain an excellent zero temperature coefficient of frequency (TCF). Experimentally, we successfully fabricated SAW one-port resonators based on the proposed structure and good characteristics of high K 2, low V p, and small TCF as simulated were confirmed. Our results show that the proposed structure provides a viable route to design SAW devices with a large bandwidth, small size, and robust temperature compensation for practical use.

Periodic Analysis of Surface Acoustic Wave Resonator with Dimensionally Reduced PDE Model Using COMSOL Code

“…As mentioned above, the operator ∇ s and Nabla operator ∇ only include the x 1 and x 3 coordinate axes, and the derived PDE-based 2D-FEM model is theoretically equivalent to the pure quasi-3D FEM model previously reported [14,20,36,47]. The computation domain of the PDE-based 2D-FEM model is a 2D plane while that of the quasi-3D FEM model is a 3D block.…”

“…Performances of those RF SAW devices are dominantly limited by their resonators. In order to meet the increasing demand for high-performance SAW devices, a new-type resonator with a more complicated structure and multilayer piezoelectric substrate has been continu-ously emerged [18][19][20]. Thus, SAW engineers are always seeking solutions to obtain more universal, fast and precise simulation tools used for characterizing the SAW resonator.…”

mm-band surface acoustic wave devices utilizing two-dimensional boron nitride

“…The acousto-electric simulation was performed based on the finite element method (FEM). Many studies have used this approach in SAW filter design, and the excellent predicting ability has been demonstrated [10][11][12][13][14][15]17,20,22 . The piezoelectric effects, the relations among stress (T), strain (S), electric field (E), and electric displacement field (D), are represented by the piezoelectric constitutive relations as 2 where c E , e, and ε rS correspond to a material's stiffness, coupling coefficient, and relative permittivity in their tensor form, respectively.…”

“…The fundamental resonance frequency (f r ) is determined by f r = v SAW /λ, where v SAW is the speed of acoustic wave propagation at the surface, and this surface acoustic wave mode is called Rayleigh mode. LiNbO 3 [9][10][11] , LiTaO 3 12 , ZnO [3][4][5][13][14][15] , AlN [16][17][18][19] , and AlScN 20,21 are the piezoelectric materials commonly used or actively studied.…”

Molecular Dynamics Simulation on Behaviors of Water Nanodroplets Impinging on Moving Surfaces

“…However, studies on water nanodroplets impinging on moving solid surfaces are still scarce, especially on high-frequency vibrating surfaces. Due to the rapid development of piezoelectric materials, the frequency of surface acoustic waves (SAW), based on the principle of the inverse piezoelectric effect [27], is up to the level of GHz [28][29][30][31][32][33]. Therefore, high vibrations of surfaces with a frequency on the order of GHz can be realized.…”