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

Rongxuan Su; Sulei Fu; Junyao Shen; Zhenglin Chen; Zengtian Lu; Mingliang Yang; Rui Wang; Fei Zeng; Weibiao Wang; Cheng Song; Feng Pan

doi:10.1021/acsami.0c12055

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

ACS Appl Mater Interfaces. 2020 Sep 16;12(37):42378-42385. doi: 10.1021/acsami.0c12055. Epub 2020 Sep 3.

Authors

Rongxuan Su¹, Sulei Fu¹, Junyao Shen¹, Zhenglin Chen², Zengtian Lu³, Mingliang Yang⁴, Rui Wang¹, Fei Zeng¹, Weibiao Wang⁴, Cheng Song¹, Feng Pan¹

Affiliations

¹ Key Laboratory of Advanced Materials (MOE), School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
² School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China.
³ School of Mechanical Engineering, Southeast University, Nanjing 211189, China.
⁴ SHOULDER Electronics Limited, Wuxi 214124, Jiangsu, China.

PMID: 32830495
DOI: 10.1021/acsami.0c12055

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 (K²) 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 K² 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 K², 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.

Keywords: Rayleigh wave; electromechanical coupling; embedded electrodes; surface acoustic wave; temperature compensation.