Investigation of electrode pitch on resonant and capacitive characteristics in X-cut LiNbO3 membrane-based laterally-excited bulk acoustic resonator. (1st April 2023)

• Record Type: Journal Article
• Authors: Zhou, Jie; Fan, Yuchen; Tong, Xin; Luo, Tiancheng; Liu, Jieyu; Zou, Yang; Liu, Wenjuan; Liu, Yan; Soon, Jeffrey Bo Woon; Cai, Yao; Sun, Chengliang
• Is Part Of: Journal of micromechanics and microengineering. Volume 33:Number 4(2023)
• Publication Date: 2023-04-01
• Subjects: laterally-excited bulk acoustic resonator -- electrode pitch -- quality factor -- effective coupling coefficient -- capacitance; Microelectromechanical systems -- Periodicals; Micromechanics -- Periodicals; 621.38105
• DOI: 10.1088/1361-6439/acbfc2
• Languages: English
• ISSNs: 0960-1317

Abstract

Abstract: The laterally-excited bulk acoustic resonators (XBARs) have been gaining attention for their use as radio frequency filters due to their ability to resonate at high frequencies (>5 GHz) and wide fractional bandwidth. However, the limited cognition about the resonant characteristics of XBARs remains an obstacle for its commercial application. In this paper, the influence of electrode pitch ( P ) on resonant frequency ( f res ), quality factor ( Q ) and effective electromechanical coupling coefficient ( K eff 2 ) in X-cut LiNbO3 membrane-based resonators are investigated for both the XBAR mode and first-order asymmetry mode ( A 1 ). The XBAR mode with f res above 8 GHz was excited at a metallization ratio ( η ) less than 0.5 when P was within 5 μ m to 10 μ m, as well as η less than 0.6 when P was within 15 μ m to 20 μ m . Meanwhile, we revealed that increasing P had negligible effect on the f res of XBAR mode but did produce a positive improvement on its K eff 2 and Q . In contrast, both f res and Q of the A 1 mode gradually declined with increasing P . In addition, we have demonstrated the disparity between simulated and calculated C 0 as a function of η, varying with P, to achieve a more accurate prediction of capacitance behavior in resonators. Overall, this work has demonstrated the complex relationship of resonant and capacitance properties of X-cut membrane-based resonators on the electrode pitch, which will aid in optimal designing of high-performance filters.