High Electromechanical Coupling Coefficient of Longitudinally Excited Shear Wave Resonator Based on Optimized Bragg Structure

Zhiheng Zhang; Weipeng Xuan; Hong Jiang; Weilun Xie; Zhaoling Li; Shurong Dong; Hao Jin; Jikui Luo

doi:10.3390/mi14112086

High Electromechanical Coupling Coefficient of Longitudinally Excited Shear Wave Resonator Based on Optimized Bragg Structure

Micromachines (Basel). 2023 Nov 11;14(11):2086. doi: 10.3390/mi14112086.

Authors

Zhiheng Zhang¹, Weipeng Xuan¹, Hong Jiang¹, Weilun Xie¹, Zhaoling Li¹, Shurong Dong², Hao Jin², Jikui Luo^{1

2}

Affiliations

¹ Ministry of Education Key Laboratory of RF Circuits and Systems, College of Electronics & Information, Hangzhou Dianzi University, Hangzhou 310005, China.
² Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang, College of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China.

Abstract

In this work, a longitudinally excited shear-wave resonator (YBAR) based on single-crystalline lithium tantalate (LiTaO₃, LT) thin film is proposed. The YBAR has a 200 nm X-cut thin film and molybdenum electrode. A high effective electromechanical coupling coefficient (k²_eff) of up to 19% for the suspension-type structure was obtained. Furthermore, a Bragg reflector (SiO₂/Pt) with optimized layer thickness ratio was employed to improve the performance of the YBAR. Compared to the acoustic wave resonators with the conventional quarter-wave (λ/4) Bragg reflector, the proposed YBAR with an optimized Bragg reflector can reflect both the longitudinal and shear waves efficiently, and resonators with spurious-free response and high quality (Q) value were achieved. This work provides a potential solution to enabling high coupling micro-acoustic resonators with high Q factor in the 5G/6G communication system.

Keywords: SM-YBAR; high electromechanical coupling; optimized Bragg structure; single-crystalline lithium tantalate thin film.

Grants and funding

This work was funded by National Key R&D Program of China (2022YFB3604500), Zhejiang Province Key R & D programs (No.2021C05004, 2023C01192), National Natural Science Foundation of China (No. 61974037, 61827806, 52205598), NSFC-Zhejiang Joint Fund for the Integration of Industrialization and information (No. U1909212, No. U20A20172). Zhejiang Province high level talent special support plan No.2022R52042.