Aluminum Nitride Based Film Bulk Acoustic Resonator With Anchor Column Structure

• Published in: Journal of microelectromechanical systems Vol. 32; no. 2; pp. 1 - 7
• Main Authors: Qu, Yuanhang, Gu, Xiyu, Zou, Yang, Wen, Zhiwei, Cai, Yao, Soon, Bo Woon, Liu, Yan, Sun, Chengliang
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-04-2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic waves; Acoustics; Aluminum; Aluminum nitride; anchor column structure; Boundary conditions; Bulk acoustic wave devices; Columnar structure; Compressive properties; Compressive stress; FBAR; Film bulk acoustic resonators; film warpage; Finite element method; Mathematical models; Multilayers; Numerical analysis; Piezoelectricity; Q-factor; Resonators; Stress; Thin films; Warpage
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2023.3243001

In order to reduce the lateral acoustic energy loss of thin film bulk acoustic resonators (FBARs), the trench structure for FBAR is generally designed to block the leakage of acoustic wave and help improving the <inline-formula> <tex-math notation="LaTeX">Q</tex-math> </inline-formula>-factor. One method the designers often used is etching the piezoelectric material around the active area of the FBAR to form the air-wall structure as a perfect reflection boundary condition. In this paper, the FBAR with trench structure is fabricated. The multilayer films in the FBAR with trench structure are easily warped due to excessive compressive stress. The numerical analysis and finite element simulation are used to verify the effects of different stresses on the devices. In order to avoid the degradation of FBAR performance caused by film warpage, the FBAR with anchor columns is proposed. The anchor columns are located on both sides of the FBAR, and they are designed to reduce film bending and the compressive stress of active area of the resonator. The measured results show that the Qs and Qp of the FBAR with anchor columns are increased by 55.8% and 21.1%, respectively, and <inline-formula> <tex-math notation="LaTeX">k_{eff}{}^{2}</tex-math> </inline-formula> improved from 5.6% to 6.7% compared with the FBAR without the anchor columns. 2022-0179