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Journal of Nanomaterials
Volume 2013, Article ID 245095, 8 pages
Research Article

The Liquid Sensor Using Thin Film Bulk Acoustic Resonator with C-Axis Tilted AlN Films

1Department of Electrical Engineering, National Sun Yat-Sen University, No. 70, Lienhai Road, Kaohsiung 80424, Taiwan
2Department of Computer and Communication, Shu-Te University, No. 59, Hengshan Road, Yanchao District, Kaohsiung 82445, Taiwan
3Department of Electronic Engineering, De Lin Institute of Technology, No. 1, Ln. 380, Qingyun Road, Tucheng District, New Taipei 23654, Taiwan

Received 15 September 2013; Accepted 1 October 2013

Academic Editor: Liang-Wen Ji

Copyright © 2013 Ying-Chung Chen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Dual-mode thin film bulk acoustic resonator (TFBAR) devices are fabricated with c-axis tilted AlN films. To fabricate dual-mode TFBAR devices, the off-axis RF magnetron sputtering method for the growth of tilted piezoelectric AlN thin films is adopted. In this report, the AlN thin films are deposited with tilting angles of 15° and 23°. The frequency response of the TFBAR device with 23° tilted AlN thin film is measured to reveal its ability to provide dual-mode resonance. The sensitivities of the longitudinal and shear modes to mass loading are calculated to be 2295 Hz cm2/ng and 1363 Hz cm2/ng with the mechanical quality factors of 480 and 287, respectively. The sensitivities of the longitudinal and shear modes are calculated to be 0 and 15 Hz cm2/μg for liquid loading.