An improvement of tilted AlN for shear and longitudinal acoustic wave |
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Authors: | Chung-Jen Chung Ying-Chung Chen Chien-Chuan Cheng and Kuo-Sheng Kao |
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Institution: | (1) Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan;(2) Department of Electrical Engineering, De Lin Institute of Technology, Taipei, Taiwan;(3) Department of Computer and Communication, SHU-TE University, Kaohsiung, Taiwan |
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Abstract: | This study investigates c-axis tilted aluminum nitride (AlN) piezoelectric films for the improvement of both shear and longitudinal
acoustic wave resonances. Solidly-mounted resonator (SMR) structure is adopted for the applications of high frequency wireless
communications and high sensitivity sensors. As to the piezoelectric layer, c-axis tilted AlN has the capability to excite
the dual-mode resonances, namely, the longitudinal and shear mode resonances. In this study, SMR devices made with a seven-layer
molybdenum/silicon dioxide (Mo/SiO2) Bragg reflector and the c-axis tilted AlN are carried out. A conventional off-axis sputtering technique is applied to grow
the tilted AlN.
The outcome frequency responses show dual resonant characteristics. However, the longitudinal resonance fades away with the
AlN c-axis tilted angle, and the quality factor of the longitudinal resonance decreases. Consequently, we make an improvement
by tilting the off-center substrates toward the sputtering source and successfully enhance the longitudinal resonance while
preserving the shear resonance at the same time. Not only the shear resonance for the liquid-based sensing application, but
also an outstanding longitudinal resonance could be obtained. The practicability of the dual-mode resonator is extended. |
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Keywords: | PACS" target="_blank">PACS 43 20 Ks 77 65 Fs 43 35 Ns 81 15 -z 77 84 -s |
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