Sc \text Al \text N-Based Bimorph Piezoelectric MEMS Microphones With Tractive Structures

Scandium-doped aluminum nitride (ScAlN) can effectively improve the piezoelectric coefficient; meanwhile, the bimorph obtains a higher sensitivity per unit area than a unimorph structure, thereby greatly improving the sensitivity of MEMS sensors. This article proposes Sc _{\text{0.1}} Al _{\text{0.9...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2024-12, p.1-9
Main Authors: Yang, Chaoxiang, Liu, Wenjuan, Wang, Yaxin, Hu, Bohao, Lu, Liangyu, Liu, Yan, Cai, Yao, Guo, Shishang, Sun, Chengliang
Format: Article
Language:English
Subjects:
Acoustic beams
Aluminum nitride
Beams
bimorph
Electrodes
Finite element analysis
high sensitivity
Micromechanical devices
Microphones
piezoelectric MEMS microphone
scandium-doped aluminum nitride (ScAlN)
Sensitivity
Stress
Structural beams
Vibrations
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Summary:Scandium-doped aluminum nitride (ScAlN) can effectively improve the piezoelectric coefficient; meanwhile, the bimorph obtains a higher sensitivity per unit area than a unimorph structure, thereby greatly improving the sensitivity of MEMS sensors. This article proposes Sc _{\text{0.1}} Al _{\text{0.9}} N-based bimorph piezoelectric MEMS microphones with tractive structures, which generate a larger high-stress area during operation compared with conventional cantilevers based on finite element method (FEM) simulation and analytical methods. Four electrical connections are designed as components with the tractive structure on the same area of only 0.4679 mm ^{\text{2}} . The devices are fabricated on a thermal oxide silicon wafer using a nine-mask process. Acoustic measurements show that the maximum unamplified sensitivity is 353.79 \mu V/Pa from the combined series-parallel electrical connection, which is 75% higher than the full series electrical connection of 208.27 \mu V/Pa. Furthermore, the combined series-parallel electrical connection exhibits grateful performance, where both unamplified and amplified minimum detectable pressure (MDP) are 2 mPa, the signal-to-noise ratio (SNR) is 48.3 dB, and the total harmonic distortion (THD) is only 0.96% at 1 kHz. This work demonstrates a small-size, high-sensitivity piezoelectric MEMS microphone with combined series-parallel connection, which has great commercial value for future scenarios.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2024.3516720