Development and analysis of piezoelectric flexural micro-machined ultrasonic transducers base on ZnO film on silicon substrate

The vibration properties of piezoelectric micro-machined ultrasonic transducers（PMUT） are investigated. For the case that the thickness of the diaphragm is much smaller than its length,the experimental results and theoretical analysis prove that the residual stress in diaphragm effects on its resonant frequency strongly.The results from the classical theory for thin plate show big discrepancies with the experimental results if its residual stress is omitted.With the residual stress in the diaphragm is considered,the analysis results could explain the resonant properties of PMUT well.The equivalent circuit of the transducers is also obtained from the measured admittance results.The resonant frequency of the PMUT is about 71 kHz and the membrane width is lmm.Some preliminary experiments were also done to demonstrate PMUT as a transmitter or a receiver of acoustic waves.The measured receiving sensitivity is -201.6 dB（ref 1 V/μPa） and the acoustic pressure output is about 137 dB（ref 1 μPa·m/V） at 71 kHz.