基于ZnO压电薄膜的弯曲振动硅微压电超声换能器的研究

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

对所研制的硅微压电超声换能器(PMUT)的振动特性进行了研究分析。对硅微压电超声换能的振动膜薄板的厚度相对于薄板的尺度(边长)而言较薄的情况,理论分析与实验结果均表明残余应力对换能器的谐振频率影响较大:不考虑残余应力的理论分析得出的换能器谐振频率与器件的实验测量的结果相差较大,而考虑残余应力的分析给出的谐振频率结果与实验结果是符合的。本文还对所制作的硅微压电超声换能器的谐振频率及导纳进行测量,并给出其等效电路参数。其中振动膜边长为1mm的换能器的谐振频率为71.25 kHz。最后对其进行了简单接收发射实验,测得谐振频率处的接收灵敏度为-201.6 dB(ref 1 V/μPa),发射电压响应约为137 dB(ref 1μPa·m/V)。

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.