Fabrication and characterization of a smart epitaxial piezoelectric micromachined ultrasonic transducer

A novel piezoelectric micromachined ultrasonic transducer (pMUT) array was designed and fabricated using epitaxially grown functional Pb(Zr0.52Ti0.48)O3 (PZT) thin film on Si(1 1 1)/γ-Al2O3(1 1 1)/SrRuO3(1 1 1) substrate for biomedical applications. The crystallographic orientation of PZT film was controlled by the incorporation of epitaxial γ-Al2O3 film on Si substrate. Modal shape of pMUT was analyzed employing advanced 3D finite element modeling taking the crystallographic anisotropy of materials and the properties of immersed medium (air or water) into account. Eigenfrequency with mode shapes has shown to have significant influence on transmitting-receiving characteristics of pMUT. Modal shapes of pMUT were also quantitatively determined using Laser Doppler Vibratometry (LDV). An excellent correlation was obtained between computational and experimental results. A significantly high sensitivity of 3.9 μV/kPa was obtained in an under-water ultrasonic wave transmission experiment conducted using fabricated pMUT as wave transmitter and a commercial transducer as receiver at a fundamental frequency of 1.20 MHz. Advanced FE computation thus serves as a tool to a priori optimize device structure for the successful transmission of ultrasonic waves with sufficient power to generate high resolution 3D imaging.