DC-Bias Effects on Sputtered PZT pMUTs with High Transmit and Receive Sensitivities in Immersion for Imaging applications

This work reports a 7.5MHz sputtered Lead Zirconate Titanate (PZT) piezoelectric micromachined ultrasonic transducer (pMUT) array that demonstrates both strong transmit (9.3kPa/V/mm ² ) and receive performance (6.5V/MPa) characterized in immersion without signal amplification and within a 5mm ² aperture. This paper presents yet higher RX sensitivities for the proposed device even with a direct connection to an oscilloscope. We elucidate the effect of DC bias on the acoustic transmit (TX) and receive (RX) characteristics of PZT pMUTs, and how these could be tuned to increase the performance of the pMUTs. The device was fabricated at wafer-scale in our 8-inch line, which is capable of physical vapor deposition (PVD) of high quality PZT.