Piezoelectric Micromachined Ultrasonic Transducer Integrated With Field Effect Transistor for Acoustic Sensing

SummaryIn this work, a piezoelectric micromachined ultrasonic transducer (PMUT) is investigated for acoustic sensing applications that utilizes an integrated field effect transistor (FET) as the readout mechanism. The FET having a 6 µm gate length and aluminum nitride (AlN) as the gate dielectric is integrated at the center of the PMUT. The acoustic waves generated by the PMUT travel across the substrate thickness and get reflected back to the FET region where they are detected by modulating the current-voltage (I-V) characteristic of the FET due to the strained channel effect. The amount of reflection, therefore I-V modulation, is affected by the acoustic properties of the material underneath the substrate, hence providing the sensing scheme. Preliminary measurements indicate that the contrast in acoustic reflection from different materials can be detected.