Curved Cantilever Actuated ScAlN PMUT for Enhanced Linearity and Transmit Sensitivity

This research introduces a novel curved cantilever-based edge-actuated Piezoelectric Micromachined Ultrasonic Transducer (PMUT) utilizing a 30% Scandium-doped Aluminum Nitride (ScAlN) thin film. The cantilever-actuated PMUT achieves a linear piston-mode operation, with 75% of the membrane area vibrating in the vertical direction. In contrast to traditional PMUTs, this design operates at 63 kHz and features a flat vibrating membrane that remains frequency insensitive to DC voltage variation. It effectively maintains linear displacement and pressure response, even at driving voltages exceeding 50 V. At similar operating frequencies, the cantilever-actuated PMUT exhibits a displacement sensitivity of 700 nm/V, comparable to the 900 nm/V of the conventional PMUT. Additionally, the edge-actuated PMUT offers improved linearity and a Figure of Merit (FOM) of 65 mPa/V/mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in transmission, which is 1.5 times larger than that of the conventional clamped PMUT.