AlN-on-Si Square Diaphragm Piezoelectric Micromachined Ultrasonic Transducer with Extended Range of Detection

We present aluminum nitride (AlN) on silicon (Si) CMOS-compatible piezoelectric micromachined ultrasonic transducers (pMUTs) with an extended detection range of up to 140 cm for touchless sensing applications. The reported performance surpasses the current state-of-art for AlN-based pMUTs in terms of the maximum range of detection using just a pair of pMUTs (as opposed to an array of pMUTs). The extended range of detection has been realized by using a larger diaphragm allowed by fabricating a thicker diaphragm than most other pMUTs reported to date. Using a pair of pMUTs, we experimentally demonstrate the capability of range-finding by correlating the time-of-flight (TOF) between the transmit (TX) and receive (RX) pulse. The results were obtained using an experimental setup where the MEMS chip was interconnected with a customized printed circuit board (PCB) using Al wire bonds.