Long-Range High-Resolution Imaging With Silicon-on-Nothing ScAlN pMUTs

This work demonstrates the imaging capabilities of a silicon-on-nothing (SON) ScAlN piezoelectric micromachined ultrasonic transducer (pMUT) array by a method of transmit beamforming followed by suitable signal postprocessing for 3-D image reconstruction. A 2.7-MHz pMUT array with 15% scandium-doped aluminum nitride (ScAlN) as the piezo thin film was implemented for this demonstration. A total of $16\,\,{3} {}\times {}{3}$ -mm dies consisting of ${34} {}\times {}{37}$ pMUT elements per die and operated as dual channels were arranged in an eight-column $\times $ two-row array configuration, resulting in a 32-channel experimental system with a $24\times6$ -mm coverage. In this work, experimental testing using single and multiple 6-mm-diameter reflectors at a different spacing from each other and a distance of 2.5 cm from the array was performed to validate the 3-D imaging capabilities of the developed 2-D SON ScAlN pMUT array with an attained lateral resolution of 5 mm.