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.