Increased Output-Pressure PMUTs with a Sloped Profile Fabricated via Surface Micromachining

This study demonstrates a new surface micromachining process capable of forming AlN piezoelectric micromachined ultrasonic transducers (PMUTs) having a sloped profile. Similar to earlier curved PMUT structures, the sloped profile increases the electromechanical coupling of the piezoelectric layer, leading to a three-fold enhancement in transmission amplitude. Unlike earlier curved PMUTs which were fabricated using complicated etching processes, the process demonstrated here is a simple surface micromachining process that is compatible with mass production processes used for industrial PMUT manufacture. Moreover, the quality factor can be improved by sloped-anchor of diaphragm with less anchor-loss.