Spontaneous Diaphragm Buckling Control Process on Piezoelectric Ultrasonic Microsensors for High Sensitivity

Abstract

Abstract A new fabrication process has been proposed for high sensitivity piezoelectric ultrasonic microsensors based on spontaneous diaphragm buckling. The buckling deflection and direction of the diaphragms strongly affect the sensitivity of the sensors; upward-deflected diaphragms cause higher sensitivity. The sensor has a tensile piezoelectric layer and a compressive thermally oxidized silicon layer in the diaphragm and the buckling behavior is determined by the combination of the stresses. The fabrication process of the piezoelectric layer has been optimized for yield of spontaneously upward buckling and height of the buckling deflection. Totally the diaphragms over 90% of fabricated 196 ones buckle spontaneously upward with deflection over 5 sensors on them higher sensitivity by 6.7 times on average than that on flat ones.