Buckling control of silicon dioxide diaphragms by lateral stress enhancement for sensitivity improvement of piezoelectric ultrasonic microsensors

Piezoelectric ultrasonic microsensors have been fabricated using sol–gel derived PZT (Pb(Zr,Ti)O3) thin films on micromachined silicon dioxide diaphragms which are made from a normal silicon wafer instead of the conventional SOI (silicon on insulator) wafer. Layered structure of the PZT capacitor part on the diaphragm has been modified in order to allow the diaphragm to cause a static deflection for sensitivity enhancement by controlling the total lateral stress in the diaphragm. Sensors having an island-like structure in the PZT layer have shown an adequate static deflection due to a lateral stress caused by silicon dioxide film and revealed over 2 times higher sensitivity than conventional sensors.