Diaphragm stress control for sensitivity improvement of piezoelectric ultrasonic microsensors on silicon dioxide diaphragms

Piezoelectric ultrasonic microsensors have been fabricated using sol-gel derived PZT (Pb(Zr,Ti)O
₃
) thin films on micromachined silicon dioxide diaphragms made from a normal silicon wafer instead of the conventional SOI (silicon on insulator) wafer process. The layered structure of the PZT capacitor part on the diaphragm has been modified in order to control the total lateral stress in the diaphragm for sensitivity enhancement. The sensors having an island-like structure in the PZT layer have shown over 2 times higher sensitivity than conventional sensors.