Diaphragm deflection control of piezoelectric ultrasonic microsensors for sensitivity improvement

Arrayed ultrasonic microsensors have been fabricated using piezoelectric PZT (Pb(Zr,Ti)O3) thin film on micromachined silicon diaphragm structures. Static deflection of the diaphragms strongly affects the sensitivity; upward-deflected diaphragms show much higher sensitivity than downward-deflected diaphragms. Array sensors have been fabricated using modified processes which enable the diaphragms on a chip to deflect upward, and sensitivity has been successfully improved 4–6 times compared to the downward diaphragms.