Stress control process through piezoelectric PZT film formation for upward-buckling of diaphragm-type ultrasonic microsensors

Upward-buckled piezoelectric diaphragm-type ultrasonic microsensors have been designed and fabricated by controlling stress in piezoelectric PZT film formation process for high sensitivity. Since upward-buckled diaphragm sensors show higher sensitivity than downward ones, a precise stress control process has been developed to enable the diaphragms to upward-buckled spontaneously by dividing PZT formation process into two parts, before and after the completion of the diaphragms. The sensors fabricated through this process show spontaneous upward-buckling deflection over 5 μm, deflection around which was able to be achieved only by re-buckling process before. The sensitivity of the upward-buckled diaphragm sensor shows 5.7 times higher on average than that with flat diaphragm.