Ultrasonic array sensor using piezoelectric film on silicon diaphragm and its resonant-frequency tuning

Ultrasonic micro-array sensors using piezoelectric PZT (Pb(Zr,Ti)O/sub 3/) thin films on silicon diaphragms have been fabricated and their resonant frequency could be tuned after the device fabrication. The resonant frequencies of elements of the fabricated sensor array have scattered in 12% due to non-uniformity of material properties, dimensions of diaphragms and film thickness. The resonant frequency of each element has been tuned to an appropriate value by applying adequate electrical poling. Finally, the three-dimensional positions of objects have been successfully determined by using the tuned array sensor.