Sensitivity Change in Piezoelectric Ultrasonic Microsensors Caused by a Variation of Diaphragm Structures

Sensitivity changes in piezoelectric-type ultrasonic microsensors; have been investigated for variations in the layered structures in their diaphragms. The structure variations have been designed for sensitivity improvement in sensors having statically downward-deflected diaphragms to reduce lateral strain cancellation on their piezoelectric layer by enhancing the strain of the structural expansion component and by suppressing the strain of the bending component. The piezoelectric layer on the front side of the diaphragm has been removed around the top electrode to make slits with various widths. Silicon-dioxide and silicon layers on the rear side of the diaphragm have been removed entirely. These two variations in the structures have been analyzed for their effectiveness in sensitivity improvement, the modified sensor structures have been fabricated, and their sensitivity have been evaluated.