A Modified Thickness Extensional Disk Transducer

Photolithography and chemical etching were investigated as a means of patterning miniature piezoelectric devices. Using a processing procedure analogous to that utilized in the production of integrated circuitry, concentrated hydrochloric acid and a commercially available photoresist were employed to fabricate a number of complex structures from soft lead zirconate titanate (PZT) substrates. Among the devices produced in this manner was a modified thickness mode resonator etched in order to destroy the simple geometry responsible for radial vibrations. The resultant transducer demonstrated significantly smaller amplitudes for lateral resonances and a marked reduction in the effective planar coupling coefficient over the unaltered disk. Consequently, it appears that photolithographic patterning will prove useful both in eliminating spurious resonances from transducers for medical imaging or nondestructive evaluation and for engineering low planar coupling coefficients into a variety of Substrate materials.