Method for making integrated matching layer for ultrasonic transducers

Abstract

A method of forming an impedance matching layer of an acoustic transducer includes geometrically patterning impedance matching material directly onto a radiating surface of piezoelectric substrate. In one embodiment, the matching layer is deposited onto the piezoelectric substrate and photolithographic techniques are utilized to pattern the matching layer to provide posts tailored to better match the piezoelectric substrate to a medium into which acoustic waves are to be transmitted. A nominal layer of metal between the posts and the piezoelectric substrate improves the attachment of the matching material to the substrate. The nominal layer may be chrome-gold and the matching material may be copper. Typically, the radiating surface is the substrate front surface from which acoustic waves are directed into a medium of interest, e.g., water or human tissue. However, the radiating surface may be the substitute rear surface, with the patterned matching layer providing acoustic matching to a backing layer for absorbing acoustic energy. In another embodiment, matching layers of different acoustic impedances are deposited and patterned on both the front and rear surfaces to provide matching for effective transmission into the medium of interest and into an acoustic absorptive backing medium.