MINIATURE DRUMHEADS - MICROFABRICATED ULTRASONIC TRANSDUCERS

Significant improvement in the performance of capacitive microfabricat ed ultrasonic transducers is reported and the modifications which enab le the progress are described. Air-coupled through-transmission of gla ss and steel at 2.3 MHz is demonstrated for the first time. Furthermor e. a 20 mu m step on a silicon wafer is detected with both amplitude a nd phase signals at 3 MHz. The same process used to fabricate the air transducers also yields immersion transducers, which are reported to o perate in water from 1 to 20 MHz with a dynamic range of 60 dB measure d at 3 MHz. It is anticipated that optimized immersion transducers wil l be able to achieve the 110 dB dynamic range of the air transducers. A brief review of the theoretical modeling of the device is also prese nted. (C) 1998 Elsevier Science B.V.