Over the past
few decades, trillions of dollars has been spent developing techniques for fabricating integrated
circuits. Considerably less effort has been spent on fabrication techniques for ultrasonic
transducers. The purpose of this thesis is to investigate the use of semiconductor processing
techniques to ultrasonic transducer manufacture. Ultrasonic transducers have a wide range of
applications including medical imaging, airborne ranging systems, non-destructive testing, and
in-situ processes monitoring. In these applications, it is desirable to a transducer which has a
large bandwidth and is efficient at converting electrical energy to acoustic energy and vice versa.
Typical ultrasonic transducers consist of piezoelectric material with one or more impedance
matching layers. These layers serve to improve the bandwidth and the efficiency of the transducer.
In this thesis, we look at using bulk micromachining to fabricate materials with well controlled
impedances for improving the quality and performance of these matching layers. An alternative
technique to the piezoelectric generation of sound is the use of electrostatic actuation. In this
thesis, we investigate the use of surface micromachining to fabricate silicon based high frequency
ultrasonic transducers for air-borne applications. This fabrication technique solves many problems
associated with air-borne transducers and promises to achieve higher efficiency and bandwidth than
conventional transducers.
