Micromachining for improvement of integrated ultrasonic transducer sensitivity

A micromachined diaphragm structure for integrated ultrasonic transducers is discussed. The micromachining significantly reduces a large parasitic capacitance, resulting in improved sensitivity compared with identical transducers on solid substrates. For the particular geometry tested, sensitivity improved 8.9 dB; this result matches a prediction of 10.9 dB, based on a simple model, reasonably well. This level of improvement is considered significant for the applications under consideration (medical imaging and nondestructive evaluation)