Detailed investigation of capacitive micromachined ultrasonic transducer design space

In this study, we present general design guidelines for MEMS ultrasonic transducers, capacitive micromachined ultrasonic transducers (CMUTs), obtained from finite element models with a statistical design of experiment approach. The design space is illustrated using 2-D response surfaces as a function of various geometrical parameters and material selections. Important transducer figure of merits such as operation frequency, fractional bandwidth, collapse voltage and transformer ratio are investigated. Our study illustrates that while keeping geometrical parameters constant, changing the material selection to silicon carbide from silicon dioxide results in a 2.4 times increase in the transformer ratio, and more than 2.5 times increase in the operating frequency while keeping the bandwidth the same. Furthermore, our studies indicate that for a CMUT membrane with an aspect ratio of 4, using a spring constant value obtained analytically results in an error of 160% for the collapse voltage and transformer ratio values.