Hexagonal Capacitance Micromachined Ultrasonic Transducer

Capacitive Micromachined Ultrasonic Transducers (CMUTs), introduced about few decades ago, have been shown to be a good alternative to conventional piezoelectric transducers in various aspects, such as sensitivity, transduction efficiency, and bandwidth. It is used in a wide range of applications including Non destructive testing applications, medical imaging, flow metering, micro/nanoelectronics and industrial cleaning etc. The advent of MEMS technology has lead to intensive study of micro machined ultrasonic transducers. They are similar to other capacitance transducers as they employ a vibrating membrane to send and receive ultrasound in air and in water. The advantage of hexagonal Capacitance micro machined ultrasonic transducers (CMUTs) is that they can be operated in the high temperature range and the transducer array can be fabricated at a lower cost. Presented in this paper is a study on some aspects of the design of a modified CMUT, which the authors believe would lead to a CMUT with many advantages, including less loading effect and higher packing density. The focus of discussion in the paper is FEM simulation of a single cell hexagonal CMUT using polysilicon as membrane material. Also discussed is the simulation study of the critical parameters which influence the operation of the CMUTs. The simulations were carried out using MATLAB and IntelliSuite 8.0. The study indicates that in the range of study, the best performance is achieved at the natural resonance frequency, which is very desirable.