Finite Element Simulation and Analysis of Capacitive Micromachined Ultrasonic Transducer
Capacitive micromachined ultrasonic transducers(CMUTs), which are suitable for operation in both air and water, have been simulated and fabricated with sacrificial release method. We have proposed four models for CMUT, that are block-shape membrane model, the BOX model, the BOX model with etch holes and the BOX model with etching channels that were more closely match the actual structure. And, the effects of those models on the resonant frequency are analyzed. It can be concluded that the value of percent difference between block-shape membrane model and the BOX model is about 8.7% when the ratio of L/W is above 4. In addition the thinner the CMUT membrane thickness, the smaller the percent difference. We analyzed the size of the etching channel. A dynamic range in less of (0.125% or 0.25%) is observed when the height ratio of cavity and (channel or hole) increased. When the width ratio of cavity and (channel or hole) is analyzed, the results obtained are also very small. Based on the analysis of the size of the etched hole, the influence of the etching channel on the structure frequency can be obtained as a result of the small percent difference.