Investigation on Design Theory and Performance Analysis of Vacuum Capacitive Micromachined Ultrasonic Transducer

Abstract

The capacitive micromachined ultrasonic transducer (CMUT), as a new acoustic-electric conversion element, has a promising application prospect. In this paper, the structure of the vacuum capacitive micromachined ultrasonic transducer is presented, and its performance-influencing factors are investigated. Firstly, the influencing factors of the performance parameters of the vacuum CMUT are analyzed theoretically based on the circular plate model and flat plate capacitance model, and the design principles of the structural parameters of the CMUT cell are proposed. Then, the finite element simulation software COMSOL Multiphysics is used to construct CMUT cell models with different membrane materials, membrane shapes, membrane radius thicknesses, and cavity heights for simulation verification. The results show that both the membrane parameters and the cavity heights affect the performance parameters of the Vacuum CMUT. In order to improve the efficiency of the CMUT, materials with low bending stiffness should be selected, and the filling factor of the membrane should be increased. In order to achieve high-transmission sound pressure, a smaller radius thickness and a larger cavity height should be selected. To achieve high reception sensitivity, a larger membrane radius thickness and a smaller cavity height should be selected. In order to obtain high fractional bandwidth, a larger membrane radius thickness should be selected. The results of this paper provide a basis for the design of Vacuum CMUT cell structure.

PMUT and CMUT Devices for Biomedical Applications: A Review

“…low-pressure chemical vapour deposition (LPCVD), which allows to effectively vacuum-fill the cavity when it is sealed. Vacuum is preferred as it allows reducing energy losses; when the CMUT works in air, it suffers from compressed gas damping of the cavity, while when it works in a liquid environment it suffers from hydrolyzation caused by the strong electric field in the cavity: vacuum sealing of the cavity can reduce both these types of losses [53]. Finally the top and bottom electrode are formed by depositing and patterning an appropriate metal (usually aluminum) on the top plate and the substrate (f).…”