Modeling And Simulating Of Capacitive Microfabricated Ultrasonic Transducers

Piezoelectric ultrasonic transducers is sound-electronic conversion device, which is generally used in the field of ultrasonic. The traditional PZT, however, is not the ultrasonic source with high efficiency because of the serious non-coupling phenomena between air and ordinary piezoelectric material. Certainly, this efficiency can be improved by increasing the coupling layer when the bandwidth is reduced at the same time. With the development of MEMS technology now, a new ultrasonic transducer, capacitive micro fabricated ultrasonic transducers is appeared. cMUT adopts the surface micro fabricated technics, many shortcoming of traditional PZT is overcame. What's more, it is a possible trend that cMUT will replace of the PZT because of being prone of manufacture, small dimension, low noise, wide working range and being easy to integrate electronically. Based on the description above, the study on cMUT is presented. According to the oversea studying experience, several cMUT structures are designed, then simulated and imitated respectively, finally, the flow of manufacture technics is proposed. The following are main achievements of this thesis: 1. the related information is referred, the updated development from oversea in the field of cMUT is understood. Main concern is principle, inside structure of fabrication of cMUT, the influence on performance by technics of machining and parameters, and the method of imitation and simulation. 2. several kinds of cMUT structure used on test are designed, and imitated and simulated with modal analysis by means of finite element analysis software ANSYS, and the structure meeting the standard is chosen according to the design principle of cMUT. 3.The module is analyzed using coupling field of ANSYS, the TRANS126 unit is chosen and programmed by ANSYS parameter design language (APDL),the structure is simulated with force electric coupling, and the structure is optimized according to result of simulation. 4. some micro fabrication techniques, such as the surface sacrificed layer technique, humid erode technique, and spatter technique are adopted. The technics flow of fabrication suitable to the structure is designed.