Characterization , Fabrication and Numerical Algorithm for constructing equivalent circuits of capacitive Micromachined Ultrasonic Transducer

• Main Authors: LIANG, CHIH-CHIUAN, 梁智全
• Other Authors: Jenho Tsao
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/89391688420220816182

碩士 === 國立臺灣大學 === 電信工程學研究所 === 90 === 　　In recent years, capacitive Micromachined Ultrasonic Transducer (cMUT) has been the objects of extensive research in ultrasonic system. The volume of the transducer is small, the cost is low and it can be integrated completely into a single chip, thus both the parasitic capacitances and noise level are reduced significantly. cMUT generate ultrasound in air more efficiently than piezoelectric transducers do due to their low mass. Moreover, the transducers are very well matched to fluid loads to result in a very high bandwidth of 50-100%. In this study, we analyze the behavior of the membrane vibration first, and then the partial differential equation consisting the physical phenomenon is derived. After that, the analytic solution of it and the mechanical impedance are also obtained in our study. The influence on resonate frequency under changing thickness, tension, and radius of the device was also discussed. cMUT is a mechanical vs. electrical transducer. Both the behaviors of membrane vibration and transform between electricity with machinery are complex, so it’s not easy to analyze the characteristic, immediately. For getting quick and precise analysis on the integration of the behavior of mechanical with electrical part, it’s necessary to develop the equivalent circuit of cMUT. We can observe the waveform of ultrasonic system in time domain by replacing the equivalent circuit of cMUT, acoustic wave propagate in media and the reflect object with all SPICE model. In addition to the discussion of the fabrication of cMUT , we also design and draw the mask patterns used to fabricate practical cMUT by NSC (Northern Region MEMS Research Center). Finally, we propose the package of die and arrangement of CMUTs array to accomplish the implementation of cMUTs.