High-sensitivity CMUT with interlayer metal architecture for medical ultrasonic systems

Abstract

This paper presents an integration of the capacitive micromachined ultrasonic transducers (CMUTs) and the transimpedance amplifier in medical ultrasound systems. The proposed CMUT and the sensing circuits are both fabricated on the same chip in a 0.18μm CMOS MEMS technology. Two interlayer metal structures are proposed to improve the sensitivity. The CMUTs are designed with 2MHz cells for medical diagnosis. The conversion efficiency of the CMUTs is 4 times and 1.8 times higher than that in the published structures.

PMUT and CMUT Devices for Biomedical Applications: A Review

“…The presence of the additional middle membrane increases the membrane displacement amplitude, and hence the effective cavity height decreases, so the pull-in voltage reduces, as seen from equation (7), while the transducer acoustic output power and sensitivity are enhanced, showing promises for high performance imaging applications. Non-uniform membranes [67], interlayer metal structures [68] or a combination of the two [69] were also employed for improving the transducer performance: non-uniform top membranes lead to softened film structures, which increase the CMUT dynamic range and bandwidth, while interlayer metal structures enhance sensitivity as they enable the realization of narrow spaces between top and bottom electrodes. By combining multiple CMUT cells in array structures, super-resolution and 3D imaging can be implemented.…”