A Compact Monolithic CMUT Receiver Front-End in a TiN-C CMOS-MEMS Platform

In this work, a compact monolithic integrated capacitive micromachined ultrasonic transducer (CMUT) receiver front-end is demonstrated based on the titanium nitride composite (TiN-C) CMOS-MEMS platform to attain a small transduction gap of 400nm for efficient electrostatic transduction. The proposed CMUT front-end was designed in a standard 0.35 μm CMOS which offers a possibility of vertically integrating MEMS structure with the on-chip circuitry. Each CMUT sensing pixel is connected to a low noise amplifier (LNA), which is fully integrated underneath the MEMS structure, forming a compact pixel size of only 200 μm by 200 μm. The prototyped CMUT receiver front-end shows a center frequency of 2 MHz with a 6 dB fraction bandwidth of 89% immersed in water. The LNA of each CMUT pixel possesses a gain of 15.7 dB and a 3 dB bandwidth of 21 MHz while only consumes 0.82 mW. Moreover, the proposed CMUT front-end exhibits an optimal sensitivity of 4.78 mV/kPa while only operating at a dc-bias of 2.5V. As a result, the proposed CMUT receiver with low power and low dc-bias is a promising candidate for mobile imaging applications that take full advantage of its high energy efficiency and small form factor.