A 200-nm-gap Titanium Nitride Composite CMOS-MEMS CMUT for Biomedical Ultrasounds

摘要

A low-pressure sealed capacitive micromachined ultrasonic transducer (CMUT) is presented with a narrow transducer gap (<;200 nm) to enable efficient capacitive transduction while a circuit-integration scheme for SNR improvement is implemented based on a tailored titanium nitride composite (TiN-C) monolithic CMOS-MEMS platform [1]. In this study, Parylene-C is selected as an encapsulation material after structural release that not only offers excellent deposition uniformity but also provides proper acoustic impedance for biomedical applications. In this work, a prototyped single-channel DI water-immersed ultrasound receiver consists of a 5×4 CMUT array that was composed of 45μm×30μm subarray membranes paired with a 20 dB fixed-gain amplifier is characterized using a standard pulser (Olympus 5072PR) and an unfocused ultrasonic probe (Panametrics-NDT C310) at 12 mm distance atop, after data calibration by a hydrophone (ONDA HNR-1000), the TiN-C CMUT exhibits a receiving sensitivity of 2.28 m V IkPa with only 40 V of dc bias.