A Cmos Mems Capacitive Differential Flow Sensor for Respiratory Monitoring

This work presents a CMOS (complementary metal oxide semiconductor) micromachined capacitive differential flow sensor for respiratory monitoring. Airflow induces a pressure change on the suspended sensing plate and causes a capacitance change with respect to the electrodes. The microstructure fabricated by post-CMOS metal etch occupies an area of 320 × 230 m and has differential sensing capacitances of 190 fF. Output waveform of consecutive breaths was successfully measured with an output noise of 140 V for a measuring bandwidth of 0.5 Hz, which was equivalent to a minimum detectable capacitance change and airflow velocity of 6.2 aF and 4.3 mm/sec, respectively.