Out-of-plane MEMS-based mechanical airflow sensor co-integrated in SOI CMOS technology

• Monolithic integration of capacitive airflow sensor with CMOS on thin film SOI technology.
• Ultra low power capacitive detection with C-f ring oscillator converter.
• 10% variation oscillating frequency under 120 m/s parallel airflow stimulus.
• Simulation/measurement chain of beam deflection under airflow.
• Generic dry release offering multisensing opportunities.

This paper demonstrates the monolithic integration of an airflow sensor based on out-of-plane movable cantilevers with a CMOS integrated circuit providing small footprint and low-power sensing. Airflow is sensed by mechanical deflection of cantilevers without static power consumption contrary to classical thermal flow sensors based on micro-heater. The interfacing circuit is a CMOS ring oscillator (RO), fabricated on the same chip with silicon-on-insulator (SOI) technology, offering unique properties such as harsh environment resistance and lower power consumption. Moreover, the additional post-processing steps required by the built-in of out-of-plane cantilevers are minimum thanks to the use of standard CMOS materials and dry etching of the sacrificial layer.The developed microsystem demonstrates 10% variation of the RO frequency for an airflow varying from 0 m/s to 120 m/s, with a static power consumption of the order of 1 μW.