A Low Power CMOS-MEMS Monolithic Integrated Dual-Mode Thermal Sensor with Thermal Conductivity Compensation for Accurate Binary Gas Measurement

This paper presents a dual-mode CMOS-MEMS thermal sensor capable of accurately measuring both the flow rate and composition of binary gas mixtures. The device was first fabricated using a 0.18 μ m 1P6M CMOS process, followed by a customized post-CMOS processing flow that enabled the simultaneous realization of a dualstructure architecture, achieving low power consumption (<3 mW). Experimental results demonstrate that the thermal conductivity sensor oriented perpendicular to the airflow sensing structure exhibits an order of magnitude lower fluctuation (<0.1%) under flow rates up to 15 SLM, confirming the stability of the conductivity response. Without compensation, the flow response for He is approximately 66% lower compared with N2. By characterizing the linear relationship of He-N2 mixtures, we achieved signal compensation with an off-line algorithm, which reduced the fluctuation to 0.78%. These results highlight the strong consistency and robustness of the monolithic integrated device, underscoring its potential for gas pipeline monitoring and flow control applications.