NH₃-Targeted Corrosion-Resistant MEMS Calorimetric Flow Sensor Based on Parylene C

This letter presents a corrosion-resistant MEMS calorimetric flow sensor that addresses reliability challenges in ammonia (NH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>) flow measurement. The employment of Parylene C anti-corrosion coating extends the sensor’s stability in 25 wt% ammonia solution to over 168 hours, demonstrating enhanced resistance to alkaline corrosion. Additionally, compared with suspended membrane designs, the adoption of porous silicon thermal isolation structure reduces the zero-flow voltage difference when measuring NH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> versus N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> from 2.02%FS to 0.07%FS, enabling mass production using an N<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>-calibration scheme. The experimental results demonstrate the sensor’s potential for replacing capillary-based flow sensors in semiconductor manufacturing.