A Micro Capacitive Humidity Sensor Based on Al-Mo Electrodes and Polyimide Film

Area of Science:

• Materials Science and Engineering
• Electrical Engineering
• Sensor Technology

Background:

• Rapid humidity sensing is critical for advanced applications, including fuel cell vehicles.
• Existing numerical models and methods for fast-response micro humidity sensors are limited.
• Parallel plate capacitors are suitable for relative humidity (RH) measurement.

Purpose of the Study:

• To develop and present a numerical model and method for a parallel plate capacitor humidity sensor.
• To analyze the dynamic characteristics of the micro humidity sensor.
• To fabricate and characterize a micro humidity sensor based on numerical predictions.

Main Methods:

• Developed a numerical model and analysis for a parallel plate capacitor.
• Fabricated the micro humidity sensor using complementary metal-oxide semiconductor (CMOS)-compatible technology.
• Utilized a P-type monocrystalline silicon wafer, polyimide film, and molybdenum-aluminum electrodes.

Main Results:

• Achieved high linearity (0.9965) and sensitivity (0.4264 pF/%RH) with low hysteresis (7.408% RH).
• Demonstrated rapid response times, with an average adsorption time of 1 second and a minimum of 850 ms.
• Exhibited excellent stability over a 240-hour test at 25 °C.

Conclusions:

• The developed numerical model and method are effective for predicting parallel plate capacitor sensor performance.
• The fabricated micro humidity sensor meets the requirements for fast and stable humidity measurements.
• This work provides a valuable tool for the design and optimization of micro humidity sensors.