Comparison and analysis of capacitive humidity sensors with water vapor inlet holes of different depths

Abstract

This paper describes the design, fabrication, and characterization of a capacitive humidity sensor with water vapor inlet holes of different depths. The humidity sensors were composed of a SiO2 insulation layer, a bottom electrode, a polyimide (PI) sensing layer, and a top electrode containing water vapor inlet holes. The sensors were 3.5 mm×3.5 mm with a 0.7-μm thick PI-based sensing layer. A humidity sensor with a partially etched PI layer in the water vapor inlet holes had the following characteristics: sensitivity 1500 fF/%RH, hysteresis 0.37%, and a response time of 70 s.