Improvement of polyimide capacitive humidity sensor by reactive ion etching and novel electrode design

Abstract

In this study, we demonstrate a highly sensitive polyimide capacitive humidity sensor achieved by reactive ion etching microstructures in polyimide film and novel electrode designs. For sensors of 3 /spl mu/m polyimide film, the sensitivity is improved from 0.8 to 1.24 (pF/%RH) over the relative humidity ranging from 50 to 80. The hysteresis is within 2.5 (%RH). The device has 1600 humidity admittance square holes etched 2 /spl mu/m deep in the polyimide sensing film, and its bottom electrode was patterned to reduce the less sensitive capacitor area to increase the dC/C ratio, and hence increase the sensitivity of the sensors.