Abstract
Polyimide films have widely been used in microcircuit fabrication and Micro-Electro-Mechanical System because they have many characteristics including low dielectric constant, easy processing, good step coverage ability, high heat resistance and chemical resistance. Reactive ion etching of polyimide films was investigated. We studied Ti is the best material for seven kinds of etching mask and found long time etching mask of polyimide films. Optimum RIE parameters including oxygen gas flow rate, CHF3 gas flow rate, chamber pressure and RF power, high aspect ratio and high etch rate were achieved with oxygen flow rate 40 sccm, CHF3 gas flow rate 5 sccm, chamber pressure 10 mtorr and RF power 100W. Because of the linear sensitivity in the wide range of humidity and good sensor performance, we use polyimide films to fabricate a capacitive-type relative humidity sensor. The fabricate sensor exposed to various test humidity conditions, has sensitivity more than 1 pF/%RH, shows good linearity and long term stability.