Preparation and Characterization of Organic Thin Films for Humdity Sensor Application with Interdigital Transducer

초록

Polymer thin films were prepared for humidity sensor applications with interdigital transducer (IDT). Plasma (co)polymerization of various single and binary monomer materials was done in a capacitive-coupled plasma (CCP) polymerization reactor in order to realize functionality of monomers in the resulting thin films. And a polyimide photoresist (PI2723-Dupont) thin film was deposited using a spin-coating technique for a microsensor application fully compatible with IC technologies. The humidity sensing properties of the polymer thin films were investigated by monitoring capacitance change in electric source frequency and humidity range of 60 Hz-100 kHz and 10-90 %RH, respectively. The IDT type polymer humidity sensors revealed better sensitivity at lower source frequency. The linearity and increment of the capacitance change became apparent with a lower discharge power and shorter plasma polymerization time for plasma polymerized thin films. The polyimide photoresist showed similar humidity sensing performance with that of commercial reference humidity sensor (Vaisala Hygrometer). Influence of the thin film preparation on the humidity sensing properties was investigated