Fabrication of thin-film transistors on polyimide films

We describe polyimide films as substrates for active thin-film electronics. Amorphous silicon thin-film transistors were fabricated on 51 mum thick polyimide foil (Kapton((R))E) at a maximum process temperature of 150degreesC. Kapton E was selected for its chemical stability, high softening or glass transition temperature, relatively low coefficient of humidity expansion, negligible heat shrinkage, low water and oxygen permeability, coefficient of thermal expansion comparable to that of thin-film electronics, and low surface roughness. The fabricated transistors have off-current of similar to2 x 10(-12) A. on-off current ratio similar to10(7), threshold voltage similar to2 V, electron mobility similar to0.5 cm(2)V(-1)s(-1) and subthreshold slope similar to0.5 V/decade. These performance parameters are similar to those of transistors fabricated at 150degreesC on glass substrates.