Thin-film transistors from very low temperature polycrystalline Si on glass substrates

Abstract

Polycrystalline Si films were deposited onto glass substrates by evaporation technique. The Hall-mobility of undoped films was investigated for process substrate temperatures from 300 to 650°C. The Hall-mobility was found to be up to about 10 cm 2/Vs for 500°C. Sb-doped n-type films exhibited a conductivity up to 10 (Ω cm) −1 deposited at about 500°C. Thin film transistors were fabricated from undoped and doped polycrystalline Si used for the channel and the source/drain contacts. The TFT mobilities were found to be 10 cm 2/Vs and 2 cm 2/Vs for a highest process temperature of 550°C and 480°C respectively. The new feature of the TFT process is that these data were obtained without using ion implantation technique. For the first time a poly-Si TFT was fabricated on soda-lime glass at a very low temperature of 480°C.