Fabrication of self-aligned TFTs with a ultra-low temperature polycrystalline silicon process on metal foils

We have fabricated self-aligned thin-film transistors (TFTs) using a ultra-low temperature (T < 200 °C) polycrystalline silicon process on stainless steel foil substrates. The overall processing scheme and technical details were discussed from the viewpoint of electrical and mechanical stabilities. Large grain poly-Si films were obtained with sequential lateral solidification (SLS) method. Plasma enhanced atomic layer deposition (PEALD) method was used to form Al2O3 gate dielectric films. The TFT performances were enhanced by plasma oxidation of the polycrystalline Si surface prior to Al2O3 gate dielectric film deposition. The fabricated TFT showed a field effect mobility of 95 cm2/Vs, a threshold voltage of −3 V and a sub-threshold swing of 0.45 V/dec.