Low-temperature passivation of amorphous-silicon thin-film transistors with supercritical fluids

Abstract

In this letter, supercritical CO2 (SCCO2) fluids technology is employed for the first time to effectively passivate the defect states in hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) at low temperature (150 degrees C). With the high transport and diffusion properties of SCCO2 fluids, it is proposed to act as a transporter in delivering the H2O molecules into the amorphous-silicon film and repairing defect states by the H2O molecules. In addition, the propyl alcohol is used as the surfactant between nonpolar-SCCO2 fluids and polar-H2O molecules for mingling H2O molecules uniformly with the SCCO2 fluids. After the treatment Of SCCO2 fluids mixed with water and propyl alcohol, the a-Si:H TFT exhibited superior transfer characteristics and lower threshold voltage. The improvement in electrical characteristics could be verified by the significant reduction of density of states in the mobility gap of amorphous-silicon.