Low-Temperature Passivation of Amorphous-Silicon Thin-Film Transistors With Supercritical Fluids

In this letter, supercritical CO
₂
(SCCO
₂
) 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 (150degC ). With the high transport and diffusion properties of fluids, it is proposed to act as a transporter in delivering the molecules into the amorphous-silicon film and repairing defect states by the molecules. In addition, the propyl alcohol is used as the surfactant between nonpolar-SCCO
₂
fluids and polar-H
₂
O molecules for mingling H
₂
O molecules uniformly with the SCCO
₂
fluids. After the treatment of SCCO
₂
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.