CF4-Plasma-Induced Fluorine Passivation Effects on Poly-Si TFTs with High- κ Pr2O3 Gate Dielectric

Abstract

High-performance polycrystalline silicon thin-film transistors ( TFTs) integrating high-κ gate dielectric and fluorine-passivated film are demonstrated. High gate capacitance density and thin equivalent-oxide thickness provided by the high-κ gate dielectric have the advantage of increasing the driving current capability of the TFT device, but an undesirable off-state leakage current could be introduced from the high electric field near the drain side. Introducing fluorine atoms into films by employing a low-temperature plasma treatment can effectively passivate the trap states. With plasma treatment on film, the electrical characteristics of TFTs can be significantly improved, including a steeper subthreshold swing, smaller threshold voltage, higher field-effect mobility, and better on/off current ratio compared with that without plasma treatment. The maximum off-state leakage current of the fluorine-passivated TFT is more than one order of magnitude lower than that of the control TFT. Furthermore, the incorporation of fluorine atoms by plasma treatment also improves the reliability of TFTs against hot carrier stressing, which is due to the formation of stronger bonds in place of weak bonds in the channel and at the gate interface. Therefore, high-performance and high-reliability TFTs with gate dielectric and plasma treatment on film are suitable for active-matrix liquid crystal display application.