High-performance poly-silicon TFTs using HfO₂ gate dielectric

High-performance low-temperature poly-Si thin-film transistors (TFTs) using high-k (HfO₂) gate dielectric is demonstrated for the first time. Because of the high gate capacitance density and thin equivalent-oxide thickness contributed by the high-k gate dielectric, excellent device performance can be achieved including high driving current, low subthreshold swing, low threshold voltage, and high ON/OFF current ratio. It should be noted that the ON-state current of high-k gate-dielectric TFTs is almost five times higher than that of SiO₂ gate-dielectric TFTs. Moreover, superior threshold-voltage (V_th) rolloff property is also demonstrated. All of these results suggest that high-k gate dielectric is a good choice for high-performance TFTs.