ABSTRACT
High-k Y2O3 thin films were investigated as the gate dielectric for amorphous indium zinc tin oxide (IZTO) thin-film transistors (TFTs). Y2O3 gate dielectric was deposited by radio frequency magnetron sputtering (RF-MS) under various working pressures and annealing conditions. Amorphous IZTO TFTs with SiO2 as the gate dielectric showed a high field-effect mobility (µFE) of 19.6 cm²/Vs, threshold voltage (Vth) of 0.75 V, on/off current ratio (Ion/Ioff) of 2.0×106, and subthreshold swing (SS) value of 1.01 V/dec. The IZTO TFT sample device fabricated with the Y2O3 gate dielectric showed an improved subthreshold swing value compared to that of the IZTO TFT device with SiO2 gate dielectric. The IZTO TFT device using the Y2O3 gate dielectric deposited at a working pressure of 5 mtorr and annealed at 400 °C in 6 sccm O2 for 1 hour showed a high µFE of 51.8 cm²/Vs, Vth of -0.26 V, Ion/Ioff of 6.0×10³, and SS value of 0.19 V/dec. With the application of a Y2O3 gate dielectric, the Vth shift improved under a positive bias stress (PBS) but was relatively unaffected by negative bias stress (NBS). These shifts were attributed to charge traps within the gate dielectric and/or interfaces between the channel and gate dielectric layer.
