Amorphous InGaZnO thin film transistors with SiO2/HfO2 double-layer gate dielectric fabricated at low temperature

Abstract Amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) with double-layer gate dielectric were fabricated at low temperature and characterized. A stacked 150 nm-thick SiO 2 /50 nm-thick HfO 2 dielectric layer was employed to improve the capacitance and leakage characteristics of the gate oxide. The SiO 2 /HfO 2 showed a higher capacitance of 35 nF/cm 2 and a lower leakage current density of 4.6 nA/cm 2 than 200 nm-thick SiO 2 . The obtained saturation mobility ( μ sat ), threshold voltage ( V th ), and subthreshold swing ( S ) of the fabricated TFTs were 18.8 cm 2  V −1  s −1 , 0.88 V, and 0.48 V/decade, respectively. Furthermore, it was found that oxygen pressure during the IGZO channel layer deposition had a great influence on the performance of the TFTs.