Influence of Al2O3 Gate Dielectric on Transistor Properties for IGZO Thin Film Transistor

Abstract

In this paper we investigated transistor properties of indium-gallium-zinc oxide (IGZO) thin film transistors (TFT) with Al2O3/SiO2 dielectric. The saturation field-effect mobility (msat) of TFTs with Al2O3 decreased about 10 % irrespective of the Al2O3 thickness. Furthermore, the threshold voltage (Vth) value of TFT with Al2O3 shifts toward positive direction about 0.5 V. We found that the SiO2/Al2O3 stack structure contains fixed charge of about -1.1 × 1011 /cm2 and dipole moment of about 0.4 V at Al2O3/SiO2 interface, and negligible fixed charge in Al2O3 layer. These indicate that the origin of the msat degradation and positive Vth shift are dominantly due to the fixed charge at IGZO/Al2O3 interface and dipole moment at Al2O3/SiO2 interface, respectively.