Comparative Study of ZrO2 and HfO2 as a High-k Dielectric for Amorphous InGaZnO Thin Film Transistors

Abstract

A comparative study is made between ZrO2 and HfO2 as a gate dielectric in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The degradation of transfer curves are observed in both dielectric devices, but much less degradation is observed in the ZrO2 dielectric one. Higher subgap density of states are extracted in HfO2 dielectric devices, which is consistent with the severe degradation of the electrical characteristics of the HfO2 device. We also observe the higher low-frequency noise in HfO2 dielectric devices compared to the ZrO2 and SiO2 dielectric ones, which is attributed to the enhanced remote phonon scattering from the HfO2 dielectric.