The Impact of Passivation Layers on the Negative Bias Temperature Illumination Instability of Ha-In-Zn-O TFT

Abstract

We systematically investigated the role of the Si O x and/or SiON x passivation layer in the amorphous hafnium indium zinc oxide (HIZO) thin film transistors (TFTs) under a negative bias temperature illumination stress (NBTIS) condition. The device instability of the TFTs with a SiO x passivation layer [threshold voltage shift (Δ V th ) ∼-6.5 V] is better than that of the TFTs with a SiO N x passivation layer (Δ V th ∼-8.5 V) in the atmosphere. However, the devices with the Si O x passivation layer showed different instabilities in the atmosphere (-6.5 V) and N 2 ambient (-5.5 V). The film analysis demonstrated the higher water permeability of the SiO x film and higher hydrogen content of the SiO N x films, suggesting the existence of not only water related positive charge traps but also hydrogen related positive charge traps under NBTIS conditions. After including the Si O x (inner)/SiO N x (outer) passivation layers, the instability of the amorphous HIZO device was drastically improved by the suppression of the positive charge trapping sites under the NBTIS conditions. © 2010 The Electrochemical Society.