Effects of Passivation Layers on the Characteristics and Stability of Indium–Gallium–Zinc Oxide Thin-Film Transistors

The characteristics and stability of bottom-gate (BG), indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs) with different types of silicon oxide (SiOx) passivation (PV) layers have been investigated. Labeled as S-SiOx or T-SiOx, the PV layers are formed in a plasma-enhanced chemical vapor deposition system using as precursor pairs either silane and nitrous oxide or tetraethyl orthosilicate (TEOS) and oxygen. For a TFT subjected to a subsequent oxidizing heat treatment, a higher proportion of T-SiOx in the PV layer leads to more resistive source/drain (S/D) regions, induces a more extensive pushing of the S/D junctions into the S/D regions, mitigates effective short-channel effects, and improves the stability of the TFT against thermal, and positive and negative gate-bias temperature stress. These changes correlate well with a lower hydrogen content in T-SiOx than in S-SiOx.