Plasma-Enhanced Atomic Layer Deposition Processed SiO<sub>2</sub> Gate Insulating Layer for High Mobility Top-Gate Structured Oxide Thin-Film Transistors

Abstract

SiO2 processed by plasma-enhanced atomic layer deposition (PEALD) was applied as a gate insulator (GI) to the top gate high mobility InZnO (IZO) thin-film transistor (TFT). In as-fabricated devices, while IZO TFTs with GI processed by PEALD shows high ON/OFF ratio characteristics, the devices with GI deposited by plasma-enhanced chemical vapor deposition showed the conductive characteristics. From the secondary ion mass spectroscopy analysis, it is inferred that PEALD processed SiO2 generates fewer free electron donating elements in the active layer. The IZO TFT with PEALD processed GI exhibits a high-field effect mobility of 32.9 cm2/ $\text{V}\,\cdot \,\text{s}$ , $V_{\mathrm{\scriptscriptstyle ON}}$ of −0.3 V, and $\Delta ~V_{\mathrm{\scriptscriptstyle ON}}$ of 0.56 V under positive bias temperature stress (1 MV/cm, 60 °C, 3600 s) after being subject to thermal annealing at 350 °C.