Comprehensive Study of Low-Frequency Noise Origins in Scaled Atomic-Layer-Deposited IGZO TFTs

Abstract

In this work, we investigate the 1/f noise, i.e., low-frequency noise (LFN), characteristics of scaled atomic-layer-deposited indium-gallium–zinc oxide (IGZO) thin-film transistors (TFTs) focusing on key factors such as: 1) varying indium (In) concentrations; 2) post-thermal annealing; and 3) channel length ( ${L}_{\text {ch}}\text {)}$ scaling. Increasing the In ratio from 2:1:1 to 7:1:1 enhances field-effect mobility ( $\mu _{\text {FE}}\text {)}$ from 11.2 to 36.6 cm2/V and reduces LFN by up to 85%, demonstrating the role of In content in improving both electrical performance and noise characteristics. Post-annealing further mitigates LFN, achieving reductions of up to 68%, depending on the IGZO compositions. As ${L}_{\text {ch}}$ scales down, the dominant LFN mechanism shows a tendency to shift from mobility fluctuations ( $\Delta $ $\mu $ ) in long-channel devices ( ${L}_{\text {ch}} = 1~\mu $ m) to carrier number fluctuations ( $\Delta $ n) in short-channel devices ( ${L}_{\text {ch}} =50$ nm), as indicated by the distinct dependence of normalized drain-current power spectral density ( ${S}_{\text {ID}}$ / ${I}_{\text {D}}^{{2}}\text {)}$ on gate overdrive voltage. This behavior, supported by LFN measurements at elevated temperatures ( $\sim 125~^{\circ }$ C) and bias temperature instability (BTI) analyses, highlights the increasing influence of near-interface traps in scaled devices.