Attaining quantitatively fewer defects in close-packed InGaZnO synthesized using atomic layer deposition

Abstract

Owing to their uniformity across large areas, low-temperature processability, and low off-current characteristics, oxide semiconductors demonstrate significant potential for integration into displays, memories, and logic devices. In the hyper scaling era, atomic layer deposition (ALD) is well suited for downsizing device fabrication, leveraging self-limiting chemical reactions to provide nanoscale control, and conformal coating on substrates with high aspect ratios. Hence, in this study, we fabricated highly oriented c-axis-aligned crystalline (CAAC) indium-gallium-zinc oxide (IGZO) thin films using plasma-enhanced ALD (PEALD), introducing an additional thermodynamic driving force for crystallization. A comparative study was conducted on the properties of CAAC-IGZO in correspondence to conventional sputter-based IGZO. In particular, photo-induced current transient spectroscopy (PICTS) is employed to map the electronic structure (density of states (DOS)) of the films, which quantitatively confirmed fewer defects in CAAC-IGZO. Fewer defects result in highly stable CAAC-IGZO transistors with positive bias stress threshold (PBTS) at 0.03 V and negative bias stress threshold (NBTS) at 0.06 V. Thus, this research on thermally and electrically stable CAAC-IGZO synthesized at low temperatures through PEALD offers insights into the processing and material perspectives for the application of oxide semiconductors in 3D integration.