Study of the interfacial reaction of high-<i>κ</i> Al2O3 gate oxides with IGZO

Abstract

High-permittivity (κ) dielectric oxides grown by atomic layer deposition (ALD) are the key to developing high-performance electronics. However, the high-κ dielectric grown by ALD causes interfacial phases due to chemically reactive species. Therefore, studying the interface between the high-κ ALD and the channel is highly desired. In this study, we investigate the interfacial reactions and diffusion behavior at the interface between ALD-grown Al2O3 and amorphous InGaZnO (IGZO) using transmission electron microscopy, depth-resolved x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, and time-of-flight secondary ion mass spectrometry depth profiling. Our results show that indium (In) out-diffusion upward to the Al2O3 dielectric layer from the IGZO layer, which is initiated by the trimethylaluminum precursor and further enhanced by thermal annealing, leads to interface degradation, defect formation, and elemental redistribution between Al2O3 and IGZO. We have carried out a comparative study investigating the interface between HfO2-ALD and IGZO, where diffusive phenomena were not observed. Our study aims to explore the quality of the interface between high-κ ALD dielectrics and underlayer amorphous oxide semiconductors.