Influence of oxidant source on the property of atomic layer deposited Al2O3 on hydrogen-terminated Si substrate

Al2O3 thin films were deposited on hydrogen-terminated Si substrate using atomic layer deposition (ALD) technique with trimethylaluminum (TMA) and an oxidant source of H2O vapor, O-2 plasma, or O-3, Substrate temperature was maintained at 350 degrees C when the Al2O3 films were grown with the oxidant sources of H2O vapor and O-3, and with the oxidant source of O-2 plasma, Al2O3 films were deposited at the substrate temperature of 200 degrees C. Growth rates of Al2O3 films on HF-cleaned Si surface were saturated at 0.08, 0.14, and 0.06 nm/cycle for H2O vapor, O-2 plasma, and O-3, respectively. Equivalent oxide thickness (EOT) and leakage current vs. physical thickness of atomic layer deposited Al2O3 films grown with various oxidant sources were also measured in this study. To investigate the main cause of different EOT with oxidant sources, interfacial properties were examined by using transmission electron microscopy (TEM) and X-ray photoelectron microscopy (XPS). In the TEM analysis, interfacial layers with the thickness of about 1.7 and 1.3 nm were observed in as deposited Al2O3 films grown using O-2 plasma and O3- We confirmed that the interfacial layers were mainly composed of SiOx in the XPS depth analysis. Using angle resolved X-ray photoelectron spectroscopy, effect of annealing on the interfacial structure of Al2O3 films grown with O-3 and O-2 plasma was also studied, and we found that after annealing, the peak corresponding to silicon suboxide and Al-silicate disappeared and fully oxidized Si4+ increased. (c) 2004 Elsevier B.V. All rights reserved.