Electron Cyclotron Resonance Plasma-Assisted Atomic Layer Deposition of Amorphous Al2O3 Thin Films

Without extra heating, Al₂O₃ thin films were deposited on a hydrogen-terminated Si substrate etched in hydrofluoric acid by using a self-built electron cyclotron resonance (ECR) plasma-assisted atomic layer deposition (ALD) device with Al(CH₃)₃ (trimethylaluminum; TMA) and O₂ used as precursor and oxidant, respectively. During the deposition process, Ar was in- troduced as a carrier and purging gas. The chemical composition and microstructure of the as-deposited Al₂O₃ films were characterized by using X-ray di®raction (XRD), an X-ray photo- electric spectroscope (XPS), a scanning electron microscope (SEM), an atomic force microscope (AFM) and a high-resolution transmission electron microscope (HRTEM). It achieved a growth rate of 0.24 nm/cycle, which is much higher than that deposited by thermal ALD. It was found that the smooth surface thin film was amorphous alumina, and an interfacial layer formed with a thickness of ca. 2 nm was observed between the Al₂O₃ film and substrate Si by HRTEM. We conclude that ECR plasma-assisted ALD can grow Al₂O₃ films with an excellent quality at a high growth rate at ambient temperature.