Impact of incorporated oxygen quantity on optical, structural and dielectric properties of reactive magnetron sputter grown high-κ HfO₂/Hf/Si thin film

Highlights: • In situ SE was used to grow HfO₂ high-κ film on Si by rf sputtering method. • Generally, an interfacial layer occurs between high-κ film and Si substrate. • To eliminate it, a thin Hf buffer layer was grown on Si prior to HfO₂ growth. • O₂ quantity has an extreme role for eliminating interfacial layer formation. • Better oxide films were obtained for O₂/Ar below 0.1 and rf sputter power ∼30 W. - Abstract: High-κ hafnium-oxide thin films have been fabricated by radio frequency (rf) reactive magnetron sputtering technique. To avoid formation of an undesired interfacial suboxide layer between Si and high-κ film, prior to HfO₂ deposition, a thin Hf buffer layer was deposited on p-type (1 0 0) Si substrate at room temperature. Effect of oxygen gas quantity in the O₂/Ar gas mixture was studied for the optical and structural properties of grown HfO₂ high-κ thin films. The grown thin oxide films were characterized optically using spectroscopic ellipsometer (SE) in detail. Crystal structure was studied by grazing incidence X-ray diffractometer (GIXRD) technique, while bonding structure was obtained by Fourier transform infrared spectroscopy (FTIR) analyses. In agreement with GIXRD and FTIR analyses, SE results show that any increment above ideal quantity of oxygen content in the gas mixture resulted in decrements in the refractive index and thickness of HfO₂ dielectric film, while increments in SiO₂ thickness. It is apparent from experimental results that oxygen to argon gas ratio needs to be smaller than 0.2 for a good film quality. The superior structural and optical properties for grown oxide film were obtained for O₂/Ar gas ratio of about 0.05–0.1 combined with ∼30 W constant rf sputtering power