Effects of oxygen content on the structural and electrical properties of Thin Yb₂O₃ gate dielectrics

This paper describes the structural properties and electrical characteristics of thin Yb₂O₃ gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were studied, as a function of the growth conditions (three various argon-to-oxygen flow ratios, 1015, 1510, and 205, and temperatures from 600 to 800°C), by X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy. It was found that Yb ₂O₃ dielectrics having a 1510 flow condition after annealing at 700°C exhibit a thinner capacitance equivalent thickness and excellent electrical properties, including the interface trap density and the hysteresis in the capacitance-voltage curves. Furthermore, this condition has a small slope in the Poole-Frenkel emission and the Schottky emission, indicating a shallow level trap and a low barrier height in the Yb₂O₃ film. These results suggest the reduction of the interfacial SiO₂ formation and minimal surface roughness due to the optimization of oxygen in the metal-oxide film.