Effects of nitrogen content on the structure and electrical properties of high-k NdO_xN_y gate dielectrics

This paper describes the structure and electrical properties of thin NdO_xN_y gate dielectrics deposited on Si(100) substrates through reactive rf sputtering. Atomic force microscopy and x-ray photoelectron spectroscopy were used to study the morphological and chemical features of these films as functions of the growth conditions (argon-to-nitrogen flow ratios of 20/5, 15/10, 10/15, and 5/20; temperatures ranging from 600 to 800 °C). The NdO_xN_y gate dielectric prepared under an Ar/N₂ flow ratio of 10/15 with subsequent annealing at 700 °C exhibited the smallest capacitance equivalent thickness and the best electrical characteristics (gate leakage current, interface-trapped charge, and hysteresis voltage in the capacitance-voltage curves). We attribute this behavior to the optimal nitrogen content in this metal oxide film suppressing the amorphous silica and silicate at the NdO_xN_y/Si interface and forming a smooth surface.