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

This paper describes the structure and electrical properties of thin Nd Ox Ny 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 205, 1510, 1015, and 520; temperatures ranging from 600 to 800 °C). The Nd Ox Ny gate dielectric prepared under an Ar N2 flow ratio of 1015 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 Nd Ox Ny Si interface and forming a smooth surface.