Effects of interstitial oxygen defects at HfOxNy/Si interface on electrical characteristics of MOS devices

Effects of the defects at high-κ dielectric/Si interface on the electrical characteristics of MOS devices are important issues. To study these issues, a low defect (denuded zone) at Si surface was formed by a high-temperature annealing in hydrogen atmosphere in this paper. Our results reveal that HfO_xN_y demonstrates significant improvement on the electrical properties of MOS devices due to its low amount of the interstitial oxygen [O_i] and the crystal-originated particles defects as well as small surface roughness at HfO_xN_y/Si interface. The current-conduction mechanism of the HfO_xN_y film at the low- and high-electrical field and high-temperature (T>100°C) is dominated by Schottky emission and Frenkel-Poole (FP) emission, respectively. The trap energy level involved in FP conduction was estimated to be around 0.5eV. Reduced gate leakage current, stress-induced leakage current and defect generation rate, attributable to the reduction of defects at HfO_xN_y/Si interface, were observed for devices with denuded zone. The variable rise and fall time bipolar-pulse-induced current technique was used to determine the energy distribution of interface trap density (D_it). The results exhibit that relatively low D_it can be attributed to the reduction of defects at Si surface. By using denuded zone at the Si surface, HfO_xN_y has demonstrated significant improvement on electrical properties as compared to SiO_xN_y.