Current-conduction and charge trapping properties due to bulk nitrogen in HfO x N y gate dielectric of metal-oxide-semiconductor devices

This work examined the effects of bulk nitrogen in HfO x N y gate dielectric on current-conduction and charge trapping of metal-oxide-semiconductor devices. The nitrogen concentration profiles in HfO x N y gate dielectric were adjusted by Hf target sputtered in an ambient of modulated nitrogen flow. The current-conduction mechanisms of HfO x N y film comprised of various nitrogen concentration profiles at the low- and high-electrical field were dominated by Schottky emission and Frenkel-Poole emission, respectively. The trap energy level involved in Frenkel-Pool conduction was estimated to be around 0.8 eV. Smaller stress-induced leakage current and flat-band voltage shift were obtained for devices with HfO x N y dielectric containing less bulk nitrogen, attributable to less interface strain∕stress and bulk trap.