Bonding states and electrical properties of ultrathin HfOxNy gate dielectrics

Hafnium oxynitride (HfOxNy) gate dielectric was prepared using reactive sputtering followed by postdeposition annealing at 650 °C in a N2 ambient. Nitrogen incorporation in the dielectric was confirmed by x-ray photoelectron spectroscopy analysis. In comparison to HfO2 of the same physical thickness, HfOxNy gate dielectric showed lower equivalent oxide thickness (EOT) and lower leakage density (J). Even after a high-temperature postmetal anneal at 950 °C, an EOT of 9.6 A with J of 0.8 mA/cm2 @−1.5 V was obtained. In contrast, J of ∼20 mA/cm2 @−1.5 V for HfO2 with an EOT of 10 A was observed. The lower leakage current and superior thermal stability of HfOxNy can be attributed to the formation of silicon–nitrogen bonds at the gate dielectric/Si interface and strengthened immunity to oxygen diffusion by the incorporated nitrogen.