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 Å 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 Å 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.
C. S. Kang, Cho, H. - J., Onishi, K., Nieh, R., Choi, R., Dr. Sundararaman Gopalan, Krishnan, S., Han, J. H., and Lee, J. C., “Bonding states and electrical properties of ultrathin HfO$_x$N$_y$ gate dielectrics”, Applied Physics Letters, vol. 81, p. 2593, 2002.