The electrical and material characterization of hafnium oxynitride gate dielectrics with TaN-gate electrode

Electrical and material characteristics of hafnium oxynitride (HfON) gate dielectrics have been studied in comparison with HfO₂. HfON was prepared by a deposition of HfN followed by post-deposition-anneal (PDA). By secondary ion mass spectroscopy (SIMS), incorporated nitrogen in the HfON was found to pile up at the dielectric/Si interface layer. Based on the SIMS profile, the interfacial layer (IL) composition of the HfON films appeared to be like hafnium-silicon-oxynitride (HfSiON) while the IL of the HfO₂ films seemed to be hafnium-silicate (HfSiO). HfON showed an increase of 300°C in crystallization temperature compared to HfO₂. Dielectric constants of bulk and interface layer of HfON were 21 and 14, respectively. The dielectric constant of interfacial layer in HfON (∼14) is larger than that of HfO₂ (∼7.8). HfON dielectrics exhibit ∼10× lower leakage current (J) than HfO₂ for the same EOTs before post-metal anneal (PMA), while ∼40× lower J after PMA. The improved electrical properties of HfON over HfO₂ can be explained by the thicker physical thickness of HfON for the same equivalent oxide thickness (EOT) due to its higher dielectric constant as well as a more stable interface layer. Capacitance hysteresis (ΔV) of HfON capacitor was found to be slightly larger than that of HfO₂. Without high temperature forming gas anneal, nMOSFET with HfON gate dielectric showed a peak mobility of 71 cm²/Vsec. By high temperature forming gas anneal at 600°C, mobility improved up to 256 cm²/Vsec.