Influence of NH3 annealing on the chemical states of HfO2/Al2O3 stacks studied by X-ray photoelectron spectroscopy

• Thin HfO2/Al2O3 film is grown on silicon substrate by atomic layer deposition.
• XPS is used to investigate the interface of HfO2/Al2O3/Si after NH3 annealing.
• The nitrogen can be doped into HfO2/Al2O3 film after NH3 annealing treatment.

The effect of NH3 annealing on the chemical properties and thermal stability of ultrathin HfO2/Al2O3 film grown on silicon substrate by atomic layer deposition are investigated as a function of post deposition annealing temperature. X-ray photoelectron spectroscopy shows that nitrogen incorporation can be approached by a NH3 annealing treatment and its composition evidently increases after annealing at 700 °C. Nitrogen atoms are found to bond to hafnium, aluminum and silicon atoms with annealing temperature above 800 °C, respectively. In addition, ultrathin Al2O3 layer is demonstrated as a robust barrier layer for preventing silicon diffusion.