Effects of annealing on tantalum pentoxide films in N-2 and N2O gas environments

The effects of annealing in N-2 and N2O gas environments on the thin tantal um pentoxide (Ta2O5) films have been comparatively studied in this research . Annealing in NO favored the stoichiometric Ta2O5 film formation because t he most significant decrease in the intensity signal of transmittance detec ted at 612 cm(-1) was obtained by Fourier transform infrared spectroscopy. Using X-ray photoelectron spectroscopy, the Ta 4f spectrum had a 1.9 eV spi n-orbit splitting between the peak signal of Ta 4f(7/2) at 26.2 eV and that of Ta 4f(5/2) at 28.1 eV, Moreover, enhancement of the intensity signal co rresponding to stoichiometric Ta2O5 at 530.7 eV was also clearly shown in O 1s spectrum. This implied that oxygen species released by NO reduce the am ount of oxygen vacancies and interfacial defects to form a thermodynamicall y stable interface. Low leakage current density, nearly no hysteresis and l ow flat-band voltage in capacitance-voltage measurements also supported the above results. However, the deficiencies induced by annealing were out-dif fusion of Si atoms into the Ta2O5 films and an increase in the interfacial thickness of silicon oxide that directly decreased the effective dielectric constant of Ta2O5.