Investigation of nitric oxide and Ar annealed SiO2/SiC interfaces by x-ray photoelectron spectroscopy

Silicon dioxide ${\mathrm{(SiO}}_{\mathrm{2}}\mathrm{)/silicon}$ carbide (SiC) structures annealed in nitric oxide (NO) and argon gas ambiences were investigated using x-ray photoelectron spectroscopy (XPS). The XPS depth profile analysis shows a nitrogen pileup of 1.6 at. % close to the NO annealed ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/SiC}$ interface. The results of $\mathrm{Si}\text{\hspace{0.05em}2p,}$ $\mathrm{C}\text{\hspace{0.05em}1s,}$ $\mathrm{O}\text{\hspace{0.05em}1s,}$ and $\mathrm{N}\text{\hspace{0.05em}1s}$ core-level spectra are presented in detail to demonstrate significant differences between NO and Ar annealed samples. A ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/SiC}$ interface with complex intermediate oxide/carbon states is found in the case of the Ar annealed sample, while the NO annealed ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/SiC}$ interface is free of these compounds. The $\mathrm{Si}\text{\hspace{0.05em}2p}$ spectrum of the Ar annealed sample is much broader than that of the NO annealed sample and can be fitted with three peaks compared with the two peaks in the NO annealed sample, indicating a more complex interface in the Ar annealed sample. Also the $\mathrm{O}\text{\hspace{0.05em}1s}$ spectrum of the NO annealed samples is narrow and symmetrical and can be fitted with only one peak whereas that of the Ar annealed sample is broad and asymmetrical and is fitted with two peaks. It is evident that the Ar annealed sample contains some structural defects at the interface, which have been removed from the interface by NO annealing as shown by $\mathrm{O}\text{\hspace{0.05em}1s}$ spectra. The $\mathrm{C}\text{\hspace{0.05em}1s}$ spectra at the interface reveal the subtle difference between NO and Ar annealed samples. An additional peak representing the interface oxide/carbon species is observed in the Ar annealed sample. At the interface, the $\mathrm{N}\text{\hspace{0.05em}1s}$ spectrum is symmetrical and can be fitted with one peak, representing the strong $\mathrm{Si\equiv N}$ bond. However, the $\mathrm{N}\text{\hspace{0.05em}1s}$ and $\mathrm{C}\text{\hspace{0.05em}1s}$ XPS spectra acquired in the bulk of the dielectric showed not only the $\mathrm{Si\equiv N}$ bond but also a trace amount of the N–C bond.