X-ray absorption and photoelectron spectroscopic study of plasma-nitrided SiO2 film

Plasma-nitrided SiO2 thin film has been analyzed by synchrotron-radiation-based x-ray absorption and photoelectron spectroscopies (XAS and XPS). High-resolution N 1s XAS and N 1s, O 1s, and Si 2p XPS spectral changes were obtained for different annealing temperatures. N 1s XPS and XAS spectra show that at room temperature, besides the main species of N[Si(O−)3−x]3, there exist free moleculelike N2 and HN[Si(O−)3]2, H2NSi(O−)3, and N–Si2O species with surface contaminants. The spectral intensities of the N2 and the HN[Si(O−)3]2, H2NSi(O−)3, and N–Si2O species decrease as the annealing temperature increases, and finally the nitrogen exists dominantly in the form of N[Si(O)3]3 species above 820K, indicating out-diffusion of molecular N2 and structural reconstruction to form a stable structure upon annealing. The Si 2p and O 1s XPS spectra show that Si>4+ 2p peak and O 1s peak appear at 103.7 and 534.0eV, respectively, which are higher binding energies than those of thermally grown oxynitride films with lower coverage on silicon. Upon annealing the sample, these peaks shift towards lower binding energy; ∼0.3eV for Si>4+ and 0.4eV for O 1s. The causes of the peaks appearance at relatively higher binding energy and the peak shift upon annealing are discussed.