Stoichiometry reversal and depth-profiling in the growth of thin oxynitride films with N₂O on Si(100) surfaces

Synchrotron based O 1s and N 1s photoabsorption spectroscopy have been used to determine the composition and thickness of oxynitride films grown in N2O on a Si(100) surface. Core-level photoabsorption spectroscopy is shown to be a very sensitive probe capable of measuring surface coverages lower than 0.1 monolayers of N (6.5×1013 N atoms/cm2). Film composition was monitored as a function of growth to demonstrate the stoichiometry reversal from primarily N terminated surfaces in thin films to nearly pure SiO2 in films thicker than ∼ 20 Å. A sample with a 60 Å oxynitride film was depth-profiled by etching in HF and was shown, via N 1s absorption spectroscopy, to have N segregation within 10 Å above the Si/SiO2 interface.