Surface stoichiometry, structure, and chemisorption on silicon nitride studied by direct recoiling, x-ray photoelectron spectroscopy, and Auger electron spectroscopy

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Abstract
The surface stoichiometry, structure, and chemisorption of O2 and H2O have been investigated for surfaces of silicon nitride prepared by (i) chemical vapor deposition (CVD) and (ii) low-energy N+2 ion nitridation of a Si(100) crystal. The technique of time-of-flight (TOF) analysis of directly recoiled (DR) particles combined with x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and Ar+ depth profiling have been used for characterization. The results show that CVD Si3N4 is terminated in a silicon rich layer upon which a one monolayer oxide is formed from O2 exposure. The initial O2 chemisorption rate is fast and saturation occurs at 15 L exposure, with the kinetics fitting a one-site model for which the modified sticking coeffient is S/Nf=3.5×10−16 cm2/atom. Chemisorption of H2O produces a surface H:O ratio of 1:1 as determined by DR. Nitridation of a Si(100) surface by low-energy N+2 produces a thin nitride film with XPS binding energies identical to those of CVD Si3N4. Depth profiling indicates nitride film thicknesses of 3 and 8 Å for 0.5- and 3.0-keV N+2 ion bombardment, respectively, in agreement with ion ranges estimated from LSS theory. Defect controlled incorporation of oxygen and carbon during N+2 bombardment is observed.