Potassium-assisted, facile oxidation of Si3N4 thin films

Abstract

X-ray photoelectron spectroscopy (XPS) was used to investigate potassium-assisted, facile oxidation of silicon nitride (Si3 N4 ) thin films on Si(100) substrates. The nitride films, 0.8–2.5 nm thick, were grown by heating the Si(100) crystal in hydrazine. Potassium (K) deposited onto the Si3 N4 surface at room temperature in a background of oxygen resulted in the formation of potassium peroxide (K2 O2 ) overlayers. Annealing the sample at 975 K for only 60 s decomposed the K2 O2 overlayer, desorbed K from the surface, and efficiently oxidized the underlying substrate. The XPS Si(2p) spectra indicate formation of silicon oxynitride on the surface. In the early stages of oxidation, up to 100% of the oxygen originally deposited as K2 O2 , was converted to silicon oxynitride after annealing. The enhanced oxidation rate under these conditions, relative to direct thermal oxidation, is attributed to the large concentration of reactive oxygen on the surface when the K2 O2 thermally decomposes.