Growth of silicon oxynitride films by atmospheric pressure plasma jet

Ultra-thin silicon oxynitride (SiO_xN_y) layers were deposited by direct interaction of plasma species formed in an atmospheric pressure plasma jet (APPJ) with a silicon wafer. APPJs have been ignited in mixtures of helium (He) together with several nitrogen-based compounds. The chemical composition of the APPJ treated silicon surfaces was analysed by ultra-high vacuum x-ray photoelectron spectroscopy (XPS). The obtained N 1s XPS spectra showed that even 5 min of APPJ treatment is sufficient to fabricate SiO_xN_y films with a few nanometre thickness. A Si substrate exposed to an APPJ generated in a mixture of He/NH₃ resulted in the most efficient growth of SiO_xN_y films, indicated by the strongest N 1s XPS signal among all studied gas mixtures. Moreover, the N 1s spectra exhibited two major characteristics of chemical bonding structures attributed to nitrogen bonded to three silicon surface atoms, N-(S)₃, and nitrogen bonded to two silicon surface atoms and one oxygen atom, (Si)_2-N-O.