Oxidation of microcrystalline Si:H:Cl films

The oxidation of microcrystalline (mc‐) silicon films, deposited from silicon tetrachloride by an rf glow discharge, was studied using x‐ray photoelectron spectroscopy (XPS). The mc‐Si films containing between 1% and 3% Cl, were exposed to 200‐Torr oxygen, or water vapors, for 50 h and their oxidation was compared to that of single‐crystal Si(100), under identical conditions. The Si 2p spectra, changing with depth, contained contributions from all oxidation states (+4, +3, +2, +1, 0), with composition depending on the reacting gas and the crystallinity of the Si substrate. Exposure to water vapors leads to heavier oxidation (higher oxidation states and thicker oxides), as compared to oxygen exposure. In both cases, the oxidation resulted in some chlorine depletion mainly in the SiO₂‐rich external surface of the mc‐Si films. As to the role of the microcrystalline structure, the most pronounced effects involved enhancement of oxidation to the Si¹⁺ and Si³⁺ states across the thicker SiO₂–Si interface.