Behavior of oxygen doped SiC thin films: An x-ray photoelectron spectroscopy study

Thin silicon carbide films have been deposited by chemical vapor deposition on p-type (100) silicon substrates. The composition and bonds formed in these films have been analyzed by x-ray photoelectron spectroscopy (XPS) and infrared spectroscopy. The native surface oxide on the silicon carbide surface induced by air exposure has also been studied. Several phases are detected in the near-surface region: elemental Si, Si oxides (mainly SiO₂), Si carbide (SiC) and Si oxicarbides (SiO_xC_y). Quantitative XPS analysis results indicate that, for atomic oxygen fractions <0.15, the Si-C phases are dominant in the films. Above this value no silicon oxicarbide is observed, but a multiphase material formed by elemental Si, Si oxides and Si carbides is observed. In spite of the film being a complex phase mixture, a simple relationship is found between the overall carbon and oxygen compositions. The carbon atomic fraction in the film decreases quasilinearly as the oxygen content increases, with a slope of about - 1. An overall composition of SiO_xC_3-x in the 0.5<x <2 range is found for the phase mixture. A comparison with silicon carbide obtained by CH⁺_n ion implantation into monocrystalline silicon is made.