CHARACTERIZATION OF TIN COATINGS AND OF THE TIN/SI INTERFACE BY X-RAY PHOTOELECTRON-SPECTROSCOPY AND AUGER-ELECTRON SPECTROSCOPY

TiN layers are prepared by RF magnetron sputtering of a Ti target in an Ar-N2 gas mixture onto monocrystalline Si(100) substrates. The chemical composition of the film is studied by X-ray photoelectron spectroscopy (XPS) analysis as a function of the DC bias voltage applied to the substrate. Increasing the bias voltage leads to a densification of the film and to a significant decrease of the amount of oxygen in the bulk. The effect on the N/Ti ratio of the ion erosion used to remove atmospheric contamination is discussed. The study of very thin films (30 angstrom) by angular XPS analyses leads to a model for the interface between the film and the Si substrate; this interface is typically 26 angstrom thick and contains SiN(x), SiO(x), TiN(x) and TiO(x) species. Auger profiles show that the N/Ti ratio is constant throughout the bulk and confirm the model chosen for the interface.