SURFACE CHEMICAL-CHANGES IN PVD TIN LAYERS INDUCED BY ION-BOMBARDMENT

TiN layers produced by the PVD method were subjected to bombardment by different ion species applied in sequence. The relative atomic concentration and the chemical states of the elements in the surface layer were determined by means of x-ray photoelectron spectroscopy. The composition and chemical states of a reference sample after wet chemical etching were taken to be representative for the stoichiometric TiN not affected by ion sputtering. For this sample characteristic line energies of Ti 2p3/2 = 454.7 eV and N 1s = 396.7 eV were found. Alternate bombardment with Ar+, N2+ and N2O+ ions (1-5 keV) results in significant compositional and chemical state changes. Ar+ bombardment leads to preferential loss of N from the outermost (1-3 nm) surface layers of the nearly stoichiometric TiN(x) (x = 1.0-1.1) without observable changes in the chemical state of the constituents. Bombardment with N2+ ions leads to a build-up of excess N (x much-greater-than 1) followed by the appearance of new N 1s and Ti2p lines at 395.8 +/- 0.3 eV and at 456.3 +/- 0.3 eV, respectively. N2O+ bombardment increases the O and decreases the N concentration together with a concomitant shot out of a Ti2p3/2 component peak at about 457.6 eV assignable to Ti2O3.