Influence of Nitrogen Impurities on Nickel and Platinum Silicide Formation

Abstract

In the present study we investigate the influence of nitrogen on the silicide formation of thin nickel and platinum films. Nitrogen is introduced by implantation either in the metal films or in the silicon substrates. We use the rare stable isotope 15N for the implantation and the nuclear reaction 15N(p,α)12C for the detection and profiling of the impurity. For nitrogen in nickel, we find that at 350 °C nitrogen is mobile. It accumulates at the bottom nickel interface and, for a dose exceeding about 0.5 × 1016 N atoms cm−2, forms a barrier to silicide formation. When nitrogen is initially in the silicon substrate, the nitrogen profile is broadened in the same proportion as the dilution of the silicon sublattice when forming the silicide. Similar experiments with platinum films showed partially different behaviors. All results are explained in terms of a model based on the moving species during the silicide formation and the chemical affinity of nitrogen to the metal and to silicon.