Sputter deposition of nitride coatings in oxygen-contaminated sputter atmospheres

Like all PVD processes, sputtering requires high–vacuum systems. The present contribution reports on the effect of the residual atmosphere and substrate material on the coating/substrate interface composition, film composition and structure of nitride hard coatings (TiNx, ZrNx, NbNx). Elevated residual gas pressures and sputter gas impurities were simulated by oxygen partial pressures. The coatings were characterized by AES, ESCA, REM and XRD. The oxygen contents of the interface region and the coatings strongly depend on the O2 pressure and the deposition conditions (substrate cleaning and bias). The oxygen enrichment in the interface is clearly bound to the coating metal. Oxygen containing ZrNx coatings are two–phase (ZrN + ZrO2), while TiNx films dissolve the oxygen (Ti(N,O)).