Self-aligned passivation on copper interconnection durability against oxidizing ambient annealing

A self-aligned niobium (Nb) passivation method has been developed in order to improve the stability of copper (Cu) in an oxidizing ambient. A Cu/Nb/SiO2/(100)Si structure was annealed between 400 and 850 °C for 30 min in a gas mixture of H2 and N2. The underlying Nb diffused to the Cu surface and turned into its nitride at 750 °C. The surface Nb nitride layer acted as a passivation layer against oxidation. The passivated Cu was found to retain its resistivity of 2.0 μΩ cm even after oxidation at 400 °C for 30 min in a dry oxygen ambient.