Barrierless Cu-Ni-Nb thin films on silicon with high thermal stability and low electrical resistivity

In this paper, we demonstrate a thin film Cu-Ni-Nb alloy deposited directly on silicon, without a designated barrier, showing very high thermal stability at a temperature up to 700 degrees C for 1 h. Thin [Nb-Ni-12]Cu-x films were sputter deposited and annealed, and their material and electrical properties were studied. The results can be explained by the "cluster-plus-glue atom" model for stable solid solutions, where [Nb-Ni-12] cuboctahedral clusters are embedded in a Cu matrix. In this model, the clusters are congruent with the Cu minimizing atomic interactions allowing a good stability. The properties of the films were found to be affected by the Ni/Nb ratios. Especially, the ( Nb1.2/13.2Ni12/13.2)(0.3)Cu-99.7 film annealed at 500 degrees C for 1 h had the lowest electrical resistivity of about 2.7 mu Omega cm. And even after 40 h annealing at 500 degrees C, it maintained a low resistivity of about 2.8 mu Omega cm, demonstrating extremely high stabilities against silicide formation.