Annealing influence on electrical transport mechanism of electroless deposited very thin Ag(W) films

Morphology and conductivity (σ) of the non-tarnishing electroless Ag(W) films for interconnect were studied as a function of thickness (d) by Atomic Force Microscopy (AFM) and Tunneling Atomic Force Microscopy methods. For d ≤ 100 nm the conductivity dependence on thickness can be modeled as percolation of the electrical transport while for thicker d > 100 nm layers it was independent on d (σ = σ₀). A simple electrical circuit model that described the experimental dependence σ(d) for both thin and thick layers was proposed. The AFM study has shown that the small network changes in the film morphology, due to vacuum annealing cause the significant (few orders of magnitude) improvements in electrical conductivity. Although, near bulk conductivity was achieved for the thicker sample, vacuum annealing was not sufficient to achieve such conductivity for very thin Ag(W) films.