Fractal analysis of electromigration-induced changes of surface topography in Au conductor lines

Evolution of surface morphology of Au conductor lines under high-density electric current is studied by scanning tunneling microscopy. The loss of conductivity of thin Au films is found to occur through formation of voids resulted from electromigration followed by the depletion of the material. It is shown that the density of electric current passing through thin conducting films greatly affects their lifetime. Fractal analysis is employed to estimate numerically changes of surface topography of Au films. The fractal dimension is shown to be an optimum prefracture criterion for thin metal films under applying electric current.