Influence of line dimensions on the resistance of Cu interconnections

As dimensions reach the deep-submicrometer level on the order of the mean-free path of electrons, increases in the resistivity of a metal corresponding to reductions of wire dimensions is a concern. To understand the resistance dependence on the dimensions, resistance of Cu versus interconnection size was analyzed. The experimental values were in good agreement with Fuchs´ size-effect theory. The resistance of Cu increased nonlinearly as line width decreased. This enhancement was attributed to the increased surface and grain boundary scattering. Almost 50% of the electrons elastically scatter during transport in wires with widths below 0.5 μm. It will he important in the future to develop interconnections with smooth surfaces on all sides to maximize elastic scattering of electrons.