Impact Of Surface And Grain Boundary Scattering On The Resistivity Of Nanometric Cu Interconnects

Abstract

This work addresses the resistivity increase in Cu interconnects with decreasing line width. Recent published resistivity data for Cu interconnect lines is found to be accurately modeled by a fixed surface scattering specularity parameter, p = 0.52, and a grain boundary reflection coefficient, R = 0.43. In this model, the resistivity contribution from surface scattering at the line top and bottom surfaces, the contribution from surface scattering at the line sidewalls, and the contribution of grain boundary scattering from within the line are simply summed with the phonon and impurity resistivity contributions following Matthiessen's rule. The more recent line resistivity reports were found to have reduced impurity contributions to resistivity and larger grain sizes than earlier reports. It is concluded that a significant mitigation of the Cu resistivity increase with decreasing line width is possible, if the grain size can be maintained larger than the electron mean free path (39 nm at room temperature).