Analysis of Al Doping Effects on Resistivity and Electromigration of Copper Interconnects

In this paper, we investigated the effect of impurity (aluminum; Al) doping on the resistivity of damascene copper (Cu) interconnects by categorizing it into surface, grain-boundary, and impurity-scattering factors by means of a comprehensive scattering model. Segregation of Al dopant atoms to the interface of the lines increases the resistivity through increased surface scattering. Electromigration (EM)-induced Cu drift is suppressed as the Al concentration increases. The EM lifetime is improved by the suppression of Cu diffusion due to the piled-up Al at the top surface of the Cu interconnects.