Diffusion and electromigration of Cu in single crystal Al interconnects

摘要

The electromigration-induced transport properties of Cu in Al-Cu alloys, and their effect on electromigration lifetimes in interconnects with bamboo grain structures are not well understood, To isolate and study the mechanisms and kinetics of Cu diffusionand electromigration in interconnects for which grain boundary transport is not dominant, we have developed a test structure consisting of parallel Al single crystal lines, with every alternate line terminating in contact pads. Cu is locally added to the same regions in all the lines, and the effect of temperature and electric field can be simultaneously characterized by analyzing the Cu concentration profile measured using electron-probe microanalysis. Comparison of the calculated values of diffusivities with the diffusivity of Cu through the Al lattice, and through dislocation cores in Al, suggests that the path of diffusion of Cu in Al single crystals is along the Al/AlO_x interface.