A NEW INVESTIGATION OF COPPER'S ROLE IN ENHANCING Al-Cu INTERCONNECT ELECTROMIGRATION RESISTANCE FROM AN ATOMISTIC VIEW

摘要

An explanation of why Cu prolongs the electromigration lifetime of Al-Cu interconnects in comparison to Al is provided based on atomistic calculations. Copper preferentially segregates to the grain-boundary (GB) interstitial sites. The overall GB diffusivity is reduced with Cu segregation at GB sites. Calculation results predict that in Al(Cu) lines, Cu will diffuse first, with Al diffusion essentially sup- pressed because of a higher diffusion activation energy. The activation energy for Cu incubation diffusion is calculated to be 0.95 eV. The predictions are in excellent agreement with experiments.