The grain growth and crystallographic orientation of the ULSI Cu interconnects within the Dmascene architecture were observed.Microstructures of the Cu interconnect depending on linewidths and anneal temperatures and impacts on the electromigration (EM) were analyzed.The grain size of Cu lines shrinked as the linewidth was reduced.The small grains and the weaker (111) texture in Cu lines were formed compared with that in Cu blanket films.The EM resistance of the Cu metallization could be improved via the grain growth and the (111) texture developed during anneal at 300℃ for 30min.The results indicate that the Cu diffusion involves interface diffusion and boundary diffusion, while the diffusion along interface plays a dominant role in EM failure for Cu lines with the narrow linewidth.