Electromigration Cu mass flow in Cu interconnections

Abstract Electromigration mass flow in Cu damascene lines which were connected to W blocking barrier contacts and were capped with either a CoWP, Ta, Ta/TaN, Pd, SiN x , or SiC x N y H z layer was investigated. Cu lines, fabricated with body centered cubic α- or tetragonal β-Ta liners, were also investigated. A thin electroless CoWP, physical vapor deposition (PVD) Ta, PVD Pd or PVD Ta/TaN cap on top of the Cu line significantly reduced the interface diffusivity and remarkably improved the electromigration lifetime when compared with lines capped with SiN x or SiC x N y H z . Activation energies for electromigration in bamboo-like Cu lines were found to be 2 eV with a CoWP cap, 1.4 eV with a PVD Pd, Ta or Ta/TaN cap, and 0.9–1 eV with a SiC x N y H z or SiN x cap. The Ta phase was found to have an insignificant effect on the Cu mass flow rate, as did the Cu texture.