Microstructure and electromigration in copper damascene lines

Grain sizes and crystallographic orientations of Cu were analyzed versus line width in damascene Cu interconnects. Pure bamboo lines were not obtained because grain size decreased as line width was reduced. Comparison of electromigration results for wide line CVD Cu (3 /spl mu/m) polycrystalline structures and narrow line (0.5 /spl mu/m) quasi-bamboo structures provided almost the same activation energy E/sub a//spl sim/0.65 eV, even though the [200] texture has rotated in the film plane for the narrow damascene lines. These results are in agreement with copper diffusion involving a slow self surface diffusion or located at the interface between Cu and SiO/sub 2/. PVD Cu samples showed a better activation energy value E/sub a/=1.02 eV.