Influence of damascene trenches on grain growth and electromigration behavior of ULSI Cu lines

In ULSI damascene-fabricated Cu lines, Cu grain structure is affected by the constraint of the trench sidewalls and then shows smaller grain size than that of Cu blanket films with similar processing conditions. The grain decreased from 80∼100 nm to 30∼40 nm, as the linewidth reduced from 4 μm to 0.5 μm. The electromigration (EM) resistance, the activation energy and the EM induced voiding distribution obtained in the wide and the narrow lines were studied as a function of linewidth and various annealing conditions. The interface diffusion, especially the sidewalls of the trenches has become an increasingly important issue with the line miniaturization and may be in turn responsible for EM failures in deep submicron Cu lines.