Effect of microstructure on electromigration kinetics in Cu lines

Strong correlation of the modes of electromigration damage and microstructure is reported for Cu films. It is found that changes in the microstructure lead to qualitative variation in electromigration damage kinetics - from the traditional open circuit due to void growth across the line, to damage growing along the line, and not leading to failure. Some of our findings are consistent with the theoretical model based on interplay between surface and grain boundary diffusion. The activation energy E_a = 0.95 eV of electromigration mass transport was measured using a modified electrical resistance method.