Electromigration-Induced Void Growth Kinetics in SiN_x-Passivated Single-Damascene Cu Lines

Basic electromigration characteristics of SiN_x-passivated single-damascene Cu lines have been investigated. The results indicate that an effective incubation time for void growth contributes to resistance change. This effective incubation time depended inversely on the square of current density. The activation energy of the effective incubation time was 1.14 ±0.27 eV. The observed critical product of electromigration was approximately 5900 A/cm. The activation energy of diffusion was 0.89 ±0.07 eV. These results indicate that the Cu/SiN_x interface diffusion activation energy and the effective charge number are similar to those of unpassivated Cu surface diffusion. However, the SiN_x-passivated interface of the sample showed significantly reduced drift velocity compared to those of the unpassivated sample.