The influence of barrier types on the microstructure and electromigration characteristics of electroplated copper

A significant effect of barrier type is found on the microstructure and electromigration resistance of electroplated Cu. Stronger (111) texture of Cu seed layer develops on more adhesive and better wetting interface of Cu/barrier, and in turn enhances the texture of electroplated Cu. The different interface interaction with different bond strength produces different degree of wetting of the Cu films on the barrier surface after thermal annealing, such that TaSiN > Ta > TaN > CVD-TaSiN > SiN, which corresponds to the results of film texture and thermal cycling stress measurements. Despite the similar grain size distribution, the electromigration lifetime of electroplated Cu differs in the same manner with the barrier type used. The difference is more pronounced as the linewidth decreases to deep sub-micron dimensions, suggesting that interface mass transport becomes more dominant in the mechanism for electromigration for narrower lines.