Reinforcement in electromigration reliability of Cu interconnects by alloying of extremely dilute MnO

Nonconformal high-aspect-ratio trenches/vias filling has limited the use of conventional sputtered Ta/TaN liner/barrier for Cu metallization on nanoscaled technology nodes. The self-forming alloyed metallization could offer an alternative barrier-layer/capping-layer thinning scheme for the downsizing Cu interconnects. This study reports an entire-wet process involving trench-filling of electroless plating Cu interconnects alloyed with and without an extremely dilute MnO content of 0.10%. The electromigration (EM) reliability and thermal stability of the Cu(MnO) metallization were evaluated for interconnect applications in integrated circuits. Incorporating the diluted MnO can significantly enhance the EM reliability by a factor of nine by shifting the failure mechanism towards void growth. The failure mode is thoroughly evaluated through analysis of the activation energies and current-density scale factors obtained from Black's equation. The proposed scheme has promised the application for the nanoscaled technology nodes. The reinforcement in EM reliability by self-forming Cu(MnO) will be elucidated.