Self-forming Al oxide barrier for nanoscale Cu interconnects created by hybrid atomic layer deposition of Cu-Al alloy

The authors synthesized a Cu-Al alloy by employing alternating atomic layer deposition (ALD) surface reactions using Cu and Al precursors, respectively. By alternating between these two ALD surface chemistries, the authors fabricated ALD Cu-Al alloy. Cu was deposited using bis(1-dimethylamino-2-methyl-2-butoxy) copper as a precursor and H-2 plasma, while Al was deposited using trimethylaluminum as the precursor and H-2 plasma. The Al atomic percent in the Cu-Al alloy films varied from 0 to 15.6 at. %. Transmission electron microscopy revealed that a uniform Al-based interlayer self-formed at the interface after annealing. To evaluate the barrier properties of the Al-based interlayer and adhesion between the Cu-Al alloy film and SiO2 dielectric, thermal stability and peel-off adhesion tests were performed, respectively. The Al-based interlayer showed similar thermal stability and adhesion to the reference Mn-based interlayer. Our results indicate that Cu-Al alloys formed by alternating ALD are suitable seed layer materials for Cu interconnects. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.