Pathfinding of Ru-Liner/Cu-Reflow Interconnect Reliability Solution

Ruthenium (Ru) and Copper (Cu) interface promotes void-free Cu gap-fill through a Cu reflow approach. However, reliability issues such as Electromigration (EM) and time-dependent dielectric breakdown (TDDB) have delayed industry adoption of Ru liner. Here, we report our findings on two EM improvement approaches and compare them to industry standard Cobalt (Co)-linerlselective-Co-cap-based Cu interconnect. Similar to Co liner, addition of a post chemical mechanical planarization (CMP) selective Co cap did improve EM performance with Ru liner. However, EM equivalence to Co-liner/Co-cap-based Cu interconnect requires the development of a new doped Ru liner in combination with the selective Co cap. We will also discuss the impact of the EM improvement approaches on key parameters of interest such as via resistance, TDDB and provide a technology scorecard.