Improvement of Ru-Co Liner for void-free Cu interconnect in extremely small pitch

While development in Copper (Cu) processes can contribute to Cu fill enhancement, optimizing the properties of the Liner can also be a significant role in Cu reflow characteristics. Therefore, this study aimed to improve Cu fill through the enhancement of the Ruthenium (Ru) and cobalt (Co) liner, particularly on 3nm-scale Cu interconnects. The surface morphology of the RuCo liner, which appears as the Co thickness increases, was improved through Atomic Layer Deposition (ALD)-like deposition of Co layer and plasma treatment between liner layers. This work provides the way to improve RuCo liner through process enhancements, resulting in a 80% reduction in void formation and enhancing Cu reflow characteristics. In addition, it was confirmed that the improved RuCo liner generates less voids depending on between chemical mechanical planarization (CMP) step to BM seed step.