Reliability study on cobalt and ruthenium as alternative metals for advanced interconnects

Cobalt and ruthenium are being proposed to replace copper in BEOL interconnects. Using intrinsic TDDB studies, we show that Co needs a barrier to prevent it from drifting into SiO ₂ , where for Ru no drift into any of the three studied dielectrics is observed. Although our intrinsic EM studies on single damascene lines filled with Co suffered from bondpad delamination and a non-optimized CMP, we could still conclude that the EM-performance is better compared to Cu filled lines, where a much better performance of Ru filled lines is demonstrated (>25×). Via failures on Ru schemes show a > 5× higher lifetime compared to Cu schemes.