The Extreme Extendibility of Cu and Post-Cu Dual Damascene BEOL Interconnect Technology

After revisiting the previous review of Cu dual damascene BEOL original definitions and continuous, sustaining innovations to the present, we combine several new breakthroughs: one novel material; one novel integration enhancement, and one novel unit process. With these, we enable renewed Cu barrier/liner scaling, renewed Page 77 of 109 damascene aspect ratio increase, and continued incremental cap scaling, all with fundamentally increased TDDB and sustained EM reliability. We can therefore target the lowest R and RC vs. wiring pitch to our knowledge, and leverage that to a significant displacement or elimination of any crossover points with alternate metals and integration schemes, even at very high aspect ratios. Finally, we add process breakthroughs that enable the first post-Cu metal damascene demonstration using rhodium (Rh), i.e. the lowest resistivity barrier-less metal nanowire option. We add certain information to support that despite the high Rh material cost, the actual manufacturing cost of ownership would be quite reasonable, due to small usage per wafer, highefficiency recovery from waste effluents, and no massive Rh expenditures such as PVD targets.