EM performance improvements for Cu interconnects with Ru-based liner and Co cap in advanced nodes : (Invited)

It has been observed that void-free Cu fill, interface control for both Cu/liner (trench sidewall and bottom) and Cu/cap (trench top), and grain size engineering are critical to improve Electromigration (EM) performance for Cu interconnects in the case of using Ru liner and Co cap. Especially, Co diffusion from the cap into a Ru liner (resulting in Co depletion at the top of Cu lines) is one of the root causes of EM degradation. A novel Co-doped Ru liner has been developed, which demonstrates a significant EM performance boost by addressing the Co diffusion issue. This Co-doped Ru liner is shown to be a promising liner of choice for Cu interconnects in advanced nodes.