Physics / mechanism
Ru, W, and Co are candidate metals replacing Cu/barrier-stack metallisation at advanced nodes (≤7 nm, trending to 2 nm and below). The driver is resistivity scaling: Cu’s effective resistivity rises sharply below ~10 nm linewidth due to surface and grain-boundary scattering (bulk ρ Cu ≈ 1.7 µΩ·cm; at 5 nm half-pitch, effective ρ can exceed 10 µΩ·cm). Ru (bulk ρ ≈ 7.6 µΩ·cm) and Co (ρ ≈ 6.2 µΩ·cm) tolerate dimensional scaling better because they permit thinner or eliminated barrier/liner layers, recovering net resistance. W dominates local interconnect and contacts (high electromigration resistance, CVD-compatible). Key parameters: mean free path, liner thickness, electromigration activation energy. TSMC/Intel/Samsung have deployed Co local interconnects at 10–7 nm; Ru is in active integration for M0/M1 at sub-3 nm.
Competitive landscape
Cu dominates semi-global and global interconnects and will persist where line dimensions stay above ~15 nm. Mo has emerged as a competing refractory metal (bulk ρ ≈ 5.3 µΩ·cm, strong electromigration performance, IBM/TSMC interest). Graphene and CNT interconnects are research-stage with no near-term HVM path.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.