TDDB improvement in Cu metallization under bias stress

Time-dependent dielectric breakdown (TDDB) between Cu interconnects is investigated. TDDB lifetime strongly depends on the surface condition of the Cu interconnect and surrounding pTEOS. A NH₃-plamsa treatment prior to cap-pSiN deposition on Cu interconnect improved the dielectric breakdown lifetime (τ_BD ) over cap-pSiN deposition only. The plasma treatment also has the beneficial effect of suppressing wiring resistance increase during pSiN deposition. These results suggest that CuO reduction to Cu, and CuN formation at the Cu interconnect surface prevents Cu silicidation during pSiN deposition. Furthermore, SiN formation and bond termination by hydrogen radicals at the pTEOS surface diminish surface defects, such as dangling bonds. TDDB lifetime also strongly depends on the Cu CMP process, in which mechanical damage of the SiO₂ surface during CMP process degrades TDDB. Adoption of a mechanical damage free slurry or a post-CMP HF treatment to remove the damaged layer from the surface improves TDDB