Improvement of TDDB reliability in Cu damascene interconnect by using united hard-mask and Cap (UHC) structure

Reliably of Cu damascene interconnects (DDIs) using United Hard-mask and Cap (UHC) structure, which involves the same material for both Hard-mask and Cap layers is investigated. Line-to-line insulating reliabilities such as a leakage current, TZDB and TDDB are greatly improved by using the UHC structure even without any barrier metal layers, indicating that the interline leakage path is not in a bulk of the low-k dielectric but the interface between the Cap and the CMP-damaged Hard-mask. This new Cu dual damascene interconnect with UHC provides the interconnect reliability of future ULSIs with ultra-thin barrier metals toward a barrier-metal-free structure.