The dielectric reliability of Cu interconnects such as intra-level leakage current and time-dependent dielectric breakdown (TDDB) is greatly dependent on the surface condition of dielectric/barrier interface. The dominant leakage path is found to be at dielectric/barrier interface. Hence, the dielectric surface should be improved to reduce surface trap states that will degrade both leakage and TDDB performance. To achieve this, process splits were performed after metal CMP. These splits include NH3, H-2 plasma and SiH4 treatments. Results showed that NH3 and H-2 plasma treatments successfully reduced surface trap density and suppressed Cu surface drift and as a result both intra-level leakage current and TDDB performance of Cu interconnects are significantly enhanced. (C) 2004 Elsevier B.V. All rights reserved.