Low-k material is susceptible to the plasma damage in fabrication of damascene structure and hence the metal barrier performance will be affected. It is very important to characterize the effect of plasma process oil metal barrier performance and fundamentally understand interfacial interaction between low-k material and metal barrier layer for implementing low-k, especially ultra low-k in Cu interconnect on 65 nm node and beyond. In this paper, we present our studies on the effects of two key plasma processes, H-2/He reactive plasma clean treatment (RPC) and H-2/N-2 etch, on the barrier layer performance. We also present a Solution to enhance the Ta barrier layer performance. The new implementation successfully prevented Cu from diffusing into polymer low-k after annealing at 200 degrees C for 1000 h. The methodology is proven to be effective for characterizing and improving pore-sealing and barrier performance for Cu/porous ultra low-k interconnect. (c) 2005 Elsevier B.V All rights reserved.