This paper reports comparative studies of TaN and SiCN as barrier for Cu-porous dielectric (k < 2.3) integration using various techniques. It was found that SiCN dielectric is much better than TaN for the Cu-Ultra low k (ULK) integration. Upon thermal annealing at 400 degrees C for different periods of time, TEM images revealed strong intermixing at the two interfaces of Cu/TaN/ULK structures but no sign of diffusion in Cu/SiCN/ ULK structure even after being annealed at 400 degrees C for 150 min. The strong intermixing in the Cu/TaN/ULK structure results from grain boundaries in the TaN film and porosity of the dielectric, while the excellent reliability of the Cu/SiCN/ULK dielectric is ascribed to the amorphous structure and high thermal stability of the SiCN film. (c) 2006 Published by Elsevier B.V.