Dielectric/metal bilayer diffusion barriers with different silicon carbide films (SiCO, SiCN, and SiC) were fabricated for use in Cu/porous low-k damascene interconnects. The bilayer sidewall barriers show significant performance improvements in terms of breakdown strength and leakage current characteristics compared with conventional physical vapor deposited metal barriers. SiC/Ta and SiCN/Ta bilayer barriers are good candidates for use in Cu/porous low-k damascene interconnects due to their superior electrical performance even after long-time thermal/electrical stress. However, the electrical characteristics of SiCO/Ta bilayer barrier showed a significant degradation after long-time thermal/electrical stress. This divergence may be attributed to the influence of the underlying dielectric layer on Ta texture in the bilayer barrier structure. The preferred a-phase Ta barrier was formed when deposited on SiCN or SiC, but the beta-phase Ta was formed when deposited on SiCO or directly on porous low-k dielectric. The unstable oxygen content in porous low-k dielectric as well as the SiCO layer are likely to be responsible for the electrical degradation of the interconnects. (c) 2005 American Vacuum Society.