Influence of the sidewall diffusion barrier on the transport properties of advanced Cu/low-k interconnects

We present the impact of the sidewall diffusion barrier on the dielectric properties of advanced Cu/porous ULK interconnects. From the temperature dependence of the leakage currents, the conduction mechanisms can be compared. The high field transport is consistent with a Poole-Frenkel model, and the low field with a variable range hopping model, from which a defect density near Fermi level is obtained. The complex surface of the etched porous ULK is better suited to a conformal and continuous barrier, such as CVD TiN, which highlight the challenge to get very thin but defect-free metal barrier for future generations.