Time-dependent-dielectric breakdown used to assess copper contamination impact on inter-level dielectric reliability

Time-Dependent-Dielectric-Breakdown tests have been conducted on differently copper-contaminated SiO/sub 2/ Metal-Oxide-Silicon (MOS) capacitors. It has been demonstrated that TDDB tests are particularly sensitive in addressing the properties of Cu-contaminated dielectric and hence are suitable for the characterization of diffusion barrier layers for Cu based interconnects. The analysis of the lifetime dependence of the interlevel dielectric (ILD) with respect to Cu contamination clearly shows that not only the metal must be well encapsulated by diffusion barrier layers, but that the amount of Cu left behind the barrier by technological process steps should be minimized. Without effective cleaning steps any effort made in providing strong diffusion barrier could vanish.