Defect reduction in Cu chemical-mechanical polishing

The chemical-mechanical polishing (CMP) of Cu is a critical step in the manufacture of ultra-large-scale integrated (ULSI) semiconductor devices. During this process, undesirable scratches are formed on the surface being polished. Recent research suggests that the “killer” scratches found on the Cu wafers are due to the soft pad asperities and not necessarily by the hard abrasives in the slurry. Figure 1 shows examples of scratches on a Cu coating due to pad asperities. This paper presents the theory and experimental validation of scratching by soft pad asperities in Cu CMP. Based on the models and experimental results, practical solutions for mitigating scratching by pad asperities in Cu CMP are suggested.