Material Removal Mechanism of Copper CMP from a Chemical-Mechanical Synergy Perspective

The material removal in chemical-mechanical planarization/polishing (CMP) of copper involves both chemical and mechanical effects. The roles of chemical corrosion, abrasive wear, and their synergistic effects on the material removal mechanism were studied by electrochemical analysis and nano-scratching method using atom force microscopy, respectively. Combining with the results of CMP experiments, dominant factors (chemistry and mechanics) in slurries within the range of pH 3.0-10.0 were assessed. Consequently, a removal mechanism map of copper CMP depending on pH values was constructed. In the alkaline slurry, the wear-corrosion effect predominated in the material removal at pH 8.0 and 9.0; while the copper removal mechanism changed to corrosion-wear action in the acidic slurry from pH 4.0 to 6.0, and good surface quality was also obtained. The results and the strategies provide thorough understanding of the material removal mechanism and further optimization of the CMP process.