The effect of frictional and adhesion forces attributed to slurry particles on the surface quality of polished copper

Abstract

The effect of frictional and adhesion forces attributed to slurry particles on the quality of copper surfaces was experimentally investigated during copper chemical mechanical planarization process. The highest frictional force of 9 Kgf and adhesion force of 5.83 nN were observed in a deionized water-based alumina slurry. On the other hand, the smallest frictional force of 4 Kgf and adhesion force of 0.38 nN were measured in an alumina slurry containing citric acid. However, frictional (6 Kgf) and adhesion (1 nN) forces of silica particles in the slurry were not significantly changed regardless of the addition of citric acid. These differences were explained by the strong adsorption of citric ions on alumina but not on silica, which was verified by the charge reversal of alumina in zeta potential measurements. Higher particle adhesion forces resulted in higher friction. A higher magnitude of particle contamination and scratches was observed on polished copper surface in slurry condition with higher adhesion and friction forces. (c) 2006 The Electrochemical Society.