Atomic force microscopy, lateral force microscopy, and transmission electron microscopy investigations and adhesion force measurements for elucidation of tungsten removal mechanisms

We investigated various interactions between alumina and tungsten films that occur during chemical mechanical polishing (CMP). Atomic force microscopy surface topography measurements of post-CMP tungsten indicate that the roughness of the tungsten is independent of polish pressure and rotation rate. Pure mechanical abrasion is therefore an unlikely mechanism of material removal during CMP. Transmission electron microscopy images corroborate these results. The adhesion force between alumina and tungsten was measured in solution. The adhesive force increased with KIO₃ concentration. Friction forces were measured in solution using lateral force microscopy. The friction force in buffered solutions was independent of KIO₃ concentration. These results indicate that interactions other than purely mechanical interactions exist during CMP.