On Direct Measurement of Forces Between CMP Polishing Pads and Abrasive Nanoparticles

The forces of interaction between ceria slurry particles, and polyurethane CMP polishing pads were measured by atomic force microscopy. To measure the forces between the ceria particles and the pads with the AFM, we attached the ceria particles to the AFM tip with epoxy. Attachment of large balls to the AFM tip has been reported before, as well as functionalizing the tip surface with various molecules. Here we report the first successful attachment of nanosize (∼50–100nm) particles to the AFM tip and the direct measurements of forces using such tips. Specifically, we report study of adhesion and long-range force between nanosize ceria particles and three different polyurethane polishing pads. The forces were measured in aqueous solutions of different pH’s ranging from 4 to 9.