Performance characterization of cerium oxide abrasives for chemical-mechanical polishing of glass

Investigation of the nature of chemomechanical polishing (CMP) for glass requires an in-depth knowledge of the influences of abrasive physical properties and slurry chemistry. In the present work, eight cerium oxide abrasives were used to polish fused silica on a polyurethane pad. Results from pre-polished surfaces re-polished in aqueous and non-aqueous suspensions and from corrosion testing of solutions recovered from abrasive suspensions were used to discern chemical, chemomechanical, and mechanical equivalents for each abrasive. Performance indices (i.e., abrasive quality values) were generated from the equivalents and related to conventional polishing of lapped surfaces. Optimally performing abrasives were found to require a balance of equivalents (i.e., set ratio) as dictated by inherent chemical activities, heat treatments, and milling. From solution chemistry testing, particle/workpiece attraction via surface charge was found to increase the chemomechanical effect. The CMP mechanism is concluded to be a chemical reaction at the particle/workpiece interface promoted primarily by mechanical interactions such as abrasion, with both cerium oxide and rare-earth oxyfluoride constituents promoting the reaction.