Composite polymer core-ceria shell abrasive particles during oxide CMP: A defectivity study

Ceria-based and fumed silica-based systems are compared for oxide chemical mechanical polishing (CMP) in terms of defectivity and removal rate (RR). Ceria-based slurries yield RR ca. threefold that of conventional silica slurries but result in enhanced defectivity. To reduce defectivity, composite structures comprising a 300 nm polymer core coated by 14 nm ceria particles have been investigated. The polymer core shows mechanical properties that are highly tunable by variation of synthesis parameters, while the major advantage of the ceria coating is an enhanced chemical action of the abrasive particles. We report the evolution of RR, root-mean-square roughness, and defects during silica CMP experiments using different abrasive types at pH 3 and 10. Interestingly, the two types of composites, achieved by either silane coupling agents or electrostatic attractive interactions between the core and the coating, exhibit different RR. This is attributed to differences in morphology and surface composition. Overall, the ceria composites result in reduced defectivity after CMP due to the springlike effect coming from the elastic component of the core, compared with conventional slurry material. (C) 2008 The Electrochemical Society.