Chemical mechanical polishing of thermal oxide films using silica particles coated with ceria

Thermal oxide covered silicon wafers were polished with slurries containing either nano-sized ceria (CeO2) or newly prepared uniform colloidal silica particles coated with ceria. The polish rate of the latter was significantly higher than that of pure ceria. The experiments were carried out using different concentrations of the abrasives at pH 4 and 10. Little effect on the polishing rates was noted when the conditions of the slurries were varied, which was explained by the compensation of two opposite polishing mechanisms.