In this study, different amounts of standard fumed silica and fumed silica contaminated by coarse particles was added as powder to a standard copper CMP slurry to investigate their effects on large particle count, mean particle size, slurry viscosity, frictional force during wafer polishing, and copper removal rate. Standard silica powder consisted of the same particles used in the standard slurry while contaminated silica powder consisted of the same particles used in the standard slurry and additional large size particles. Large particle count analysis indicated that slurry dispersion itself generated large size particles in the slurries. The addition of 0.3% and 1% contaminated silica to the standard slurry caused significant increases in large particle count, and the mean particle size increased with the amount of contaminated silica added to the standard slurry. The slurry viscosity generally increased with the amount of standard and contaminated silica added to the standard slurry under the shear rate of 100 s-1. The standard slurry and slurries added with 0.3% and 1% contaminated silica were used to polish 200-mm blanket copper wafers on the APD-500 polisher that has the unique ability to measure frictional force in real time during polishing. The coefficient of friction increased with the amount of contaminated silica added to the standard slurry. In general, the removal rates for the slurry added with 1% contaminated silica were higher than the standard slurry and slurry added with 0.3% contaminated silica.