We use oxide chemical mechanical planarization (CMP) as a convenient test vehicle for comparing the material removal rate and defectivity induced by different silica abrasives. The effect of particle shape is investigated by comparing fumed and colloidal silica. In particular, the effect of a polymer core on the behavior of a composite abrasive is explored. Overall, fewer and shallower scratches are detected for the composites with a colloidal silica shell as compared with colloidal silica, as well as composites with a fumed silica shell. It is difficult to control the shape and dimension of the fumed silica and fumed silica-based composite agglomerates. Both the length and depth of microscratches increase with particle size and irregularity. Under the same pH conditions, fumed silica and fumed silica-coated abrasives lead to a comparable scratch depth. Fumed silica exhibits agglomerates of greater hardness but higher overall particle stability with respect to its composites, which show lower hardness and lower overall particle stability. (c) 2008 The Electrochemical Society.