Shape classification of fumed silica abrasive and its effects on chemical mechanical polishing

Abstract The performance of chemical mechanical polishing (CMP) was determined by the morphological characteristics of the abrasive particle. In this study, the shape of the aggregate of fumed silica was confirmed by a method of characterizing the morphology of the particles using transmission electron microscopy (TEM). Each aggregate was classified into four types—linear, branched, ellipsoidal, and spheroidal—and the shape distribution of a fumed-silica slurry was investigated with different specific surface areas. The CMP performance of fumed silica slurries at 90 m2/g with numerous linear-shaped aggregates and 400 m2/g with the highest portion of spheroidal aggregates were compared to that of colloidal silica slurry. A model for the effects of bumpy abrasives on CMP explained the reason for this result by using penetration depth and MRR with various numbers of contact bumps. Furthermore, a mixture of spherical and non-spherical abrasives in a ratio of 4:1 exhibited an improved CMP performance.