Preparation of Mg-Doped Colloidal Silica Abrasives and Their Chemical Mechanical Polishing Performances on Sapphire

In the present paper, Mg-doped colloidal silica abrasives were synthesized by seed-induced growth method. A detailed analysis was presented to characterize the composition and morphology of Mg-doped colloidal silica abrasives by using time-of-flight secondary ion mass spectroscopy and scanning electron microscopy. The chemical mechanical polishing (CMP) performances of the Mg-doped colloidal silica abrasives on sapphire substrates were investigated. Experiment results indicate that the material removal rate (MRR) of the Mg-doped colloidal silica abrasives is obviously higher than that of pure colloidal silica abrasive under the same testing conditions. And surfaces polished by composite colloidal abrasives exhibit lower surface roughness than that pure colloidal silica abrasive. Furthermore, the acting mechanism of the Mg-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that NaAlMg(Si4O10)(2) appears in the slurry after polishing, implying the tribochemistry reaction occurs during CMP. The chemical reaction between magnesium and Al2O3 on the surface of sapphire substrate during CMP can promote the chemical effect in CMP and lead to the increasing of MRR.