Synthesis of Sm-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing performances on sapphire substrates

SiO 2 abrasive is one of the most effective abrasives used in chemical mechanical polishing (CMP) due to its uniform size, good dispersibility and good chemical reactivity. In this paper, a series of novel Sm-doped colloidal SiO 2 composite abrasives were synthesized by seed-induced growth method. The composite abrasives were characterized by using scanning electron microscopy, time-of-flight secondary ion mass spectrometry analysis (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). The structure of the composite abrasive is core-shell type with silica as a core and a coated growth layer (including SiO 2 , Sm 2 Si 2 O 7 and Sm(OH) 3 as shell via chemical bonds and hydrogen bonds . The CMP properties of the composite abrasives on sapphire substrates were further studied and the results show that the Sm-doped colloidal SiO 2 composite abrasives give lower polished surface roughness (Ra) and higher MRR than that of the pure colloidal SiO 2 abrasive under the same polishing conditions. By TOF-SIMS and XPS analyses on the polished slurries, the acting mechanisms of Sm-doped colloidal SiO 2 composite abrasives on sapphire were explored also.