Preparation of Allotropic Composite Abrasives SSiO2/MSiO2 with Core/Shell Structure

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Core/shell structured composite abrasives with solid-silica (SSiO2) cores and mesoporoussilica (MSiO2) shells were synthesized using tetraethylorthosilicate as silica source, ammonia solution as catalyst and cetyltrimethylammonium bromide as sacrificial template. The prepared abrasives were characterized by small angle XRD, FESEM, HRTEM, FTIR, TGA, nitrogen adsorptiondesorption isotherm and the corresponding pore size distribution. The results show that the MSiO2 shells (70-80 nm in thickness) with radial pores are evenly coated on the external surfaces of the SSiO2 cores (210-230 nm).The BET surface area of the prepared abrasives is 558.2 m/g. The mesochannels (2-3 nm in pore size) in the (MSiO2) shell are perpendicular to the surface of the SSiO2 core. The topography, roughness and profile curve of silicon wafers with a SiO2 surface film of ca 1200 nm were investigated by AFM before and after chemical-mechanical polishing in the presence of abrasives. By comparison with the conventional abrasives SSiO2, the composite abrasives are in favor of decreasing the surface roughness and increasing the material removal rate of the polished wafers. The MSiO2 shells of the prepared composite abrasives may be contribute to optimize the real interfacial contact between abrasives and wafer surface through certain mechanical and/or chemical effects.