Ceria coated hexagonal mesoporous silica core-shell composite particle abrasives for improved chemical-mechanical planarization performance

The structure design of abrasive particles provides an available approach for improving both surface roughness and polishing efficiency in chemical-mechanical planarization/polishing (CMP) applications. In this work, the hexagonal mesoporous silica (H-mSiO(2)) particles with parallel channels were prepared via a modified tyltrimethylammonium bromide-assisted template method. And the ceria nanoparticles attached to H-mSiO(2) was achieved by a solution synthesis technique. The core-shell structure of the as-prepared H-mSiO(2)-CeO2 composites was characterized in terms of X-ray diffraction, field emission scanning electron microscope, high-resolution transmission electron microscope, nitrogen adsorption/desorption measurement, and STEM-EDX mapping techniques. The oxide-CMP performance of the H-mSiO(2)-CeO2 composite particles as abrasives was evaluated in terms of surface finish and material removal rate. For comparison, the commercial ceria abrasives and solid silica (sSiO(2))-CeO2 composite particles with non-porous sSiO(2) cores were also tested under the same CMP conditions. Oxide-CMP results revealed that the H-mSiO(2)-CeO2 composite abrasives contributed to the finish reduction, efficiency improvement, and scratch elimination with respect to conventional ceria abrasives. By comparing with rigid solid silica (sSiO(2))-CeO2 particles, the non-rigid H-mSiO(2)-CeO2 composites revealed a reduced surface roughness (0.17nm vs. 0.33nm, root-mean-square values), a low topographical variation (+/- 0.4nm vs.+/- 0.8nm), and an improved removal rate (203nm/min vs. 144nm/min). The improved CMP performance might be attributed to the enhanced overall elastic response and reduced particle density, resulting from their hexagonal meso-silica cores with abundant parallel channels. Moreover, the increased Ce3+ concentration also contributed the improvement of polishing efficiency. This work describes an effort to explore the relationship between the meso-silica structure and finishing performance of the ceria-based core-shell abrasives for optimizing oxide-CMP characteristics.