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

Abstract

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-mSiO2) particles with parallel channels were prepared via a modified tyltrimethylammonium bromide-assisted template method. And the ceria nanoparticles attached to H-mSiO2 was achieved by a solution synthesis technique. The core–shell structure of the as-prepared H-mSiO2–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-mSiO2–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 (sSiO2)–CeO2 composite particles with non-porous sSiO2 cores were also tested under the same CMP conditions. Oxide–CMP results revealed that the H-mSiO2–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 (sSiO2)–CeO2 particles, the non-rigid H-mSiO2–CeO2 composites revealed a reduced surface roughness (0.17 nm vs. 0.33 nm, root-mean-square values), a low topographical variation (± 0.4 nm vs. ± 0.8 nm), and an improved removal rate (203 nm/min vs. 144 nm/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.