Composite particles with dendritic mesoporous-silica cores and nano-sized CeO2 shells and their application to abrasives in chemical mechanical polishing

The structure and mechanical/chemical performance of particle abrasives in polishing slurries play an important role in chemical mechanical polishing (CMP) processes. In the present paper, the CeO2-based novel abrasive particles containing dendritic mesoporous silica (D-mSiO(2)) cores and nano-sized CeO2 shells present potential applications in high-efficiency and defect-free CMP, resulting from their special mechanical and/or chemical characteristics. The D-mSiO(2) cores of composites were prepared via a modified biphase stratification approach, and the nano-sized CeO2 particles were coated via an In-situ chemical precipitation technique. The composition and structure of as-synthesized samples were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and nitrogen sorption-desorption measurements. The effect of the core category for the CeO2-based composite particles on oxide-CMP performance was evaluated in termers of material removal rate (MRR) and root-mean-square (RMS) roughness (determined by atomic force microscopy). Experimental results indicated that the as-obtained D-mSiO(2)/CeO2 abrasives exhibited a comparable RMS roughness (0.18 +/- 0.02 nm) with respect to the polystyrene/CeO2 abrasives (0.15 +/- 0.02 nm) with polymer cores. However, the MRR of the DmSiO(2)/CeO2 abrasives (85 nm/min) was three times larger than that of the PS/CeO2 abrasives (26 nm/min). The enhanced polishing efficiency may be attributed to the differences of the mechanical behavior and surface atom structure of the nano-sized CeO2 particles of the composites after treatment by high-temperature calcination. The improved oxide-CMP behavior of D-mSiO(2) /CeO(2)composite particles may result from the spring-like effect coming from the elastic component of the cores, and the enhanced surface hardness and tribo-chemical activity of CeO2 particles in the shells.