Core/shell composites with polystyrene cores and meso-silica shells as abrasives for improved chemical mechanical polishing behavior

摘要

The core/shell-structured organic/inorganic composite abrasive has an important potential application in damage-free chemical mechanical polishing (CMP) due to its non-rigid mechanical property. In this work, the PS/MSiO2 composites, containing polystyrene (PS) sphere (211 +/- 4 nm) cores and mesoporous silica shells (31 +/- 3 nm in thickness) were synthesized through directed surface sol-gel process of tetraethylorthosilicate on the polymer cores in the presence of the cetyltrimethylammonium bromide surfactant. For comparison, the conventional core/shell PS/NSiO2 composites with non-porous silica shells were also prepared via a modified Stober procedure that involved the hydrolysis of TEOS under acidic condition. The physical properties of the samples were examined by small-angle X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, field emission scanning electron microscopy, and nitrogen adsorption-desorption. As novel abrasives, the core/shell-structured PS/MSiO2 composites were introduced into the CMP process for silicon oxide films. The oxide-CMP performance among conventional solid silica particles, PS/NSiO2 composites, and novel PS/MSiO2 composites was explored by atomic force microscopy. Polishing results indicated that the substrate revealed a comparable root-mean-square surface roughness (0.25 +/- 0.03 and 0.22 +/- 0.02 nm, respectively) after CMP with PS/NSiO2 and PS/MSiO2 abrasives under the same polishing conditions. However, the material removal rate of the PS/MSiO2 composites (123 +/- 15 nm/min) was about three times larger than that of the PS/NSiO2 composites (47 +/- 13 nm/min). The reduced surface roughness and improved removal rate might be due to the optimization of the physical and/or chemical environments in the local contacting region between abrasives and substrates. The as-synthesized core/shell PS/MSiO2 composites with mesoporous shells are expected to exhibit an important potential application in efficient and damage-free CMP.