Core-shell structured polystyrene coated silica composite abrasives with homogeneous shells: The effects of polishing pressure and particle size on oxide-CMP

To improve the structural stability of the core-shell organic-inorganic composite abrasives during chemical mechanical polishing (CMP) processes, the polystyrene (PS) coated silica composites with homogeneous shells (amorphous silica networks, 15-20 nm in thickness) were synthesized via the sol-gel process of tetraethoxysilane at acidic aqueous condition in the presence of PS colloids (210-540 nm). Transmission electron microscopy and scanning electron microscopy were applied to characterize the as-synthesized samples. The effects of particle sizes and polishing pressures on oxide CMP performance were explored by atomic force microscopy. The results indicated that the obtained composite abrasives exhibited excellent polishing performance and structural stability during polishing processes. With the increase of the polishing pressures (13.8-41.4 kPa), the layer removal rate (RR) increased correspondingly, while the root-mean-square (RMS) roughness of polished substrates decreased firstly and then increased. Moreover, the RR and RMS for the composite abrasives increased with the increase of PS core sizes. At a given polishing pressure of 27.6 kPa, the highest RR (82.5 ± 7 nm/min) was obtained for the PS coated silica composites with largest cores (ca. 540 nm), while the lowest RMS roughness (0.189 ± 0.02 nm) was observed for the composites with smallest cores (ca. 210 nm). Furthermore, the polishing results in our CMP experiments were rationalized according to the indentation-based material removal mechanism (Chen et al. Appl Surf Sci 2012; 258:8469-74).