The Effects of Shell Morphologies on the Polishing Performance of PS/SiO₂ Composite Abrasives

The PS/SiO₂ composite abrasives with different shell morphologies were prepared using polystyrene (PS) as a core and silica as a shell. The shell morphologies were controlled by adjusting the hydrolysis condition of tetraethylorthosilicate. The obtained samples were analyzed by scanning electron microscopy, transmission electron microscopy and fourier transform infrared spectrum. The chemical mechanical polishing performances of the PS/SiO₂ composite abrasives on silicon dioxide layer were investigated by atomic force microscopy. Results indicate that the shell of the composites was composed of SiO₂ nanoparticles (discontinuous shell) under alkaline hydrolysis condition and amorphous form (continuous shell) under acidic condition, respectively. Compared with the single and the mixed abrasives, the improved polishing behavior was resulted from the synergistic effect of the PS core and the silica shell. The elastic PS core was benefit to reduce surface roughness and mechanical damage. Meanwhile, the coated silica shell was useful to increase material removal rate. The PS/SiO₂composite abrasives with continuous shell displayed a better structure stability and a lower root-mean-square roughness value (RMS=0.136 nm) than those of the abrasives with discontinuous shell. However, there was an unobvious effect of shell morphologies on material removal rate.