Effects of mixed ultrafine colloidal silica particles on chemical mechanical polishing of sapphire

摘要

The effects of ultrafine colloidal silica particles adsorbed on the surfaces of large silica particles in slurries used for the chemical mechanical polishing of sapphire were studied. Sapphire wafers were polished using hybrid silica particles that were composed of a mixture of ultrafine (4 nm) colloidal silica particles and large (20, 55, and 105 nm) silica particles. Dynamic light scattering results showed that the hybrid particles became larger after mixing. Transmission electron microscopy images revealed that the ultrafine particles adhered to the surfaces of the large particles and that the surface shape of the hybrid particles were changed by the mixing process. Atomic force microscopy and polishing results showed that the surface roughnesses and material removal rates of sapphire substrates were improved by using the hybrid particles. The coefficient of friction between the surface of the sapphire substrate and the hybrid particles was higher than that obtained using single-sized particles. These results confirm that the hybrid silica particles enhanced the performance of sapphire polishing. (C) 2018 The Japan Society of Applied Physics