Characterization of sapphire chemical mechanical polishing performances using silica with different sizes and their removal mechanisms

Sapphire chemical mechanical polishing (CMP) performances using silica particles with different sizes have been studied. We find that MRR by 10 nm silica slurry could appear rather high, approaching to that by 100 nm silica slurry. The removal mechanisms of sapphire using different sizes silica have been investigated via X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. XPS results reveals that the surface polished by 10 nm silica could also present aluminum silicate resulting from solid-solid state reaction with silica and sapphire, the same with that by 100 nm silica. The effects of silica nanoparticle size on the formation and removal of soft product layer on the atomic step smooth surface are studied through AFM analysis. 10 nm silica particles could exhibits the smaller residual product on the surface, and the reaction model of sapphire with silica particles of different sizes is proposed. Meanwhile, 10 nm silica particles could realize smoother surface of 0.06 nm and straighter atomic step edge.