Study on material removal mechanism of sapphire wafer with CeO2 coated diamond composite abrasives via green polishing

Toxic and polluted ingredients are normally employed in the chemical mechanical polishing of sapphire wafers, which results in widespread environmental pollution. Thus, developing a novel green polishing technology is a significant challenge to achieve ultra-smooth and efficient polishing. In this study, novel CeO2 coated diamond composite abrasives were used in the semi-fixed abrasive polishing of sapphire wafers, which were successfully synthesized by a modified precipitation approach without using explosive hazardous chemicals. During the whole polishing process, the polishing slurry only contains deionized water, without any other chemical reagents, to avoid environmental pollution. Polishing results showed that the surface roughness of sapphire polished by the composite abrasives was reduced to 6.1 nm, which was 26.5 % lower than that of pure diamond. Meanwhile, the material removal rate was 1.46 nm/min, with an improvement of 10.6 %, as well as a reduction in residual stress by approximately 29.8 %. Combined with the theory of micro-contact mechanics, the polishing mechanism and interfacial contact behavior of composite abrasives were investigated in depth through the analysis of polished sapphire surface and wear debris. The improvement of polishing performance may be attributed to the enhancement of solid-state reaction and its mutual balance with the mechanical removal action of composite abrasives.