Influence of SiO2–ZnO mixed soft abrasive on tribological behavior and polishing performance of sapphire wafer

Abstract

The use of reactive soft abrasives, capable of undergoing solid-state reactions with sapphire, is a promising approach for low-damage and low-contamination machining of sapphire wafers. This study calculates the Gibbs free energy change of these chemical reactions based on thermodynamic principles. SiO2–ZnO mixed soft abrasives were selected for the polishing of sapphire wafers. Friction and wear experiments were conducted to explore the tribological behavior of sapphire wafers with various mixed abrasives, leading to the optimization of the abrasive composition. The results show that mixed abrasives significantly enhance the material removal rate (MRR) of sapphire wafers. As the proportion of SiO2 in the mixture increases, the MRR correspondingly rises. Specifically, an SiO2–to–ZnO ratio of 2:1 in the mixed abrasives results in a 91.68% increase in MRR compared to using SiO2 abrasives alone. Based on these findings, five grinding discs with different abrasive ratios were prepared using a resin binder for mechanical–chemical polishing experiments on sapphire wafers. The polishing results corroborate those of the friction and wear experiments, confirming that an increased SiO2 content in the mixed abrasive discs leads to higher MRR. With a 2:1 ratio of SiO2 to ZnO in the mixed abrasive disc, the MRR is enhanced by 342.9% compared to discs with only SiO2 abrasives, while reducing the surface roughness to 3.21 nm. In the SiO2–ZnO mixed abrasives, the inclusion of ZnO enhances chemical reactions during polishing. Aided by the mechanical removal efficacy of SiO2, this approach significantly increases MRR while maintaining superior polishing quality.