Diamond Lapping of Sapphire Wafer with Addition of Graphene in Slurry

In this paper, a novel method with addition of graphene in diamond slurry is proposed to conduct CMP lapping of sapphire wafer. Two kinds of graphenes are added including graphene oxide (GO), reduced graphene oxide (RGO). Effect of three important processing parameters on material removal rate (MRR) and surface roughness is investigated, including graphene type, graphene weight fraction, and ultrasonication time. Weight fractions of various graphenes versus diamond slurry are controlled in the range from 0.5 to 2.0 wt%. Results indicate that addition of graphene in diamond slurry can significantly increase MRR of sapphire wafer. MRR of sapphire wafer is proportional to graphene weight fraction. At higher weight fraction, GO/diamond slurry leads to higher MRR than RGO/diamond slurry does. MRR by the pure diamond is 285.80 nm/min, while MRR by the diamond/GO(2.0wt%) with 48-hour ultrasonication is 832.1 nm/min. Surface roughness is inversely proportional to graphene weight fraction and proportional to graphene particle size. Ultrasonication is able to efficiently reduce graphene particle size. RGO/diamond slurry can result in lower surface roughness than GO/diamond slurry.