Preparation and mechanism study of Al2O3-CeO2 mixed abrasive slurry for A-plane sapphire chemical mechanical polishing

To address the low removal rate, severe surface damage, and unclear mechanism of A-plane sapphire during chemical mechanical polishing, a novel Al 2 O 3 -CeO 2 mixed-abrasive slurry was developed by integrating the mechanical abrasion of Al 2 O 3 with the chemical reactivity of CeO 2 . The optimal formulation, containing 2 wt% Al 2 O 3 , 0.2 wt% CeO 2 , 0.15 wt% sodium hexametaphosphate, 0.7 wt% isooctanol polyoxyethylene ether, and 0.5 wt% sodium D-gluconate with aminomethyl propanol as pH regulator, yields an atomically smooth surface (Ra = 0.079 nm) and a high removal rate (MRR = 905 nm/h). XPS analysis reveals that a hydrated Al-OH layer and a CeAl x O y soft phase form on the sapphire via interfacial solid-state reaction, and are removed by mechanical shearing of the mixed abrasives.