The Effect of pH on Sapphire Chemical Mechanical Polishing

In this paper, the effect of pH on sapphire chemical mechanical polishing (CMP) was investigated. The sapphire removal rate increased with ascending pH until 8. To investigate the electrostatic force between colloidal silica abrasive and sapphire surface, the zeta potential of sapphire surface and colloidal silica abrasive were studied. The sapphires immersed into the slurry containing 20 wt% colloidal silica were observed with scanning electron microscopy (SEM). For further insights into the mechanism of sapphire CMP with different pH values, particle size of the colloidal silica was used to analyze the mechanical function. Finally, the chemical actions between sapphire (Al2O3) and colloidal silica (SiO2) during sapphire CMP as a function of pH value were discussed.