It is likely that a smaller amount
ofH2O2 is sufficient to modify the surface of CeO2 abrasive at higher
pH value. More Ce3+ on the surface of abrasive in slurry could be
beneficial for the CMP process due to the ease of forming a Ce(OH)3
hydration layer which would accelerate the process of CMP based
on Cook’s theory [13]. Therefore, the increase in pH value leads to
the increase of the ratio of Ce4+ ions to Ce3+ ions for the oxidization
effect of hydrogen peroxide despite the lower concentration, which
contributes to the decrease in MRR in Fig. 3(b).