Role of abrasives in high selectivity STI CMP slurries

In this study chemical mechanical planarization slurries for shallow trench isolation exhibiting high oxide to nitride polish rate selectivity were investigated and it was found that the abrasives play a major role in suppressing the nitride polish rate and enhancing selectivity. When glutamic acid is used as a selectivity enhancing additive, only ceria based slurries exhibit high selectivity while silica based slurries show low selectivity under identical conditions. A mechanism involving active sites on the ceria abrasive and interaction of glutamic acid with the active sites is proposed to explain the role of abrasive in enhancing selectivity.