Effect of slurry pH on the defects induced during the plug isolation chemical mechanical polishing

In the present work, major polishing defects such as micro dishing and polishing residues induced during the landing plug isolation (LPI) chemical mechanical polishing (CMP) were quantitatively examined in slurries with different pH by combining chemical dipping test and analytical method such as scanning electron microscopy and transmission electron microscopy. From the results of the dipping test, we found that the solution alkalinity accelerates micro dishing of borophosphosilicate glass (BPSG) layer to 60 nm in value, which is responsible for preferential accumulation of polishing residue at this site. This is attributed to more rapid chemical dissolution of BPSG than that of nitride film during LPI CMP in alkaline slurry. By introducing acidic slurry, we succeed in the effective reduction in the micro dishing and total number of the polishing residue Nr, generated during CMP in conventional silica-based alkaline slurry.