Effect of diluted colloidal silica slurry mixed with ceria abrasives on CMP characteristic

Abstract

In this paper, we have studied the CMP characteristics of mixed abrasive slurry (MAS) retreated by adding of ceria abrasives within 1:10 diluted silica slurry (DSS). We focused on how these mixed ceria abrasives affect the material removal in order to determine the optimal recipe conditions through the correlation between the mixed contents of ceria abrasives and CMP performances. The slurry designed for optimal performance should produce reasonable removal rates, acceptable polishing selectivity with respect to the underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and non-uniformity. As a result, the oxide CMP process using diluted mixed abrasive slurry has problems of higher material removal rate at wafer center. But, we solved the questions in consecutive order by pH control. We obtained the comparable slurry characteristics to original silica slurry in the viewpoint of high removal rate and low non-uniformity. Finally, our proposed ceria-MAS can be useful to save a slurry consumption of high cost since we used 1:10 diluted mixed abrasive slurry.