Reverse selectivity – High silicon nitride and low silicon dioxide removal rates using ceria abrasive-based dispersions

Preferential removal of silicon nitride over silicon dioxide using 0.25 wt.% ceria abrasives and 0.32 wt.% poly(acrylicacid-co-diallyldimethylammonium chloride). At this concentration, the polymer adsorbs strongly on ceria, blocking the interaction of surface Ce 3+ species with the oxide film and suppresses its removal but has no effect the nitride removal rate. At lower values of X, the ratio of the amount of polymer to ceria, the blockage is not complete. We show that by adding poly(acrylicacid-co-diallyldimethylammonium chloride), a cationic polymer with a weight average molecular weight of about 4200 g/mole, to ceria-based dispersions, it is possible to achieve a silicon nitride removal rate (RR) of >100 nm/min and a silicon dioxide RR of