Preparation of Stable Alumina Suspensions for Chemical Mechanical Polishing

Alumina abrasives are well-known for their high material removal rates in chemical mechanical polishing (CMP), but poor suspension stability remains a key limitation to their performance. This study aims to identify effective dispersants to enhance the dispersion stability of alumina suspensions, which are crucial for CMP in semiconductor manufacturing. A systematic investigation is conducted to examine the effects of silica sol and three organic dispersants, namely, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyvinylpyrrolidone (PVP), on the dispersion behavior of alumina suspensions. The results demonstrate that silica sol displays much better dispersion performance than the organic dispersants. The dispersion stability of alumina suspensions increases with SiO₂ content in silica sol up to 10 wt %, where uniform particle distribution, a zeta potential of -39.1 mV, and optimal dispersion were achieved before declining at higher contents. Further analysis shows that silica sol stabilizes alumina particles through electrostatic and chemical interactions, forming a dense, stable adsorption layer on their surface. The resulting electrostatic repulsion effectively prevents agglomeration, thereby ensuring a stable alumina suspension. These results show that silica sol stabilizes alumina suspensions through chemical bonding and electrostatic repulsion, enabling uniform, long-term dispersion for high-performance CMP applications.