| Chemical mechanical polishing (CMP) is used by the semiconductor manufacturing industry to polish materials under high shear for the fabrication of microelectronic devices such as computer chips. Under these high shear conditions, slurry particles can form agglomerates causing defects, which cost the semiconductor industry billions of dollars annually.;The shear thickening behavior of colloidal silica CMP slurries (28-38 wt%) under high shear was studied using a rotating rheometer with parallel-plate geometry. The colloidal silica slurries showed continuous thickening and irreversible behavior at high shear rates (>10,000 s-1). Changing the silica concentration, adding monovalent chloride salts (NaCl, KCl, CsCl, and LiCl), adjusting the pH (pH 4 to pH 10.5), and mixing two particle sizes (d = 20 nm and 100 nm) within the slurry altered the thickening behavior of the slurries. Shear thickening behavior can be eliminated with certain large to small particle ratios. |
