Chemical-mechanical polishing of tungsten: an electrophoretic mobility investigation of alumina-tungstate interactions

摘要

Electrophoretic mobility (zeta potential) measurement was used to investigate the interaction of tungstate ions and alumina particles in aqueous media. In the absence of tungstate ions, the isoelectric point (iep) of alumina was observed at pH 8.5. The iep shifted to lower pH values with increase in tungstate ion concentration. The alumina particles became negatively charged over the entire experimental pH range (>=pH3) when the tungstate concentration in the system was raised to 10~-5) M. The results suggest that tungstate ions are strongly chemisorbed by alumina and that adsorption may provide a pathway for metal removal during chemical mechanical polishing (CMP). Implications for colloidal stability in CMP systems and for post-CMP slurry treatment and recycle are discussed.