Enhanced tungsten chemical mechanical polishing using stable alumina slurries

The chemical mechanical polishing of tungsten using stabilized alumina slurries has been investigated. To stabilize the alumina slurries in the presence of high concentration of an oxidizer [K3Fe(CN)(6)] at acidic pH, a combination of anionic (sodium dodecyl sulfate, SDS) and nonionic (polysorbate 80, Tween 80) surfactants were added. Static electrochemical measurements were carried out to compare the slurries with and without the surfactant. Chemical mechanical polishing experiments showed that the removal rate of tungsten decreases in the presence of a stable slurry. These experiments have also shown that the local roughness of the polished surface can be reduced significantly using a stable slurry. Finally, the adhesion of alumina particles on tungsten and silica surfaces has been reduced by more than an order of magnitude due to the presence of the surfactant. (C) 1999 The Electrochemical Society. S1099-0062(98)05-060-3. All rights reserved.