MECHANISMS OF COPPER REMOVAL DURING CHEMICAL-MECHANICAL POLISHING

Schemes using chemical mechanical polishing of copper have been propos ed for the patterning of interconnections in copper multilevel metalli zation. In this article, the phenomena involved in the removal of copp er during copper chemical mechanical polishing are investigated. The c oncentration of chemical etchant in the polish slurry is varied to inv estigate the chemical component, and the applied pressure is varied to investigate the mechanical component. Two slurries, an ammonium hydro xide plus ferricyanide slurry and a nitric acid slurry, are used to po lish both copper and Cu2O thin films. Removal of copper or Cu2O is hyp othesized to be a result of mechanical abrasion, while the role of the chemical etchant is to dissolve the material abraded from the surface rather than to etch the material directly from the surface. (C) 1995 American Vacuum Society.