Microstructural Effects During Chemical Mechanical Planarization of Copper

Die-stacking schema using through-wafer interconnects require vias to be filled with electroplated Cu, resulting in thick copper films and requiring an aggressive first-step chemical mechanical planarization (CMP). This work investigates the effects of microstructure on CMP of copper films, which are not presently well understood. Bulk and local removal rates are investigated for several different microstructures. Surface orientation maps are created, and the orientations of individual grains are correlated with topographical data to elucidate local removal behavior. Cu removal depends on the details of the microstructure, and certain microstructures allow for either faster or more uniform removal of thick Cu films.