Novel 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 CMP. This work investigates the effects of microstructure on CMP of copper films, which are not presently well understood. Bulk and local removal rates were investigated for several different microstructures. Surface orientation maps were created and the orientations of individual grains were correlated with topographical data to elucidate local removal behavior. Cu removal depends on the details of the microstructure, and certain microstructures allowed for either faster or more uniform removal of thick Cu films.
Andersen, Patrick J.; Bentancur, Mariela N.; Moll, Amy J.; and Frary, Megan. (2010). "Microstructural Effects During Chemical Mechanical Planarization of Copper". Journal of the Electrochemical Society, 157(1), H120-H126. http://dx.doi.org/10.1149/1.3254163