Intensive investigation of copper CMP over the past decade has revealed that consumable technology is of critical importance. There are several reasons for this, but all are ultimately due to the chemical and material properties of copper and associated barrier layers. Moreover, in comparison to conventional dielectric polishing, copper CMP (and, perhaps, metal CMP in general) is of a much more chemical nature. This is a consequence of the fact that metal removal generally requires an oxidation-reduction mechanism while, in contrast, dielectric removal typically requires only simple hydrolysis. As any chemist knows, oxidation-reduction reactions are often notoriously hard to control and easily upset by contaminants. Of course, contaminants can be intentionally added to the chemistry for beneficial purposes in which case they become known as “proprietary additives”.

In addition, to the removal chemistry, abrasive and pad technology has also undergone considerable evolution. Indeed, free abrasive, fixed abrasive, and abrasiveless technologies have all been developed. In the case of fixed abrasive polishing, this has required modification of the pads as well, however conventional and abrasiveless polishing can be carried out with conventional polyurethane pads. This picture is further complicated by the various available hardware configurations and the use of multiplaten processes.