Local area alloying to prevent copper dishing during chemical mechanical polishing (CMP)

摘要

According to the present invention, the dishing of copper during chemical mechanical polishing (CMP) process can be significantly reduced, and in most instances eliminated, by the use of electroplated alloys of copper whereas the alloying metal forms a continuous solid solution with the copper. By forming electroplated alloys of copper with metals that form continuous solid solutions therewith, a deposition layer of such an alloy on the surface of a barrier metal layer allows for lowering the selectivity of the slurry polish used during the CMP process towards the alloy. The alloys of copper with metals that form a continuous solid solution in an electroplating process changes the oxidation characteristics, mechanical properties, electrical properties, stiffness parameters and hardness parameters of the copper. The change in these properties allows the alloy layer and barrier layer to be polished at an equivalent rate until the entire barrier layer has been polished. In this manner, dishing of the copper in the trenches of a wafer from the CMP process can be avoided.