A modified Damascene electrodeposition process for bottom-up filling of recessed surface features

Abstract

A modification of the conventional Damascene metallization process is described whereby selective removal of the thin wetting/seed layer from the sidewalls and free surfaces enables selective nucleation and bottom-up electrodeposition of metals and alloys in recessed surface features. The process is demonstrated by filling sub-micrometer trenches with electrodeposited Ni. A conventional PVD Cu seed layer is etched to remove Cu from the sidewalls and free surface while leaving a continuous Cu wetting layer intact on the trench bottom. The underlying non-wetting barrier layer provides a conductive path for electrodeposition from contacts on the perimeter of the work piece to the trench bottom. The robustness of the bottom-up Ni electrodeposition process is greatly increased by the addition of 2-mercaptobenzimidazole (MBI) to the plating bath. The additive hinders spurious nucleation of Ni on residual Cu patches that may remain on the free surface.