Copper chemical-mechanical-polishing (CMP) dishing

TLDR: In this article, a method for forming inlaid copper interconnects in an insulating layer without the normally expected dishing that occurs after chemical-mechanical polishing of the excess copper is disclosed.

Abstract: A method is disclosed for forming inlaid copper interconnects in an insulating layer without the normally expected dishing that occurs after chemical-mechanical polishing of the excess copper. This is accomplished by forming a conformal blanket barrier layer over a substrate including a composite groove/hole structure already formed in an insulating layer and then growing a copper seed layer over the barrier layer. A layer of photoresist is next deposited over the substrate filling the composite structure. The photoresist layer, seed layer and the barrier layer are then removed by chemical-mechanical polishing, leaving the seed layer and the barrier layer on the inside walls of the composite structure, however. Then the photoresist is removed from the composite structure, and replaced, in its place, with electroless plated copper, which forms a dome-like protrusion extending from the composite structure. When the substrate is subjected to chemical-mechanical polishing in order to remove the excess copper, the dome-like structure prevents the dishing of the copper metal. In a second embodiment, the seed layer and the barrier layer are chemical-mechanical polished without first depositing a photoresist layer. Copper metal is next selectively formed by electroless plating having a dome-like protrusion, which in turn is removed by chemical-mechanical polishing without the detrimental formation of dishing in the copper metal.