Process for cmp removal of excess trench or via filler metal which inhibits formation of concave regions on oxide surface of integrated circuit structure

Abstract

A process-is disclosed for planarizing an integrated circuit structure by chemical mechanical polishing (CMP) after filling, with at least one metal, a plurality of trenches and/or vias formed in a silicon oxide layer on the integrated circuit structure. The process, which is capable of inhibiting formation of concave surface portions on the silicon oxide surface, during the CMP process, in regions where said trenches and/or vias are closely spaced apart, comprises forming, over a layer of silicon oxide of an integrated circuit structure, an antireflective coating (ARC) layer of dielectric material capable of functioning as a stop layer in a CMP process to remove metal; and using this ARC layer as a stop layer to assist in removal of excess metal used to fill trenches and/or vias formed in the oxide layer. The particular material chosen for the ARC layer should have a lower etch rate, in a CMP process to remove metal, than does the underlying oxide dielectric layer. Trenches and/or vias are formed through the ARC layer and the oxide dielectric layer. These trenches and/or vias are then filled by depositing at least one metal layer over the ARC layer. Excess trench and/or via filler metal is then removed from the top surface of the ARC layer by subjecting the metal to a CMP step which is selective to the ARC layer, thereby permitting the ARC layer to function as a CMP stop layer which protects the underlying oxide dielectric layer from exposure to the CMP process. Since the ARC layer has a lower etch rate, in the CMP process to remove metal, than does the oxide dielectric layer, the formation of dished or concave regions in the surface is inhibited, including those regions where the trenches and/or vias are closely spaced apart.