Method for improving faceting effect in dual damascene process

Abstract

A new method is provided for creating the interconnect pattern for dual damascene structures. The dual damascene structure is created in two overlying levels of dielectric, a first etch stop layer is deposited over the surface of the substrate, a second etch stop layer is deposited between the two layers of dielectric. A first etch penetrates both layers of dielectric, a second etch penetrates the top dielectric layer. Before the second etch is performed, a layer of ARC is deposited. For the second etch a polymer rich etchant is used to protect the sidewalls of the opening. The second etch leaves in place a fence of material (containing C, H, F and oxide compounds) that is formed around the upper perimeter of the opening through the lower layer of dielectric. This fence protects the upper corners of the lower opening of the dual damascene structure and is removed in a two step procedure. At the completion of this two step procedure the upper corners of the lower opening of the dual damascene structure have retained a rectangular profile. A final step removes the photoresist (that has been used to create the interconnect line opening) from the surface of the second layer of dielectric while the remnants of the ARC material are also removed.