Dual damascene copper interconnect to a damascene tungsten wiring level

Abstract

A method and structure for fabricating a dual damascene copper interconnect which electrically contacts a damascene tungsten wiring level. The method forms a first layer on a semiconductor substrate, a silicon nitride layer on the first layer, and a silicon dioxide layer on the silicon nitride layer. The first layer includes damascene tungsten interconnect regions separated by insulative dielectric material. A continuous space is formed by etching two contact troughs through the silicon dioxide and silicon nitride layers to expose damascene tungsten interconnect regions, and by etching a top portion of the silicon dioxide layer between the two contact troughs. A reduced-height portion of the silicon dioxide layer remains between the two contact troughs. The continuous space is filled with damascene copper. The resulting dual damascene copper interconnect electrically contacts the exposed damascene tungsten interconnect regions.