Tungsten local interconnect for silicon integrated circuit structures, and method of making same

Abstract

A local interconnect for an integrated circuit structure is described capable of bridging over a conductive element to electrically connect together, at the local interconnect level, non-adjacent conductive portions of the integrated circuit structure. After formation of active devices and a conductive element of an integrated circuit structure in a semiconductor substrate, a silicon oxide mask is formed over the structure, with the conductive element covered by the silicon oxide mask. Metal silicide is then formed in exposed silicon regions beneath openings in the mask. The portion of the silicon oxide mask covering the conductive element is then retained as insulation. A silicon nitride etch stop layer and a planarizable dielectric layer are then formed over the structure. An opening is then formed through such silicon nitride and dielectric layers over the conductive element and exposed metal silicide regions adjacent the conductive element. Conductive metal is then deposited over the entire structure to fill the opening. The conductive metal thereby forms a local interconnect which bridges over the conductive element to electrically connect the respective exposed metal silicide regions adjacent the conductive element, with the silicon oxide retained over the conductive element providing insulation to electrically separate the local interconnect from the conductive element. A formula is also provided for calculating the thickness range of the silicon oxide mask layer when a silicon nitride etch stop layer is utilized.