Dual damascene interconnect process with borderless contact

Abstract

A dual damascene process is disclosed for forming contact and via interconnects without borders. A nitride layer is first formed on a dielectric layer to function as a hard-mask. Metal line trench is first etched into the nitride layer and then into the dielectric layer. Then, a second photoresist layer is used to pattern contact or via hole over line trench opening and the dielectric layer is further etched through the line trench into the dielectric layer until the substructure of the substrate is reached. It is disclosed that by using the nitride layer as a hard-mask, the registration or alignment tolerance between the contact/via hole pattern and the metal line pattern can be relaxed substantially and not use a border as is conventionally practiced in order to assure proper registration between the patterns. The borderless interconnect is achieved by filling the composite line opening and the hole opening with metal and chemical mechanical polishing. The process enables cost reduction and productivity in the semiconductor manufacturing line.