Method for fabricating high circuit density, self-aligned metal linens

Abstract

A method is disclosed for fabricating patterned conductive lines which are self-aligned with underlying contacts windows. A layer of a photosensitive material such photoresist is formed over a dielectric layer. The photoresist layer is processed to have fully developed areas corresponding to contact windows, partially developed areas corresponding to the patterned conductive lines and undeveloped areas which correspond to field areas where the entire dielectric layer is maintained. The dielectric layer is preferably a compound dielectric layer to reduce interlevel shorts. Through the use of selective etch steps, the compound dielectric layers aid in the formation of the patterned conductive line and contact window structure. A series of reactive ion etch (RIE) steps are performed. The first RIE step, highly selective to dielectric material as compared to photoresist, etches the fully developed areas at least partially through the dielectric thickness. In the second RIE step, the photoresist which protected dielectric in the conductive line areas is removed. The third RIE step is also selective to dielectric material as compared to photoresist and etches the dielectric to form channels where the conductive lines are formed, and completes the etching in the contact window areas. The remaining resist is then removed. The channels and contacts are overfilled with a deposition of a conductive material. This conductive material is then planarized by either a RIE process or a chemical-mechanical polishing step.