Interfacial layers for electromigration resistance improvement in damascene interconnects

Abstract

Protective caps residing at an interface between metal lines and dielectric diffusion barrier (or etch stop) layers are used to improve electromigration performance of interconnects. Protective caps are formed by depositing a first layer of aluminum-containing material over an exposed copper line by treating an oxide-free copper surface with an organoaluminum compound in an absence of plasma at a substrate temperature of at least about 350° C. The formed aluminum-containing layer is passivated either partially or completely in a chemical conversion which forms Al—N, Al—O or both Al—O and Al—N bonds in the layer. Passivation is performed in some embodiments by contacting the substrate having an exposed first layer with an oxygen-containing reactant and/or nitrogen-containing reactant in the absence of plasma. Protective caps can be formed on substrates comprising exposed ULK dielectric. The aluminum-containing layer residing on the dielectric portion will typically spontaneously form non-conductive layer comprising Al—O bonds.