Self-aligned composite M-MOx/dielectric cap for Cu interconnect structures

摘要

An interconnect structure is provided that has improved electromigration resistance as well as methods of forming such an interconnect structure. The interconnect structure includes an interconnect dielectric material having a dielectric constant of about 4.0 or less. The interconnect dielectric material has at least one opening therein that is filled with a Cu-containing material. The Cu-containing material within the at least one opening has an exposed upper surface that is co-planar with an upper surface of the interconnect dielectric material. The interconnect structure further includes a composite M-MOx cap located at least on the upper surface of the Cu-containing material within the at least one opening. The composite M-MOx cap includes an upper region that is composed of the metal having a higher affinity for oxygen than copper and copper oxide and a lower region that is composed of a non-stoichiometric oxide of said metal. The interconnect structure further includes a dielectric cap located on at least an upper surface of the composite M-MOx cap.