PROTECTION OF SEED LAYERS DURING ELECTRODEPOSITION OF METALS IN SEMICONDUCTOR DEVICE MANUFACTURING

A protective layer is formed over a copper seed layer on a semiconductor substrate prior to electroplating. The protective layer is capable of protecting the copper seed layer from oxidation and from dissolution in an electrolyte during initial phases of electroplating. The protective layer, in some embodiments, prevents the copper seed layer from contacting atmosphere, and from being oxidized by atmospheric oxygen and/or moisture. The protective layer contains a metal that is less noble than copper (e.g., cobalt), where the metal can be in an oxidized form that is readily soluble in a plating liquid. In one embodiment a protective cobalt layer is formed by depositing cobalt metal by chemical vapor deposition over copper seed layer without exposing the copper seed layer to atmosphere, followed by subsequent oxidation of cobalt to cobalt oxide that occurs after the substrate is exposed to atmosphere. The resulting protective layer is dissolved during electroplating.