Manufacturable CoWP metal cap process for copper interconnects

A method of electrolessly plating on copper contained in or on a semiconductor wafer comprising the steps of:

• providing a semiconductor wafer having copper areas and non-copper areas;
• applying to the semiconductor wafer an aqueous solution of palladium acetate, acetic acid, and chloride so as to form a palladium seed layer on the copper areas only and not on the non-copper areas;
• applying to the semiconductor wafer a complexing solution to remove palladium ions adsorbed on the non-copper areas;
• and
• electrolessly plating the copper with a plating solution comprising cobalt, tungsten and phosphorus so as to deposit a layer of cobalt, tungsten and phosphorus on the palladium seed.