Method for forming a copper damascene structure over tungsten plugs with improved adhesion, oxidation resistance, and diffusion barrier properties using nitridation of the tungsten plug

A method for forming a copper damascene structure over tungsten plugs using nitridation of said tungsten plugs to provide improved oxidation resistance of the tungsten plugs, improved adhesion between the tungsten plugs and the damascene structure, and an improved barrier to the copper in damascene structure diffusing into the tungsten plugs, comprising the steps of:

• a. providing a substrate structure, having at least one device layer thereon;
• said device layer having a first dielectric layer thereover;
• said dielectric layer having tungsten plugs therein providing a conductive path between the surface of said dielectric layer and said device layer;
• b. nitridizing said tungsten plugs to form a tungsten nitride (WNx) layer on said tungsten plugs;
• c. depositing a second dielectric layer over said WNx layer and said first dielectric layer;
• d. patterning said second dielectric layer to form a trench in said second dielectric layer;
• whereby said WNx layer is exposed in said trench;
• e. forming a barrier layer in said trench;
• f. depositing a copper metal layer over said barrier layer;
• and
• g. planarizing said copper metal layer and said second dielectric layer to form a damascene structure.