Copper interconnect structure and method of formation

A method for forming a copper interconnect structure within a semiconductor device comprising the steps of:

• providing a semiconductor substrate;
• forming a first dielectric layer overlying the semiconductor substrate;
• patterning the first dielectric layer to form a first opening and a second opening within the first dielectric layer;
• forming a copper layer, the copper layer lying within the first opening and the second opening;
• removing a portion of the copper layer to form a first copper interconnect within the first opening and a second copper interconnect within the second opening;
• exposing a portion of the first copper interconnect and a portion of the second copper interconnect to a plasma consisting essentially of hydrogen and nitrogen;
• forming a first silicon oxynitride layer overlying the first copper interconnect and the second copper interconnect after the step of exposing the first copper interconnect and the second copper interconnect to the plasma, the first silicon oxynitride layer having a first absorptive coefficient;
• forming a second silicon oxynitride layer abutting the first silicon oxynitride layer, the second silicon oxynitride layer having a second absorptive coefficient;
• forming a second dielectric layer overlying the second silicon oxynitride layer;
• forming a photoresist mask overlying the second dielectric layer, wherein the photoresist mask is formed using electromagnetic radiation, the electromagnetic radiation having an exposure wavelength, wherein the first absorptive coefficient is less than the second absorptive coefficient at the exposure wavelength;
• and
• using the photoresist mask to pattern the second dielectric layer.