Prevention of Cu degradation using in situ N2 plasma treatment in a dual-damascene process

The surface state of copper after an etching process using CF4 gas has been analyzed. Copper surface stability against corrosion is evaluated through a storage test performed under high-humidity conditions after the etching process. The storage test reveals that the copper surface suffered from both corrosion and oxidation. The copper degradation is caused by a postreaction between moisture and residual fluorine, wherein the resulting oxygen-containing copper film features a rough surface morphology. We examined in situ plasma treatments with several gases to reduce corrosive reactions. Results indicate that in situ N2 plasma treatment removes fluorine residue from the copper surface, and that this treatment effectively stabilizes the copper surface against corrosive conditions.