Effects of Gas Species on Charging Induced Tungsten Plug Corrosion during Post Metal Etch Process

Effects of gas species on charging induced tungsten plug corrosion during post metal etch process have been investigated. It was found that the O2 plasma in the dry strip process induces considerable charge build-up, which subsequently results in the tungsten plug corrosion in the solvent with pH value larger than 4.0. Experiments were performed in various strip chambers in order to find effective methods to avoid the charging by the O2 plasma. Adding H2 or H2O to the O2 plasma during the strip process or additional H2O plasma treatment right after the O2 plasma strip process were proven to be an effective way to prevents the charge build-up by the O2 plasma. Mechanisms for the charge build-up by the O2 plasma and the drastic reduction of the charging by H-related compounds are discussed.