Selective CVD-W for capping damascene Cu lines

Abstract

The use of selective chemical vapor deposited tungsten (CVD-W) to cap Cu lines in polyimide is shown to be compatible with planarization by chemical-mechanical polishing (damascene), minimal Cu is removed during the preclean, and selective CVD-W results in no significant yield loss and nearly complete oxidation protection. The W cap also suppresses Cu hillock formation during subsequent thermal cycling. The best results were achieved by a wet-etch removal of the chemical-mechanical polish stop layer and a wet etch of the Cu as a preclean.