SELECTIVE CVD-W FOR CAPPING DAMASCENE CU LINES

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 durin g the preclean, and selective CVD-W results in no significant yield lo ss and nearly complete oxidation protection. The W cap also suppresses Cu hillock formation during subsequent thermal cycling. The best resu lts were achieved by a wet-etch removal of the chemical-mechanical pol ish stop layer and a wet etch of the Cu as a preclean.