High reliability Cu interconnection utilizing a low contamination CoWP capping layer

Copper (Cu) damascene interconnects with a cobalt tungsten phosphorus (CoWP) capping layer were developed using an alkaline-metal-free electrodes plating process without palladium (Pd) catalyst activation. The wafer contamination level after processing is consistent with requirements for present LSI fabrication lines. Within wafer CoWP deposition uniformity is high and interconnects wire resistance increases by less than 5% after deposition. Electromigration (EM) testing shows no failures after two thousand hours and stress induced voiding (SIV) testing shows no failure after three thousand hours. This EM result is a 2 order or magnitude improvement over a non CoWP process.