Light enhanced tungsten via corrosion

Recently it has been found that tungsten vias exposed during post-metal etch wet cleans are susceptible to galvanic corrosion in a 0.5 micron CMOS process. It was found that the amount of light exposure during the clean, time exposed to the clean solution, structural layout, and clean tool dependencies all contribute to the corrosion. A mechanism for the tungsten corrosion is proposed in this paper.