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The tungsten filled via plug process is commonly used in sub-half micron CMOS process technologies. As process technologies shrink beyond the 0.25 /spl mu/m generation, the metal overlap over the via also reduces. This results in vias which are not fully covered by the overlying interconnect lines. In the evaluation of such structures, we have observed a new failure mechanism resulting in completely unfilled vias due to electrochemical corrosion accelerated by a positive charge on specific structures.