Initial void chacterization in 30nm wide polycrystalline Cu line using a local sense EM test structure

Small EM voids in 30nm wide polycrystalline Cu lines which are formed earlier than full voids are characterized using local sense EM test structure. The growth of these initial voids is stopped after a rapid 1-10 Ohm resistance increase. The void mechanism follows a proposed model of polycrystalline Cu grain depletion. It is also shown that by detecting the initial voids, simple and cost effective single level Cu lines can be a promising test method to assess EM reliability in the early stages of process development for scaled Cu interconnects.