Annealing impact on damascene Cu resistivity and microstructures

The effect of different post electroplating anneals on dual damascene Cu microstructures and via chain yields using both rapid thermal processing and furnace anneal were investigated. It was found the grain size, (111) texture and Cu line resistance varied strongly with the annealing conditions. The minimum feature of trench width or height imposes physical limit to the average grain size. The Cu line resistivity increases rapidly as the feature size becomes smaller than 0.2 μm. Electron scattering from both sidewalls and grain boundaries played significant roles even at geometries several times of the electron mean free path in Cu