Study of microstructure and resistivity evolution for electroplated copper films at near-room temperature

A study on the self-annealing of various electroplated (ECP) blanket copper films of different thickness is performed on 8 wafers. Uncorrelated evolution of sheer resistance/resistivity and stress as a function of time has been exhibited. The initiation of self-annealing was faster for thicker ECP Cu films. These thicker films demonstrated a higher fraction of sheet resistance and resistivity drop as compared to thinner ones. They recorded a lower residual stress as well. One important observation is that the decrease of the resistivity during self-annealing correlates well with an abrupt rise in its standard deviation, with the resistivity measurements taken evenly across the entire wafer surface. Non-uniform distribution in grain size and the occurrence of grain growth when the film starts to self-anneal is speculated to be the cause for this observation. This is further supported by the AFM results. (C) 2001 Elsevier Science Ltd. Ah rights reserved.