Study of electromigration void nucleation time in Cu interconnects with doping elements

This study shows that in Cu interconnects with different doping elements (e.g., Al, Co, Mn) electromigration failure times may be significantly increased because of an incubation time prior to the usual void formation. The presence of a significant incubation time provides a change from the common value of 1 to a value of 2 of the current exponent of Black’s equation, mostly used for lifetime extrapolation at use conditions. Moreover, an increase of the activation energy up to 1.4 eV has been experimentally obtained. This gives additional room for reliability lifetime extension.

Figure optionsDownload as PowerPoint slideHighlights
► Electromigration lifetime of Cu interconnects with a few percent of Al or Co or Mn is increased.
► We model an incubation time or void nucleation time before void growth.
► The model changes the current exponent n used for lifetime extrapolation from usual n = 1 to n = 2.
► The model also provides an increase of activation energy of metal atoms diffusion mechanism.