Void formation, growth and movement characteristics of copper interconnect samples have been investigated in-situ on fully embedded test structures inside a SEM. In this study locally Al-alloyed copper interconnects and interconnects with a CoWP surface coating were investigated in addition to pure copper interconnects. After the failure of the sample or after significant voiding was observed, the cathode via region of the samples were prepared for subsequent SEM/EBSD and/or TEM analysis. The position of grain boundaries and the orientations of the grains in the vicinity of voids were obtained by SEM/EBSD. TEM was used to investigate the structure of the copper/capping layer interface. The distribution of the alloying element Al was investigated by means of TEM/EDS in the case of CuAl interconnects. The in-situ experiments as well as the sample preparation procedure was specifically tailored in order to be able to perform post-mortem TEM and EBSD investigations.