Room-temperature microstructural evolution of electroplated Cu studied by focused ion beam and positron annihilation lifetime spectroscopy

Focused ion beam (FIB) microscopy was used to obtain the time dependent transformation fraction and positron annihilation lifetime spectroscopy (PALS) was employed to analyze the vacancy-type defects in electroplated copper (Cu) during room-temperature microstructrual evolution. It was found that PALS is more sensitive than FIB to show the room-temperature microstructual evolution of electroplated Cu at the first stage of self-annealing. The majority of defects in electroplated Cu are dislocation-bound vacancies and vacancy clusters. Both the size and the concentration of the defects are similar for the two samples at the completion of electroplating. During the incubation time, the mean size of vacancy-type defects increases. After the onset of visible grain growth, the size of vacancy-type defects decreases. The detail evolutions of defects differ with the two samples. The role of the evolution of codeposited species was also discussed.