Impact of the electrodeposition chemistry used for TSV filling on the microstructural and thermo-mechanical response of Cu

In this study, the role of electrodeposition chemistry on thermo-mechanical behavior of different Cu-films is examined. For this study, three different Cu electrodeposition chemistries were analyzed using Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), Focused Ion Beam (FIB), Laser Scanning method, Electron Backscattered Diffraction, and the Nano-indentation techniques. It is found that the level of impurity in Cu-films, resulting from the used electrodeposition additives, has a significant impact on their microstructural and thermo-mechanical behavior. Cu-films having high impurity content showed residual stress levels that are three times higher than the less impure Cu-films. This implies that the use of such impure electrodeposition chemistry for the filling of TSVs will result in high residual stresses in the Cu-TSV, thus inducing higher stresses in Si, which could be a reliability concern. Therefore, the choice of the used electrodeposition chemistry for the filling of TSVs should not be limited only to the achievement of a void free Cu-TSV, as consideration ought to be given to their thermo-mechanical response.