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

Abstract

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.