Ross, G.G.RossVuorinen, V.V.VuorinenKrause, M.M.KrauseReissaus, S.S.ReissausPetzold, M.M.PetzoldPaulasto-Kröckel, M.M.Paulasto-Kröckel2022-03-052022-03-052017https://publica.fraunhofer.de/handle/publica/25366210.1016/j.microrel.2017.07.044An identified reliability challenge of significant importance to Cu-Sn bonding for 3D integration is Cu-Sn intermetallic void formation. Voids, often referred to as Kirkendall voids, form within the inter-diffusional zone between Cu and Sn, more specifically within the intermetallic compound Cu3Sn. The root-cause(s) of void formation is not well understood, therefore this study is designed to understand under what conditions voids form. The two main hypotheses for the root-causes of void formation are (i) the imbalance of diffusion rates between Cu and Sn during the formation of Cu-Sn intermetallic compounds and the resulting residual stresses and (ii) the co-deposition of impurities during Cu electroplating to void formation. Therefore, an ex- and in-situ x-ray diffraction (XRD) study is used to probe the material state as a function of thermal annealing, and a time-of-flight mass spectroscopy (ToF-SIMS) study is used to detect impurities co-deposited during Cu electroplating and to understand the effects of thermal annealing on the impurities' kinetic behaviour.en621journal article