X-ray micro-beam diffraction measurement of the effect of thermal cycling on stress in Cu TSV: A comparative study

Microelectronic devices are subjected to constantly varying temperature conditions during their operational lifetime, which can lead to their failure. In this study, we examined the impact of thermal cycling on the evolution of stresses in Cu TSVs using synchrotron-based X-ray micro-diffraction. Two test conditions were analyzed: as-received and 1000 cycled samples. The principal and shear stresses in the 1000 cycled sample were five times greater than in the as-received sample. This was attributed to the increased strain hardening upon thermal cycling. The variation in stresses with thermal cycling is a clear indication that the impact of Cu TSV proximity on front-end-of-line (FEOL) device performance will fluctuate throughout the lifetime of the 3D stacked dies, and thus should be accounted for during FEOL keep-out-zone design rule development.