Experimental Stress Characterization and Numerical Simulation for Copper Pumping Analysis of Through-Silicon Vias

In this paper, a 3-D thermomechanical model of through-silicon vias (TSVs) has been analyzed and verified with in situ microscale strain measurements by synchrotron X-ray microdiffraction. Thereafter, a comprehensive stress/strain analysis on copper pumping and back-end-of-line (BEOL) cracking issues has been carried out. In addition, a design-of-experiments-based approach has been used to understand the effect of various parameters on copper pumping and BEOL stress. The results show that the smaller TSV diameter and thinner silicon die help reduce the copper pumping and thus mitigate BEOL stress.