Lifetime modeling of copper metallization for SiC power electronics

Changing the metallization material for power electronics from aluminum to copper to increase the lifetime needs a deeper understanding of how the materials behave during production and service. Electrochemical deposited copper (ECD) and sputtered aluminum layers are characterized. Nanoindentation measurements in combination with reverse simulation is used to fit material models. Fatigue experiments show that higher strength and stain hardening in copper layers reduces the fatigue damage on free surfaces. The damage behavior remains similar, dislocation movement on slip-planes out of the surface. Wafer bow measurements are used to characterize the stress development in the layers up to 400°C. For annealed ECD copper the intrinsic stress is higher compared to AlCu.