Fatigue tolerance of nanostructured Cu/interlayer bilayers: Tuned by heterogeneous interface

In this paper, interlayers with different characteristics (crystalline Cr vs amorphous CuZr) were used for nanostructured Cu films adherent to polyimide substrates. Impact of heterogeneous interface on the fatigue behavior was investigated by using microstructural examinations in combination with molecular dynamics simulations. It is revealed that the Cr interlayer deteriorated the fatigue property of Cu films because of the formation of voids at the Cu/Cr interface during cyclic loading. By contrast, the CuZr interlayer improved the fatigue performance of Cu films, which can be attributed to the strengthened constraint effect on dislocation motion and the excellent interface compatibility associated with the absorption of dislocations. These findings provide new insight in tailoring the interlayers to achieve optimized performance for nanostructured Cu/interlayer bilayers as extensively applied in microelectronics field.