Effect of environment on fatigue strength of Cu/Si interface in nanoscale components

The effect of environment on the fatigue strength of a Cu/Si interface in nanoscale components is investigated by performing cyclic bending experiments on nano-cantilever specimens with the interface between a 200-nm-thick Cu layer and a Si substrate. Prior to the fatigue experiments, half of the nano-cantilever specimens are treated for 15 min in an environmental chamber with a temperature of 80 °C and a relative humidity of 80%. For both the environmentally treated and non-treated specimens, cracks initiate at the Cu/Si interface edge at a lower stress level for cyclic loading than for monotonic loading due to irreversible deformation of the Cu layer. Finite element analysis reveals that the fatigue region of the Cu layer is near the interface edge within scale of 100 nm. Comparison of S–N curves obtained from the environmentally treated and nano-treated nano-cantilever specimens indicates that the environmental treatment reduces the fatigue strength of the Cu/Si interface.