Improving fatigue performance of Cu films on polyimide substrates through AC-strain treatment

This study investigates the effect of high-frequency alternating current (AC) treatment on the fatigue performance of 100 nm-thick Cu films on polyimide substrates. The films were subjected to 500 kHz AC at 2% tensile strain for 20 min. Fatigue tests revealed a significant enhancement in fatigue life, surpassing the performance of the thermally annealed sample at 300 °C for 30 min. Electron backscatter diffraction analysis revealed that the AC-strain treatment promotes grain growth and microstructural optimization. This enhancement is attributed to the synergistic effects of electron wind force and tensile strain, which enhance atomic migration and grain boundary motion, thereby enabling directional grain growth and texture optimization. These findings demonstrate that AC-strain treatment provides an effective and controllable strategy for enhancing the structural reliability and fatigue resistance of metallic films.