Improving bending fatigue lifetime and interfacial adhesion of Cu–Mn flexible interconnects using self-forming nanolayer

Abstract The long-term reliability of flexible electronics depends on the durability of metallic interconnects. Fatigue failure in these interconnects is driven by two mechanisms: crack initiation from surface extrusions and delamination at the metal/polymer interface. Here, we propose a Cu–Mn alloy interconnect that utilizes a self-forming nanolayer to simultaneously address both failure modes. Through postannealing of a vapor-deposited Cu–Mn film, manganese diffuses to form an ∼20 nm thick manganese oxide (MnO x ) layer at both the surface and the interface. This surface MnO x layer effectively suppresses extrusions, the primary sites for fatigue cracks. Concurrently, the interfacial MnO x layer enhances adhesion energy to 10.77 J/m 2 , a ∼2.2-fold improvement over annealed pure Cu, thus preventing delamination. As a result, the Cu–Mn interconnects exhibit a significant enhancement in fatigue lifetime, confirming the dual role of MnO x in improving both surface stability and interfacial integrity. This work provides a unified and experimentally validated strategy for improving the reliability of flexible electronic interconnects.