Analysis of copper ion filaments and retention of dual-layered devices for resistance random access memory applications

For improvement of switching uniformity, we propose a dual-layer structure with different resistance values in each layer. During the forming process, a current path is created in a high-resistance region which localizes filament formation in ultra-thin low resistance regions. The localized filament, whose existence is confirmed by conductive atomic force microscopy (CAFM), dramatically improves switching uniformity. In addition, pulse switching is demonstrated by application of alternating voltages of ±2 V for 1 μs. Analysis of Cu ion retention provides considerable insight into the resistance memory. A dual-layer oxide with excellent device performance and yield shows good promise for future non-volatile memory applications.