Improved resistive switching phenomena and mechanism using Cu-Al alloy in a new Cu:AlO_x/TaO_x/TiN structure

Improved resistive switching phenomena such as device-to-device uniformity, lower formation voltage (2.8 V) and RESET current, >500 program/erase cycles, longer read endurance of >10⁶ cycles with a program/erase pulse width of 1 μs, and data retention of >225 h under a low current compliance of 300 μA have been discussed by using Cu-Al alloy in Cu:AlO_x/TaO_x/TiN conductive bridging resistive random access memory (CBRAM) device for the first time. The switching mechanism is based on a thinner with dense Cu filament formation/dissolution through the defects in the Cu:AlO_x/TaO_x/TiN structure owing to enhance memory characteristics. These characteristics have been confirmed by measuring randomly picked 100 devices having via-hole size of 0.4 × 0.4 μm². The Cu-Al alloy becomes Cu:AlO_x buffer layer and Ta₂O₅ becomes TaO_x switching layer owing to Gibbs free energy dependency. All layers and elements are observed by high-resolution transmission electron microscope (HRTEM) image and energy dispersive X-ray spectroscopy (EDX). By developing a numerical equation in between RESET current and formation voltage, it is found that a higher rate of Cu migration is observed owing to both the defective switching layer and larger size, which results a lower formation voltage and RESET current of the Cu:AlO_x/TaO_x/TiN structure, as compared to Cu/Ta₂O₅/TiN under external positive bias on the Cu electrode. This simple Cu:AlO_x/TaO_x/TiN CBRAM device is useful for future nanoscale non-volatile memory application.