Improved resistive switching phenomena and mechanism using Cu-Al alloy in a new Cu: AlOx/TaOx/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 >10(6) cycles with a program/erase pulse width of 1 mu s, and data retention of >225 h under a low current compliance of 300 mu A have been discussed by using Cu-Al alloy in Cu: AlOx/TaOx/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: AlOx/TaOx/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 x 0.4 mu m(2). The Cu-Al alloy becomes Cu: AlOx buffer layer and Ta2O5 becomes TaOx 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:AlOx/TaOx/TiN structure, as compared to Cu/Ta2O5/TiN under external positive bias on the Cu electrode. This simple Cu:AlOx/TaOx/TiN CBRAM device is useful for future nanoscale non-volatile memory application. (C) 2015 Elsevier B.V. All rights reserved.