Impact of AlOx layer on resistive switching characteristics and device-to-device uniformity of bilayered HfOx-based resistive random access memory devices

Abstract

An AlOx layer was deposited on HfOx, and bilayered dielectric films were found to confine the formation locations of conductive filaments (CFs) during the forming process and then improve device-to-device uniformity. In addition, the Ti interposing layer was also adopted to facilitate the formation of oxygen vacancies. As a result, the resistive random access memory (RRAM) device with TiN/Ti/AlOx (1 nm)/HfOx (6 nm)/TiN stack layers demonstrated excellent device-to-device uniformity although it achieved slightly larger resistive switching characteristics, which were forming voltage (VForming) of 2.08 V, set voltage (VSet) of 1.96 V, and reset voltage (VReset) of −1.02 V, than the device with TiN/Ti/HfOx (6 nm)/TiN stack layers. However, the device with a thicker 2-nm-thick AlOx layer showed worse uniformity than the 1-nm-thick one. It was attributed to the increased oxygen atomic percentage in the bilayered dielectric films of the 2-nm-thick one. The difference in oxygen content showed that there would be less oxygen vacancies to form CFs. Therefore, the random growth of CFs would become severe and the device-to-device uniformity would degrade.