Understanding of Selector‐Less 1S1R Type Cu‐Based CBRAM Devices by Controlling Sub‐Quantum Filament

Abstract

AbstractThis study demonstrates a systematic approach to design a sub‐quantum selector‐less conductive bridge random access memory (CBRAM) which can work as one‐selector‐one‐resistor device in Cu/Ti/HfO2/TiO2/TiN material stack, can work nicely from sub‐µA to sub‐nA range. Optimized high thermal forming scheme is investigated to control the anatomy of filament formation at sub‐nA current level. The thickness of HfO2 layer plays a crucial role in determining such behavior. Hence, in this study the precise stack engineering is proposed and the selector‐less device design which can show highly stable one‐selector‐one‐resistor type performance at sub‐quantum level is identified. The TiO2‐based selector device is verified experimentally and theoretically. The presence of 1 eV deep level traps by CuO defect sites in HfO2 matrix with calculated nearest neighbor of 0.7 nm along with the presence of TiO2 selector layer, is the origin of highly nonlinear behavior. The devices show ultra‐low leakage current of 300 fA (system limitation) and operated with ultra‐low power of 5 pW, very high resistance ratio of 3 × 103, with high nonlinearity of 3 × 103. This work establishes the possibility to design ultra‐low power nonvolatile sub‐quantum CBRAM device which can fulfill the needs of internet of things applications after optimization.