Fabrication of a Cu‐Cone‐Shaped Cation Source Inserted Conductive Bridge Random Access Memory and Its Improved Switching Reliability

Conductive bridge random access memory (CBRAM) has been regarded as a promising candidate for the next‐generation nonvolatile memory technology. Even with the great performance of CBRAM, the global generation and overinjection of cations after much repetitive switching cannot be prevented. The overinjection of cations into an electrolyte layer causes high‐resistance‐state resistance (RHRS) degradation, on/off ratio reduction, and eventual switching failure. It also degrades the switching uniformity. In this work, a Cu‐cone‐structure‐embedded TiN/TiO2/Cu cone/TiN device is fabricated to alleviate the problems of Cu‐based CBRAM, mentioned above. The fabrication method of the device, which is useful for laboratory scale experiment, is developed, and its superior switching performance and reliability compared with the conventional planar device. The insertion of the Cu cone structure allows the placement of only a limited amount of cation source in each cell, and the embedded conical structure also concentrates the applied electric field, which enables filament growth control. Furthermore, the concentrated field localizes the resistive switching on the tip area of the cone structure, which makes the effective switching area about tens of nanometers even for the much larger area of the entire electrode (several µm2). This work proposes Cu‐cone‐embedded conductive bridge random access memory (CBRAM), whose stack is TiN/TiO2/Cu cone/TiN. The applied electric field is concentrated on the tip of the conical structure, which induces single‐filament formation and enhances the switching reliability. Moreover, the effective switching area is reduced to tens of nanometers due to the locally concentrated field, and a scalability effect is achieved.