Research On Performance And Storage Structure Of Impedance Memory Based On Standard Logic

Conventional nonvolatile memories, flagged with Flash memory, have achieved great success. However, Flash memory is expected to come across physical limitation with scaling down. In order to develop a new generation nonvolatile memory, a number of new technologies have been extensively studied. Resistive Random Access Memory (RRAM) is considered as one of the most promising candidates because of its simple structure, high scalability, fast speed, low power consumption, good compatibility with standard logic process and low cost. Whereas the shortcoming of RRAM, such as widespread switching parameters distribution, high-density application, poor retention and low operating yield, RRAM needs to be improved.Wide range of materials and structures have been found to exhibit resistive switching behaviors, including perovskite structure ternary oxide, binary metal oxide and organic materials. Besides the performance of speed and power consumption, the compatibility with CMOS process and cost of integration are also important to determine which kinds of materials to be used. Usually, Tantalum is used as barrier, so TaOx-based RRAM will not bring any polluting elements into RRAM process, with superiority of low cost and compatibility. As previously reported, TaOx-based RRAM performance is not ideal, with low HRS/LRS, high power consumption. In this regard, this paper proposes a new bilayer structure of Ta2O5/TaOx, which may increases switching window, lower power consumption, and control set/reset position for making switching parameters centralized. In addition,3D integration and planar integration process of Ta2O5/TaOx respectively for high-density and embedded application are proposed.Based on128kbit AlOx/WOy RRAM chip integrated on SMIC0.18um, array results of resistive switching are proved, such as distribution of HRS/LRS and set/reset voltage. This paper analyzes the roles that two thin films act in switching process and device switching mechanism. By comparing different process conditions and operating algorithm, data retention of AlOx/WOy bilayer structure has been studied. Retention fail decreases after deoxidized gas annealing, while, retention fail increases with strengthening operating algorithm.Besides, this paper presents influences of different Forming polarity on AlOx/WOy structure performance and gives energy band interpretation based on film composition. AlOx layer with gradient oxygen vacancies is sensitive to Forming polarity. When forced by positive forming voltage, the device shows good switching characteristic, endurance and reading disturbance; while forced by negative forming voltage, the device shows low operating yield and breakdown, with oxygen vacancies removing away from AlOX/Al2O3interface.