Resistive Switching Mechanisms For Nonvolatile Resistive Random Access Memory Based On SiO_x Thin Film

With the development of the microelectronic technology, the disadvantages of the existing memory technology have become prominent increasingly. The random access memories such as SRAM and DRAM are volatile, and the nonvolatile memory technology,such as the Flash technology based traditional floating gate, has met serious technical difficulties. And, the most important issue is the scalability has continued to shrink. Apart from decreasing the process geometries, some new physical phenomena have been introduced to the storage technology with the increasing demand of high-capacity, low-cost memory technology. Nonvolatile resistive switching memory (RRAM) is a potential candidate for replacing Flash and DRAM in future generation nodes considering its high scalability, integration density, high speed, low-cost, simple structure and compatibility with existing CMOS process. Thus understanding the resistive switching mechanism is essential for predicting and controlling the scaling and reliability performances of the RRAM.The resistive property of Si-rich SiOx RRAM is researched in this thesis. First, the DC Current-Voltage characteristics of RRAM device are measured, the basic electrical characteristics of RRAM device and the resistance switching mechanism have been analyzed and summarized by changing the measurement conditions. The resistance switching mechanism, which is boiled down to oxygen vacancy dominated conductive filament mechanism, attribute to the change of oxygen vacancy concentration due to the oxidation-reduction reaction in switching layer. Also, the on-state and off-state conduction mechanism of the device are analyzed by fitting the I-V curve, it is found that the Ohmic conduction mechanism is for on-state, and Schottky emission for off-state. Finally, the reliability of the device is analyzed, including stability, endurance, retention characteristics, etc. The TiN/SiOx/Pt structure resistive devices show good stability and fatigue properties. Furthermore, the main factors affect the device characteristics were analyzed, including the device area, the compliance current, Vstop and other factors.The experimental results show that TiN/SiOx/Pt structure resistive switching device has good scalability, thus the multilevel storage can be realized by setting different compliance current.While we can analyze the microscopic physical mechanism based on the experimental data qualitatively, but the microscopic filaments growth and rupture processes, the filament morphology, and the location where filament rupture taken place, also the factors accelerate the migration of oxygen vacancies during the reset process need to be studied. This paper also provides a temperature and electric field-driven ion migration model of resistive switching in bipolar metal-oxide RRAMs. which accounts for set-reset characteristics, correctly describing the set and reset transitions and allowing scaling projections for TiN/SiOx/Pt RRAM. Also, the location where filament rupture taken place was confirmed, a place close to the top electrode, and it is found that the electric field and temperature have played an important role in ion migration according to the simulation. Finally, the resistance switching model, oxygen vacancy dominated conductive filament mechanism, proposed before was confirmed combined with the experiment results and the simulation.