Research On Mechanism Of Switching And Endurance Failure In Oxide-based Resistive Switching Memory

Recently, the popularization of high-tech products such as smart phones, tablet PCs and smart appliances in people’s lives, makes the role of the Non-Volatile Memory (NVM) more and more important. However, the mainstream NVM Flash based on floating gate structure has encountered a serious technical bottlenecks to further scaling down. Therefore, researchers have started study on new generation of memory technology. Because of high speed, low power consumption, and good compatibility with traditional CMOS processes, Resistive Random Access Memory (RRAM) is considered as one of the strongest competition of the next generation NVM. Nevertheless, there is a lot of problems, such as, unclear resistive switching mechanism, poor uniformity of electrical parameters.In this thesis, we choose Oxide-based (HfO2) RRAM with simple structure and stable performance to carry out research work on resistive switching mechanism and endurance failure.Firstly, we fabricated the oxide-based RRAM with good performance by adjusting the process parameters and the thickness of resistive layer and oxygen storage layer of device. The structure is W/Ti/HfO2/Pt.Test and analyze the electronic performance during SET, RESET and Cycle Test using semiconductor parameter analyzer. By statistically analyzing the VSET and ISET of1900cycle and inferring the physical nature of the programming process, we drew a conclusion that the most direct factor in switching process is electric field other than current. This makes the foundation for resistive switching mechanism.Propose a mechanism model of resistive switching controlled by electric field based on the oxygen ions hopping. Analyze the migration of oxygen ions controlled by electric field, and derive the relation of RESET time and the applied electric field using the proposed model. In addition, we calculate the temperature effect on the relation between RESET time and electric field.Design experiments about the RESET time test using the pulse generator and the oscilloscope, obtaining different RESET time under different electric field, and compare the experimental values and theoretical values, which has a good agreement with each other.Analyze the endurance failure of device according to the electric performance of the cycle operation. Then propose two reasons of the failure:the loss of oxygen ions and the negative breakdown of the oxide layer. And design comparative experiments to study the influence of annealing on the negative breakdown voltage of RRAM, achieving a method to improve endurance.