Simulation Of Si Doping Behavior In Ta₂O₅ Based Resistive Random Access Memory

With the reduction of feature size,Flash memory has entered the post-Moore era,and its development is more and more difficult.At the same time,the shortcoming is gradually emerging.Resistive random access memory（RRAM）has many advantages such as high storage density,high read speed and write speed,low power consumption,simple structure and good compatibility with CMOS,which is promising to become the next generation of new nonvolatile memory.Tantalum pentoxide（Ta₂O₅）stands out from many resistive materials due to its excellent electrical properties,but Ta₂O₅-based RRAM（Ta₂O₅-RRAM）also faces the problems of high SET voltage and poor uniformity of resistance switching.According to the relevant information,it is known that the cause of the above problems is the high formation energy of oxygen vacancy,the high randomness of oxygen vacancy generation,and the poor uniformity of the conductive filament composed of oxygen vacancies.To solve the above problems,doping process is considered as a simple and effective solution.Based on the first principles,the influence of Si doping on the electrical characteristics of Ta₂O₅was simulated by VASP software,and then the influence of Si doping on the performance of Ta₂O₅-RRAM device was predicted.The main research contents are as follows:1.the influence of Si doping on the spatial structure of Ta₂O₅is analyzed.The generation of oxygen vacancy cannot cause changes in the coordination number of oxygen atoms in undoped Ta₂O₅.By contrast,the generation of 3f-V_Ocauses the coordination number of oxygen atoms to change and forms a local structure like SiO₂in Si-doped Ta₂O₅,which affects its electronic structure.2.The effect of Si doping on oxygen vacancy formation energy and its micro mechanism are investigated.By comparing the formation energy of oxygen vacancy in undoped and Si-doped Ta₂O₅,we know that Si doping can effectively reduce the formation energy of oxygen vacancy.The reason why Si doping reduces the formation energy of oxygen vacancies is explained from atomic radius,number of valence electrons,and Coulomb force.3.The effect of Si doping on the density of states（DOS）is studied.The DOS mainly reflects the effect of defects on the band gap energy levels.For a single defect,Si doping cannot promote defect energy levels generate in the band gap,but slightly reduces the band gap width.We supplement the study of the electronic characteristics of the composited defect,and the results show that the single oxygen vacancy and the compound oxygen vacancy share the task of current transport in the low resistance state of Ta₂O₅-RRAM.4.It is verified that there is an internal effect between Si doping and oxygen vacancy.The simulation results show that there is an interaction effect between Si doping and oxygen vacancies,which makes oxygen vacancies tend to form around Si doping,thereby suppressing the randomness of oxygen vacancy generation and improve the uniformity of resistance switching.The work results show that Si doping can reduce the formation energy of oxygen vacancies,thereby reducing the SET voltage of the device.At the same time,it can also reduce the random generation of oxygen vacancies to improve the uniformity of the device resistance switching.This work can provide a theoretical reference for improving the reliability of Ta₂O₅-RRAM and related processing methods.