Research On The Performance Of Selector Based On TiO₂ Interface

Metal oxide semiconductor(MOS)transistor-based memories,such as Resistive Random Access Memory(RRAM),Ferromagnetic Random Access Memory(FRAM),and NAND flash memory,have been playing an important role in the development of the semiconductor industry for decades.Among them,the development of resistive random access memory is more concerned by experts and scholars because of its simple structure,low power consumption and high integration.The most common structure in a single memory cell of a RRAM array is a "sandwich" structure,and the arrangement of the array is more realistic and feasible in order to achieve higher integration and achieve multiple times of storage density.The misunderstanding of the memory cell caused by the excessive crosstalk current is the biggest problem faced by the cross array structure.Various methods have been studied in the industry to suppress leakage current.The selectors have emerged under various conditions.One of the parameters affecting the performance of the selector is the nonlinearity in the IV curve of the selector This paper aims to study the generation and improvement of the nonlinearity of the selector from the perspective of microelectronics.In this article,first briefly outline the role of the selector in reducing the leakage current of all unselected cells in the cross-point memory array.Then classify the common structures of the selectors from the most common Si-based NPN and NIPIN,mixed-ionic-electronic-conduction hybrid selectors,metal-insulator-metal(MIM)selectors,a structure having a metal-semiconductor-metal(MSM)structure doped with Si and a metal-insulator-semiconductor(MIS).Review of current research on various selector principles,including traditional silicon-based semiconductor devices,oxide diodes,threshold switching,and oxide tunneling,mixed ionic electronic conduction.The mechanism of various types of de-vices summarized at present is analyzed.Finally,some key parameters affecting the performance of the selector are summarized.Based on first principles,this paper discusses the working principle of the gate and optimizes its performance from the perspective of theoretical calculation.It is found that the introduction of the interface is improved relative to the nonlinearity of the bulk,and the change of the electrode also affects the nonlinearity of the device,and the electronic relationship between the interface structure and the rectification of the device.Firstly,the rationality of the model and the stability of the constructed interface are discussed.The influence of the Graphene electrode on the TiO2 layer is determined by LDOS to illustrate the rationality of the three-layer structure,and then the electronic properties between the interfaces are determined.A chemical bond that maintains a stable interface.The applied voltage is found to increase the model nonlinearity and the threshold voltage after the electrode is increased.The applied electric field simulation analyzes the potential and the atomic population analysis from the start to the conduction to find the interface barrier and the existence of the barrier.The non-linear improvement caused by the formation of the conductive filaments such that the threshold voltage is shifted back and the current is reduced is delayed.It is analyzed that the selector nonlinearity of the Graphene/TiO2/Graphene structure is derived from the interface barrier.On the basis of improving the nonlinearity of the existence of the interface barrier of the electrode,the influence of the change of the electrode on the nonlinearity of the selector is discussed and the reason for the difference in nonlinearity is discussed from the perspective of microelectronics.The IV characteristics of Pt/TiO2/Pt,Au/TiO2/Au and Ti/TiO2/Ti devices were compared and analyzed for two models with large nonlinear differences.The LDOS shows that the Ti electrode has the greatest influence on the TiO2 resistive layer,which changes from semiconductor to metal.The contact between the display interfaces in the device LDOS as the electrode of the Pt is a Schottky contact.Differential charge density map analysis shows the transfer of electrons into the TiO2 resistive layer in Pt.The potential perpendicular to the interface also clearly shows that there is a barrier at the interface of the Pt/TiO2/Pt structure,and there is no barrier at the interface of the Ti/TiO2/Ti structure.And in the potential,it can be seen that there is a significant potential difference between the Pt electrode and the TiO2 resistive layer,and the potential difference between the Ti electrode and the TiO2 resistive layer is not obvious.Therefore,the analysis results in the contact potential difference between the upper and lower surfaces to form an interface barrier,which reduces the leakage current of the device and increases the rectifying ability of the device.In summary,with respect to the TiO2 bulk,increasing the Graphene electrode increases the nonlinearity and the threshold voltage shifts back.However,different metal electrodes also affect the nonlinearity of the device.The magnitude of the nonlinearity is closely related to the contact potential difference between the metal electrode and the resistive layer.The conclusions of this paper provide a certain degree of theoretical guidance for the performance improvement of TiO2-based selectors.