The Influence Of Regulating Conductive Filaments On Parameter Uniformity In Atomic Switches

With the explosive growth of digital data in the era of the Internet of Things,fast and scalable memory technologies are being researched for data storage and data-driven computation.Among the emerging memories,resistive switching（RS）based resistance random access memories（RRAMs）are attracting lots of attention due to their simple metal–insulator–metal structures,low power consumption,good cyclic endurance,long retention characteristics,low fabrication cost,ultrafast switching,and CMOS compatibility.At present,although people of different material RRAM extensively studied to explain the observed phenomenon of resistance change,but the resistance switching mechanism of RRAM has been controversial,such as conductive filament conductive filaments（CFs）in its formation,microstructure,composition and dissolution and other key issues.At the same time,although RRAM has many advantages,there are many problems that must be overcome before commercialization can be realized,including high formation voltage,poor switching parameter uniformity.Ion-RRAM based on its different working mechanism,which can be divided into electrochemical metallization mechanism（ECM）/atomic switches,valence change mechanism（VCM）,and thermochemical mechanism（TCM）.In this paper,aiming at the problem of poor uniformity of switching parameters,the action mechanism affecting the uniformity of RRAM device parameters based on atomic switch base is studied from three aspects:formation position,dissolution of position and degree,and the number of CFs,the main work carried out and the main results obtained are:（1）Control the position of CFs:The ion concentration of anode metal and ion diffusion coefficient in the solid electrolyte determine the switching voltage of the device and the diameter of the CFs formed.We adopted the method of high-energy heavy ion irradiation and used Ta⁵⁺irradiation Cu/Ta₂O₅/Pt device with energy of 125MeV to regulate the density of RS layer and create defects or pores,reduce the barrier height of redox reaction and realize the rapid migration of a large number of ions.Continuous defects or holes optimization across the RS layer generated after Ta⁵⁺bombardment can provide preferential growth locations for CFs and increase the diameter of CF s,which reduces the switching voltage and improves data retention.（2）Control the dissolution of CFs:The transition of RRAM between high resistance state（HRS）and low resistance state（LRS）is controlled by CFs formation/dissolution.The dissolution of CFs in a single-layer device is very random,resulting in poor uniformity of RS parameters and unstable HRS.The SiO₂/Ta₂O₅structure controls the dissolution of CFs in an ultra-thin Ta₂O₅ layer,which reduces the randomness of CFs dissolution during cycling.Ag/SiO₂/Ta₂O₅/Pt devices with high consistency,stability and low voltage operation were prepared.（3）Control the number of CFs:Inorganic materials prepared by physical vapor deposition are often amorphous,and the CFs formed in them are very much and difficult to control.And solid polymer electrolyte（SPE）with molecular structure design,the advantages of abundant material system,easy to limit the number of CFs.PVP is amorphous with many ion transport channels,the PVP-based RRAM have poor cyclic endurance（less than 50 cycles）and poor uniformity.PVA is hypocrystalline with few ion transport channels,and PVA-based RRAM can hardly perform RS behavior.This experiment summarizes the factors that affect the reliability of RRAM by studying the morphology and number of CFs in planar devices.Combining the two characteristics of materials,the number of CFs in the functional layer is controlled.While obtaining highly uniform Ag/PVA/PVP/Pt devices,the effect of Joule heat on the stability of SPE-based devices was studied.