Research On Regulation Of Nitrogen-accommodation Region In SiN_x-based Resistive Switching Devices

Recently,resistive random access memory?RRAM?has been widely investigated as a leading candidate for next generation nonvolatile memory?NVM?applications.Among them,SiN_x-based RRAM devices have become the hot research topic due to their advantages of ultra-low power,fast operation,high density,and COMS compatibility.However,its research is still in the stage of mechanism analysis and performance improvement and the formation and fracture process of conductive filaments of devices have not been clearly determined.The nitrogen ion reservoir model is based on the migration of nitrogen ions and Si dangling bonds?Si-DBs?,which effectively explains the conductive process of the device.From the perspective of metal electrodes,this paper studies the influence of metal electrodes on the nitrogen ion reservoir,and further explores the conduction mechanism of SiN_xRRAM devices.The specific research contents are as follows:1.Effect of metal top electrode types on nitrogen ion reservoir.Conductive model of nitrogen ion reservoir was constructed by analyzing the resistive switching properties and conductive mechanisms of three?Ta/SiN_x/Pt,Mo/SiN_x/Pt and Ag/SiN_x/Pt?devices.Ta and Ag devices show stable and bipolar resistive switching characteristics.In contrast,Mo device displays unstable RS behavior.The conductive channel is composed of Si-DBs in Ta and Mo devices,while that is composed of metal filaments in Ag device.The nitrogen ion reservoir model is only suitable for devices based on nitrogen ion conductivity.Ta is more active than Mo and has a higher nitrogen accommodation ability,So Ta electrode has a larger nitrogen ion reservoir which lead to the device behave good RS characteristic.In contrast,the unstable RS of the Mo/SiN_x/Pt device is ascribed to the low nitrogen-accommodation ability of the Mo electrode.Therefore,the size of the nitrogen ion reservoir of the metal electrode can affect the RS properties of the device.By using more active electrode can improve the size of nitrogen ion reservoir and get better performance of the device.2.Effect of thickness of metal electrode on nitrogen ion reservoir.We fabricated six devices with Ta electrodes of different thickness values?8 nm,10nm,15 nm,30nm,40 nm,and 50nm?in a Ta/SiN_x/Pt structure and then systematically studied their performance.The high electrode thickness devices show stable and self-compliant bipolar RS characteristics,while low electrode thickness devices display unstable RS behavior.XRD and AFM analysis showed that the crystal structure and roughness of the device electrode did not change significantly due to the thickness change.Therefore,this difference is attributed to the change of the nitrogen ion reservoir.When the thickness of the top electrode of the device is very thin,the size of the nitrogen ion reservoir is limited,and the nitrogen ions are in a state of being crowded and unstable in the reservoir,which leads to more unstable channel formation and fracture process,then the set voltage(V_set)is very large and displays a random behavior.It can be concluded from the experimental results that adjusting the thickness of the metal electrode can change the size of the nitrogen ion reservoir.