Studies On The SiN_x-based RRAM With Multilayer Structure

With the rapid development of big data,cloud computing,internet of things(Io T)and artificial intelligence(AI),there is an increasing market demand for Non-Volatile Memory.However,traditional semiconductor memory approaches their physical limitations as a result of the down-scaling of feature size of the device as well as Moore's law,which is about to fail completely.Therefore,it has been urgent to look for new memories with more excellent performance,higher speed,higher density,better reliability and lower power.Resistance random access memory(RRAM)has attracted great attention from both academic and industrial fields due to its simple structure,fast switching speed,high density,low cost,good retention,low power consumption as well as its compatibility with conventional Si complementary metal-oxide-semiconductor processing.Among those resistive switching materials,Si N_x-based RRAM is more attractive because of its excellent characteristics,including lower voltage,higher switching speed,robust endurance,and good retention.Therefore,this thesis mainly focuses on building multilayer structure Si N_x-based RRAM device to improve its RS performance.The main research contents and results are as follows:1.The essay concentrates on analyzing the Ta/Si N_x/Al O_x/Pt RRAM devices from DC switching,resistive switching mechanism,and conduction mechanism.The Al O_xfilms were deposited by plasma enhanced atomic layer deposition(PEALD),we found that Ta/Si N_x/Al O_x/Pt device exhibited nonlinear I-V characteristics in the LRS.Then the role of the inserted Al O_xlayers in the RS and conduction mechanism of the Ta/Si N_x/Al O_x/Pt device is discussed in details.The nonlinear characteristics are attributed to the Schottky barrier formed at the metal and semiconductor interface.The conduction mechanism is governed by the serially connected conducting paths made up of Si dangling bonds and tunneling barrier formed by the Al O_xinterface layer.In addition,the devices also show other excellent RS performances,such as good endurance(>10²),stable memory window,gradual reset characteristics.We also study the effect of the thickness of the Si N_xlayer on device performance.We found the I_offvalues for different thicknesses were different due to its surface roughness and leakage current.2.In this paper,in order to further improve the reliability of the device,the characteristic of Ta/Si N_x/Al N/Pt RRAM devices are investigated.The devices show stable bipolar resistive switching behavior.The conduction mechanism is dominated by ohmic conduction in the LRS,the Schottky emission and trap-controlled space charge limited conduction are responsible in the HRS.The resistive switching behavior of Ta/Si N_x/Al N/Pt RRAM devices is attributed to the formation and rupture of the conduction path,which is composed of nitrogen vacancies.Compared with the single-layer cell,switching current of double-layer cell is as low as 1m A.It's known that the self-heating effect and high local temperature would result in uncontrolled filament shapes with current overshoot and reliability issues.However,inserting the Al N layer with high thermal conductivity thus improving conductive filament controllability by suppressing local heating effect.In addition,the devices also show promising switching performance with robust endurance(>10³)and good retention.We also study the effect of the thickness of the Al N layer on device performance.