Measurement Of The Charge Neutrality Level At The Interface Of Hafnium Oxide Based Resistive Random Access Memory

Resistive random access memory(RRAM)has the advantages of large reserves,small device area,low power consumption,and compatibility with traditional processes.It is expected to replace Flash memory.Research on RRAM is to solve the critical technical bottleneck caused by the charge leakage problem of Flash memory due to the reduced feature size.A variety of materials can be selected for the RRAM functional layer.Among them,the hafnium oxide(HfO₂)with wide band gap and high dielectric constant are widely used in RRAM research.The contact interface between the metal electrode and the functional layer of the hafnium oxide-based resistive random access memory(HfO₂-RRAM)is mainly the schottky barrier modulation.The barrier height of the contact interface is related to the interface state,and the interface state depends on the oxygen vacancy concentration of the contact interface.The charge neutrality level is a parameter that characterizes the concentration of oxygen vacancies,which is helpful for the analysis of the interface state density and the device performance.However,there is currently no systematic study on the charge neutrality level at the interface.In this work,we studied the specific relationship between the charge neutrality level and the interface barrier height,put forward the feasible measurement technology method of the charge neutrality level,and conducted the experimental test and simulation verification.Firstly,a model of the contact interface between metal and hafnium oxide(HfO_x)thin films is established on the basis of the metal-semiconductor contact theory.The model is used to analyze the formation of the potential barrier at the interface,to clarify the current transport process under the action of the schottky barrier,and to introduce the experimental and test methods of the barrier height.Then,using the model to analyze the relationship between the charge neutrality level and the barrier height at the interface.This paper proposes a theoretical method to test the charge neutrality level using the relationship between the work function and the barrier height.Finally,the electrical characteristics of the device with different metal electrodes(Ti,Cu,Ti N,Ni and Pt)deposited on the HfO_xfilm prepared by the reactive magnetron sputtering are tested by a semiconductor parameter analyser.And the MATLAB is used to establish the equivalent resistance model of RRAM based on different resistance states.By comparing the calculation results of the charge neutrality level at the interface of the HfO_xfilm with different argon to oxygen ratios,the relationship between the charge neutrality level and the device performance is explored.The comparison of simulation and test results proves the validity of the model.Combining the experimental data of different electrode devices to modify the model,and the barrier heights of simulations under different electrodes are obtained.The calculation result of charge neutrality level in the simulation model is 0.577e V,which is close to the test result of 0.587 eV.