Study On The Application Of BiFeO₃ Film In Resistive Random Access Memory

With the continuous development of big data era,cloud storage,industrial 4.0,Internet of Things technology and mobile Internet,semiconductor memory is one of the important carriers of information technology.Currently,the widely used Flash memory technology faces the bottleneck of unable to effectively store charge in the process of miniaturization,and various circles have begun to explore and develop new storage material storage technology.The rapid development of resistive random access memory(RRAM)is one of the most popular research hotspots at present.The RRAM device of Bismuth iron oxide(BiFeO₃)film as a resistive switching layer was firstly investigated.It has been found that Pt/BiFeO₃/TiN devices have typical bipolar resistive properties with a 10³memory window.By analyzing the current-voltage curves of devices with different sizes,the result shows that the Pt/BiFeO₃/TiN device belongs to the conductive filament mechanism dominated by oxygen vacancies.According to the current mechanism fitting analysis,it is found that the current mechanism is Ohmic mechanism in the low resistance state,and the Schottky emission mechanism in the high resistance state.By analyzing the results of the current mechanism,we successfully clarify the switching mechanism of the BiFeO₃-based RRAM.Furthermore,we focused on the RRAM device of BiFeO₃/HfO₂bilayer structure.The results have shown that Pt/BiFeO₃/HfO₂/TiN and Pt/HfO₂/TiN devices have stable bipolar resistive switching properties.The memory window of Pt/HfO₂/TiN is approximately 10².With inserting an ultra-thin BiFeO₃film(2 nm),and the memory window of Pt/BiFeO₃/HfO₂/TiN device is increased to 10⁴.Multilevel storage capability is demonstrated by varying the stop voltage(V_stop)in the RESET process.Moreover,remarkable pulse endurance of 10⁸cycles is achieved in HfO₂-based RRAM by inserting an ultra-thin BiFeO₃layer.Based on I-V curve fitting and temperature dependent current measurements,both devices are demonstrated as Schottky conduction mechanism in high resistance state,and low resistance state is dominated by Ohmic mechanism.X-ray photoelectron spectroscopy(XPS)and electrical properties indicate that the ultra-thin BiFeO₃layer can store oxygen,which will increase the Schottky distance of the conductive filament and the Schottky barrier between the conductive filament and the TiN electrode.Thus,the memory window of the device is enlarged.The inserting ultra-thin BiFeO₃layer plays a role of increasing memory window,improving pulse endurance,and acquiring multilevel storage capability in the device,which provides materials and structural support for high performance,high density memory device arrays.Lastly,we also studied the RRAM device with Hf doped ITO film as the electrode material.Compared with TiN/ZrO₂/ITO device,the TiN/ZrO₂/Hf:ITO device has self-compliance current property,and the power consumption of the device is greatly reduced.After Hf doping,the memory window is increased from 10 to 100,and operating power is reduced to 800 n W.Through material characterization,electrical performance testing and I-V fitting,we have discovered that the combination of hafnium elements and oxygen ions to form a barrier layer is the main reason for the reduced power consumption of the device.In summary,this thesis focuses on the performance of RRAM device with BiFeO₃film that acts as resistive switching layer and inserting layer.Experimentally,we achieve the memory cell with large memory window,remarkable pulse endurance cycles and high uniformity.Moreover,concerning with BiFeO₃film,we establish physical models and make an in-depth explanation on remarkable electrical performance and resistive switching mechanism.The research of BiFeO₃film in RRAM device has vital scientific significance and application prospect.