Preparation And Performance Optimization Of NbO_x Based Selector

With the continuous development of cloud computing,artificial intelligence and other science and technology,application data showed explosive growth,and the demand for capacity of information storage has been increasing during the past days.In order to overcome the bottleneck of ultra-high density integration technology caused by the physical limit of traditional flash memory,new non-volatile memory such as resistive random access memory(RRAM)has been widely studied.As the preferred solution of high density storage,its memory cell was stacked in a crossbar structure to achieve the highest integration density in theory.However,this structure had serious crosstalk problem,which would affect device performance and cause information misreading.Therefore,in order to solve this problem,the one-selector one-memory(1S-1R)structure has been proposed.By taking advantage of the threshold switching characteristics of the selector,it served as a rectifier device,effectively inhibiting the leakage current and realizing the integration of large-scale arrays.Currently,a new selector based on insulate-metal transition(IMT)effect includes NbO_x,VO_x,etc.materials,which have been widely studied due to their simple structure and easy preparation.This paper mainly focused on the preparation and performance optimization of NbO_x selector.By preparing and testing NbO_x selector,the threshold switching performance of devices was studied.The performance of the device was improved by optimizing the structure and annealing process.And the main research work was summarized as follows:1.The Ti/NbO_x/Pt selectors were prepared by magnetron sputtering and were characterized.It was found that the NbO_x film in the device was amorphous.Then,the threshold switching performance of the device was studied.As the compliance current(CC)of the device increases,the OFF state resistance remains constant,resulting in the increase of the selectivity.The device had excellent stability below 800?A CC.In addition,the threshold switching performance of the device was analyzed by studying the thickness of NbO_x film,and the physical mechanism was explained by constructing a model.2.On the basis of Ti/NbO_x/Pt selector,a thin Ti film was inserted between the bottom electrode Pt and NbO_x film to prepare Ti/NbO_x/Ti/Pt selector device.It was found that the Ti/NbO_x/Ti/Pt device could work stably under ultra-large CC by testing its threshold switching performance.Compared with Ti/NbO_x/Pt devices,Ti interlayer device has higher selectivity,better consistency and stability.The reason why it could working under ultra-large CC was explained by establishing a model.Then,the performance of the device was tested after forming process,and the device still exhibited well performance.3.In order to further optimize the threshold switching performance of Ti/NbO_x/Ti/Pt devices,metal oxide films(Ga O_x,Mg O_x and Zr O_x)with different thickness were inserted between Ti and NbO_x films and their threshold switching performances were studied.The results showed that the Ga O_x intercalated device had excellent stability when the CC range from 1 to 5 m A,the Mg O_x intercalated device had excellent stability when the CC range from5 to 30 m A,and the performance of Zr O_xintercalated device was poor.By introducing appropriate metal oxide intercalation layer,the minimum working current of the device could be effectively reduced and the stability of the device could be improved.Therefore,Ti/NbO_x/Ti/Pt devices could be modified with different metal oxides to meet the actual application requirements.4.The annealing process was used to optimize the threshold switching performance of Ti/NbO_x/Pt devices.NbO₂ and Nb₂O₅ diffraction peaks appear in the XRD patterns of The NbO_x films after the annealing process,and the content of Nb⁴⁺in the films was increased.The electrical test results showed the improvement of the consistency of voltage and OFF state resistance of the annealed device.Besides,the annealed device was found to be able to resist overshoot current by pulse test without CC protection.The annealing process could optimize the threshold switching performance of Ti/NbO_x/Pt devices.Then a model was established to explain the improvement of threshold switching performance of annealed device.