Study On Nitride-based Resistive Random Access Memory

Nonvolatile memory(NVM)will play a very important role in the next-generation digital technologies,including the Internet of Things(Io T).The resistive random access memory has been favored by a lot of researchers because of its simple structure,high compatibility with traditional CMOS process,fast operation speed,high integration,low power consumption and multi-level storage.In this paper,Si Nx is chosen to be the resistance switching layer,and an in-depth research about it is carried out.The specific contents are as follows:1.Optimize the process to fabricate Si Nx-based RRAM devices.The Si Nx films with different stoichiometric ratios were prepared by controlling the ratio of Si H4 and NH3 in PECVD process.Three different metals-wolfram,magnesium and copper were selected to be the materials for the top electrode of the device,and the effects of different top electrodes on the device performance will be compared.2.The resistive change phenomenon of W / Si Nx / Pt devices was studied.First,apply appropriate test conditions to each device.When Si H4:NH3 = 1:7 / 1:1 / 2:1,the set voltage of these devices is 1.6V,1.1V and 1.4V,the reset voltage is-2.5V,-1.9V and-2V,the reset current is-8m A,-0.67 m A and-3.7m A,the storage windows are about 70,60 and 20,and the self-compliance can be achieved.When Si H4:NH3 = 1:7,the device is initially in the insulation state,a forming voltage is needed to show the normal I-V characteristics,and the device has a good electrical parameters consistency.When Si H4:NH3 = 1:1 / 2:1,the devices are initially in the conduction state,and the electrical parameters are more dispersed.It is shown that the resistive switching mechanism of the W / Si Nx / Pt device is based on the formation and fracture of the conductive filament formed by the nitrogen vacancies,and the conductive mechanism is the space charge limiting current.Devices grown by different ratios of Si H4 to NH3 were placed in the same test conditions to analyze the effect of the stoichiometric ratio of the element in the resistive material on the performance of the W / Si Nx / Pt device.When Si H4:NH3 = 1:7,the switching voltage of the device is larger than that of the dvices when Si H4:NH3 = 1:1 / 2:1,and the switching voltage of the devices is almost the same when Si H4:NH3 = 1:1 and Si H4:NH3 = 2:1.With the increase of the ratio of Si H4 to NH3,the resistance of the device decreases.3.In this paper,the resistance characteristics of Mg / Si Nx / Pt and Cu / Si Nx / Pt devices are researched in-depth.The resistance switching of the device is mainly based on the formation and fracture of the metal conductive filament.In the low resistance state,the device follows the ohmic's conduction mechanism.When the device is in its high resistance state,both the ohmic's conduction mechanism and space charge limited current conduction mechanism work inside the device.The effects of the reset cutoff voltage,compliance current and the resistive layer grown under different conditions on the resistance switching parameters of the device were investigated.With the ratio of Si H4 to NH3 increases,the forming voltage increases,the set voltage decreases,the reset voltage remains unchanged,the decreases,the resistance in low resistance state is basically unchanged,and the resistance in high resistance state decreases.The influence of two different active metals-magnesium and copper as the top electrode of the ~ / Si Nx / Pt device is also demonstrated in this paper.The experimental results and theoretical analysis showed that the device with copper as the top electrode has smaller forming voltage as well as greater conversion voltage.