Research On High Dielectric Compound Oxide In Charge Trap Memory

As the main carrier of information,memory is an important pillar supporting the continuous development of all walks of life in modern society.Therefore,memory with high storage capacity has always been a research hotspot.The memory of SONOS(Silicon-Oxide-Nitride-Oxide-Silicon)type structure uses Si₃N₄ to replace the polysilicon floating gate layer,which effectively improves the leakage current problem of the traditional floating gate memory and enhances the reliability of the device,which has received extensive attention.However,as the charge trapping layer of the device,Si₃N₄ has a shallow trap energy level,which is not conducive to the trapping of charges,and the problem of charge leakage caused by the decrease of the size of the device is inevitable.Therefore,it is necessary to find an alternative memory with better performance.important issues.The application of High-k materials to the charge trapping memory structure,instead of the traditional SiO₂ and Si₃N₄,provides an extremely effective solution for solving the leakage current problem caused by the size reduction and improving the data retention performance of the device,and has a good application prospect.Therefore,thesis adopts the high-k material HfO₂-ZrO₂ as the charge trapping layer of the device.The charge storage capability of the device under different process conditions is explored,and its storage mechanism is attempted to be analyzed.The content is summarized as follows:1.Based on the traditional SONOS structure,according to the properties of the high-k material and the characteristics of each functional layer,the high-k material Al₂O₃ is selected as the tunneling layer and barrier layer of the device.Through experimental verification,single-layer HZO is selected as the device.charge trapping layer.The charge-trapping memory of p-Si/Al₂O₃/HZO/Al₂O₃/Pt structure was fabricated by PLD system.HZO films were prepared at different growth temperatures.Through AFM test,it was found that the HZO films grown at 300°C had the lowest roughness and the highest surface flatness,so 300°C was used as the growth temperature of the films.The cross section of the sample was tested by SEM,the thickness of each dielectric layer was successfully calibrated,and its growth rate was determined.2.The electrical performance of the prepared HZO charge trapping memory was tested to analyze its storage characteristics.The results show that the HZO memory has excellent storage performance and good data retention ability.When the applied voltage is±12V,the maximum storage window is obtained,which is 8.9V,and the charge storage density is about 1.42×10¹³cm^-2.Several groups of samples were prepared,The influence of different annealing processes on the device storage window was analyzed The results showed that the device annealed at 800°C had the best storage performance,because when the annealing temperature was too high,the interface The deterioration of internal diffusion will seriously affect the storage performance of the device;while the samples annealed in N₂ andO₂ atmospheres have a storage window of 1.4V and 6.9V at a scan voltage of±10V,respectively,and the corresponding charge storage densities are1.6×10¹²cm^-2,1.10×10¹³cm^-2.3.By XRD and XPS test of HZO film,the change of its structure and composition was analyzed.By drawing the energy band map of the device,the storage mechanism of the HZO charge trapping memory is attempted to be analyzed.The research shows that:in theO₂ atmosphere,after annealing at 800?for 90s,a crystallization peak appears.According to the analysis,this peak corresponds to the(111)crystal plane of tetragonal ZrO₂,which is different from the normal temperature Compared with the monoclinic phase formed by pressing,the tetragonal phase of ZrO₂ has a higher dielectric constant and smaller grain size in the crystalline film,which is beneficial for the device to obtain a larger storage window and a smaller operating voltage.Higher charge storage density;and XPS analysis results show that the Hf4f orbital and Zr3d orbital binding energies of the HZO film treated with high temperature rapid annealing are higher than those of the HZO film without annealing treatment,which indicates that after high temperature annealing treatment,the Hf-O bonds in the HZO film and the number of Zr-O bonds increases,resulting in more defect states,which explains the change of the corresponding storage window at different temperatures.Finally,according to the virtual crystal approximation theory,the energy band structure of the HZO charge trapping memory is estimated,and the read and write mechanism of the device is analyzed according to the energy band spectrum.P/E speed,and according to the data retention characteristic analysis,the P/E speed is improved without sacrificing the retention performance,which indicates the excellent charge trapping ability of the HZO device.