The Study Of Fabrication And Electronic Properties Of Hafnium Oxide Based FeFET Gate Structure

Ferroelectric random access memory(FRAM)which is one of the most promising new types of memory technologies has many advantages,such as low power consumption,high read/write speed,good radiation resistance and non-volatile properties.As time goes by,the 1T1C-type FRAM using conventional perovskite ferroelectric thin films has been increasingly difficult to meet the application requirements,due to the big thickness of ferroelectric thin films,large memory cell area and low storage capacity.Recently,with the development of Hafnium oxide(HfO2)ferroelectric thin films,1T-type FRAM which is compatible with CMOS process has becoming a hotspot in research.And it is expected to break through the bottleneck of capacity limitations of FRAM.This essay focuses on the fabrication process and electrical properties of ferroelectric gate based on HfO2 materials.The main research results are as follows:(1)In order to study the effect of the insulator layer in the MFIS ferroelectric grid on the performance of the ferroelectric thin film,a high-k dielectric film and SBT thin films were prepared by RF magnetron sputtering and sol-gel method,respectively.The dielectric constant of the medium is 12.In a MFIS(Pt/SBT/HfO2/Si)gate structure,we verified the effect of the high-k layer on the performance of the ferroelectric gate based on a conventional SBT thin film,and considered that appropriately reducing the thickness of the insulating layer is in favor of obtaining a larger storage window.(2)Ferroelectric hafnium oxide(HZO)thin films were prepared by atomic layer deposition method.The electrical properties of HZO thin films was characterized and studied based on the MFM(Metal-Ferroelectric-Metal)structure.Compared with the traditional SBT ferroelectric thin film,HZO ferroelectric thin film has better electrical properties,such as a larger residual polarization(?17 ?C/cm2),a thinner physical thickness(9 nm?18 nm),a larger coercive electric field(?1.5 MV/cm).At the same time,the MFIS(TiN/HZO/HfO2/Si)gate structure capacitance based on the novel ferroelectric film HZO was studied experimentally.After measuring the samples,we found that the fabricated MFIS gate structure has no wake-up effect.Without annealing,it has a better fatigue resistance,After 109 fatigue test cycles,the change of rate of the residual polarization is less than 10%.At the test temperature of 60?,the retention performance of the MFIS gate structure is still very stable.These test results show that the fabricated MFIS gate structure capacitor based on HZO film has good electrical properties.(4)As for the extreme application environment in aerospace of the 1T type ferroelectric memory,the total dose radiation effect of the MFIS(TiN/HZO/HfO2/Si)gate structure capacitance was investigated.The dose rate for this irradiation experiment was 50 rad(Si)/s.There dose level are 200 rad(Si),500 rad(Si),1 Mrad(Si),3 Mrad(Si),and 5 Mrad(Si),respectively.The test results show that the change of rate of the residual polarization of the MFIS gate structure after irradiation is within 5%,and the change of rate of the retention performance is 8%.The basic and pre-irradiation electrical properties remain the same,which proves that the MFIS gate structure capacitor based on prepared HZO film has a very good radiation resistance.