Preparation And Device Performance Of Low-power Memory Materials Based On V₂O₅

Phase change memory（PCRAM）as one of the most competitive new memory technologies in the next generation,has been developed by leaps and bounds in the past ten years.With the development of phase change memory technology itself,the related basic research is also a research hotspot in information,materials and other related fields in recent years.The advantages of PCRAM in many memories are obvious,such as fast read-write speed,good fatigue,low power consumption and compatibility with CMOS technology.However,there are still some problems to be solved:1.The stability and speed of phase change materials can not be better in the process of phase change;2.High power consumption in the process of reset;3.The reliability of traditional phase change materials still needs to be solved improve.Phase change materials are the foundation and core of phase change memory.The performance of phase change material determines the performance of phase change memory.In this paper,based on the research of our group and the traditional variable material GST,we explore a new phase change material with excellent performance.We take V₂O₅as the basic research material,then study the preparation and device performance of V₂O₅low-power storage material,analyze the phase transition performance and phase transition mechanism of V₂O₅and V₂O₅doped with Sb,Ge₈Te₉₂and Ge₂Sb₂Te₅materials,so as to improve the stability of PCRAM The problems of poor performance,slow phase transition speed and low power consumption are of great significance for the development and research of PCRAM.Through the current research,we get the following conclusions:（1）Study on the properties of V₂O₅phase change material.During the heating process,the phase transition of V₂O₅occurs at 320^oC and 345^oC,and two obvious abrupt changes of V₂O₅resistance are observed.The ten-year data keep at 200^oC.The crystallization mechanism of one-dimensional growth is the main reason for the rapid phase transformation.The phase structure shows that microcrystalline phase and polycrystalline phase are formed successively with the phase transformation.Micro area element scanning showed that the distribution of V and O elements was uniform.The scratch test shows that it has good adhesion.In the V₂O₅based phase change memory,multi-level storage is realized.With low set and reset voltages(V_SET～1.20V,V_RESET～2.80V),the storage speed can reach 100ns,and the power required to complete the set reset process is 0.68m W,which is far less than 1.22m W of GST.The results show that V₂O₅phase change material has high thermal stability,fast phase transition speed and multi-stage storage function,which makes V₂O₅have a good application prospect in phase change memory.（2）Preparation and research of V₂O₅/Sb phase change films with superlattice structure.The results show that the films with superlattice structure have accurate stoichiometry and good dispersion.Compared with sb thin films,V₂O₅/Sb superlattice films have better thermal stability(T_c～240^oC,T_10-year～172.9^oC).The grains in V₂O₅/Sb thin films become smaller due to the inhibition of V₂O₅.The vibrational peaks of Sb-Sb and V-O bonds are observed by Raman spectroscopy and the multilayer structures before and after crystallization are observed by transmission electron microscopy.These indicate that the interaction between the two crystal systems improves the properties of V₂O₅/Sb films The phase change memory device based on V₂O₅（1nm）/Sb（9nm）has low set voltage(V_SET～2.24V),and can realize ultra-low power consumption(2.25×10^-12J)and ultra-high speed（8ns）SET→RESET operation,which makes V₂O₅/Sb superlattice structure have a good application prospect in PCRAM.（3）The stability and properties of V₂O₅/Ge₈Sb₉₂composite films were studied.The V₂O₅/Ge₈Sb₉₂films prepared by the composite method have high crystallization temperature（～233^oC）,large amorphous resistance（～3.4×10⁷Ω）and good data holding temperature（～171.2^oC）.When the electrode contacts with the electrode,the crystallization rate of the film is 85.5%.By adding V₂O₅interlayer,the thermal stability and reliability of Ge₈Sb₉₂film are greatly improved.The surface roughness of V₂O₅/Ge₈Sb₉₂film is small before and after crystallization,which ensures the contact between electrode and phase change material.During the crystallization process,the crystallization of V₂O₅/Ge₈Sb₉₂was inhibited,and the grain size was only 5.0nm.Phase change memory device（PCM）based on V₂O₅（1nm）/Ge₈Sb₉₂（9nm）material has lower set voltage(V_SET～1.85V).These studies show that V₂O₅/Ge₈Sb₉₂composite multilayer films have high stability,small grain size and low operational performance,and have potential applications in high-density PCRAM.To sum up,the main idea of this paper is to explore a new phase change material V₂O₅and explore different film structures based on V₂O₅to seek and improve its electrical phase transition properties.