Study On The Mechanism And Properties Of Oxygenated Amorphous Carbon Based Resistive Random Access Memories

As the performance of traditional CMOS devices is approaching their physical limits,on the one hand,methods for increasing the storage capacity of conventional semiconductor memories,such as flash memory,by further shrinking device feature sizes will be limited.On the other hand,as the flash feature size shrinks,the thickness of the gate oxide layer and the size of the floating gate will also shrink,resulting in a series of problems such as dielectric breakdown and the amount of stored charge being too small to distinguish the stored information.Moreover,as people's requirements for information storage performance become higher and higher,the longer switching time?on the order of?s?and the lower number of erasable?10⁶orders?of flash memory can no longer meet people's needs.Therefore,in the past few decades,several new types of non-volatile devices with different storage mechanisms have been proposed,such as phase change memory,magnetic memory,ferroelectric memory,and resistive random access memory?RRAM?.Among them,RRAM has received extensive attention due to its simple structure and easy three-dimensional integration.The storage medium of RRAM covers a wide range of materials,including various inorganic and organic materials.Among them,carbon-based materials have attracted great research interest due to their simple composition,chemical stability and biocompatibility.However,for cation-based RRAM,the low resistivity of pure carbon material prepared by sputtering and the usually poor high temperature retention characteristics of carbon-based RRAM have hindered the development of such devices.For anion-based RRAM,the resistance mechanism of carbon-based materials remains unclear.In addition,it is very important to study the failure mechanism of RRAM to optimize the structure of RRAM and promote its practical application.In view of the problems existing in carbon-based RRAM,this paper has carried out the following two aspects of research.1.The preparation of the cation-based RRAM of carbon-based materials.By incorporating oxygen into the process of preparing a carbon film by sputtering a graphite target,the proportion of sp³/sp² carbon atoms in the carbon material is greatly increased,and the resistivity of the deposited film is effectively improved,making it suitable for RRAM.It has been found that as the partial pressure of oxygen in the sputtering atmosphere increases,the deposition rate of the film decreases or even the film cannot be formed.The high temperature retention characteristics of the memory are better when the oxygen content in the film is increased.Combined with the device's two-step RESET process and temperature-sensitive V_Forming,the better high temperature retention of higher oxygen content film can be attributed to fewer structural defects in it and its chemical inertness.2.The preparation of anion-based RRAM for oxygenated amorphous carbon?a-CO_x?materials.It has been found to have excellent consistency and the DC I-V characteristic curve for almost 1000 tests is almost the same.Considering the facts that the use of inert electrodes?W and Pt?,the holes and bubble suspected from the eruption of gas observed in SEM and so on,it is thought that the resistive mechanism of the prepared a-CO_x RRAM is the electrochemical redox reaction of graphite filaments assisted by oxygen.Further research has found that the thermal breakdown of dielectrics caused by highly spatially concentrated resistive behavior and the stress generated by the formation of oxygen at the electrode interface are the causes of permanent failure of the device.