Kinetics of Ion Drift
In previous chapters, we have shown that various metal species, including barrier metals and self-forming barrier metals, can penetrate into dielectrics under BTS. Generally, the existence of metal contamination inside dielectrics will significantly degrade dielectric reliability, causing early breakdown and large leakage current . Therefore, a main interest is to understand the impact of this metal contamination on dielectric reliability. Before we can proceed further on this topic, however, there is one question that needs to be clarified: the kinetics issue. How fast can these metallic species migrate inside the dielectrics? A key parameter needed to describe the kinetics is diffusivity (D). With a known stressing condition, diffusivity can be used to calculate the distribution of metal contamination inside the dielectric, from which the total number of metal species within the dielectric can be estimated. Also, the effective electric field distribution inside the dielectric, after including the ionic field effect, can be evaluated [2, 3]. These factors are crucial in order to predict the dielectric lifetime, which we will discuss further in Chap. 9. In addition, the operation of memory devices that uses the drift of ions to perform functions, such as resistive switches and solid electrolyte devices, relies on the buildup of a conductive metallic filament between the electrodes. To decide the working temperature and the threshold electric field needed for switching, it is necessary to know the metal migration speed inside the dielectric .
KeywordsExternal Electric Field Resistive Switch Dielectric Interface Threshold Electric Field Effective Electric Field
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