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The question of whether resistance switching in conducting bridge random access memory (CBRAM) devices occurs through a single filament which repeatedly undergoes nucleation and rupture or through different filaments for different cycles is difficult to ascertain using conventional electrical tests on metal–insulator–metal (MIM) capacitor structures. In order to profile the spatial location of the conductive filament during multiple switching cycles, we make use of the Ni–HfO 2 –Si based metal–insulator–semiconductor (MIS) stack with a transistor test structure so that the lateral location of the filament along the source to drain can be probed electrically by considering the weighted ratio of source and drain currents measured. Our analysis reveals that filaments can evolve in spatially uncorrelated locations and switching is not always caused by the same filament over and over again. A simple statistical model is also provided to justify the inferences of the electrical study. The probability of a new filament nucleating elsewhere in the dielectric is a strong function of the oxide barrier thickness as well as the curvature radii of the previously ruptured metal filament edges. [ABSTRACT FROM AUTHOR]

Resistive switching materials are promising candidates for nonvolatile data storage and reconfiguration of electronic applications. Intensive studies have been carried out on sandwiched metal-insulator-metal structures to achieve high density on-chip circuitry and non-volatile memory storage. Here, we provide insight into the mechanisms that govern highly reproducible controlled resistive switching via a nanofilament by using an asymmetric metal-insulator-semiconductor structure. In-situ transmission electron microscopy is used to study in real-time the physical structure and analyze the chemical composition of the nanofilament dynamically during resistive switching. Electrical stressing using an external voltage was applied by a tungsten tip to the nanosized devices having hafnium oxide (HfO2) as the insulator layer. The formation and rupture of the nanofilaments result in up to three orders of magnitude change in the current flowing through the dielectric during the switching event. Oxygen vacancies and metal atoms from the anode constitute the chemistry of the nanofilament. [ABSTRACT FROM AUTHOR]

Resistive switching in transition metal oxides could form the basis for next-generation non-volatile memory (NVM). It has been reported that the current in the high-conductivity state of several technologically relevant oxide materials flows through localized filaments, but these filaments have been characterized only individually, limiting our understanding of the possibility of multiple conductive filaments nucleation and rupture and the correlation kinetics of their evolution. In this study, direct visualization of uncorrelated multiple conductive filaments in ultra-thin HfO2-based high-κ dielectric resistive random access memory (RRAM) device has been achieved by high-resolution transmission electron microscopy (HRTEM), along with electron energy loss spectroscopy (EELS), for nanoscale chemical analysis. The locations of these multiple filaments are found to be spatially uncorrelated. The evolution of these microstructural changes and chemical properties of these filaments will provide a fundamental understanding of the switching mechanism for RRAM in thin oxide films and pave way for the investigation into improving the stability and scalability of switching memory devices. [ABSTRACT FROM AUTHOR]

We study the mechanism of filamentation in resistive switching (RS) memory from an electrical perspective using a conventional metal–insulator–semiconductor (MIS) high- \kappa metal gate transistor test structure and propose the possibility of using the same transistor structure for both logic and RS memory applications. The filament location is measured after every SET transition, and our investigations point to a “pseudorandom” nature of filament nucleation. Migration of highly diffusive nickel from source/drain silicide contacts toward the active silicon channel region transforms the existing MIS stack to MIM, thereby enabling the RS phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: We present electrical evidence on asymmetric metal–insulator–semiconductor (MIS) based test structures in support of the presence of two different independent switching mechanisms in a resistive random access memory (RRAM) device. The valid mechanism for switching depends on the compliance capping (Igl ) for forming/SET transition. Our results convincingly show that low compliance based switching only involves reversible oxygen ion drift to and from oxygen gettering gate electrodes, while high compliance switching involves formation and rupture of conductive metallic nanofilaments, as verified further by our physical analysis investigations. We have observed this unique dual mode switching mechanism only in NiSi-based gate electrodes, which have a moderate oxygen solubility as well as relatively low melting point. [Copyright &y& Elsevier]