Live demonstration: A TiO2 ReRAM parameter extraction method

2022 IFIP/IEEE 30th International Conference on Very Large Scale Integration (VLSI-SoC)

The intrinsic behavioral variability in resistive switching devices (also known as "memristors" or "ReRAM devices") can be a reliability limiting factor or an opportunity for applications where randomness of resistance switching is essential, such as hardware security and stochastic computing. The realistic assessment of ReRAM-based circuits & systems towards practical exploitation requires variability-aware ReRAM modeling. In this context, here we present a versatile, circuit-level implementation strategy to incorporate cycle-tocycle (C2C) variability to the ReRAM model parameters in SPICE simulations. We evaluated the proposed approach with threshold-based models of a voltage-controlled bipolar ReRAM device and managed to reproduce the main features observed in experimental curves for different pulsed voltage inputs. With key upgrades, compared to previous approaches found in the literature, our strategy enables the enhancement of any ReRAM device model towards the exploration of new ways to make the most of the C2C ReRAM variability, and to test the robustness of any designed circuits & systems against ReRAM variability.

Science in China Series F: Information Sciences, 2011

Resistive random access memory (RRAM or ReRAM) is a non-volatile memory (NVM) technology that consumes minimal energy while offering sub-nanosecond switching. In addition, the data stability against high temperature and cycling wear is very robust, allowing new NVM applications in a variety of markets (automotive, embedded, storage, RAM). Based on sudden conduction through oxide insulators, the characteristics of RRAM technology

2022 IEEE International Symposium on Circuits and Systems (ISCAS)

Mass characterisation of emerging memory devices is an essential step in modelling their behaviour for integration within a standard design flow for existing integrated circuit designers. This work develops a novel characterisation platform for emerging resistive devices with a capacity of up to 1 million devices on-chip. Split into four independent sub-arrays, it contains on-chip column-parallel DACs for fast voltage programming of the DUT. On-chip readout circuits with ADCs are also available for fast read operations covering 5-decades of input current (20 nA to 2 mA). This allows a device's resistance range to be between 1 kΩ and 10 MΩ with a minimum voltage range of ±1.5 V on the device.

2015

The inquiry of this dissertation was the development of a memristor device for ReRAM applications. All two terminal devices which show resistive switching and are non-volatile memories are memristor devices. ReRAM devices pose a challenge for successful CMOS integration due to their high variability of switching parameters, which to date is not fully understood. This experimental design is focused on providing insights into this reoccurring problem of ReRAM devices. A ReRAM device was fabricated using MgO in the form of a metal-insulator-metal structure as Pt/MgO/Ta/Ru; by magnetron sputtering and the use of a shadow mask. The fabrication process resulted in four samples with di erent thickness of the MgO thin lm. The samples were study in a two-step process. The rst step involved a series of I/V tests undertaken to investigate, resistance ratios, switching cycles, and statistical distribution. The second step applied a percolation model based on circuit breakers to simulate the int...

2020

Resistive random access memory (RRAM) devices represent promising candidates for emerging non-volatile data storage applications and neuromorphic computing. In those devices, the resistance of a dielectric -often a binary oxide- is switched between a low resistance state (LRS) and one or more high resistance states (HRS) by the application of an appropriate external electrical bias. This resistance switching could be filamentary, i.e., involves the formation of a conductive filament. This filament can be thought of as chains of conductive oxygen vacancies (intrinsic resistance switching) or metallic atoms from an active device electrode (extrinsic resistance switching). In this thesis, the relationship between device electrode material and its resistance switching mechanism in SiOx (x∼1.9)-based RRAM devices was studied. Although it’s widely reported that RRAM devices with electrochemically active top electrodes, such as Ag, switch extrinsically, I show that both mechanisms and thei...

IEEE Transactions on Electron Devices, 2015

Research on memory devices is a highly active field and many new technologies are being constantly developed. However, characterising them and understanding how to bias for optimal performance is becoming an increasingly tight bottleneck. Here we propose a novel technique for extracting biasing parameters conducive to desirable switching behaviour in a highly automated manner, thereby shortening process development cycles. The principle of operation is based on first: applying variable amplitude, pulse-mode stimulation on a test device in order to induce switching multiple times, next: collecting data on how pulsing parameters affect the device's resistive state and finally: choosing the most suitable biasing parameters for the application at hand. The utility of the proposed technique is validated on T iOx-based prototypes, where we demonstrate the successful extraction of biasing parameters that allow operation of our devices both as multi-state and binary resistive switches.

IEEE Electron Device Letters, 2000

arXiv: Applied Physics, 2018

The emergence of memristor technologies brings new prospects for modern electronics via enabling novel in-memory computing solutions and affordable and scalable reconfigurable hardware implementations. Several competing memristor technologies have been presented with each bearing distinct performance metrics across multi-bit memory capacity, low-power operation, endurance, retention and stability. Application needs however are constantly driving the push towards higher performance, which necessitates the introduction of standard characterisation protocols for fair benchmarking. At the same time, opportunities for innovation are missed by focusing on excessively narrow performance aspects. To that end our work presents a complete, technology agnostic, characterisation methodology based on established techniques that are adapted to memristors/RRAM characterisation needs. Our approach is designed to extract information on all aspects of device behaviour, ranging from deciphering underl...

Journal of Physics D: Applied Physics, 2014

This work exploits the switching dynamics of nanoscale resistive random access memory (ReRAM) cells with particular emphasis on the origin of the observed variability when cells are consecutively cycled/programmed at distinct memory states. It is demonstrated that this variance is a common feature of all ReRAM elements and is ascribed to the formation and rupture of conductive filaments that expand across the active core, independently of the material employed as the active switching core, the causal physical switching mechanism, the switching mode (bipolar/unipolar) or even the unit cells' dimensions. Our hypothesis is supported through both experimental and theoretical studies on TiO 2 and In 2 O 3 : SnO 2 (ITO) based ReRAM cells programmed at three distinct resistive states. Our prototypes employed TiO 2 or ITO active cores over 5 × 5 µm 2 and 100 × 100 µm 2 cell areas, with all tested devices demonstrating both unipolar and bipolar switching modalities. In the case of TiO 2 -based cells, the underlying switching mechanism is based on the non-uniform displacement of ionic species that foster the formation of conductive filaments. On the other hand, the resistive switching observed in the ITO-based devices is considered to be due to a phase change mechanism. The selected experimental parameters allowed us to demonstrate that the observed programming variance is a common feature of all ReRAM devices, proving that its origin is dependent upon randomly oriented local disorders within the active core that have a substantial impact on the overall state variance, particularly for high-resistive states.