Consejo Superior de Investigaciones Científicas · Universidad de Sevilla
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Unified RTN and BTI statistical compact modeling from a defect-centric perspective
G. Pedreira, J. Martin-Martinez, P. Saraza-Canflanca, R. Castro-Lopez, R. Rodriguez, E. Roca, F.V. Fernandez and M. Nafria
Journal Paper - Solid-State Electronics, vol. 185, article 108112, 2021
ELSEVIER    DOI: 10.1016/j.sse.2021.108112    ISSN: 0038-1101    » doi
[abstract]
In nowadays deeply scaled CMOS technologies, time-dependent variability effects have become important concerns for analog and digital circuit design. Transistor parameter shifts caused by Bias Temperature Instability and Random Telegraph Noise phenomena can lead to deviations of the circuit performance or even to its fatal failure. In this scenario extensive and accurate device characterization under several test conditions has become an unavoidable step towards trustworthy implementing the stochastic reliability models. In this paper, the statistical distributions of threshold voltage shifts in nanometric CMOS transistors will be studied at near threshold, nominal and accelerated aging conditions. Statistical modelling of RTN and BTI combined effects covering the full voltage range is presented. The results of this work suppose a complete modelling approach of BTI and RTN that can be applied in a wide range of voltages for reliability predictions.

Quail eggs in artificial nests change their coloration when exposed to ambient conditions: implication for studies on nest predation
G. Liñan Cembrano, M. Castro, J.A. Amat, A. Perez, M.A. Rendón and C. Ramo
Journal Paper - PeerJ 9:e11725, 2021
PEERJ    DOI: 10.7717/peerj.11725    ISSN: 2167-8359    » doi
[abstract]
Quail eggs have been widely used in field experiments, mainly to study factors associated with the risk of nest predation. Some shortcomings of using quail eggs in this type of study have been previously addressed (e.g., these eggs might be too big for some predators of eggs of small birds). Here, we show experimental evidence of another shortcoming of the use of these eggs in field experiments. Quail eggs exposed to sunlight rapidly faded in colour after three days, both in the visible and UV spectra, and this change was related to the amount of solar radiation received. This caused changes in the camouflage of the eggs, which may be perceived by predators with different visual systems (dichromatic, trichromatic, and tetrachromatic (for both violet- and UV-sensitive species)). Therefore, the results of field studies of nest predation using quail eggs might be questioned in those cases in which the camouflage has been altered due to the rapid changes in coloration, as this can affect the resulting predation rates. We recommend that researchers planning to use quail eggs should perform a prospective assessment of changes in coloration of eggs exposed to environmental conditions in the nest sites used by the target species.

Statistical Characterization of Time-Dependent Variability Defects using the Maximum Current Fluctuation
P. Saraza-Canflanca, J. Martin-Martinez, R. Castro-Lopez, E. Roca, R. Rodriguez, F.V. Fernandez and M. Nafria
Journal Paper - IEEE Transactions on Electron Devices, first online, 2021
IEEE    DOI: 10.1109/TED.2021.3086448    ISSN: 0018-9383    » doi
[abstract]
This article presents a new methodology to extract, at a given operation condition, the statistical distribution of the number of active defects that contribute to the observed device time-dependent variability, as well as their amplitude distribution. Unlike traditional approaches based on complex and time-consuming individual analysis of thousands of current traces, the proposed approach uses a simpler trace processing, since only the maximum and minimum values of the drain current during a given time interval are needed. Moreover, this extraction method can also estimate defects causing small current shifts, which can be very complex to identify by traditional means. Experimental data in a wide range of gate voltages, from near-threshold up to nominal operation conditions, are analyzed with the proposed methodology.

Insights into the Dynamics of Coupled VO2 Oscillators for ONNs
J. Núñez, J.M. Quintana, M.J. Avedillo, M. Jiménez, A. Todri-Sanial, E. Corti, S. Karg and B. Linares-Barranco
Journal Paper - IEEE Transactions on Circuits and Systems II: Express Briefs, first online, 2021
IEEE    DOI: 10.1109/TCSII.2021.3085133    ISSN: 1549-7747    » doi
[abstract]
The collective behavior of many coupled oscillator systems is currently being explored for the implementation of different non-conventional computing paradigms. In particular, VO2 based nano-oscillators have been proposed to implement oscillatory neural networks that can serve as associative memories, useful in pattern recognition applications. Although the dynamics of a pair of coupled oscillators have already been extensively analyzed, in this paper, the topic is addressed more practically. Firstly, for the application mentioned above, each oscillator needs to be initialized in a given phase to represent the input pattern. We demonstrate the impact of this initialization mechanism on the final phase relationship of the oscillators. Secondly, such oscillatory networks are based on frequency synchronization, in which the impact of variability is critical. We carried out a comprehensive mathematical analysis of a pair of coupled oscillators taking into account both issues, which is a first step towards the design of the oscillatory neural networks for associative memory applications.

Statistical threshold voltage shifts caused by BTI and HCI at nominal and accelerated conditions
J. Diaz-Fortuny, P. Saraza-Canflanca, R. Rodriguez, J. Martin-Martinez, R. Castro-Lopez, E. Roca, F.V.Fernandez and M. Nafria
Journal Paper - Solid-State Electronics, vol. 185, article 108037, 2021
ELSEVIER    DOI: 10.1016/j.sse.2021.108037    ISSN: 0038-1101    » doi
[abstract]
In nowadays deeply scaled CMOS technologies, time-zero and time-dependent variability effects have become important concerns for analog and digital circuit design. For instance, transistor parameter shifts caused by Bias Temperature Instability and Hot-Carrier Injection phenomena can lead to progressive deviations of the circuit performance or even to its catastrophic failure. In this scenario, and to understand the effects of these variability sources, an extensive and accurate device characterization under several test conditions has become an unavoidable step towards trustworthy implementing the stochastic reliability models and simulation tools needed to achieve reliable integrated circuits. In this paper, the statistical distributions of threshold voltage shifts in nanometric CMOS transistors will be studied at nominal and accelerated aging conditions. To this end, a versatile transistor array chip and a flexible measurement setup have been used to reduce the required testing time to attainable values.

Cognitive Radio Circuits and Systems - Application to Digitizers
H. Aboushady, A. Sayed, L.A. Camuñas-Mesa and J.M. de la Rosa
Conference - IEEE International Symposium on Circuits and Systems ISCAS 2020
[abstract]
This paper gives an overview of Cognitive-Radio (CR) circuits and systems, that will enable the implementation of new technology paradigms such as software-defined electronics and Artificial Intelligence (AI) managed Internet-of-Things (IoT). A survey of the state of the art, trends and design challenges is presented from a top-down perspective - from system-level to circuit and chip implementation. As an application, special emphasis is put on analog/digital interfaces as one of the key building blocks in CR-based devices. Cutting-edge architectures - mostly based on ΣΔ Modulators (ΣΔMs) - are discussed, as well as the best candidate circuit strategies to implement CR-based digitizers in deep nanometer CMOS.

Implementation of binary stochastic STDP learning using chalcogenide-based memristive devices
C. Mohan, L.A. Camuñas-Mesa, J.M. de la Rosa, T. Serrano-Gotarredona and B. Linares-Barranco
Conference - IEEE International Symposium on Circuits and Systems ISCAS 2020
[abstract]
The emergence of nano-scale memristive devices encouraged many different research areas to exploit their use in multiple applications. One of the proposed applications was to implement synaptic connections in bio-inspired neuromorphic systems. Large-scale neuromorphic hardware platforms are being developed with increasing number of neurons and synapses, having a critical bottleneck in the online learning capabilities. Spike-timing-dependent plasticity (STDP) is a widely used learning mechanism inspired by biology which updates the synaptic weight as a function of the temporal correlation between pre- and post-synaptic spikes. In this work, we demonstrate experimentally that binary stochastic STDP learning can be obtained from a memristor when the appropriate pulses are applied at both sides of the device.

Circuit reliability prediction: challenges and solutions for the device time-dependent variability characterization roadblock
M. Nafria, J. Diaz-Fortuny, P. Saraza-Canflanca, J. Martin-Martinez, E. Roca, R. Castro-Lopez, R. Rodriguez, P. Martin-Lloret, A. Toro-Frias, D. Mateo, E. Barajas, X. Aragones and F.V. Fernandez
Conference - IEEE Latin America Electron Devices Conference LAEDC 2021
[abstract]
The characterization of the MOSFET Time-Dependent Variability (TDV) can be a showstopper for reliability-aware circuit design in advanced CMOS nodes. In this work, a complete MOSFET characterization flow is presented, in the context of a physics-based TDV compact model, that addresses the main TDV characterization challenges for accurate circuit reliability prediction at design time. The pillars of this approach are described and illustrated through examples.

HardBlock: Demonstrator of physically binding an IoT device to a non-fungible token in Ethereum blockchain
J. Arcenegui, R. Arjona and I. Baturone
Conference - Design, Automation and Test in Europe DATE 2021
[abstract]
Nowadays, blockchain is a growing technology in the Internet of Thing (IoT) ecosystem. In this work, we show a demonstrator of an IoT device bound to a Non-Fungible Token (NFT) based on the ERC-721 standard of Ethereum blockchain. The advantages of our solution is that IoT devices can be controlled securely by events from the blockchain and authenticated users, besides being able to carry out blockchain transactions. The IoT device generates its own Blockchain Account (BCA) using a secret seed firstly generated by a True Random Number Generator (TRNG) and then reconstructed by a Physical Unclonable Function (PUF). A Pycom Wipy 3.0 board with the ESP32 microcontroller is employed as IoT device. The internal SRAM of the microcontroller acts as PUF and TRNG. The SRAM is controlled by a firmware developed in ESP-IDF. A smart contract developed in Solidity using Remix IDE creates the token. Kovan testnet and a Graphical User Interface programmed in Python are employed to show the results.

A Quantum-Resistant and Fast Secure Boot for IoT Devices using Hash-Based Signatures and SRAM PUFs
R. Román and I. Baturone
Conference - EAI International Conference on Safety and Security in Internet of Things SaSeIoT 2021
[abstract]
Abstract not available

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