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Optical refractive index measurements of AlGaAs at high temperature for fully automated molecular beam epitaxy growth of Bragg mirrors
No full textThis work was partly supported by LAAS-CNRSmicro and nanotechnologies platform member of the FrenchRENATECH network.International audienceAbstract In-situ measurement is a key feature to better understand and precisely control the growth of complex structures, such as vertical-cavity surface-emitting lasers. In this work, we are showing the precise measurement of optical indices of AlGaAs at 600 °C over a wide spectral range (450–1400 nm). To do so, in-situ spectral reflectance measurement is used, combined with ex-situ layer thickness and composition measurement by x-ray diffraction enabling for precise determination of the optical indices with an accuracy better than 1%. To validate our measurements, we realized the complete automation of the growth of a GaAs/AlAs 940 nm-DBR by molecular beam epitaxy, without the need to pre-calibrate cells fluxes. The fabricated DBR shows a deviation of 0.2 nm of the stop-band central-wavelength compared to the targeted one. This approach holds significant interest for the III–V semiconductor community and epitaxial growth techniques
Policy Safety Testing in Non-Deterministic Planning: Fuzzing, Test Oracles, Fault Analysis
No full textInternational audienceRecent work has introduced methodology for testing learned action policies in AI Planning, aiming to effectively identify bug states where policy behavior is sub-optimal. While this work focused on cost-optimality in classical planning, here we apply the core ideas to safety testing in planning with initial-state and action-outcome non-determinism. We cover the entire testing pipeline, introducing fuzzing algorithms to find unsafe policy runs, as well as test oracles to identify bugs where such unsafe behavior could be avoided. Going beyond the previous framework, we introduce a final step to the pipeline, identifying faults which we define to be specific policy decisions – state/action pairs – transitioning from a safe state (where a safe policy exists) to an unsafe state (where no such policy exists). We adapt a range of known algorithms for these purposes, including also approximate ones bounding the number of times we are allowed to diverge from the learned policy. We run comprehensive experiments evaluating each part of our pipeline. Key takeaways are that safety testing can be quite cheap, in contrast to cost-optimality testing; and that variants of Tarjan’s algorithm tend to be highly effective for this purpose
Thin film LiNbO 3 surface preparation using SC-1
No full textInternational audienceThis study investigates the use of Standard Cleaning 1 (SC-1), a routine treatment in silicon micro-/nano-fabrication, as a step in the processing of photonic structures and waveguides on thin films of lithium niobate on insulator (LNOI). We investigate the use of SC-1 for surface preparation and as a cleaning method to remove residual byproducts after ICP etching, evaluating its impact on etching dynamics and the quality of the LiNbO 3 thin film. Our results demonstrate that SC-1 cleaning removes a surface layer of LiNbO 3 characterized by higher oxygen vacancies. These oxygen vacancies accelerate the etching process and lead to faster under-etching of Si 3 N 4 capping layers on LiNbO 3 , causing pattern delamination, particularly at sub-micron scales where under-etching is more detrimental. Finally, we show that carrying out a SC-1 treatment preliminary to Si 3 N 4 capping layer deposition enables the fabrication of Si 3 N 4 gratings with sub-100 nm width on LiNbO 3 thin films
Mécanismes physiques de HEMT GaN révélés par l'instabilité de la tension de seuil
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In-situ-monitored Chemical Vapor Deposition of silicon oxynitride layers
No full textInternational audienceFollowing the implementation of in-situ monitoring systems in other types of deposition equipment [5,6], we report here the development of a combination of reflectometry and optical emission spectroscopy (OES) and its use on a Inductive-Coupled-Plasma PECVD tool to not only gain greater control on the deposited material compositions and thicknesses but also to help reduce the number of calibration runs
Développement de procédés de gravure RIE et d'implantation ionique pour la fabrication de composants de puissance en diamant CVD
No full textNational audienceThe ever-increasing demand for electrical energy has led to the development of power components able to meet energy requirements. Today, the majority of these devices are made from silicon. However, they are confronted with the limits of the intrinsic properties of this material. To overcome these constraints, research has focused on the manufacture of power devices based on wide bandgap semiconductors, which offer better electronic properties, particularly in terms of breakdown voltage, high temperatures and high currents operation. Among these materials, diamond appears to be the most promising candidate for the fabrication of power devices, because of its electronic properties. In this context, our work is a continuation of the ANR MOVeToDIAM project, coordinated by LAAS-CNRS, launched in November 2017 and finished in 2022. The aim of this project was to develop technologies for the fabrication of two demonstrators on diamond: vertical TMBS (Trench MOS Barrier Schottky) diodes and vertical P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistors with a U-gate, able to withstand 6000 V and 1200 V respectively at room temperature. The first phase of our work involved developing a dry etching process, RIE-ICP (Reactive Ion Etching – Inductively Coupled Plasma), required for the fabrication of the U-shaped gate in MOSFET transistors as well as the MESA structure of TMBS diodes. Finally, we studied boron ion implantation on p-type CVD diamond layers to achieve localized high boron doped layers with low resistivity. We have characterized the implanted layers using various techniques. Methods such as secondary ion mass spectrometry (SIMS), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) were used to study the structure of the diamond layers. Electrical properties, in particular sheet resistance, mobility and carrier concentration, were determined using four-point measurements and complemented by the Hall effect technique. In addition, photoluminescence and cathodoluminescence techniques were used to analyse the defects present in these implanted layers.L'augmentation croissante de la demande en énergie électrique a conduit au développement de composants de puissance capables de répondre aux besoins énergétiques. Aujourd'hui, la majorité de ces composants sont fabriqués à base de silicium. En revanche, ces dispositifs sont confrontés aux limites des propriétés intrinsèques de ce matériau. Pour surmonter ces contraintes, la recherche s'est orientée vers la fabrication de composants de puissance à base de semi-conducteurs à large bande interdite, qui offrent des propriétés électroniques supérieures, notamment en termes de tenue en tension, de fonctionnement à haute température et forts courants. Parmi ces matériaux, le diamant apparaît comme le candidat le plus prometteur pour la réalisation de composants de puissance, en raison de ses propriétés électroniques. Dans ce cadre, nos travaux s'inscrivent dans la continuité du projet ANR MOVeToDIAM, coordonné par le LAAS-CNRS, lancé en novembre 2017 et achevé en 2022. Ce projet avait pour objectif de développer des technologies pour la fabrication de deux démonstrateurs : des diodes TMBS (Trench MOS Barrier Schottky) verticales et des transistors MOSFET (Metal Oxide Semiconductor Field Effect Transistor) verticaux à canal P avec une grille en U en diamant, capables de supporter respectivement 6000 V et 1200 V à température ambiante. La première phase de nos travaux a consisté à développer un procédé de gravure sèche RIE-ICP (Reactive Ion Etching – Inductively Coupled Plasma) nécessaire pour réaliser la grille en U de transistors MOSFET et également la structure MESA de diodes TMBS. Enfin, les couches de diamant CVD dopées au bore par implantation ionique ont été étudiées afin d'évaluer l’efficacité du dopage, à travers l'analyse de la structure du diamant et des propriétés électriques après dopage. L'objectif est d'obtenir un dopage localisé de ces couches dopées au bore avec une faible résistivité. Ces couches ont été caractérisées à l'aide de différentes techniques. Les méthodes telles que la spectrométrie de masse d'ions secondaires (SIMS), la microscopie électronique en transmission (TEM) et la microscopie à force atomique (AFM) ont été utilisées pour étudier la structure de nos couches diamant. Les propriétés électriques notamment la résistance par carré, la mobilité et la concentration des porteurs libres ont été déterminées à partir de mesures quatre pointes et complétées par la technique d’effet Hall. Par ailleurs, les techniques de photoluminescence et de cathodoluminescence ont été employées afin d'analyser les défauts présents dans les couches implantées
A bibliometric literature review of integrated data and model based diagnosis approaches for the industry 4.0
No full textInternational audienceThe increasing presence of Cyber-Physical Systems and the Internet of Things has accelerated the digital transformation of industrial environments, commonly known as Industry 4.0. In this context, Artificial Intelligence techniques are increasingly used to support automatic diagnostic tasks. This paper presents a systematic literature review of hybrid diagnostic systems that combine Model-Based Diagnosis (MBD), which relies on physical models to detect abnormal behavior, and Data-Based Diagnosis (DBD), which uses machine learning to identify faults from data. The review has two objectives: (i) to examine how MBD and DBD methods have been combined to improve diagnostic performance, and (ii) to identify integration opportunities through existing machine learning frameworks to support reusable and adaptive solutions. A bibliometric analysis was conducted following a simplified PRISMA 2020 methodology. From over 1,300 records, 75 articles were selected and analyzed. Most hybrid systems adopt a serial architecture where DBD classifiers analyze residuals from MBD for fault detection and isolation. The most common applications are found in smart manufacturing and energy systems, and as for the most used machine learning techniques, there are those of deep learning and ensemble methods. Challenges remain regarding real-time scalability, interpretability, and standardization. This review provides a structured foundation for designing explainable, efficient, and reusable diagnostic solutions for Industry 4.0
What's inside your industrial black-box component? Let's analyze some micro-architectural signals!
No full textInternational audienceWith the growing complexity of systems, design phases increasingly rely on the interaction of several industrial actors. This makes it more difficult, especially at the hardware level, for an end-user to know what is being inserted at each stage, even for very specific needs, and can be a blocking point for revising the system later on.In terms of security, using only a high level of abstraction alone does not protect against several attacks or malicious acts that exploit the target’s low-level characteristics. Since only third parties know the implementation details of the component for which they are responsible, there is an increasing need for direct monitoring of signals coming from the micro-architecture to cover attacks targeting this layer. Suppliers may intentionally or not produce a component that is vulnerable to attacks against the micro-architecture. To detect attacks at this level, we propose a mechanism to extract a large set of signals and select to most relevant ones to study the behavior of industrial-type systems. These systems often have small processors with lightweight operating systems, sometimes with real-time constraints.To simulate various such systems, we have built an FPGA platform for continuous monitoring of the micro-architectural signals, based on LiteX, with different choices of parameters such as CPUs and peripherals. Our work extends the MATANA framework, which enables run-time detection of Cache Side-Channel and Return-Oriented Programming attacks. We are also extending the framework to support hardware trojans targeting industrial systems, with automated insertion tools. Experiments are designed for high bandwidth data transfer to a host computer
High-Temperature Dual-Rail Contactless MEMS Logic for Industrial Edge Computing
No full textInternational audienceSensors are advancing to integrate smart functionalities within the same package to enhance data sensing capabilities. However, implementing in-sensor computing at high temperatures is challenging due to CMOS limitations. To overcome this, we introduce the first demonstration of electromechanical computing using a process flow similar to conventional MEMS sensors, enabling seamless in-MEMS-sensor computing at elevated temperatures. Our approach uses a contactless mechanism, addressing the reliability issues of existing digital circuits based on MEMS relays and ensuring durability under significant temperature fluctuations. We demonstrate NOT logic operation as well as state propagation through a cascade of 10 pipelined gates, paving the way for digital processing within the MEMS sensor's physical layer. Additionally, our devices operate at temperatures up to at least 473 K, opening new possibilities for in-sensor computing in extreme environments
Engineering Ni-Silicide Nanocontacts for 3D Silicon Devices via Geometrical Confinement Control
No full textInternational audienceNanoscale Ni-silicide alloys are critical components for future generations of 3D electronic devices based on active Si nanostructures, with applications in nanoelectronics, energy conversion, and sensing. This study investigates how geometrical confinement in such nanostructures influences diffusion-driven silicidation, ultimately determining the alloy formation sequence, phase composition, and volumetric expansion. The silicidation of controlled Ni volumes is investigated on vertical silicon nanowires (NW) and nanosheets (NS) under various annealing conditions. The silicide phases and interface morphologies are characterized using high-resolution (scanning) transmission electron microscopy (HR-TEM, HR-STEM), energy-dispersive X-ray spectroscopy (EDX), and four-dimensional scanning transmission electron microscopy (4D-STEM) for nanoscale Ni−Si phase mapping. Under conditions of strong geometric confinement, NiSi2 is observed to form with faceted, prism-like morphologies aligned with Si (111) planes, features not typically present in planar or bulk samples. This anisotropic growth is associated with preferential Ni diffusion along nanostructure surfaces and limited Si counterdiffusion through the silicide. The resulting NiSi2 interfaces are structurally distinct and may contribute to reduced contact resistance in both p-type and n-type silicon nanostructures, supporting their integration in 3D device architectures