Integrated Circuits/Microchips

With the world marching inexorably towards the fourth industrial revolution (IR 4.0), one is now embracing lives with artificial intelligence (AI), the Internet of Things (IoTs), virtual reality (VR) and 5G technology. Wherever we are, whatever we are doing, there are electronic devices that we rely indispensably on. While some of these technologies, such as those fueled with smart, autonomous systems, are seemingly precocious; others have existed for quite a while. These devices range from simple home appliances, entertainment media to complex aeronautical instruments. Clearly, the daily lives of mankind today are interwoven seamlessly with electronics. Surprising as it may seem, the cornerstone that empowers these electronic devices is nothing more than a mere diminutive semiconductor cube block. More colloquially referred to as the Very-Large-Scale-Integration (VLSI) chip or an integrated circuit (IC) chip or simply a microchip, this semiconductor cube block, approximately the size of a grain of rice, is composed of millions to billions of transistors. The transistors are interconnected in such a way that allows electrical circuitries for certain applications to be realized. Some of these chips serve specific permanent applications and are known as Application Specific Integrated Circuits (ASICS); while, others are computing processors which could be programmed for diverse applications. The computer processor, together with its supporting hardware and user interfaces, is known as an embedded system.In this book, a variety of topics related to microchips are extensively illustrated. The topics encompass the physics of the microchip device, as well as its design methods and applications

Self-Healing of Open-Circuit Faults in Organic Thin-Film Transistor-Based Flexible Electronics

Flexible electronics has attracted tremendous attention due to the fast-growing market for portable devices and sensors. However, these devices usually suffer from internal and external forces, which can lead to the failure of interconnects in the circuit. To address this issue, some passive and active strategies have been developed for improving the reliability of interconnects in circuits. Although all these strategies are effective in tackling problems related to the mechanical stress, they have inherent limit in dealing with other failure causes or repairing the open fault. Therefore, in this dissertation, a particle-based self-healing (PBSH) technique has been developed. The detailed study starts with an overall review of the state of the art in techniques developed for improving the reliability of interconnects in flexible circuits. Then the mechanisms of the PBSH technique are analysed and the chemical treatment of metal particles are explored. The physical modelling of the healing is established, and relations between the healing time with the suspension concentration, electric field, length of open gap, and external resistance are verified by experimental results. In addition, to avoid the inherent conductivity of the suspension and the aggregation of micro-particles, they are modified by the oleic acid. This chemical treatment of metal particles improves the uniformity of the suspension and sets a threshold electric field for the occurrence of self-healing. As a key component in flexible circuits, an organic thin-film transistor (OTFT) fabricated by all inkjet-printing process has been developed and characterised in this study. This transistor uses 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPSPentacene) as the semiconductor, poly (vinyl cinnamate) (PVC) as the dielectric, silver as the electrodes, and CYTOP as the encapsulation. Based on this device, two basic circuits: the current mirror and the common-source (CS) amplifier have been successfully built on flexible substrates. The proper functioning of the printed devices and circuits becomes the base for the study of the self-healing in flexible circuits. Subsequently, the PBSH in OTFT device and circuit interconnects is verified. This technique can successfully repair open faults at both source and drain sides in OTFT device interconnects. Simultaneously, it can heal open faults occurring at different locations in flexible current mirror and common-source amplifier circuits biased at the static state. Moreover, the self-healing is also proved to be effective and stable in common-source amplifier when processing alternating current (AC) signals. In order to demonstrate the feasibility of the PBSH technique in real-world applications, more performance characterisations have been conducted. The bending test shows the reliability and stability of the healing in the bent condition. And the dualfaults test verifies the ability of the PBSH technique for healing more than one open fault in interconnects. In addition, methods of packaging the circuit and confining the healing material in the expected region are also developed, which prove the feasibility and manufacturability of the PBSH technique in integrated circuits. This study sets a new benchmark for improving the reliability of inkjet-printed flexible circuits

High voltage metal oxide thin film transistors to drive arrays of dielectric elastomer actuators

This thesis advances the field of high-voltage thin film transistors (HVTFTs) and dielectric elastomer actuators (DEAs) by demonstrating a strategy for low-voltage addressing of an array of high voltage soft actuators suspended on a flexible substrate. First, I present the first HVTFTs operating at 1 kV drain-source voltage, switching with an on-off ratio of 20 at 80 V gate-source voltage. The HVTFTs can operate at high voltage thanks to geometrical features increasing the breakdown voltage: a thick gate dielectric composed of a bilayer of alumina (100 nm) and Parylene-C (1 um), a long semiconducting channel (500 um), and a 150 &mlong non-gated region between the drain and the gate electrode called the offset gate. The use of an amorphous oxide semiconductor (AOS), zinc tin oxide (ZTO), enables a high on-currents of 0.1 mA. The ZTO was synthesized by a sol-gel process after spin-coating on a flexible polyimide substrate, previously passivated with alumina. I optimized the HVTFT switching properties by doping the ZTO layer with yttrium (5%). It improved the on-off ratio up to 1000 at 500 V operation voltage by decreasing the leakage current down to 100 nA. Then, I show the first integration of HVTFTs with DEAs. My ZTO HVTFTs switch DEAs on and off with only 30 V gate voltage under a bias voltage of 1.4 kV. The system time response in 50 ms. The demonstrator is a 4x4 array of diaphragm DEAs. A layer of 4x4 DEAs is suspended over a layer of 4x4 HVTFTs built on flexible polyimide. The DEAs and the HVTFTs were interconnected thanks to a flexible PCB in a resistive load inverter circuit architecture. A flexible 3D printed chamber was constantly biasing the DEA diaphragms with a back-pressure. The DEAs were made of PDMS and the active region is defined by overlapping carbon-PDMS electrodes. The device operates down to a 5mm radius of curvature. Finally, I demonstrate latching of the HVTFT and the DEA by using triboelectric sensors. Under a constant 500 V circuit bias, the control of the HVTFT gate with triboelectric generators enabled 4s latching of the inverter output voltage at 470 V for the off-state and at 120 V for the on-state. The latching of the DEAs with the HVTFT circuit finally proves that this approach can lead to a bistable control of DEAs. This PhD thesis results show that my HVTFTs are versatile components usable not only to address DEAs but also to interface low voltage sensors with high voltage actuators

Miniaturized Transistors, Volume II

In this book, we aim to address the ever-advancing progress in microelectronic device scaling. Complementary Metal-Oxide-Semiconductor (CMOS) devices continue to endure miniaturization, irrespective of the seeming physical limitations, helped by advancing fabrication techniques. We observe that miniaturization does not always refer to the latest technology node for digital transistors. Rather, by applying novel materials and device geometries, a significant reduction in the size of microelectronic devices for a broad set of applications can be achieved. The achievements made in the scaling of devices for applications beyond digital logic (e.g., high power, optoelectronics, and sensors) are taking the forefront in microelectronic miniaturization. Furthermore, all these achievements are assisted by improvements in the simulation and modeling of the involved materials and device structures. In particular, process and device technology computer-aided design (TCAD) has become indispensable in the design cycle of novel devices and technologies. It is our sincere hope that the results provided in this Special Issue prove useful to scientists and engineers who find themselves at the forefront of this rapidly evolving and broadening field. Now, more than ever, it is essential to look for solutions to find the next disrupting technologies which will allow for transistor miniaturization well beyond silicon’s physical limits and the current state-of-the-art. This requires a broad attack, including studies of novel and innovative designs as well as emerging materials which are becoming more application-specific than ever before

Micro- and nano-devices for electrochemical sensing

Electrode miniaturization has profoundly revolutionized the field of electrochemical sensing, opening up unprecedented opportunities for probing biological events with a high spatial and temporal resolution, integrating electrochemical systems with microfluidics, and designing arrays for multiplexed sensing. Several technological issues posed by the desire for downsizing have been addressed so far, leading to micrometric and nanometric sensing systems with different degrees of maturity. However, there is still an endless margin for researchers to improve current strategies and cope with demanding sensing fields, such as lab-on-a-chip devices and multi-array sensors, brain chemistry, and cell monitoring. In this review, we present current trends in the design of micro-/nano-electrochemical sensors and cutting-edge applications reported in the last 10 years. Micro- and nanosensors are divided into four categories depending on the transduction mechanism, e.g., amperometric, impedimetric, potentiometric, and transistor-based, to best guide the reader through the different detection strategies and highlight major advancements as well as still unaddressed demands in electrochemical sensing

Digital Microfluidics for Isothermal Nucleic Acid Amplification: Exploring Sensing Methodologies

Digital Microfluidics (DMF) has recently emerged as a promising candidate for nucleic acid amplification for molecular diagnostics, by virtue of its precise control over unit droplets without the need of any propulsion devices, ease of integration with chemical/biological reac-tions and multiplex assay capabilities. Nevertheless, current scientific research is still far from accomplishing the full potential of the technique, so new, innovative nanotechnology/biotech-nology hybrid approaches are necessary. As such, the purpose of this work is to contribute for the paradigm shift of nucleic acid amplification from central laboratories to point-of-care (POC) by designing and fabricating DMF devices compatible with isothermal nucleic acid amplifica-tion (loop-mediated isothermal amplification - LAMP). For biological validation of the devices, detection of cancer biomarker c-Myc is performed, and further real-time amplification moni-toring is attempted through several methodologies, namely fluorescence, impedance and elec-trochemical measurements. The DMF devices produced herein enable optimal temperature control, crucial for LAMP reactions, and further allow for a novel methodology of reagent mix-ing, based on dual actuation with back-and-forth motion and actuation frequency tuning. Such innovations lead to successful amplification of 0.5 ng/μL or 90 pg of c-Myc in one hour, in line with the range reported in the literature, and further monitoring of the LAMP reaction profile by microscopy-based fluorescence measurements. Impedimetric and electrochemical method-ologies did not meet the tight criteria required for biomarker detection, yet the developments achieved herein open the path for other applications. Lastly, the dielectric layer (key element of a DMF device) was optimized to assure long reactions (up to two hours) without device degradation.A microfluídica digital (MFD) surgiu como uma tecnologia promissora para amplificação de ácidos nucleicos em diagnóstico molecular, permitindo controlo sobre gotas unitárias sem necessidade de dispositivos de propulsão, facilidade de integração com reações químicas/bi-ológicas e capacidade de realização de ensaios simultâneos. Contudo, a investigação científica atual ainda está longe de atingir o máximo potencial da técnica, pelo que são necessárias abordagens novas, inovadoras e híbridas de nanotecnologia e biotecnologia. Como tal, o pro-pósito deste trabalho é contribuir para a mudança de paradigma da amplificação de ácidos nucleicos de laboratórios centralizados para ponto-de-atendimento (PDA) através do desenho e fabricação de dispositivos de MFD compatíveis com amplificação isotérmica de ácidos nu-cleicos (loop-mediated istothermal amplification - LAMP). Para validação biológica dos dispo-sitivos, será detetado o biomarcador de cancro c-Myc, e testada a monitorização da amplifica-ção em tempo real através de várias metodologias, nomeadamente medidas de fluorescência, impedância ou medidas eletroquímicas. Os dispositivos MFD produzidos permitem um con-trolo ótimo da temperatura, crucial para reações LAMP, e introduzem uma metodologia para mistura de reagentes, com movimentos em vaivém e ajuste da frequência de atuação. Tais inovações conduziram à amplificação de 0.5 ng/μL ou 90 pg de c-Myc em uma hora, em linha com o intervalo relatado na literatura, permitindo ainda monitorização do perfil da reação LAMP através de medidas de fluorescência mediadas por microscopia. As metodologias impe-dimétricas e eletroquímicas não cumpriram os exigentes critérios requeridos para deteção de biomarcadores, no entanto, os desenvolvimentos alcançados abrem caminho para outras apli-cações. Por último, a camada dielétrica (elemento-chave de um dispositivo MFD) foi otimizada para assegurar reações mais longas (até duas horas) sem degradação do dispositivo

Liquid Metal Printing with Scanning Probe Lithography for Printed Electronics

In den letzten Jahren hat das „Internet der Dinge“ (Englisch Internet of Things, abgekürzt IoT), das auch als Internet of Everything (Deutsch frei „Internet von Allem“) bezeichnet wird, mit dem Aufkommen der „Industrie 4.0“ einen Strom innovativer und intelligenter sensorgestützter Elektronik der neuen Generation in den Alltag gebracht. Dies erfordert auch die Herstellung einer riesigen Anzahl von elektronischen Bauteilen, einschließlich Sensoren, Aktoren und anderen Komponenten. Gleichzeitig ist die herkömmliche Elektronikfertigung zu einem hochkomplexen und investitionsintensiven Prozess geworden. In dem Maße, wie die Zahl der elektronischen Bauteile und die Nachfrage nach neuen, fortschrittlicheren elektronischen Bauteilen zunimmt, steigt auch die Notwendigkeit, effizientere und nachhaltigere Wege zur Herstellung dieser Bauteile zu finden. Die gedruckte Elektronik ist ein wachsender Markt, der diese Nachfrage befriedigen und die Zukunft der Herstellung von elektronischen Geräten neu gestalten könnte. Sie erlaubt eine einfache und kostengünstige Produktion und ermöglicht die Herstellung von Geräten auf Papier- oder Kunststoffsubstraten. Für die Herstellung gibt es dabei eine Vielzahl von Methoden. Techniken auf der Grundlage der Rastersondenlithografie waren dabei schon immer Teil der gedruckten Elektronik und haben zu Innovationen in diesem Bereich geführt. Obwohl die Technologie noch jung ist und der derzeitige Stand der gedruckten Elektronik im industriellen Maßstab, wie z. B. die Herstellung kompletter integrierter Schaltkreise, stark limitiert ist, sind die potenziellen Anwendungen enorm. Im Mittelpunkt der Entwicklung gedruckter elektronischer Schaltungen steht der Druck leitfähiger und anderer funktionaler Materialien. Die meisten der derzeit verfügbaren Arbeiten haben sich dabei auf die Verwendung von Tinten auf Nanopartikelbasis konzentriert. Die Herstellungsschritte auf der Grundlage von Tinten auf Nanopartikelbasis sind komplizierte Prozesse, da sie das Ausglühen (Englisch Annealing) und weitere Nachbearbeitungsschritte umfassen, um die gedruckten Muster leitfähig zu machen. Die Verwendung von Gallium-basierten, bei/nahe Raumtemperatur flüssigen Metallen und deren direktes Schreiben für vollständig gedruckte Elektronik ist immer noch ungewöhnlich, da die Kombination aus dem Vorhandensein einer Oxidschicht, hohen Oberflächenspannungen und Viskosität ihre Handhabung erschwert. Zu diesem Zweck zielt diese Arbeit darauf ab, Methoden zum Drucken von Materialien, einschließlich Flüssigmetallen, zu entwickeln, die mit den verfügbaren Druckmethoden nicht oder nur schwer gedruckt werden können und diese Methoden zur Herstellung vollständig gedruckter elektronischer Bauteile zu verwenden. Weiter werden Lösungen für Probleme während des Druckprozesses untersucht, wie z. B. die Haftung der Tinte auf dem Substrat und andere abscheidungsrelevante Aspekte. Es wird auch versucht, wissenschaftliche Fragen zur Stabilität von gedruckten elektronischen Bauelementen auf Flüssigmetallbasis zu beantworten. Im Rahmen der vorliegenden Arbeit wurde eine auf Glaskapillaren basierenden Direktschreibmethode für das Drucken von Flüssigmetallen, hier Galinstan, entwickelt. Die Methode wurde auf zwei unterschiedlichen Wegen implementiert: Einmal in einer „Hochleistungsversion“, basierend auf einem angepassten Nanolithographiegerät, aber ebenfalls in einer hochflexiblen, auf Mikromanipulatoren basierenden Version. Dieser Aufbau erlaubt einen on-the-fly („im Fluge“) kapillarbasierten Druck auf einer breiten Palette von Geometrien, wie am Beispiel von vertikalen, vertieften Oberflächen sowie gestapelten 3D-Gerüsten als schwer zugängliche Oberflächen gezeigt wird. Die Arbeit erkundet den potenziellen Einsatz dieser Methode für die Herstellung von vollständig gedruckten durch Flüssigmetall ermöglichten Bauteilen, einschließlich Widerständen, Mikroheizer, p-n-Dioden und Feldeffekttransistoren. Alle diese elektronischen Bauelemente werden ausführlich charakterisiert. Die hergestellten Mikroheizerstrukturen werden für temperaturgeschaltete Mikroventile eingesetzt, um den Flüssigkeitsstrom in einem Mikrokanal zu kontrollieren. Diese Demonstration und die einfache Herstellung zeigt, dass das Konzept auch auf andere Anwendungen, wie z.B. die bedarfsgerechte Herstellung von Mikroheizern für in-situ Rasterelektronenmikroskop-Experimente, ausgeweitet werden kann. Darüber hinaus zeigt diese Arbeit, wie PMMA-Verkapselung als effektive Barriere gegen Sauerstoff und Feuchtigkeit fungiert und zusätzlich als brauchbarer mechanischer Schutz der auf Flüssigmetall basierenden gedruckten elektronischen Bauteile wirken kann. Insgesamt zeigen der alleinstehende, integrierte Herstellungsablauf und die Funktionalität der Geräte, dass das Potenzial des Flüssigmetall-Drucks in der gedruckten Elektronik viel größer ist als einzig die Verwendung zur Verbindung konventioneller elektronischer Bauteile. Neben der Entwicklung von Druckverfahren und der Herstellung elektronischer Bauteile befasst sich die Arbeit auch mit der Korrosion und der zusätzlichen Legierung von konventionellen Metallelektroden in Kontakt mit Flüssigmetallen, welche die Stabilität der Bauteil beinträchtigen könnten. Zu diesem Zweck wurde eine korrelierte Materialinteraktionsstudie von gedruckten Galinstan- und Goldelektroden durchgeführt. Durch die kombinierte Anwendung von optischer Mikroskopie, vertikaler Rasterinterferometrie, Rasterelektronenmikroskopie, Röntgenphotonenspektroskopie und Rasterkraftmikroskopie konnte der Ausbreitungsprozess von Flüssigmetalllinien auf Goldfilmen eingehend charakterisiert werden. Diese Studie zeigt eine unterschiedliche Ausbreitung der verschiedenen Komponenten des Flüssigmetalls sowie die Bildung von intermetallischen Nanostrukturen auf der umgebenden Goldfilmoberfläche. Auf der Grundlage der erhaltenen zeitabhängigen, korrelierten Charakterisierungsergebnisse wird ein Modell für den Ausbreitungsprozess vorgeschlagen, das auf dem Eindringen des Flüssigmetalls in den Goldfilm basiert. Um eine ergänzende Perspektive auf die interne Nanostruktur zu erhalten, wurde die Röntgen-Nanotomographie eingesetzt, um die Verteilung von Gold, Galinstan und intermetallischen Phasen in einem in das Flüssigmetall getauchten Golddraht zu untersuchen. Schlussendlich werden Langzeitmessungen des Widerstands an Flüssigmetallleitungen, die Goldelektroden verbinden, durchgeführt, was dazu beiträgt, die Auswirkungen von Materialwechselwirkungen auf elektronische Anwendungen zu bewerten