Methods and tools for the design of RFICs

Ambient intelligence is going to focus the next advances in wireless technologies. Hence, the increasing demand on radio frequency (RF) devices and applications represents, not only a challenge for technological industries to improve its roadmaps, but also for RF engineers to design more robust, low-power, small-size and low-cost devices. Regarding to communication robustness, in the latest years, differential topologies have acquired an important relevance because of its natural noise and interference immunity. Within this framework, a differential n-port device can still be treated with the classical analysis circuit theory by means of Z-,Y-, h-parameters or the most suitable S-parameters in the radio frequency field. Despite of it, Bockelman introduced the mixed-mode scattering parameters, which more properly express the differential and common-mode behavior of symmetrical devices. Since then, such parameters have been used with a varying degree of success, as it will be shown, mainly because of a misinterpretation. Thereby, this thesis is devoted to extend the theory of mixed-mode scattering parameters and proposes the methodology to analyze such devices. For this proposal, the simplest case of a two-port device is developed. By solving this simple case, most of the lacks of the current theory are filled up. As instance, it allows the characterization and comparison of symmetric and spiral inductors, which have remained a controversy point until now. After solving this case, the theory is extended to a n-port device. Another key point on the fast and inexpensive development of radio frequency devices is the advance on fast CAD tools for the analysis and synthesis of passive devices. In the case of silicon technologies, planar inductors have become the most popular shapes because of its integrability. However, the design of inductors entails a deep experience and acknowledge not only on the behavior of such devices but on the use of electromagnetic (EM) simulators. Unfortunately, the use of EM simulators consumes an important quantity of time and resources. Thereby, this thesis is devoted to improve some of the aspects that slow down the synthesis process of inductors. Therefore, an ‘ab initio’ technique for the meshing of planar radio frequency and microwave circuits is described. The technique presented can evaluate the losses in the component with a high accuracy just in few seconds where an electromagnetic simulator would normally last hours. Likewise, a simple bisection algorithm for the synthesis of compact planar inductors is presented. It is based on a set of heuristic rules obtained from the study of the electromagnetic behavior of these planar devices. Additionally, design of a single-ended to differential low noise amplifier (LNA) in a CMOS technology is performed by using the methods and tools described.L'enginyeria de radiofreqüència i la tecnologia de microones han assolit un desenvolupament inimaginable i avui en dia formen part de la majoria de les nostres activitats diàries. Probablement, la tecnologia mòbil ha tingut un desenvolupament més ràpid que qualsevol altre avenç tecnològic de l'era digital. Avui en dia, podem dir que el paradigma de la mobilitat s'ha assolit i tenim accés ràpid a internet des de qualsevol lloc on podem estar amb un dispositiu de butxaca. No obstant això, encara hi ha fites per endavant. Es més que probable que el paradigma de l’ "ambient intelligence” sigui el centre dels pròxims avenços en les tecnologies sense fils. A diferencia del paradigma de l"ambient intelligence', l'evolució de la tecnologia de la informació mai ha tingut l'objectiu explícit de canviar la societat, sinó que ho van fer com un efecte secundari, en canvi, les visions d' “ambient intelligence” proposen expressament el transformar la societat mitjançant la connexió completa i la seva informatització. Per tant, l'augment de la demanda de dispositius de ràdio freqüència (RF) i de les seves possibles aplicacions representa, no només un repte per a les indústries tecnològiques per millorar els seus plans de treball, sinó també per als enginyers de RF que hauran de dissenyar dispositius de baixa potència, més robusts, de mida petita i de baix cost. Quant a la robustesa dels dispositius, en els últims anys, les topologies de tipus diferencial han adquirit una important rellevància per la seva immunitat natural al soroll i resistència a les interferències. Dins d'aquest marc, un dispositiu de nports diferencial, encara pot ser tractat com un dispositiu 2nx2n i la teoria clàssica d'anàlisi de circuits (és a dir, la temia de quadripols) es pot aplicar a través de paràmetres Z, Y, h o els paràmetres S, més adequats en el camp de freqüència de ràdio. Tot i això, Bockelman i Eisenstadt introdueixen els paràmetres S mixtos, que expressen més adequadament el comportament diferencial i en mode comú de dispositius simètrics o asimètrics. Des de llavors, aquests paràmetres s'han utilitzat amb un grau variable d'èxit, com es mostrarà, principalment a causa d'una mala interpretació. D'aquesta manera, la primera part d'aquesta tesi està dedicada a estendre la teoria dels paràmetres S de mode mixt i proposa la metodologia d'anàlisi d'aquest tipus de dispositius i circuits. D'aquesta forma, en el Capítol 2, es desenvolupa el cas més simple d'un dispositiu de dos ports. En resoldre aquest cas simple, la major part de les mancances de la teoria actual es posen de relleu. Com a exemple, pennet la caracterització i la comparació de bobines simètriques i espiral no simètriques, que han estat un punt de controvèrsia fins ara. Després de resoldre aquest cas, al Capítol 3 s'estén la teOIia a un dispositiu de n-ports dels quals un nombre pot ser single-ended i la resta diferencials. És en aquest moment quan la dualitat existent entre els paràmetres S estàndard i de mode mixt es pot veure clarament i es destaca en el seu conjunt. Aquesta teoria permet, tanmateix, estendre la teoria clàssica d'amplificadors quan s'analitzen per mitjà de paràmetres S. Un altre punt clau en el desenvolupament ràpid i de baix cost dels dispositius de radiofreqüència és l'avenç en les eines CAD ràpides per a l'anàlisi i síntesi dels dispositius passius, en especial dels inductors. Aquests dispositius apareixen tot sovint en el disseny de radio freqüència degut a la seva gran versatilitat. Tot i que hi ha hagut múltiples intents de reemplaçar amb components externs o circuits, fins i tot actius, en el cas de les tecnologies de silici, els inductors planars s'han convertit en les formes més populars per la seva integrabilitat. No obstant això, el disseny d'inductors implica conèixer i posseir una experiència profunda no només en el comportament d'aquests dispositius, però també en l'ús de simuladors electromagnètics (EM). Desafortunadament, l'ús dels simuladors EM consumeix una quantitat important de temps i recursos. Per tant, la síntesi dels inductors representa un important inconvenient actualment. D'aquesta manera, la segona part d'aquesta tesi està dedicada a millorar alguns dels aspectes que frenen el procés de síntesi dels inductors. Per tant, en el Capítol 4, es descriu una tècnica 'ab initio' de generació de la malla per bobines planars en ràdio freqüència i microones. La tècnica es basa en l'estudi analític dels fenòmens d'aglomeració de corrent que tenen lloc a l'interior del component. En aquesta avaluació, no es requereix una solució explícita dels corrents i de les càrregues arreu del circuit. Llavors, el nombre de cel•les de la malla assignades a una tira de metall donada, depèn del valor inicialment obtingut a partir de l'estudi analític. La tècnica presentada pot avaluar les pèrdues en el component amb una gran precisió només en uns pocs segons, quan comparat amb un simulador electromagnètic normalment es necessitaria hores. De la mateixa manera, en el Capítol 5 es presenta un senzill algoritme de bisecció per a la síntesi d'inductors planars compactes. Es basa en un conjunt de regles heurístiques obtingut a partir de l'estudi del comportament electromagnètic d'aquests dispositius planars. D'aquesta manera, el nombre d'iteracions es manté moderadament baix.D'altra banda, per tal d'accelerar l'anàlisi en cada pas, s'utilitza un simulador ràpid electromagnètic planar, el qual es basa en el coneixement que es té del component sintetitzat. Finalment, en el Capítol 6, la metodologia de paràmetres S de mode mixt proposada i les eines CAD introduides s'utilitzen àmpliament en el disseny d'un amplificador de baix soroll “single-ended” a diferencial (LNA), mitjançant una tecnologia estàndard CMOS.L'amplificador de baix soroll és un dels components claus en un sistema de recepció de radio freqüència, ja que tendeix a dominar la sensibilitat i la figura de soroll (NF) de tot el sistema. D'altra banda, les característiques d'aquest circuit estan directament relacionades amb els components actius i passius disponibles en una tecnologia donada. Per tant, la tecnologia escollida, el factor de qualitat dels passius, i la forma com es caracteritzen tindran un alt impacte en les principals figures de mèrit del circuit real

Modeling methodology of high-voltage substrate minority and majority carrier injections

This paper presents a modeling methodology for substrate current coupling mechanisms. An enhanced model of the diode ensuring continuity of minority carriers is used to build an equivalent schematic, accounting for minority and majority carrier propagation in the substrate. For the first time a typical H-bridge structure is simulated with the proposed methodology. The parasitic current injected in the substrate by a high-voltage structure is simulated in a circuit-level simulator as well as with a finite elements method. Both are compared to measurements and show a very good agreement. The simulation resources needed by the proposed equivalent schematics are thus greatly reduced in regard to the finite element approach, offering an efficient tool for substrate modeling in smart power IC's

Thermal optimization of a polyimide V-groove actuator for a walking micro-robot

The objective of this thesis was to develop a Finite Element Model for the Polyimide V-groove actuator (fabricated by T. Ebefors, Sweden). Extensive FEM simulations for this MEMS actuator were performed using ANSYS 5.6. An optimization module was used to improve the performance of the existing design. A substantial improvement in the performance was observed for the proposed design. In short, this research established a methodology that can be extended for modeling and simulation of other MEMS devices. A computer simulated FEM model for heat and deflection analysis was validated for two configurations of the Polyimide V-groove Actuator (i.e. a Serpentine Heater Configuration and a Polysilicon Heater Configuration). Some differences between the simulated and experimental results (reported by T. Ebefors) were noted in the low frequency domain. The role of various parameters including thermal conductivity and wall temperature has been investigated to eliminate these discrepancies. To improve the performance of the actuator, different design geometries were proposed and each design was simulated for various frequencies. Significant performance improvement was observed for the case of uniform diaphragm thickness at the V-groove bottom . The optimization module of ANSYS was used for optimizing the thickness of the silicon diaphragm (referred to as single variable optimal design ). Steady state analysis showed that there is an improvement in the deflection and the force developed for the single variable optimal design over T. Ebefors\u27 design. Transient analysis showed improvement in the cooling characteristics of the single variable optimal design over T. Ebefors\u27 design. In the second optimization exercise (referred to as overall optimization ), all the dimensions of the V-grooves were used as design variables. A three times increase in the deflection was observed in the overall optimal design as compared to the single variable optimal design. Also, there is a three times reduction in the maximum force developed by the overall optimal design. Transient analysis revealed that the overall optimal design has better cooling characteristics compared to the single variable optimal design. Hence, for an application where the applied force is not a critical factor, the overall optimal design would be suitable, e.g. if a lightweight mirror is mounted on the end of the actuator, the mirror can be moved through a larger distance. For micro robotics applications, the optimal design with a single variable could be useful, where the load carrying capacity of this design is superior

Flexible stretchable electronics for sport and wellbeing applications

Wearable electronics are becoming increasingly widespread in modern society. Though these devices are intended to be worn, integrated into clothing and other everyday objects, the technologies and processes used to manufacture them is no different than those that manufacture laptops and mobile phones. Many of these devices are intended to monitor the user’s health, activity and general wellbeing, within clinical, recreational and assistive environments. Consequently, the inherent incompatibility of these rigid devices with the soft, elastic structure of the human body can in some cases can be uncomfortable and inconvenient for everyday life. For devices to take the step from a ‘wearable’ to an ‘invisible’, a drastic rethinking of electronics manufacturing is required.The fundamental aim of this research is to establish parameters of usefulness and an array of materials with complimentary processes that would assist in transitioning devices to long term almost invisible items that can assist in improving the health of the wearer. In order to approach this problem, a novel architecture was devised that utilised PDMS as a substrate and microfluid channels of Galinstan liquid alloy for interconnects. CO2 laser machining was investigated as a means of creating channels and vias on PDMS substrates. Trace speeds and laser power outputs were investigated in order to find an optimal combination. The results displayed upper limits for power densities; where surpassing this limit resulted in poor repeatability and surface finish. It was found that there was an optimal set of trace speeds that ranged from approximately 120mm/s to 190mm/s that resulted in the most reliable and repeatable performance. Due to the complex nature of a materials variable energy absorption properties, it is not possible to quantify a single optimal parameter set.To understand the performance of these devices in situ, finite element analysis was employed to model deformations that such a device could experience. The aims here were to investigate the bond strength required to prevent delamination, between the silicon-PDMS and PDMS-PDMS bonds, in addition to the stress applied to the silicone die during these deformations. Based upon the applied loads the required bond strengths would need to be at least ~65kPa to maintain PDMS-PDMS adhesion during these tests, while stress on the silicone-PDMS adhesion required an expected v higher ~160kPa, both of which are within the reach of existing bonding techniques that are capable of withstanding a pressure of ~600kPa before failure occurs. Stress on the silicon die did not exceed ~7.8 MPa during simulation, which is well below the fracture stress.By developing knowledge about how various components of such a system will respond during use and under stress, it allows future engineers to make informed design decisions and develop better more resilient products.</div

Transient Safe Operating Area (tsoa) For Esd Applications

A methodology to obtain design guidelines for gate oxide input pin protection and high voltage output pin protection in Electrostatic Discharge (ESD) time frame is developed through measurements and Technology Computer Aided Design (TCAD). A set of parameters based on transient measurements are used to define Transient Safe Operating Area (TSOA). The parameters are then used to assess effectiveness of protection devices for output and input pins. The methodology for input pins includes establishing ESD design targets under Charged Device Model (CDM) type stress in low voltage MOS inputs. The methodology for output pins includes defining ESD design targets under Human Metal Model (HMM) type stress in high voltage Laterally Diffused MOS (LDMOS) outputs. First, the assessment of standalone LDMOS robustness is performed, followed by establishment of protection design guidelines. Secondly, standalone clamp HMM robustness is evaluated and a prediction methodology for HMM type stress is developed based on standardized testing. Finally, LDMOS and protection clamp parallel protection conditions are identifie

Resilient and Real-time Control for the Optimum Management of Hybrid Energy Storage Systems with Distributed Dynamic Demands

A continuous increase in demands from the utility grid and traction applications have steered public attention toward the integration of energy storage (ES) and hybrid ES (HESS) solutions. Modern technologies are no longer limited to batteries, but can include supercapacitors (SC) and flywheel electromechanical ES well. However, insufficient control and algorithms to monitor these devices can result in a wide range of operational issues. A modern day control platform must have a deep understanding of the source. In this dissertation, specialized modular Energy Storage Management Controllers (ESMC) were developed to interface with a variety of ES devices. The EMSC provides the capability to individually monitor and control a wide range of different ES, enabling the extraction of an ES module within a series array to charge or conduct maintenance, while remaining storage can still function to serve a demand. Enhancements and testing of the ESMC are explored in not only interfacing of multiple ES and HESS, but also as a platform to improve management algorithms. There is an imperative need to provide a bridge between the depth of the electrochemical physics of the battery and the power engineering sector, a feat which was accomplished over the course of this work. First, the ESMC was tested on a lead acid battery array to verify its capabilities. Next, physics-based models of lead acid and lithium ion batteries lead to the improvement of both online battery management and established multiple metrics to assess their lifetime, or state of health. Three unique HESS were then tested and evaluated for different applications and purposes. First, a hybrid battery and SC HESS was designed and tested for shipboard power systems. Next, a lithium ion battery and SC HESS was utilized for an electric vehicle application, with the goal to reduce cycling on the battery. Finally, a lead acid battery and flywheel ES HESS was analyzed for how the inclusion of a battery can provide a dramatic improvement in the power quality versus flywheel ES alone

Gallium Nitride (GaN) specific mechanical phenomena and their influence on reliability in power HEMT operation

In den letzten Jahren ist Gallium Nitride (GaN) auf dem Markt für Leistungsbauelemente in größerem Maßstab angekommen, wodurch die Notwendigkeit eines tieferen Verständnisses der grundlegenden Interaktionen im Chip notwendig geworden ist. Umfangreiche Forschung wurde auf dem Gebiet der elektrischen Effekte durchgeführt, da dort die wichtigsten Unterschiede gegenüber Silicon (Si) liegen. Im Gegensatz zur generellen Forschungsrichtung fokussiert sich diese Arbeit auf neue mechanische und thermo-mechanische Phänomene, die bisher in Si Bauteilen nicht vorhanden waren. In Kapitel 3 wird die Wechselwirkung von mechanischer Spannung, Temperatur und elektrischem Feld besprochen. Die physikalischen Effekte, die diese Zustandsgrößen verbinden, werden im Detail erklärt und es wird gezeigt, welche Effekte aufgrund ihrer Größe sicher vernachlässigt werden können und welche einer näheren Untersuchung bedürfen. In Kapitel 4 werden die thermischen Fähigkeiten bei massiver thermischer Überlastung, die durch einen Kurschluss verursacht wird, diskutiert. Der Testaufbau, auf dem die Chips bis zum Ausfall gestresst werden, wird vorgestellt. Anschließend werden die ausgefallenen Bauelemente analysiert und die Grundursache mit Hilfe von der Finite Element Analysis (FEA) und einer umfassenden, detaillierten physikalischen Fehleranalyse erklärt. Zusätzliche Vorschläge für Verbesserungen in diesem speziellen Versagensmodus werden am Ende gegeben. Kapitel 5 gibt Einblicke in die Resonanzphänomene bei GaN. Da GaN piezoelektrisch ist kann es als Aktuator fungieren, um den gesamte Chip in Resonanz zu bringen. Dieses Phänomen ist vermessen worden und wird anschließend durch FEA simuliert. Die Simulation wird dann gegen die Messung validiert, um die Richtigkeit der Simulation sicherzustellen. Aus diesen Simulationen werden Schlussfolgerungen bezüglich der Zuverlässigkeit der beiden am meisten gefährdeten Schichten, der GaN Schicht und Chip Verbindungsschicht, gezogen. Zusätzlich werden am Ende Extremfälle diskutiert, die einen Ausblick auf kommende Chipgehäuse geben sollen.In recent years Gallium Nitride (GaN) has entered the market for power devices on a broader scale, increasing the need for a deeper understanding of fundamental interactions within such devices. Extensive research has been conducted in the field of electric effects since the main differences of GaN over Silicon (Si) lie there. In contrast to this, this thesis will focus on new mechanical and thermo-mechanical phenomena, previously not occurring in Si devices. Chapter 3 will introduce the interactions of the mechanical stress, the temperature and the electric field. The effects connecting these state variables are explained in detail and it will be shown which effects can be neglected and which ones need closer investigations. In Chapter 4 the thermal capabilities under massive thermal overload, caused by a short circuit pulse, are discussed. The setup, which is used to stress the chips until failure, is presented. Failed devices are analyzed extensively by in depth physical failure inspection methods. Root cause analysis is done by means of Finite Element Analysis (FEA) and in depth physical failure analysis, finally enabling to provide suggestions for improvements in this particular failure mode. Chapter 5 will elaborate on resonance phenomena in GaN. Since GaN is piezoelectric it can act as an actuator to resonate the whole chip assembly. This phenomenon is measured in two steps and subsequently investigated by FEA. The Finite Element (FE) simulation results are validated against the measurements to ensure the correctness of the FE model. From these simulations conclusions regarding the reliability of the two most failure prone layers, namely the GaN stack and the die attach layer, are drawn. Additionally extreme cases are discussed giving an outlook on this issue in advanced package assemblies

Modeling of reverse current effects in trench-based smart power technologies

The increase in complexity in todays automotive products is driven by the trend to implement new features in the area of safety, comfort and entertainment. This significantly raises the safety requirements of new ICs and the identification of possible sources of failures gains in priority. One of these failure sources is the injection of parasitic currents into the common substrate of a chip. This does not only occur during exceptions in the operation of the IC but also affects applications which require switching of inductive loads. The difficulty to handle substrate current injection originates from its nonlocality as it potentially influences the entire IC. In this thesis a point-to-point modeling scheme for Spice-based circuit simulation is proposed. It addresses parasitic coupling effects caused by minority carrier injection into the substrate of a deep-trench based BCD technology. Since minority carriers can diffuse over large distances in the common substrate and disturb circuits in their normal operation, a quantitative approach is necessary to address this parasitic effect early during design. An equivalent circuit based on the chip's design is extracted and the coupling effect between the perturbing devices and the susceptible nodes is represented by Verilog-AMS models. These models represent the three main components in the coupling path which are the forward biased diode at the perturbing device, the reverse biased diode at the susceptible node, and the intermediary common substrate of the chip. An automated layout extraction framework identifies the injectors of the minority carriers and the sensitive devices. Additionally, it determines the relevant parameters for the models. The curve fitting functions of the models are derived from calibrated TCAD simulations which are based on the measurement results of two dedicated test chips. The test chips were specifically designed to provide detailed analysis capabilities of this parasitic coupling effect. This led to a design which contains several different injector nodes and a large number of susceptible nodes spread over the entire area of the chip. Additionally, the chip incorporates the most commonly used layout-based guard structures to obtain an in-depth insight on their efficiency in recent BCD technologies. Based on the results obtained by measurements of the test chips the underlying physics of the coupling effect are discussed in detail. Minority carrier injection in the substrate is not much different to the operating principle of a bipolar transistor and the differences and similarities between them are presented. This forms the basis of the model development and explains how the equations of the Verilog-AMS models were derived. Finally, the entire simulation flow is evaluated and the simulation results are compared to measurements of the chip

High Efficiency IGBTs through Novel Three-Dimensional Modelling and New Architectures

New Insulated Gate Bipolar Transistor (IGBT) designs are reliant on simulation tools, such as Sentaurus technology computer-aided design (TCAD) models, which allow for rapid device development that could not be achieved by manufacturing prototypes due to the cost and time associated with fabrication. These simulations are, though, computationally expensive and typically most design engineers develop these TCAD models only in two dimensions. This leads to inaccuracies in the model output since manufactured transistors are inherently three-dimensional (3D). Based upon a commercial IGBT, this thesis begins by outlining the development of a 3D TCAD model using design details provided by the manufacturer. Large variations between the experimental data from the manufactured device and the simulation model lead to the discovery of widespread birds-beaking within the IGBT – an uncontrollable processing defect that the manufacturer was unaware of. This thesis presents a new simulation technique to account for this processing error while minimising computational effort and investigates the consequence of this birds-beak on the reliability of the device. The verified 3D IGBT model was also used to determine an optimum cell design that considered critical 3D effects omitted from previous studies. An extensive literature review for the Reverse-Conducting IGBT (RC-IGBT) is provided. It is shown that despite the benefits of the RC-IGBT, the device suffers from many undesirable design trade-offs that have prevented its widespread use. The RC-IGBT designs that have currently been proposed in literature, either present a trade-off in performance, an inability to be manufactured, or a requirement for a custom gate drive. This thesis presents a new RC-IGBT concept, the ‘Dual Implant SuperJunction (SJ) RC-IGBT’ that addresses these concerns and is manufacturable using current state of the art techniques. The concept and proposed manufacturing method enables, for the first time, a full SuperJunction structure to be achieved in a 1.2kV device. In addition, an investigation into a coordinated switching scheme using both a silicon IGBT and silicon-carbide MOSFET was undertaken, which aimed to improve turn-off losses within the IGBT without sacrificing on-state losses. Thermal modelling of the power devices switching under inductive load was explored as the system was optimised to use a SiC MOSFET in excess of its nominal ratings, reducing the overall system cost.EPSRC Doctoral Training Partnership scheme (grant RG75686

Single-molecule detection and microfluidics: generating systems for the in vitro diagnostics of stroke

There is currently no available molecular diagnostic test for stroke; the common modality for diagnosis consists of computed tomography or magnetic resonance imaging. Unfortunately, the use of these diagnostic regimens can delay proper therapeutic treatment, which requires administration within the first 3 h of a stroke event. We are developing a molecular assay that can report, in near real time and at the point-of-care, the presence or absence of biomarkers specifically targeted for the diagnosis of ischemic or hemorrhagic stroke. The proposed strategy uses blood-borne mRNAs that are either under-expressed or over-expressed as a result of tissue damage within the brain. The ability to report on these diagnostic markers is enabled through the use of a fluidic bio-processor fabricated in polymers via micro-replication to provide autonomous sample processing. This bio-processor comprises a fluidic motherboard that possesses task-specific modules for the selection of white blood cells from a blood sample, cell lysis and solid-phase extraction of the mRNA markers, ligase detection reaction to identify the mRNA markers and an optical module for multiplexed detection. The sample-processing pipeline was streamlined to generate a rapid assay turn-around-time by employing single-molecule detection. The output of the clinical sample processing hardware are molecular beacons undergoing single pair Fluorescence Resonance Energy Transfer (spFRET) that are digitally counted to provide exquisite analytical sensitivity for the expression profiling of the relevant mRNA markers. The presentation will discuss the use of spFRET for mRNA expression profile with comparisons made to quantitative real-time PCR