A Petri-Net-Based Scheduling Strategy for Dual-Arm Cluster Tools With Wafer Revisiting

International audienceThere are wafer fabrication processes in cluster tools that require wafer revisiting. The adoption of a swap strategy for such tools forms a 3-wafer cyclic (3-WC) period with three wafers completed in each period. It has been shown that, by such a scheduling strategy, the minimal cycle time cannot be reached for some cases. This raises a question of whether there is a scheduling method such that the performance can be improved. To answer this question, a dual-arm cluster tool with wafer revisiting is modeled by a Petri net. Based on the model, the dynamical behavior of the process is analyzed. Then, a 2-wafer cyclic (2-WC) scheduling strategy is revealed for the first time. Cycle time analysis is conducted for the proposed strategy to evaluate its performance. It shows that, for some cases, the performance obtained by a 2-WC schedule is better than that obtained by any existing 3-WC ones. Thus, they can be used to complement each other in scheduling dual-arm cluster tools with wafer revisiting. Illustrative examples are given

Cluster tools with chamber revisiting-modeling and analysis using timed Petri nets

Timed Petri nets are formal models of discrete concurrent systems. Since the durations of all activities are included in the model descriptions, many performance characteristics can be derived from such models. In the case of cluster tools, net models represent the flow of wafers through the chambers of the tool as well as consecutive actions performed by the robotic transporter. Steady-state performance of cluster tools with chamber revisiting is investigated in this paper. A systematic development of detailed tool schedules, based on a general behavioral description of the tool, is proposed and is used to derive the corresponding Petri net models. Symbolic performance characteristics of the modeled tools are obtained by using place invariants, without exhaustive reachability analysis. Simple examples presented in the paper can be easily extended in many ways

Operational Models for Evaluating the Impact of Process Changes on Cluster Tool Performance

This thesis describes operational models that integrate process models to expedite process change decisions for cluster tool performance improvement. The process engineer attempting a process change needs to wait for the industrial engineer to approve the change after making sure it does not degrade cluster tool performance. Having a model that integrates process parameters into the operational model of the tool helps the process engineer quantify the impact of process changes on tool performance.This makes the process change decision faster. Two integrated models for understanding cluster tool behavior have been developed here. One is a network model that evaluates the total time needed to process a lot of wafers for a given sequence of activities involved in the process. Including a manufacturing process model (in the form of a Response Surface Model) gives an integrated network model that relates the total lot processing time to process parameters like temperature and pressure and to process times. The second model developed is an integrated simulation model that can be used when the sequence of wafer moves is not given but is determined by a scheduling rule. The model can be used to quantify the impact of changes to process parameters and product characteristics like deposition thickness on total lot processing time. The thesis contains examples that illustrate the types of insights that one can gain into cluster tool behavior from using these integrated models

Black Silicon for Photodiodes: Experimentally Implemented and FDTD Simulated

Die hier vorgelegten experimentelle Ergebnisse zeigen die Herstellung von schwarzem Siliziumzur Anwendung in Photodioden im Bereich zwischen 200 nm und 800 nm durchPlasmabearbeitung. Berechnungen verschiedener Nano-strukturgeometrien mit der Finite-Differenzen-Methode im Zeitbereich (FDTD) werden mit Ulbricht-kugel Reflexionmessungenvon physikalischen Strukturen verglichen. Die spektrale Empfindlichkeit der schwazenSiliziumphotodioden im roten Bereich (675 nm – 750 nm) treffen das 0.5 A/W Ziel. Im blauenBereich (375 nm-425 nm) wird eine Verbesserung von Photodioden in der Wafermitte von +0.07A/W im Vergleich zu oxide-bedeckten Photodioden erreicht. Klare Unterschiede zwischenverschiedenen Spitzen der Nanostrukturen werden experimentell und theoretisch belegt. Sie sindentscheidend, um die Reflexion gering zu halten.Das Entstehen der Nanostrukturen in unserer SF6/O2 Plasmamischung wird durch dieSiliziumätzrate in Abhängigkeit von der Fluorkonzentration (mit einem veränderlichen Fuor-zu-Sauerstoff Verhältnis) in zwei Bereichen erklärt. In einem Bereich gibt es überschüssigeFluorradikalerzeugung (schwache Passivierung) und im anderen überschüssigeFluorradikalverbrauch (starke Passivierung). Dies wird experimentell gezeigt.Inhärente Ungleichmäßigkeiten in der Plasmaanlage, die ein kleines Prozessfenster mit extremanisotropischen Nanostrukturen und nachteiliger Mitte-zu-Rand Waferuniformitaet ergeben,werden durch die Einführung von einem Nanoloading Schritt beseitigt. Die Siliziumoberflächewird am Anfang mit einer Reihe von sehr uniformen Nanopfeiler geaetzt. Diese Nanoloading-Maske wird anschließend mit Chemikalien, die allein keine Nanostrukturen ergeben,plasmageätzt. Die entsprechenden Ergebnisse sind isotropischer und haben Eigenschaften, die fürReflexionsabsenkung erwünscht sind. Dadurch entwickeln wir eine Abkoppelung zwischen dieAbhängigkeit der erreichbaren Nanostrukturgeometrien und Plasmaanlagengeometrie.Erweitertes Nanoloading wird benutzt, um die Prozesse erfolgreich von blanken zu maskiertenScheiben zu transferieren.FDTD Ergebnisse zeigen, dass der größte Teil der Lichtabsorbtion im Bereich vom 200 nm zu800 nm direkt in der Antireflexschicht der Nanostrukturen stattfindet. Dies ist im starkenVergleich zu der Situation mit einer normalen Antireflexschicht. Weitere FDTD Simulationenuntersuchen die Periodizität von Nanostrukturen, und zeigen deutliche Gittereigenschaften. Dieideale Breite der Strukturen für Reflexionsabsenkung wird zwischen 100 nm und 200 nm iminteressanten Spektralbereich (200 nm - 800 nm) berechnet. Periodische Strukturen mit Breitenüber 200 nm reflektieren Licht in verschiedene Gitterordnungen. Die ideale Strukturhöhe fürvernachlässigbare Reflexion wird in diesem Bereich mindestens 500 nm. Allerdings, erweisensich die periodischen Stuktursimulationen nicht als die richtige Methode, um die UlbrichtkugelMessungen von physikalischen Strukturen zu beurteilen. Das Hauptproblem ist eine Überlappungzwischen Nanostrukturen (z.B. ungetrennt während eines Plasmaprozesses) stört die Zustände fürPeriodizität (die Diffraction in die Komponentwinkeln) entsprechend der Breite der Stukturen,und stoert auch die Gradient-brechungsindex (Dadurch ist Reflexion erhöht. FDTD Simulationenwerden am Besten in Übereinstimmung mit den Eigenschaften der physikalischen selbstorganisierten Nanostrukturen gebracht, wenn eine nichtperiodische Oberfläche mit einer simuliertwird.Randbedingungen für FDTD in Bezug auf Simulationen von nicht-senkrecht einfallendem Lichtin 2D werden diskutiert. Dispersion im Injektionswinkel führt zu Schwierigkeiten, wenn manRechnungen mit einer Breitbandquelle durchführen will, weil nur einfallendes Licht mit derzentralen Wellenlänge den vorgegebenen Einfallswinkel hat. Die größte und kleinste Wellenlängeim Quellspektrum zeigen die stärkste Abweichung. Alle Wellenlägen einzeln nacheinander zusimulieren würde zu einer nicht akzeptablen Rechenzeit führen. Die hier gezeigte Lösung teilt daskomplete gewünschte Spektrum, in kleinere simulierbare Bänder, und ergibt ausreichendeErgebnisse und schränkt gleichzeitig Dispersionsfehler ein. Weiterhin wird es hier gezeigt, dass6eine moegliche Verbesserung der winkel-abhängigen PML Leistung erreichbar ist, wenn einGradientindex vor der PML eingeführt wird.Es wird experimentell bewiesen, dass Reflexionsabsenkung nicht immer mit ausreichendenelektrischen Eigenschaften verbunden ist, weil das Plasmaätzen um die Oberflächentopographiezu ändern auch stark die Lebensdauer der Minoritätträger wegen eines Anstieges vonRekombination durch Gitterschädigung und einer allgemeinen Vergrößerung in Oberflächeändert.The experimental results presented here show the creation of black silicon throughplasma processing and its subsequent implementation as an anti-reflective coating forphotodiodes in the range of 200 nm to 800 nm. Finite difference time domain (FDTD)calculations of various nano-structure geometries are compared to integrating sphere reflectionmeasurements of physical structures. The spectral sensitivity of manufactured black siliconphotodiodes in the red region (675 nm to 750 nm) meets the set 0.5 A/W target, while in the blueregion (375 nm to 425 nm) an improvement of +0.07 A/W over oxide covered diodes is achievedfor center cites. Clear separation between nano-structure tips is experimentally demonstrated asthe deciding factor to improve reflection suppression.The appearance of nano-structures on the silicon surface when processed in the SF6/O2plasma mixture is explained by generalizing the etch rate of silicon dependant on fluorineconcentration (with a varying fluorine to oxygen gas ratio) into two regions, one of excessfluorine generation (weakly passivating) and one of excess fluorine consumption (stronglypassivating). This is experimentally verified.Inherent non-uniformities of the plasma processing chamber which yield a small processwindow of extremely anisotropic nano-structures and a poor center-to-edge wafer uniformity areeliminated by the introduction of a nano-loading step. The silicon wafer surface is first etchedwith a set of highly uniform nano-pillars. The nano-loading mask is subsequently plasma etchedutilizing gas compositions that do not by themselves result in the appearance of nano-structureson the silicon wafer surface. This yields new less-anisotropic geometries with properties moredesirable for reflection suppression and decouples the dependence of attainable nano-structuregeometry on plasma chamber geometry. An extended nano-loading approach is successfullyapplied to transfer plasma processes from blank wafers to masked wafers.FDTD results show that the majority of light absorption in the spectrum from 200 nm to800 nm takes place within the silicon nano-structure antireflective coating, in contrast to thesituation encountered with a standard anti-reflective coating. The periodicity of nano-structures isinvestigated with FDTD and clear diffraction grating properties are demonstrated. The idealwidth of nano-structures for reflection suppression is calculated to be between 100 nm and 200nm for the light spectrum of interest (200 nm to 800 nm). Any periodic structure with widths over200 nm will begin diffracting light into non-specular angles. The ideal structure height iscalculated to be (at least) 500 nm. However, the periodic structure simulations do not prove to bethe most accurate way to evaluate the measured specular and diffuse components of real physicalstructures. The problem being that overlapping nano-structures (for example unseparated throughthe plasma etch process) disturb the conditions of periodicity (diffraction into component angles)corresponding to the structures overall width. FDTD simulations are best correlated to the opticalproperties of physical self-organized nano-structures (integrating sphere measurements ofspecular and diffuse components) when a non-periodic surface is simulated.Boundary conditions for the FDTD are discussed in the process of simulating non-normalincidence light on 2D structures. Dispersion in the injection angle for a simulation createsdifficulties in simulating broadband spectrums in a single simulation, as only the centerwavelength possesses the correct theta, while the smallest and largest wavelength in the incidentexperience the most extreme error in incident theta. Simulating each wavelength is not possible asit yields �incalculable� computational times. The solution provided breaks the desired spectruminto several smaller spectrums and gives satisfactory results while limiting the amount ofdispersive error

Memory Hierarchy Design for Next Generation Scalable Many-core Platforms

Performance and energy consumption in modern computing platforms is largely dominated by the memory hierarchy. The increasing computational power in the multiprocessors and accelerators, and the emergence of the data-intensive workloads (e.g. large-scale graph traversal and scientific algorithms) requiring fast transfer of large volumes of data, are two main trends which intensify this problem by putting even higher pressure on the memory hierarchy. This increasing gap between computation speed and data transfer speed is commonly referred as the “memory wall” problem. With the emergence of heterogeneous Three Dimensional (3D) Integration based on through-silicon-vias (TSV), this situation has started to recover in the past years. On one hand, it is now possible to improve memory access bandwidth and/or latency by either stacking memories directly on top of processors or through abstracted memory interfaces such as Micron’s Hybrid Memory Cube (HMC). On the other hand, near memory computation has become worthy of revisiting due to the cost-effective integration of logic and memory in 3D stacks. These two directions bring about several interesting opportunities including performance improvement, energy and cost reduction, product miniaturization, and modular design for improved time to market. In this research, we study the effectiveness of the 3D integration technology and the optimization opportunities which it can provide in the different layers of the memory hierarchy in cluster-based many-core platforms ranging from intra-cluster L1 to inter-cluster L2 scratchpad memories (SPMs), as well as the main memory. In addition, by moving a part of the computation to where data resides, in the 3D-stacked memory context, we demonstrate further energy and performance improvement opportunities

Surface-Enhanced Spectroelectrochemistry using Synchrotron Infrared Radiation

Electrochemical reactions are inherently heterogeneous, occurring at the interface between a solid electrode and an electrolyte solution. Therefore, detailed mechanistic understanding requires the electrode/solution interface (ESI) to be interrogated. Doing so with spectroelectrochemical techniques generally encounters several analytical challenges. Sampling the ESI requires a surface-sensitive spectroscopy capable of addressing a buried interface, placing strong limitations on photon energy and spectroelectrochemical cell design. Furthermore, dynamic measurements are fundamentally limited by the finite rise time of the electrode. For many important processes with characteristic timescales in the milli- to microsecond regime, achieving a suitably low rise time requires the use of an electrode with critical dimensions in the hundreds of micrometers, i.e. a microelectrode. In this thesis, I develop the spectroscopic platform necessary to perform surface-sensitive, time-resolved infrared measurements in the milli- to microsecond regime. I will make the case that an infrared spectroelectrochemical technique, namely attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), is applicable because it is intrinsically surface-sensitive, yields detailed information on molecular structure, and is compatible with a range of electrocatalytic metals. I will show that the small size of the microelectrode requires an unconventional infrared source, namely highly focused synchrotron radiation. This thesis will present the characterization of a new internal reflection element which is fully compatible with ATR-SEIRAS and easily amenable to microfabrication. A custom horizontal microscope endstation will be developed at the mid-IR beamline at the Canadian Light Source. Its general utility beyond the primary goal of this thesis will be demonstrated with imaging experiments of a simple interfacial reaction in a microfluidic device. Finally, a 500 micrometer wide linear microelectrode compatible with ATR-SEIRAS will be fabricated and preliminary kinetic measurements of a model electrochemical process, namely the potential-induced desorption of 4-methoxypyridine, will be discussed

Development of a low-debris laser driven soft x-ray source for lithographic applications

This work comprehensively describes the design, build and characterisation of a low-debris laser driven soft x-ray source for a variety of applications in particular lithography, in combination with the optimized multilayer structures in order to use the source output as efficiently as possible. The aim of this work was to study the debris emission from different target materials and to minimise or eliminate debris from laser irradiated thin tapes used in multi-shot and long run-time applications. VHS video tape is used as the primary test target in this work and is made of a Mylar (C10H8O4) carrier film coated with a fine magnetic powder of both Fe2O3 and chromium dioxide CrO2 together with a backing layer of carbon black for static control and a binding agent (polyester-polyurethane). VHS video tape is inexpensive, readily available and amenable for use in multi-hour experiments at high repetition rate. The x-ray source described here is built around a 1064 nm Nd:YAG laser, frequency doubled to 532 nm (green) or tripled to 355 nm, with a pulse length of ~800 ps and a repetition rate up to 50 Hz. A versatile cubic target chamber was designed to accommodate the source and a set of computer controlled stage motors are used to allow positioning of the x-ray emission point. A glass plate between the focusing lens and the target prevents the lens from being coated with debris and the use of a low pressure N2 buffer gas (2-6 mbar) was explored as collisions of atomic size debris particles with gas molecules reduces their kinetic energy and consequently their adhesion to the surrounding surfaces. The chamber can also be continually pumped close to the laser-tape interaction point to ensure continuous removal of debris particles. In the VHS video tape target, the source emitted a range of x-ray wavelengths between 0.19 and 2.3nm relevant to kα line emission of both Fe (7.1 keV) and O (0.5 keV) resolved using the mica crystal spectroscopy. In copper target, a 0.13nm wavelength of k edge (8.9 keV) was resolved, and a 0.79nm x-ray light of Al k edge (1.5 keV) was obtained in aluminium tape target. The measured flux of x-ray photons under vacuum was (7.3 × 109 Photons/s) at 100mJ laser energy and the calculated efficiency of the system (laser energy in versus x-rays out) was (1.1 × 10-6). C/Cr multilayer mirrors of variable layer numbers (N= 30- 200) were designed using the IMD software. A magnetron sputtering technique was used to fabricate the multilayers which were then probed using a hard x-ray diffraction method (Cu Kα radiation, λ = 0.154 nm) to characterize their reflectivity, bi-layers structure and surface roughness. Atomic force microscope was used to determine the surface topography and to analyze the surface structure imperfections such as roughness and stress induced damage. The design developed and refined over the course of this work has been shown to be better at reducing target debris than other mitigation strategies described in the literature. A reduction of "large" and potentially damaging particles ranging from 140 to 5 microns in size by a factor of 28 was achieved, and a 10% reduction in the flux of small particles (~5 microns) was observed if only a buffer gas was used. A reduction of 50% in the flux of these smaller particles was seen if both buffer gas and pumping strategies were employed. This should provide longer life time for the delicate optics used in close proximity to a long run time laser plasma x-ray source, and at the same time reduces the cost of running such sources for a range of different applications.Open Acces

Cross-Layer Rapid Prototyping and Synthesis of Application-Specific and Reconfigurable Many-accelerator Platforms

Technological advances of recent years laid the foundation consolidation of informatisationof society, impacting on economic, political, cultural and socialdimensions. At the peak of this realization, today, more and more everydaydevices are connected to the web, giving the term ”Internet of Things”. The futureholds the full connection and interaction of IT and communications systemsto the natural world, delimiting the transition to natural cyber systems and offeringmeta-services in the physical world, such as personalized medical care, autonomoustransportation, smart energy cities etc. . Outlining the necessities of this dynamicallyevolving market, computer engineers are required to implement computingplatforms that incorporate both increased systemic complexity and also cover awide range of meta-characteristics, such as the cost and design time, reliabilityand reuse, which are prescribed by a conflicting set of functional, technical andconstruction constraints. This thesis aims to address these design challenges bydeveloping methodologies and hardware/software co-design tools that enable therapid implementation and efficient synthesis of architectural solutions, which specifyoperating meta-features required by the modern market. Specifically, this thesispresents a) methodologies to accelerate the design flow for both reconfigurableand application-specific architectures, b) coarse-grain heterogeneous architecturaltemplates for processing and communication acceleration and c) efficient multiobjectivesynthesis techniques both at high abstraction level of programming andphysical silicon level.Regarding to the acceleration of the design flow, the proposed methodologyemploys virtual platforms in order to hide architectural details and drastically reducesimulation time. An extension of this framework introduces the systemicco-simulation using reconfigurable acceleration platforms as co-emulation intermediateplatforms. Thus, the development cycle of a hardware/software productis accelerated by moving from a vertical serial flow to a circular interactive loop.Moreover the simulation capabilities are enriched with efficient detection and correctiontechniques of design errors, as well as control methods of performancemetrics of the system according to the desired specifications, during all phasesof the system development. In orthogonal correlation with the aforementionedmethodological framework, a new architectural template is proposed, aiming atbridging the gap between design complexity and technological productivity usingspecialized hardware accelerators in heterogeneous systems-on-chip and networkon-chip platforms. It is presented a novel co-design methodology for the hardwareaccelerators and their respective programming software, including the tasks allocationto the available resources of the system/network. The introduced frameworkprovides implementation techniques for the accelerators, using either conventionalprogramming flows with hardware description language or abstract programmingmodel flows, using techniques from high-level synthesis. In any case, it is providedthe option of systemic measures optimization, such as the processing speed,the throughput, the reliability, the power consumption and the design silicon area.Finally, on addressing the increased complexity in design tools of reconfigurablesystems, there are proposed novel multi-objective optimization evolutionary algo-rithms which exploit the modern multicore processors and the coarse-grain natureof multithreaded programming environments (e.g. OpenMP) in order to reduce theplacement time, while by simultaneously grouping the applications based on theirintrinsic characteristics, the effectively explore the design space effectively.The efficiency of the proposed architectural templates, design tools and methodologyflows is evaluated in relation to the existing edge solutions with applicationsfrom typical computing domains, such as digital signal processing, multimedia andarithmetic complexity, as well as from systemic heterogeneous environments, suchas a computer vision system for autonomous robotic space navigation and manyacceleratorsystems for HPC and workstations/datacenters. The results strengthenthe belief of the author, that this thesis provides competitive expertise to addresscomplex modern - and projected future - design challenges.Οι τεχνολογικές εξελίξεις των τελευταίων ετών έθεσαν τα θεμέλια εδραίωσης της πληροφοριοποίησης της κοινωνίας, επιδρώντας σε οικονομικές,πολιτικές, πολιτιστικές και κοινωνικές διαστάσεις. Στο απόγειο αυτής τη ςπραγμάτωσης, σήμερα, ολοένα και περισσότερες καθημερινές συσκευές συνδέονται στο παγκόσμιο ιστό, αποδίδοντας τον όρο «Ίντερνετ των πραγμάτων».Το μέλλον επιφυλάσσει την πλήρη σύνδεση και αλληλεπίδραση των συστημάτων πληροφορικής και επικοινωνιών με τον φυσικό κόσμο, οριοθετώντας τη μετάβαση στα συστήματα φυσικού κυβερνοχώρου και προσφέροντας μεταυπηρεσίες στον φυσικό κόσμο όπως προσωποποιημένη ιατρική περίθαλψη, αυτόνομες μετακινήσεις, έξυπνες ενεργειακά πόλεις κ.α. . Σκιαγραφώντας τις ανάγκες αυτής της δυναμικά εξελισσόμενης αγοράς, οι μηχανικοί υπολογιστών καλούνται να υλοποιήσουν υπολογιστικές πλατφόρμες που αφενός ενσωματώνουν αυξημένη συστημική πολυπλοκότητα και αφετέρου καλύπτουν ένα ευρύ φάσμα μεταχαρακτηριστικών, όπως λ.χ. το κόστος σχεδιασμού, ο χρόνος σχεδιασμού, η αξιοπιστία και η επαναχρησιμοποίηση, τα οποία προδιαγράφονται από ένα αντικρουόμενο σύνολο λειτουργικών, τεχνολογικών και κατασκευαστικών περιορισμών. Η παρούσα διατριβή στοχεύει στην αντιμετώπιση των παραπάνω σχεδιαστικών προκλήσεων, μέσω της ανάπτυξης μεθοδολογιών και εργαλείων συνσχεδίασης υλικού/λογισμικού που επιτρέπουν την ταχεία υλοποίηση καθώς και την αποδοτική σύνθεση αρχιτεκτονικών λύσεων, οι οποίες προδιαγράφουν τα μετα-χαρακτηριστικά λειτουργίας που απαιτεί η σύγχρονη αγορά. Συγκεκριμένα, στα πλαίσια αυτής της διατριβής, παρουσιάζονται α) μεθοδολογίες επιτάχυνσης της ροής σχεδιασμού τόσο για επαναδιαμορφούμενες όσο και για εξειδικευμένες αρχιτεκτονικές, β) ετερογενή αδρομερή αρχιτεκτονικά πρότυπα επιτάχυνσης επεξεργασίας και επικοινωνίας και γ) αποδοτικές τεχνικές πολυκριτηριακής σύνθεσης τόσο σε υψηλό αφαιρετικό επίπεδο προγραμματισμού,όσο και σε φυσικό επίπεδο πυριτίου.Αναφορικά προς την επιτάχυνση της ροής σχεδιασμού, προτείνεται μια μεθοδολογία που χρησιμοποιεί εικονικές πλατφόρμες, οι οποίες αφαιρώντας τις αρχιτεκτονικές λεπτομέρειες καταφέρνουν να μειώσουν σημαντικά το χρόνο εξομοίωσης. Παράλληλα, εισηγείται η συστημική συν-εξομοίωση με τη χρήση επαναδιαμορφούμενων πλατφορμών, ως μέσων επιτάχυνσης. Με αυτόν τον τρόπο, ο κύκλος ανάπτυξης ενός προϊόντος υλικού, μετατεθειμένος από την κάθετη σειριακή ροή σε έναν κυκλικό αλληλεπιδραστικό βρόγχο, καθίσταται ταχύτερος, ενώ οι δυνατότητες προσομοίωσης εμπλουτίζονται με αποδοτικότερες μεθόδους εντοπισμού και διόρθωσης σχεδιαστικών σφαλμάτων, καθώς και μεθόδους ελέγχου των μετρικών απόδοσης του συστήματος σε σχέση με τις επιθυμητές προδιαγραφές, σε όλες τις φάσεις ανάπτυξης του συστήματος. Σε ορθογώνια συνάφεια με το προαναφερθέν μεθοδολογικό πλαίσιο, προτείνονται νέα αρχιτεκτονικά πρότυπα που στοχεύουν στη γεφύρωση του χάσματος μεταξύ της σχεδιαστικής πολυπλοκότητας και της τεχνολογικής παραγωγικότητας, με τη χρήση συστημάτων εξειδικευμένων επιταχυντών υλικού σε ετερογενή συστήματα-σε-ψηφίδα καθώς και δίκτυα-σε-ψηφίδα. Παρουσιάζεται κατάλληλη μεθοδολογία συν-σχεδίασης των επιταχυντών υλικού και του λογισμικού προκειμένου να αποφασισθεί η κατανομή των εργασιών στους διαθέσιμους πόρους του συστήματος/δικτύου. Το μεθοδολογικό πλαίσιο προβλέπει την υλοποίηση των επιταχυντών είτε με συμβατικές μεθόδους προγραμματισμού σε γλώσσα περιγραφής υλικού είτε με αφαιρετικό προγραμματιστικό μοντέλο με τη χρήση τεχνικών υψηλού επιπέδου σύνθεσης. Σε κάθε περίπτωση, δίδεται η δυνατότητα στο σχεδιαστή για βελτιστοποίηση συστημικών μετρικών, όπως η ταχύτητα επεξεργασίας, η ρυθμαπόδοση, η αξιοπιστία, η κατανάλωση ενέργειας και η επιφάνεια πυριτίου του σχεδιασμού. Τέλος, προκειμένου να αντιμετωπισθεί η αυξημένη πολυπλοκότητα στα σχεδιαστικά εργαλεία επαναδιαμορφούμενων συστημάτων, προτείνονται νέοι εξελικτικοί αλγόριθμοι πολυκριτηριακής βελτιστοποίησης, οι οποίοι εκμεταλλευόμενοι τους σύγχρονους πολυπύρηνους επεξεργαστές και την αδρομερή φύση των πολυνηματικών περιβαλλόντων προγραμματισμού (π.χ. OpenMP), μειώνουν το χρόνο επίλυσης του προβλήματος της τοποθέτησης των λογικών πόρων σε φυσικούς,ενώ ταυτόχρονα, ομαδοποιώντας τις εφαρμογές βάση των εγγενών χαρακτηριστικών τους, διερευνούν αποτελεσματικότερα το χώρο σχεδίασης.Η αποδοτικότητά των προτεινόμενων αρχιτεκτονικών προτύπων και μεθοδολογιών επαληθεύτηκε σε σχέση με τις υφιστάμενες λύσεις αιχμής τόσο σε αυτοτελής εφαρμογές, όπως η ψηφιακή επεξεργασία σήματος, τα πολυμέσα και τα προβλήματα αριθμητικής πολυπλοκότητας, καθώς και σε συστημικά ετερογενή περιβάλλοντα, όπως ένα σύστημα όρασης υπολογιστών για αυτόνομα διαστημικά ρομποτικά οχήματα και ένα σύστημα πολλαπλών επιταχυντών υλικού για σταθμούς εργασίας και κέντρα δεδομένων, στοχεύοντας εφαρμογές υψηλής υπολογιστικής απόδοσης (HPC). Τα αποτελέσματα ενισχύουν την πεποίθηση του γράφοντα, ότι η παρούσα διατριβή παρέχει ανταγωνιστική τεχνογνωσία για την αντιμετώπιση των πολύπλοκων σύγχρονων και προβλεπόμενα μελλοντικών σχεδιαστικών προκλήσεων