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Focused Ion Beam (FIB) technology is a versatile tool that can be applied in many fields to great effect, including semiconductor device prototyping, Transmission Electron Microscopy (TEM) sample preparation, and nanoscale tomography. Developments in FIB technology, including the availability of alternative ion sources and improvements in automation capacity, make FIB an increasingly attractive option for many tasks. In this thesis, FIB systems are applied to photonic device fabrication and modification, semiconductor reverse engineering, and the production of structures for the study of nanoscale radiative heat transfer. Optical facets on silicon nitride waveguides were produced with plasma FIB (PFIB) and showed an improvement of 3 ± 0.9 dB over reactive ion etched (RIE) facets. This process was then automated and is capable of producing a facet every 30 seconds with minimal oversight. PFIB was then employed to develop a method for achieving local backside circuit access for circuit editing, creating local trenches with flat bases of 200 x 200 μm. Gas assisted etching using xenon difluoride was then used in order to accelerate the etch process. Finally, several varieties of nanogap structure were fabricated on devices capable of sustaining temperature gradients, achieving a minimum gap size with PFIB of 60 nm. / Thesis / Master of Applied Science (MASc)

Vacuum technology is ubiquitous in the high tech industries and scientific endeavors. Since vacuum pumps are critical to operation, semiconductor manufacturers desire reliable operations, ability to schedule downtime, and less costly maintenance services. To better cope with difficult maintenance issues, interests in novel fault diagnosis techniques are growing. This study concerns model based fault diagnosis and isolation (MB-FDI) of dry vacuum pumps in the semiconductor industry. Faults alter normal operation of a vacuum pump resulting in performance deviations, discovered by measurements. Simulations using an appropriate mathematical model with suitably chosen parameters can mimic faulty behavior. This research focuses on the construction of a detailed multi-stage dry vacuum pump model for MB-FDI, and the development of a simple and efficient FDI method to analyze common incipient faults such as particulate deposition and gas leak inside the pump. The pump model features 0-D thermo-fluid dynamics, scalable geometric representations of Roots blower, claw pumps and inter-stage port interfaces, a unified pipe model seamlessly connecting from free molecular to turbulent regimes, sophisticated internal leakage model considering true pump geometry and tribological aspects, and systematic assembly of a multi-stage configuration using single stage pump models. Design of a simple FDI technique for the dry vacuum pump includes staged fault simulations using faulty pump models, parametric study of faulty pump behaviors, and design of a health indicator based on classification. The main research contributions include the developments of an accurate multi-stage dry pump model with many features not found in existing pump models, and the design of a simple MB-FDI technique to detect and isolate the common faults found in dry vacuum pumps. The proposed dry pump model can pave the way for the future development of advanced MB-FDI methods, also performance improvement of existing dry vacuum pumps. The proposed fault classification charts can serve as a quick guideline for vacuum pump manufactures to isolate roots causes from faulty symptoms. / text

The Asymmetric Spacer layer Tunnel (ASPAT) diode is a new diode invented in the early 90s as an alternative to the Schottky barrier diode (SBD) technology for microwave detector applications due to its highly stable temperature characteristics. The ASPAT features a strong non-linear I-V characteristic as a result of tunnelling through a thin barrier, which enables RF detection at zero bias from microwaves up to submillimetre wave frequencies. In this work, two heavily doped GaAs contact layer on top and bottom layers adjacent to lightly doped GaAs intermediate layers, enclose undoped GaAs spacers with different lengths sandwiching an undoped AlAs layer that acts as a tunnel barrier. The ultimate ambition of this work was to develop a MMIC detector as well as a frequency source based on optimized ASPAT diodes for millimetre wave (100GHz) applications. The effect of material parameter and dimensions on the ASPAT source performances was described using an empirical model for the first time. Since this is a new device, keys challenges in this work were to improve DC and RF characteristic as well as to develop a repeatable, reproducible, and ultimately manufacturable fabrication process flow. This was investigated using two approaches namely air-bridge and dielectric-bridge fabrication process flows. Through this work, it was found that the GaAs/AlAs heterostructures ASPAT diode are more amenable to the dielectric-bridge technique as large-scale fabrication of mesa area up to 4×4Âμm2 with device yields exceeding 80% routinely produced. The fabrication of the ASPAT using i-line optical lithography which has the capability to reduce emitter area to 4×4Âμm2 to lower down the device capacitance for millimetre wave application has been made feasible in this work. The former challenge was extensively studied through materials and structural characterisations by a SILVACO physical modelling and confirmed by comparison with experimental data. The I-V characteristic of the fabricated ASPAT demonstrated outstanding scalability, demonstrating robust processing. A fair comparison has been made between ASPAT and SBD fabricated in-house; indicating ASPAT is extremely stable to the temperature. The RF characterisations were carried out with the aid of Keysight ADS software. The DC characteristic from fabricated GaAs/AlAs ASPAT diodes were absorbed into an ADS simulation tool and utilized to demonstrate the performance of MMIC 100GHz detector as well as 20GHz/40GHz signal generators. Zero bias ASPAT with mesa area of 4×4Âμm2 with video resistance of 90KΩ, junction capacitance of 23fF and curvature coefficient of 23V-1 has demonstrated detector voltage sensitivity above 2000V/W, while the signal source conversion loss and conversion efficiency are 28dB and 0.3% respectively. An estimate noise equivalent power (NEP) for this particular device is 18.8pW/Hz1/2.

<p dir="ltr">With increasing power densities in electronic devices, effective thermal management has become an indispensable aspect of electronic systems design. Although phase change materials (PCMs) have been studied as a potential solution, their integration into microelectronic and high-power devices presents a significant challenge due to low thermal conductivity and lack of effective thermal pathways from the heat source to the heat sink. While much work has focused on integrating thermal storage into heat sinks, this dissertation instead investigates integrating PCMs between the heat source and the heat sink in different configurations. By placing the energy storage closer to the heat source, the thermal resistance is reduced, which improves the overall thermal performance of the device. Specifically, this work explores the efficacy of two approaches: (1) direct embedding of a PCM within the die for mobile electronics applications and (2) integration of an auxiliary composite PCM/copper thermal energy storage (TES) component in combination with active liquid cooling for high-power power electronics modules.</p><p><br></p><p dir="ltr">The first study explores die-level thermal management for microelectronics using PCMs. Silicon chips with PCM embedded within the die are modeled using ParaPower, a fast-analysis tool, and a genetic algorithm is used to efficiently optimize the distribution of high-conductivity silicon pathways and high thermal capacitance PCM zones. A thermal test vehicle (TTV) of a realistic microelectronics form factor with an embedded PCM layer is first designed, and a process is developed to fabricate such a TTV. This study is the first to successfully fabricate a TTV with fully encapsulated PCM and validate its thermal response across various operational scenarios. For temperature cycling tests (where the TTV temperature fluctuates between predetermined hot and cold setpoints), the embedded-PCM TTVs extend the operational time by up to 2.8x compared to a baseline all-silicon TTV. For duty cycling tests (with a fixed duration of the periodic heating pulses and off times), the embedded-PCM TTVs suppress the hotspot temperature rise by up to 14% and stabilize quasi-steady state temperature fluctuations by up to 65% through repeated PCM melting and solidification cycles. Thermal performance enhancements are observed even for high heat fluxes of ~65W/cm² . Specifically, a TTV with an embedded square-shaped PCM reservoir reduces temperature instability by an average of 40% across a range of cycle durations.</p><p><br></p><p dir="ltr">The second study investigates the effectiveness of different integration strategies for an auxiliary composite PCM/copper TES block integrated alongside a cold plate, for thermal management of high-power power electronics modules, specifically for electric vehicles. These systems are evaluated for realistic drive cycles of various driving intensities. Computational results indicate that this approach is most effective when the composite TES block is positioned directly above the heat-generating silicon carbide dies. This configuration excels at stabilizing transient temperature fluctuations and absorbing thermal shocks, achieving reductions of up to approximately ~33% compared to current thermal management techniques. This strategy is particularly effective for stop-and-go drive cycles characterized by high rates of acceleration and deceleration, low average driving speeds, and frequent stops, typical of driving schedules for public transport buses and mail delivery vehicles.</p><p><br></p><p dir="ltr">The results from both thermal management approaches demonstrate that the integration of a PCM cooling solution in close proximity to the heat source can significantly enhance its effectiveness by absorbing power bursts and limiting temperature instability via repeated melting and solidification. The contributions of this dissertation include the development of an effective optimization strategy for generating optimized PCM distributions, which reduces the maximum temperature and temperature oscillations in a device with significant computational efficiency. (The same optimization strategy can be applied to other thermal management design challenges.) Notably, TTVs of realistic microelectronics form factors with embedded PCM were designed, modeled, fabricated, and validated. With the PCM thermal buffers, the engineered solution demonstrated superior performance compared to a baseline all-silicon TTV. The second study into the integration of composite PCM/copper TES blocks into high-power power electronics modules established trade-offs between different architectures across various performance metrics, and highlighted its effectiveness for drive cycles with varying intensities. These findings offer an important contribution to the development of embedded thermal management techniques for electronic systems design, which will be critical for the advancement of next-generation microelectronics and high-power devices.</p>

Ce travail de thèse présente une étude sur les propriétés de nanostructures de type bâtonnets quantiques et de leur application pour les télécommunications optiques. Durant la dernière décennie, ces nanostructures, ont démontré des propriétés optiques et électroniques intéressantes en raison notamment d’un fort confinement quantique dans les trois dimensions d'espace. Cette thèse porte sur la conception et la fabrication d'émetteurs optiques intégrés à base de ce matériau et de leur implémentation dans des systèmes de communication. La première partie de ce travail analyse les propriétés de ces nanostructures, théorique et expérimentale. Elles sont utilisées comme matériau actif de lasers modulés directement en amplitude. Les propriétés dynamiques de ces lasers sont ensuite évaluées et des transmissions sur fibre optique entre 0 et 100 km sont ensuite démontrées en utilisant un filtre étalon permettant d’augmenter en particulier le taux d’extinction dynamique. En s’appuyant sur cette démonstration basée sur des éléments discrets, une version monolithique intégrant un laser et un résonateur en anneaux a été réalisée. La dernière partie de ce travail porte sur des lasers à blocage de mode à base de ce matériau et en particulier sur les méthodes d’intégration sur substrat InP. En particulier, un design de miroir de Bragg innovant a été développé à cet effet et une démonstration d'un laser a blocage de mode intégré avec un amplificateur optique à semi-conducteur a finalement été réalisée / This PhD dissertation presents a study on the properties of the novel quantum dash nanostructures and their properties for application in optical telecommunications. Over the last decade, scientific community has gained considerable interest over these nanostructures and several demonstrations have been made on their interesting optical and electronic properties, notably owing to their strong quantum confinement. This dissertation focuses on conception, fabrication and system demonstration of integrated optical transmitters based on quantum dash material. A first part of this work analyses the properties of qdashes theoretically and experimentally for their use as an active material in directly modulated lasers. The dynamic properties of this material are then evaluated leading to an optical transmission distances in range of 0-100km under direct modulation. The transmission is particularly studied with a passive optical filter to enhance the dynamic extinction ratio, the use of such passive filters is studied in detail. An innovative and fully integrated optical transmitter is finally demonstrated by integrating a ring-resonator filter to a distributed feedback laser. The second part of this work focuses on mode locked lasers based on this material and in particular the methods of integration of such devices on InP are explored. Thus an innovative Bragg mirror design is developed leading to a mode locked laser integrated with a semiconductor optical amplifier