Multi-level analysis of atomic layer deposition barrier coatings on additively manufactured plastics for high vacuum applications

While hardware innovations in micro/nano electronics and photonics are heavily patented, the rise of the open-source movement has significantly shifted focus to the importance of obtaining low-cost, functional and easily modifiable research equipment. This thesis provides a foundation of open source development of equipment to aid in the micro/nano electronics and photonics fields. First, the massive acceptance of the open source Arduino microcontroller has aided in the development of control systems with a wide variety of uses. Here it is used for the development of an open-source dual axis gimbal system. This system is used to characterize optoelectronic properties of thin transparent films at varying angles. Conventionally, the ubiquity of vacuum systems in semiconductor fabrication has precluded the development of an open-source development in the “fab” environment and thus has high foundational and operational costs. In order to make vacuum systems and their components cost-effective in a research environment there has been a paradigm shift towards refurbishing and repairing instead of replacing legacy systems. These legacy systems are built, and operate on the principle that the vacuum industry is a small industry, and hence only a small number of sizes and types of parts may be used to reduce costs. The assumption that the vacuum industry is a small industry is no longer valid. The semiconductor industry alone, which is a subset of the vacuum industry, was worth over USD 481b and increasing. Hence,there is a need to not only introduce new methods but also new materials that make up these systems. Additive manufacturing is a low-waste, low-capital cost way to make custom equipment. The most popular materials used in additive manufacturing processes are polymer blends. 3-D printing using Fused Filament Fabrication (FFF) methods has been used to create custom objects for laboratories. However, the use of polymer-based materials is conspicuously absent in the development of vacuum systems, especially those that are used for semiconductor fabrication. There are two major problems identified when polymeric materials are used to make vacuum systems: finding a way to prevent outgassing (which can subsequently lead to contamination), and sealing them so that they can hold a vacuum. This work has demonstrated how an inorganic barrier layer introduced via Atomic Layer Deposition (ALD) can alleviate outgassing to a large extent under high vacuum levels (1E-6 to 1E-7 torr). Recognizing the importance of ALD alumina in back end of the line (BEOL) semiconductor processing, films were deposited on 3-D printed polymer-based substrates with differing constituents. These samples were tested in a bespoke gas analysis chamber for outgassing characterization. Surface and bulk characterization was completed using various tools such as scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX), x-ray photoelectron spectroscopy (XPS), attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) and others. Additionally, spectroscopic ellipsometry (SE) was used to understand how the concept of thickness of a film deposited on a porous polymer-based sample does not correlate directly with its conventional definition. Also, an effort is made to understand the mechanism of ALD alumina deposition on porous plastic surfaces.It was concluded that this deposition is a complex amalgamation of physical and chemical properties of both the polymer and the precursor gases. Finally, recommendations are made for AM materials to be used in vacuum systems

An Experimental and Numerical Study on Glass Frit Wafer-to-Wafer Bonding

A thermo-mechanical wafer-to-wafer bonding process is studied through experiments on the glass frit material and thermo-mechanical numerical simulations to evaluate the effect of the residual stresses on the wafer warpage. To experimentally characterize the material, confocal laser profilometry and scanning electron microscopy for surface observation, energy dispersive X-ray spectroscopy for microstructural investigation, and nanoindentation and die shear tests for the evaluation of mechanical properties are used. An average effective Young’s modulus of 86.5 ± 9.5 GPa, a Poisson’s ratio of 0.19 ± 0.02, and a hardness of 5.26 ± 0.8 GPa were measured through nanoindentation for the glass frit material. The lowest nominal shear strength ranged 1.13 ÷ 1.58 MPa in the strain rate interval to 0.33 ÷ 4.99 × 10 (Formula presented.) s (Formula presented.). To validate the thermo-mechanical model, numerical results are compared with experimental measurements of the out-of-plane displacements at the wafer surface (i.e., warpage), showing acceptable agreement

Bio-Inspired Materials for Biomedical Applications

Evolved in a huge number of different materials and structures, nature represents a great inspiration for scientists and researchers, which continuously focuses attention on the development of novel approaches and functional biomaterials to mimic the complex architectures and functions of the human body. Bioinspired engineering is considered today as a valuable tool for the design of clinically relevant materials and structures for regenerative sciences and, in this direction, many progresses have been recently made by the scientific research in the biomedical field. This book aims at collecting some recent works addressed to the definition of novel bioinspired approaches in bioengineering and biotechnology, presenting interesting scientific results and a comprehensive overview of attracting materials in research papers and review articles

Advances in panel glass packaging of mems and sensors for low stress and near hermetic reliability

MEMS based sensing is gaining widespread adoption in consumer electronics as well as the next generation Internet of Things (IoT) market. Such applications serve as primary drivers towards miniaturization for increased component density, multi-chip integration, lower cost and better reliability. Traditional approaches like System-on-Chip (SoC) and System on Board (SoB) are not ideal to address these challenges and there is a need to find solutions at package level, through heterogeneous package integration (HPI). However, existing MEMS packaging techniques like laminate/ceramic substrate packaging and silicon wafer level packaging face challenges like standardization, heterogeneous package integration and form factor miniaturization. Besides, application specific packages take up the largest fraction of the total manufacturing cost. Therefore, advanced packaging of MEMS sensors for HPI plays a critical role in the short and long run towards the SOP vision. This dissertation demonstrates a low stress, reliable, near-hermetic ultra-thin glass cavity MEMS packages as a solution that combines the advantages of LTCC/laminate substrates and silicon wafer level packaging while also addressing their limitations. These glass based cavity packages can be scaled down to 2x smaller form factors (<500μm) and are fabricated out of large panel fabrication processes thereby addressing the cost and form factor requirements of MEMS packaging. Flexible cavity design, advances in through-glass via technologies and dimensional stability of thin glass also enable die stacking and 3D assembly for sensor-processor integration towards sensor fusion. The following building block technologies were explored: (a) reliable cavity formation in thin glass panels (b) low stress glass-glass bonding, and (c) high throughput, fully filled through-package-via metallization in glass. Three main technical challenges were overcome to realize the objectives: (a) glass cracking, side wall taper, side wall roughness and defects, (b) interfacial voids at glass-polymer-glass interface and (c) electrical opens and high frequency performance of copper paste filled through-package-vias in glass.M.S

Packaging Technologies for Millimeter Scale Microsystems in Harsh Environment Applications

Microsystems capable of sensing temperature, pressure and other parameters are needed for many applications, for example, gathering information in downhole environments for oil and gas exploration. Certain target locations limit the size of the microsystems to millimeter or even sub-millimeter scale. In addition, the high temperature, high pressure, and corrosive ambient environments are challenging for microsystems. Target environments include 125°C temperature, 50 MPa pressure, and salinity standards consistent with American Petroleum Institute (API) brine (8% NaCl + 2% CaCl2). Other chemicals including hydrocarbons and cement slurry are also found in these environments. The system package plays a critical role as it protects the system components against environment, while also providing the physical coupling to the environment, e.g., for communication modules and pressure sensors. The package must be made of mechanically and chemically robust materials. High temperature assembly steps must be avoided in the packaging process (such as bonding above 200°C), because these steps are generally incompatible with embedded batteries and polymer-based sensors. The development of system package and relevant technologies is the focus of this dissertation. This dissertation first describes the design and fabrication of sapphire-on-steel packages in two sizes (0.8 mm and 8 mm), which are capable of isolating high pressure while allowing optical communication. These packages have been operated with embedded electronics at 125ºC and ≈70 MPa in API brine, hydrocarbons, and cement slurry. Additionally, polymer-in-tube packages are reported, which allow the embedded pressure sensors to couple with the environment. These packages have been successfully operated with embedded electronics and sensors at 125ºC and 50 MPa in API brine. A third approach of encapsulation that is reported involves polymer film encapsulation, which has the potential to significantly improve the chemical resistance of microsystems. Finally a batch-mode packaging process is presented based on micro-crimping, enabling room temperature assembly for sub-millimeter scale packages made by metal alloys. This packaging process has been demonstrated by a 5×5 array of 0.5 mm packages. These packages have survived at least 200 MPa pressure and at least 72 h in API brine.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135761/1/yushuma_1.pd

Recent Developments in Tough Hydrogels for Biomedical Applications

A hydrogel is a three-dimensional polymer network with high water content and has been attractive for many biomedical applications due to its excellent biocompatibility. However, classic hydrogels are mechanically weak and unsuitable for most physiological load-bearing situations. Thus, the development of tough hydrogels used in the biomedical field becomes critical. This work reviews various strategies to fabricate tough hydrogels with the introduction of non-covalent bonds and the construction of stretchable polymer networks and interpenetrated networks, such as the so-called double-network hydrogel. Additionally, the design of tough hydrogels for tissue adhesive, tissue engineering, and soft actuators is reviewe

Solid Oxide Fuel Cells: Numerical and Experimental Approaches

Solid oxide fuel cell (SOFC) is a promising electrochemical technology that can produce electrical and thermal power with outstanding efficiencies. A systematic synergetic approach between experimental measurements and modelling theory has proved to be instrumental to evaluate performance and correct behaviour of a chemical process, like the ones occurring in SOFC. For this purpose, starting from SIMFC (SIMulation of Fuel Cells) code set-up by PERT-UNIGE (Process Engineering Research Group) for Molten Carbonate Fuel Cells [1], a new code has been set-up for SOFCs based on local mass, energy, charge and momentum balances. This code takes into account the proper reactions occurring in the SOFC as well as new geometries and kinetics thanks to experiments carried out on single cells and stack in ENEA laboratories of C.R. Casaccia and VTT Fuel Cell Lab in Finland. In particular using an innovative experimental setup it has been possible to study experimentally the influence of a multicomponent mixtures on the performance of SOFC and also validate locally a 2-D model developed starting from SIMFC code. The results obtained are good, showing a good agreement between experimental and numerical results. The obtained results are encouraging further studies which allow the model validation on a greater quantity of data and under a wider range of operating conditions