Stretchable electronic platform for soft and smart contact lens applications

A stretchable platform with spherical-shaped electronics based on thermo- plastic polyurethane (TPU) is introduced for soft smart contact lenses. The low glass transition temperature of TPU, its relatively low hardness, and its proven biocompatibility (i.e., protection of exterior body wounds) fulfill the essential requirements for eye wearable devices. These requirements include optical transparency, conformal fitting, and flexibility comparable with soft contact lenses (e.g., hydrogel-based). Moreover, the viscoelastic nature of TPU allows planar structures to be thermoformed into spherical caps with a well-defined curvature (i.e., eye’s curvature at the cornea: 9 mm). Numerical modeling and experimental validation enable fine-tuning of the thermo - forming parameters and the optimization of strain-release patterns. Such tight control is proven necessary to achieve oxygen permeable, thin, nonde- velopable, and wrinkle-free contact lenses with integrated electronics (silicon die, radio-frequency antenna, and stretchable thin-film interconnections). This work paves the way toward fully autonomous smart contact lenses potentially for vision correction or sensing applications, among others

AN INTEGRATED ELECTROMAGNETIC MICRO-TURBO-GENERATOR SUPPORTED ON ENCAPSULATED MICROBALL BEARINGS

This dissertation presents the development of an integrated electromagnetic micro-turbo-generator supported on encapsulated microball bearings for electromechanical power conversion in MEMS (Microelectromechanical Systems) scale. The device is composed of a silicon turbine rotor with magnetic materials that is supported by microballs over a stator with planar, multi-turn, three-phase copper coils. The micro-turbo-generator design exhibits a novel integration of three key technologies and components, namely encapsulated microball bearings, incorporated thick magnetic materials, and wafer-thick stator coils. Encapsulated microball bearings provide a robust supporting mechanism that enables a simple operation and actuation scheme with high mechanical stability. The integration of thick magnetic materials allows for a high magnetic flux density within the stator. The wafer-thick coil design optimizes the flux linkage and decreases the internal impedance of the stator for a higher output power. Geometrical design and device parameters are optimized based on theoretical analysis and finite element simulations. A microfabrication process flow was designed using 15 optical masks and 110 process steps to fabricate the micro-turbo-generators, which demonstrates the complexity in device manufacturing. Two 10 pole devices with 2 and 3 turns per pole were fabricated. Single phase resistances of 46Ω and 220Ω were measured for the two stators, respectively. The device was actuated using pressurized nitrogen flowing through a silicon plumbing layer. A test setup was built to simultaneously measure the gas flow rate, pressure, rotor speed, and output voltage and power. Friction torques in the range of 5.5-33µNm were measured over a speed range of 0-16krpm (kilo rotations per minute) within the microball bearings using spin-down testing methodology. A maximum per-phase sinusoidal open circuit voltage of 0.1V was measured at 23krpm, and a maximum per-phase AC power of 10µW was delivered on a matched load at 10krpm, which are in full-agreement with the estimations based on theoretical analysis and simulations. The micro-turbo-generator presented in this work is capable of converting gas flow into electricity, and can potentially be coupled to a same-scale combustion engine to convert high-density hydrocarbon energy into electrical power to realize a high-density power source for portable electronic systems

Performance Comparison of Phase Change Materials and Metal-Insulator Transition Materials for Direct Current and Radio Frequency Switching Applications

Advanced understanding of the physics makes phase change materials (PCM) and metal-insulator transition (MIT) materials great candidates for direct current (DC) and radio frequency (RF) switching applications. In the literature, germanium telluride (GeTe), a PCM, and vanadium dioxide (VO2), an MIT material have been widely investigated for DC and RF switching applications due to their remarkable contrast in their OFF/ON state resistivity values. In this review, innovations in design, fabrication, and characterization associated with these PCM and MIT material-based RF switches, have been highlighted and critically reviewed from the early stage to the most recent works. We initially report on the growth of PCM and MIT materials and then discuss their DC characteristics. Afterwards, novel design approaches and notable fabrication processes; utilized to improve switching performance; are discussed and reviewed. Finally, a brief vis-á-vis comparison of resistivity, insertion loss, isolation loss, power consumption, RF power handling capability, switching speed, and reliability is provided to compare their performance to radio frequency microelectromechanical systems (RF MEMS) switches; which helps to demonstrate the current state-of-the-art, as well as insight into their potential in future applications

Heterogeneous 2.5D integration on through silicon interposer

© 2015 AIP Publishing LLC. Driven by the need to reduce the power consumption of mobile devices, and servers/data centers, and yet continue to deliver improved performance and experience by the end consumer of digital data, the semiconductor industry is looking for new technologies for manufacturing integrated circuits (ICs). In this quest, power consumed in transferring data over copper interconnects is a sizeable portion that needs to be addressed now and continuing over the next few decades. 2.5D Through-Si-Interposer (TSI) is a strong candidate to deliver improved performance while consuming lower power than in previous generations of servers/data centers and mobile devices. These low-power/high-performance advantages are realized through achievement of high interconnect densities on the TSI (higher than ever seen on Printed Circuit Boards (PCBs) or organic substrates), and enabling heterogeneous integration on the TSI platform where individual ICs are assembled at close proximity

Flexible, Photopatterned, Colloidal Cdse Semiconductor Nanocrystal Integrated Circuits

As semiconductor manufacturing pushes towards smaller and faster transistors, a parallel goal exists to create transistors which are not nearly as small. These transistors are not intended to match the performance of traditional crystalline semiconductors; they are designed to be significantly lower in cost and manufactured using methods that can make them physically flexible for applications where form is more important than speed. One of the developing technologies for this application is semiconductor nanocrystals. We first explore methods to develop CdSe nanocrystal semiconducting “inks” into large-scale, high-speed integrated circuits. We demonstrate photopatterned transistors with mobilities of 10 cm2/Vs on Kapton substrates. We develop new methods for vertical interconnect access holes to demonstrate multi-device integrated circuits including inverting amplifiers with ~7 kHz bandwidths, ring oscillators with \u3c10 µs stage delays, and NAND and NOR logic gates. In order to produce higher performance and more consistent transistors, we develop a new hybrid procedure for processing the CdSe nanocrystals. This procedure produces transistors with repeatable performance exceeding 40 cm2/Vs when fabricated on silicon wafers and 16 cm2/vs when fabricated as part of photopatterned integrated circuits on Kapton substrates. In order to demonstrate the full potential of these transistors, methods to create high-frequency oscillators were developed. These methods allow for transistors to operate at higher voltages as well as provide a means for wirebonding to the Kapton substrate, both of which are required for operating and probing high-frequency oscillators. Simulations of this system show the potential for operation at MHz frequencies. Demonstration of these transistors in this frequency range would open the door for development of CdSe integrated circuits for high-performance sensor, display, and audio applications. To develop further applications of electronics on flexible substrates, procedures are developed for the integration of polychromatic displays on polyethylene terephthalate (PET) substrates and a commercial near field communication (NFC) link. The device draws its power from the NFC transmitter common on smartphones and eliminates the need for a fixed battery. This allows for the mass deployment of flexible, interactive displays on product packaging

Fabrication of 3D Air-core MEMS Inductors for High Frequency Power Electronic Applications

AbstractWe report a fabrication technology for 3D air-core inductors for small footprint and very-high-frequency power conversions. Our process is scalable and highly generic for fabricating inductors with a wide range of geometries and core shapes. We demonstrate spiral, solenoid, and toroidal inductors, a toroidal transformer and inductor with advanced geometries that cannot be produced by wire winding technology. The inductors are embedded in a silicon substrate and consist of through-silicon vias and suspended windings. The inductors fabricated with 20 and 25 turns and 280-350 μm heights on 4-16 mm2 footprints have an inductance from 34.2 to 44.6 nH and a quality factor from 10 to 13 at frequencies ranging from 30 to 72 MHz. The air-core inductors show threefold lower parasitic capacitance and up to a 140% higher-quality factor and a 230% higher-operation frequency than silicon-core inductors. A 33 MHz boost converter mounted with an air-core toroidal inductor achieves an efficiency of 68.2%, which is better than converters mounted with a Si-core inductor (64.1%). Our inductors show good thermal cycling stability, and they are mechanically stable after vibration and 2-m-drop tests.</jats:p

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

Through-Silicon Vias in SiGe BiCMOS and Interposer Technologies for Sub-THz Applications

Im Rahmen der vorliegenden Dissertation zum Thema „Through-Silicon Vias in SiGe BiCMOS and Interposer Technologies for Sub-THz Applications“ wurde auf Basis einer 130 nm SiGe BiCMOS Technologie ein Through-Silicon Via (TSV) Technologiemodul zur Herstellung elektrischer Durchkontaktierungen für die Anwendung im Millimeterwellen und Sub-THz Frequenzbereich entwickelt. TSVs wurden mittels elektromagnetischer Simulationen modelliert und in Bezug auf ihre elektrischen Eigenschaften bis in den sub-THz Bereich bis zu 300 GHz optimiert. Es wurden die Wechselwirkungen zwischen Modellierung, Fertigungstechnologie und den elektrischen Eigenschaften untersucht. Besonderes Augenmerk wurde auf die technologischen Einflussfaktoren gelegt. Daraus schlussfolgernd wurde das TSV Technologiemodul entwickelt und in eine SiGe BiCMOS Technologie integriert. Hierzu wurde eine Via-Middle Integration gewählt, welche eine Freilegung der TSVs von der Wafer Rückseite erfordert. Durch die geringe Waferdicke von ca. 75 μm wird einen Carrier Wafer Handling Prozess verwendet. Dieser Prozess wurde unter der Randbedingung entwickelt, dass eine nachfolgende Bearbeitung der Wafer innerhalb der BiCMOS Pilotlinie erfolgen kann. Die Rückseitenbearbeitung zielt darauf ab, einen Redistribution Layer auf der Rückseite der BiCMOS Wafer zu realisieren. Hierzu wurde ein Prozess entwickelt, um gleichzeitig verschiedene TSV Strukturen mit variablen Geometrien zu realisieren und damit eine hohe TSV Design Flexibilität zu gewährleisten. Die TSV Strukturen wurden von DC bis über 300 GHz charakterisiert und die elektrischen Eigenschaften extrahiert. Dabei wurde gezeigt, dass TSV Verbindungen mit sehr geringer Dämpfung <1 dB bis 300 GHz realisierbar sind und somit ausgezeichnete Hochfrequenzeigenschaften aufweisen. Zuletzt wurden vielfältige Anwendungen wie das Grounding von Hochfrequenzschaltkreisen, Interposer mit Waveguides und 300 GHz Antennen dargestellt. Das Potential für Millimeterwellen Packaging und 3D Integration wurde evaluiert. TSV Technologien sind heutzutage in vielen Anwendungen z.B. im Bereich der Systemintegration von Digitalschaltkreisen und der Spannungsversorgung von integrierten Schaltkreisen etabliert. Im Rahmen dieser Arbeit wurde der Einsatz von TSVs für Millimeterwellen und dem sub-THz Frequenzbereich untersucht und die Anwendung für den sub-THz Bereich bis 300 GHz demonstriert. Dadurch werden neue Möglichkeiten der Systemintegration und des Packaging von Höchstfrequenzsystemen geschaffen.:Bibliographische Beschreibung List of symbols and abbreviations Acknowledgement 1. Introduction 2. FEM Modeling of BiCMOS & Interposer Through-Silicon Vias 3. Fabrication of BiCMOS & Silicon Interposer with TSVs 4. Characterization of BiCMOS Embedded Through-Silicon Vias 5. Applications 6. Conclusion and Future Work 7. Appendix 8. Publications & Patents 9. Bibliography 10. List of Figures and Table