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

THz Ultra-wideband Passive Devices: Design, Simulation and Characterization

The last decades have seen an increasing interest in the THz research field, leading to a substantial improvement in technology and the emergence of new applications. In particular, the research on radio astronomy instrumentation has pushed millimeter and sub-millimeter technology boundaries and redefined state of the art.\ua0 Nonetheless, the requirements set for the next generation of radio astronomy receivers will demand remarkable technological development, especially in terms of RF and IF bandwidth. Addressing this need, the present licentiate thesis focuses on the design, simulation and characterization of ultra-wideband THz passive devices for the next generation of radio astronomy receivers. As THz receivers mixers are implemented with thin-film technology, waveguide to substrate transitions have a fundamental role in the performance and bandwidth of such systems. The critical requirements for these transitions are a proper impedance matching and the minimization of insertion loss. In this thesis, a waveguide to slotline superconducting transition based on substrateless finlines is proposed. The transition was designed for prospective broadband SIS mixer design in the frequency range 211-375 GHz. The experimental verification at cryogenic temperatures shows a remarkable fractional bandwidth of 55%. Although this transition represents a substantial improvement over existing designs, it is important to note that it transforms a waveguide propagation mode into slotline mode. For the majority of modern SIS mixers, microstrip line topology is the most suitable. Hence, the ongoing development is focused on broadband slotline to microstrip transitions. In this work, a slotline to microstrip transition based on Marchand Balun is designed, simulated and fabricated. The electromagnetic simulations showed promising results, and the cryogenic characterization at 4K is ongoing.For most modern polarization-sensitive THz receivers, 90\ub0 waveguide twists are essential interconnection parts. Since compactness and low insertion loss are critical requirements, single step-twists have emerged as an attractive solution. In this work, a novel compact wideband 90-degree twist for the 140-220 GHz band is presented. Furthermore, the proposed twist has a performance tolerant to small geometry variation, and hence it is especially suited for fabrication by direct milling. The experimental verification shows 44% fractional bandwidth with return loss better than 20 dB over most of the band

Ytterbium ion trapping and microfabrication of ion trap arrays

Over the past 15 years ion traps have demonstrated all the building blocks required of a quantum computer. Despite this success, trapping ions remains a challenging task, with the requirement for extensive laser systems and vacuum systems to perform operations on only a handful of qubits. To scale these proof of principle experiments into something that can outperform a classical computer requires an advancement in the trap technologies that will allow multiple trapping zones, junctions and utilize scalable fabrication technologies. I will discuss the construction of an ion trapping experiment, focussing on my work towards the laser stabilization and ion trap design but also covering the experimental setup as a whole. The vacuum system that I designed allows the mounting and testing of a variety of ion trap chips, with versatile optical access and a fast turn around time. I will also present the design and fabrication of a microfabricated Y junction and a 2- dimensional ion trap lattice. I achieve a suppression of barrier height and small variation of secular frequency through the Y junction, aiding to the junctions applicability to adiabatic shuttling operations. I also report the design and fabrication of a 2-D ion trap lattice. Such structures have been proposed as a means to implement quantum simulators and to my knowledge is the first microfabricated lattice trap. Electrical testing of the trap structures was undertaken to investigate the breakdown voltage of microfabricated structures with both static and radio frequency voltages. The results from these tests negate the concern over reduced rf voltage breakdown and in fact demonstrates breakdown voltages significantly above that typically required for ion trapping. This may allow ion traps to be designed to operate with higher voltages and greater ion-electrode separations, reducing anomalous heating. Lastly I present my work towards the implementation of magnetic fields gradients and microwaves on chip. This may allow coupling of the ions internal state to its motion using microwaves, thus reducing the requirements for the use of laser systems

Plasmonic-Organic and Silicon-Organic Hybrid Modulators for High-Speed Signal Processing

High-speed electro-optic (EO) modulators are key devices for optical communications, microwave photonics, and for broadband signal processing. Among the different material platforms for high-density photonic integrated circuits (PIC), silicon photonics sticks out because of CMOS foundries specialized in PIC fabrication. However, the absence of the Pockels effect in silicon renders EO modulators with high-efficiency and large modulation bandwidth difficult. In this dissertation, plasmonic and photonic slot waveguide modulators are investigated. The devices are built on the silicon platform and are combined with highly-efficient organic EO materials. Using such a hybrid platform, we realize compact and fast plasmonic-organic hybrid (POH) and silicon-organic hybrid (SOH) modulators. As an application example, we demonstrate for the first time an advanced terahertz communication link by directly converting data on a 360 GHz carrier to a data stream on an optical carrier. For optical transmitter applications, we overcome the bandwidth limitation of conventional SOH modulators by introducing a high-k dielectric microwave slotline for guiding the modulating radio-frequency signal which is capacitively-coupled to the EO modulating region. We confirm the viability of such capacitively-coupled SOH modulators by generating four-state pulse amplitude modulated signals with data rates up to 200 Gbit/s

Radio Frequency Micro/Nano-Fluidic Devices for Microwave Dielectric Property Characterizations

In this dissertation, a number of different topics in microwave dielectric property measurements have been covered by a systematic approach to the goals of development of dielectric spectroscopy and study of its high electric field effects with integrated on-chip microwave microfluidic / nanofluidic devices. A method of parasitic effects cancellation for dielectric property measurement is proposed, analyzed, and experimentally evaluated for microwave characterization of small devices and materials that yield low intensity signals. The method dramatically reduces parasitic effects to uncover the otherwise buried signals. A high-sensitive radio frequency (RF) device is then developed and fabricated to detect small dielectric property changes in microfluidic channel. Sensitivity improvement via on-chip transmission line loss compensation is then analyzed and experimentally demonstrated. Different samples are measured and high sensitivity is achieved compared to conventional transmission-line-based methods. High DC electric field effects on dielectric properties of water are investigated with microwave microfluidic devices. Gold microstrip-line-based devices and highly-doped silicon microstrip-line-based devices are exploited. Initiation process of water breakdown in a small gap is discussed. Electrode surface roughness is examined and its effect on observed water breakdown is investigated. It is believed that electrode surface roughness is one of critical factors for the initiation process of water breakdown in small gap system. Finally, water dielectric property subjected to uniform DC electric field in 260 nm planar microfluidic channels is experimentally studied via silicon microstrip-line-based devices. When applied DC field is as high as up to ~ 1 MV/cm, the water is sustained and no breakdown is occurred. Strong water dielectric saturation effects are observed from measured water dielectric spectroscopy. An on-chip, broadband microwave dielectric spectrometer with integrated transmission line and nanofluidic channels is designed, fabricated and characterized through microwave S-parameter measurements. Heavily-doped Si material is used to build the microstrip line to provide broadband characterization capability. 10 nm deep planar Si nanofluidic channels are fabricated through native oxide etch and wafer bonding process. It is the first effort to build the microstrip line with periodically loaded individual sub-10 nm nanofluidic channels to conduct the broadband high frequency characterization of materials within confined space. The functionality of the device is demonstrated by the measurement of DI water. It behaves well and has great potentials on the study of confinement effects of fluids and molecules. Further work includes development of parasitic signal de-embedding procedures for accurate measurements

High Performance Integrated Beam-Steering Techniques for Millimeter-Wave Systems

Recently, the research and development of low cost and highly efficient millimeter-wave (mmWave) systems with beam-steering capabilities have significantly advanced to address the ever-increasing demand for future wireless ultra-broadband applications. These applications include, but are not limited to, automotive anti-collision surveillance radar, smart navigation systems, improved wireless tracking, satellite communication, imaging, 5G wireless communication, and 60GHz multi-gigabit wireless personal and local area network (WPAN/WLAN). In general, beam-steering capability significantly relaxes the overall system power budget and minimizes the interference. In communication applications, it enhances the link robustness through multi-path mitigation and increases the channel and the aggregated channel throughput by exploiting the spatial dimension. In imaging/radar systems, beam-steering is essential for achieving the required resolution (angle-of-arrival). In this work, I have proven many beam-steering advantages in this work through the development of a ray-tracing based wireless channel model, which has been used to extract the antenna system requirements and to quantitatively illustrate the usefulness of the presented beam-steerable systems. Despite the advantages it provides, the realization of this electronic beam-steerable mmWave antenna system is quite challenging. In general, the mmWave components' design, integration, fabrication and testing processes are far more complex than their lower frequency counterparts. This can be attributed to the significant losses and parasitics experienced at mmWave frequencies, as well as the lack of reliable design models. Systems with fully integrated (on-chip) antennas and passives have been widely studied and presented at mmWave range; however, the performance (low antenna gain, high phase noise, etc…), the cost (die size is huge), and thermal problems are still major issues for these systems. Hybrid integration tackles these problems by combining a compact and low power consumption die (or multiple dies) with high performance off-chip passives (antenna, feed network, passive phase shifters, resonators, etc…); however, this integration is costly. In addition, there is a challenge associated with the implementation of high performance components at mmWave range. This is mainly due to the use of advanced/non-standard types of fabrication technologies and complex integration/packaging techniques. Investigation, optimization, development of a highly efficient and yet very low cost mmWave beam-steering solution calls for a multi-disciplinary approach which involves EM theory, optimization techniques, microwave circuits, wireless communications, Silicon micro-fabrication, layout design, parasitics modeling/extraction and MEMS technology. The proposed study introduces a high performance beam-steering mmWave antenna system along with its integration with the active components with special consideration to the fabrication cost. The new high resistivity Silicon (HRS) dielectric waveguide (DWG) based platform, which has recently been developed at CIARS (Centre for Intelligent Antenna and Radio Systems), is extended and used for wireless mmWave systems with beam-steering antennas. Electronic beam-steering can be implemented through beam-switching configurations (simple, fast but coarse) or phase array configurations (complex but high performance for large arrays). A novel low cost, highly efficient and compact switched-beam antenna is proposed for the automotive radar application. The design optimization along with the fabrication and measurement details have been discussed. For phased array applications, various HRS DWG-based antenna designs have been proposed and discussed in this study. Among them is the novel pixelated antenna which represents a new systematic procedure for designing a compact and low cost dielectric antenna for mmWave/sub-THz applications. I have developed a method using Genetic Algorithm to optimize the shape of the antenna in a compact space for any given specifications. The other important component is the phase shifter. Low-cost, compact and easily integrated phase shifters with low insertion loss and low power consumption are highly desirable for a wide range of applications. In addition, minimal insertion loss variations for the full range of phase shift over a wide frequency band is a critical requirement. I have carefully studied the effects of phase shifters non-idealities, taking into consideration the phased array system level requirements and presented two novel HRS DWG-based phase shifters. Among the proposed phase shifters is a structure that changes the phase of the propagating mode by varying the propagation constant using a high dielectric constant (40-170) slab of Barium Lanthanide Tetratitanates. This leads to a compact phase shifter design. The additional advantage of this phase shifter is that it focuses the fields in a lossless air gap (new low loss guiding structure). Different types of the proposed phase shifter have been developed and successfully tested including electrically controlled ones. Finally, I present new techniques for low cost and efficient integration for the proposed high quality mmWave passives with active components.4 month

Polymer-Based Micromachining for Scalable and Cost-Effective Fabrication of Gap Waveguide Devices Beyond 100 GHz

The terahertz (THz) frequency bands have gained attention over the past few years due to the growing number of applications in fields like communication, healthcare, imaging, and spectroscopy. Above 100 GHz transmission line losses become dominating, and waveguides are typically used for transmission. As the operating frequency approaches higher frequencies, the dimensions of the waveguide-based components continue to decrease. This makes the traditional machine-based (computer numerical control, CNC) fabrication method increasingly challenging in terms of time, cost, and volume production. Micromachining has the potential of addressing the manufacturing issues of THz waveguide components. However, the current microfabrication techniques either suffer from technological immaturity, are time-consuming, or lack sufficient cost-efficiency. A straightforward, fast, and low-cost fabrication method that can offer batch fabrication of waveguide components operating at THz frequency range is needed to address the requirements.A gap waveguide is a planar waveguide technology which does not suffer from the dielectric loss of planar waveguides, and which does not require any electrical connections between the metal walls. It therefore offers competitive loss performance together with providing several benefits in terms of assembly and integration of active components. This thesis demonstrates the realization of gap waveguide components operating above 100 GHz, in a low-cost and time-efficient way employing the development of new polymer-based fabrication methods.A template-based injection molding process has been designed to realize a high gain antenna operating at D band (110 - 170 GHz). The injection molding of OSTEMER is an uncomplicated and fast device fabrication method. In the proposed method, the time-consuming and complicated parts need to be fabricated only once and can later be reused.A dry film photoresist-based method is also presented for the fabrication of waveguide components operating above 100 GHz. Dry film photoresist offers rapid fabrication of waveguide components without using complex and advanced machinery. For the integration of active circuits and passive waveguides section a straightforward solution has been demonstrated. By utilizing dry film photoresist, a periodic metal pin array has been fabricated and incorporated in a waveguide to microstrip transition that can be an effective and low-cost way of integrating MMIC of arbitrary size to waveguide blocks

High Temperature Materials Characterization And Sensor Application

This dissertation presents new solutions for turbine engines in need of wireless temperature sensors at temperatures up to 1300oC. Two important goals have been achieved in this dissertation. First, a novel method for precisely characterizing the dielectric properties of high temperature ceramic materials at high temperatures is presented for microwave frequencies. This technique is based on a high-quality (Q)-factor dielectrically-loaded cavity resonator, which allows for accurate characterization of both dielectric constant and loss tangent of the material. The dielectric properties of Silicon Carbonitride (SiCN) and Silicoboron Carbonitride (SiBCN) ceramics, developed at UCF Advanced Materials Processing and Analysis Center (AMPC) are characterized from 25 to 1300oC. It is observed that the dielectric constant and loss tangent of SiCN and SiBCN materials increase monotonously with temperature. This temperature dependency provides the valuable basis for development of wireless passive temperature sensors for high-temperature applications. Second, wireless temperature sensors are designed based on the aforementioned hightemperature ceramic materials. The dielectric constant of high-temperature ceramics increases monotonically with temperature and as a result changes the resonant frequency of the resonator. Therefore, the temperature can be extracted by measuring the change of the resonant frequency of the resonator. In order for the resonator to operate wirelessly, antennas need to be included in the design. Three different types of sensors, corresponding to different antenna configurations, are designed and the prototypes are fabricated and tested. All of the sensors successfully perform at temperatures over 1000oC. These wireless passive sensor designs will significantly benefit turbine engines in need of sensors operating at harsh environment

Si Waveguide Technology for High Performance Millimeter-Wave/Terahertz Integrated Systems

The terahertz (THZ) spectrum (0.3 – 3 THz) offers new opportunities to a wide range of emerging applications which demand high-quality THz sources, detectors, amplifiers, and integrated circuits. On-chip integration of planar transmission line passive components degrades their performance due to the conduction loss. Therefore, a hybrid integrated technology in which all of the high-quality passive components are implemented using a suitable off-chip planar integrated technology and the active devices are placed on-chip, has become the most promising approach. In this thesis, a low-cost and low-loss silicon-on-glass (SOG) integrated circuit technology is proposed for THz/millimeter-wave (mmW) applications. Highly-resistive intrinsic silicon (Si) is selected as the main guiding region due to its high transparency at mmW/THz frequency ranges and the maturity of Si-devices fabrication. In the proposed technology, all of the passive components and waveguide connections are made of highly-resistive Si on a glass substrate. The proposed technique leads to a high-precision and low-cost fabrication process, wherein the alignment between the sub-structures is automatically achieved during the fabrication process. This is performed by photolithography and dry etching of the entire integrated passive circuit layout through the Si layer of the SOG wafer. The SOG dielectric ridge waveguide, as the basic component of the SOG integrated circuit, is theoretically and experimentally investigated. A test setup is designed to measure propagation characteristics of the proposed SOG waveguide. Measured dispersion diagrams of the SOG dielectric waveguides show average attenuation constants of 0.63 dB/cm, 0.28 dB/cm, and 0.53 dB/cm over the frequency ranges of 55 – 65 GHz, 90 – 110 GHz, and 140 – 170 GHz, respectively. Extending the SOG platform toward the THz range is achieved by new SOG waveguide structures wherein the glass substrates below the Si channels are etched to reduce the effect of greater glass material loss at higher frequencies (i.e., > 200 GHz). To fabricate these structures, the glass substrate is etched in hydrophilic acid before bonding to the Si. Four new SOG configurations, called the suspended SOG, corrugated SOG, rib SOG, and U-SOG waveguides are proposed with their respective fabrication techniques for the THz range of frequencies. In the suspended SOG waveguide, a periodic configuration of Si beams supports the Si guiding channel over the etched grove on the glass substrate. Measurements of two suspended SOG waveguides show low attenuation constants of 0.031 dB/λ0 and 0.042 dB/λ0 (on average) over the frequency ranges of 350 - 500 GHz and 400 - 500 GHz, respectively. It is theoretically demonstrated that the rib SOG and U-SOG waveguides are promising candidates for THz high-density and low-loss integrated circuits. Rib SOG waveguide and U-SOG waveguide test devices are designed over the frequency bands of 0.8 – 0.9 THz and 0.9 – 1.1 THz. The proposed SOG waveguide technology can easily be extended to several THz with no limitations. A new mmW low-loss dielectric phase shifter integrated in the corrugated SOG platform is designed, fabricated, and measured. Phase shifts of 111 ° and 129 ° at frequencies of 85 GHz and 100 GHz, with maximum insertion losses of 0.65 dB and 2.5 dB, are achieved during measurements of the proposed phase shifter. Millimeter-wave integrated SOG tapered antennas are developed and implemented. The idea of a suspended SOG tapered antenna is demonstrated to enhance the radiation efficiency and the gain of the SOG tapered antenna over 110 – 130 GHz. The suspended SOG tapered antenna, which can function under two orthogonal mode excitations, shows measured efficiencies of higher than 90 % for the two vertical polarizations

A New Silicon-Based Dielectric Waveguide Technology for Millimeter-Wave/Terahertz Devices and Integrated Systems

In recent decades, the millimeter-Wave (mmWave)/THz band has attracted great attention in the research community. The Terahertz frequency band runs from approximately 300 GHz to 3 THz, an incredible 2700 GHz of bandwidth. The Terahertz frequency range has traditionally been considered as the RF "no man's land", between electronic and optical technologies. Many efforts have been made to extend existing active and passive devices to take advantage of these higher frequencies. The development of a universal technology for integrating various functionalities in the THz region is the ultimate goal of many researchers. The primary focus of this research is to develop a novel silicon waveguide-based technology for implementing various structures and devices in the mmWave and THz range of frequencies. The structures introduced in this study are designed based on High Resistivity Silicon (HRS). Two technologies are developed and investigated at the Centre for Intelligent Antenna and Radio Systems (CIARS): Silicon-On-Glass (SOG) and Silicon Image Guide (SIG) technologies. The proposed technologies provide a low-cost, highly efficient, and integratable platform for realization a variety of mmWave/THz systems suitable for various applications such as sensing, communication, and imaging. A comprehensive study is conducted for functionality and error analysis of the proposed technologies. Also, a vast range of passive structures such as bends, dividers, and couplers are designed, fabricated and successfully tested with desired performance at the mmWave range of frequencies. Additionally, three types of dielectric waveguide antennas are designed and optimized: parasitic tapered antenna, groove grating antenna, and strip grating antenna. Another focus of this thesis is to investigate the behavior of resonance structures, operating based on Whispering Gallery Modes (WGMs). The WG mode is a special type of high order mode of a circular shaped resonator, and offers very unique properties, which make it very suitable for sensing applications. In this research, an efficient algorithm is developed for analyzing the WGM resonators. Then, the proposed HRS platforms are used for implementing various WGM resonance configurations. The introduced WGM structures are employed for two major applications: DNA sensing and resonance tuning. The results for DNA testing are quite impressive in being able to distinguish between different kinds of DNA. To demonstrate the usefulness of the developed HRS structures, a number of complex systems including, a Butler matrix network, a finger-shaped phase shifter, and tunable WGM resonance structures are designed, optimized, and realized in this report. As part of this research, a novel Microwave-Photonic idea is proposed for sensing purposes. The core of the system is based on the WGM resonance structures implemented on the HRS platforms. The proposed system is tested and promising results are achieved.4 month