Dissertations / Theses on the topic 'Microelectromechanical systems – Micromachining'

Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 15, 2008) Includes bibliographical references.

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.
Committee Chair: John Papapolymerou; Committee Chair: Manos Tentzeris; Committee Member: Gordon Stuber; Committee Member: John Cressler; Committee Member: John Z. Zhang; Committee Member: Joy Laskar

This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on  measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device  conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved.

QC 20140328

Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 16, 2008) Includes bibliographical references.

Surface micromachining of micro-electro-mechanical systems (MEMS), like all other fabrication processes, has inherent variation that leads to uncertain material and dimensional parameters. To obtain accurate and reliable predictions of mechanism behavior, the effects of these variations need to be analyzed. This thesis expands already existing tolerance and uncertainty analysis methods to apply to micro compliant mechanisms. For simple compliant members, explicit equations can be used in uncertainty analysis. However, for a nonlinear implicit system of equations, the direct linearization method may be used to obtain sensitivities of output parameters to small changes in known variables. This is done by including static equilibrium equations and pseudo-rigid-body model relationships with the kinematic vector loop equations. Examples are used to show a comparison of this method to other deterministic and probabilistic methods and finite element analysis.

This thesis reports the development of high-performance symmetric and decoupled micromachined gyroscopes for tactical-grade inertial measurement applications. The symmetric structure allows easy matching of the resonance frequencies of the drive and sense modes of the gyroscopes for achieving high angular rate sensitivity
while the decoupled drive and sense modes minimizes mechanical cross-coupling for low-noise and stable operation. Three different and new symmetric and decoupled gyroscope structures with unique features are presented. These structures are fabricated in four different micromachining processes: nickel electroforming (NE), dissolved-wafer silicon micromachining (DWSM), silicon-on-insulator (SOI) micromachining, and silicon-on-glass (SOG) micromachining. The fabricated gyroscopes have capacitive gaps from 1.5µ
m to 5.5µ
m and structural layer thicknesses from 12µ
m to 100µ
m, yielding aspect ratios up to 20 depending on the fabrication process. The size of fabricated gyroscope chips varies from 1x1mm2 up to 4.2x4.6mm2. Fabricated gyroscopes are hybrid-connected to a designed capacitive interface circuit, fabricated in a standard 0.6µ
m CMOS process. They have resonance frequencies as small as 2kHz and as large as 40kHz
sense-mode resonance frequencies can be electrostatically tuned to the drive-mode frequency by DC voltages less than 16V. The quality factors reach to 500 at atmospheric pressure and exceed 10,000 for the silicon gyroscopes at vacuum. The parasitic capacitance of the gyroscopes on glass substrates is measured to be as small as 120fF. The gyroscope and interface assemblies are then combined with electronic control and feedback circuits constructed with off-the-shelf IC components to perform angular rate measurements. Measured angular rate sensitivities are in the range from 12µ
V/(deg/sec) to 180µ
V/(deg/sec), at atmospheric pressure. The SOI gyroscope demonstrates the best performance at atmospheric pressure, with noise equivalent rate (NER) of 0.025(deg/sec)/Hz1/2, whereas the remaining gyroscopes has an NER better than 0.1(deg/sec)/Hz1/2, limited by either the small sensor size or by small quality factors. Gyroscopes have scale-factor nonlinearities better than 1.1% with the best value of 0.06%, and their bias drifts are dominated by the phase errors in the demodulation electronics and are over 1deg/sec. The characterization of the SOI and SOG gyroscopes at below 50mTorr vacuum ambient yield angular rate sensitivities as high as 1.6mV/(deg/sec) and 0.9mV/(deg/sec), respectively. The NER values of these gyroscopes at vacuum are smaller than 50(deg/hr)/Hz1/2 and 36(deg/hr)/Hz1/2, respectively, being close to the tactical-grade application limits. Gyroscope structures are expected to provide a performance better than 10 deg/hr in a practical measurement bandwidth such as 50Hz, provided that capacitive gaps are minimized while preserving the aspect ratio, and the demodulation electronics are improved.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Allen, Mark; Committee Member: Allen, Sue; Committee Member: Glezer, Ari; Committee Member: Koros, Williams; Committee Member: Prausnitz, Mark. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This thesis reports development of three different high performance, low g-sensitive micromachined gyroscopes having single, double, and quadruple masses. The single mass gyroscope (SMG) is developed for comparison of its performance with the double mass gyroscope (DMG) and quadruple mass gyroscope (QMG). DMG is a tuning fork gyroscope, diminishing the effects of unpredictable g-loadings during regular operation, while QMG is a twin tuning fork gyroscope, developed for a uniform and minimized g-sensitivity. DMG and QMG use novel ring spring connections for merging the masses in drive modes, providing uniform and anti-phase drive mode vibrations that minimize the cross-coupling and the effects of intrinsic and extrinsic accelerations on the scale factor and bias levels of the gyroscopes. The sense mode of each mass of the multi-mass gyroscopes is designed to have higher resonance frequencies than that of the drive mode for possible matching requirements, and these sense modes have dedicated frequency tuning electrodes for frequency matching or tuning. Detailed performance simulations are performed with a very sophisticated computer model using the ARCHITECT software. These gyroscopes are fabricated using a standard SOIMUMPs process of MEMSCAP Inc., which provides capacitive gaps of 2 µ
m and structural layer thickness of 25 µ
m. Die sizes of the fabricated gyroscope chips are 4.1 mm x 4.1 mm for the single mass, 4.1 mm x 8.9 mm for the double mass, and 8.9 mm x 8.9 mm for the quadruple mass gyroscope. Fabricated gyroscopes are tested with dedicated differential readout electronics constructed with discrete components. Drive mode resonance frequencies of these gyroscopes are in a range of 3.4 kHz to 5.1 kHz. Depending on the drive mode mechanics, the drive mode quality (Q) factors of the fabricated gyroscopes are about 300 at atmospheric pressure and reaches to a value of 2500 at a vacuum ambient of 50 mTorr. Resolvable rates of the fabricated gyroscopes at atmospheric pressure are measured to be 0.109 deg/sec, 0.055 deg/sec, and 1.80 deg/sec for SMG, DMG, and QMG, respectively. At vacuum, the respective resolutions of these gyroscopes improve significantly, reaching to 106 deg/hr with the SMG and 780 deg/hr with the QMG, even though discrete readout electronics are used. Acceleration sensitivity measurements at atmosphere reveal that QMG has the lowest bias g-sensitivity and the scale factor g sensitivity of 1.02deg/sec/g and 1.59(mV/(deg/sec))/g, respectively. The performance levels of these multi-mass gyroscopes can be even further improved with high performance integrated capacitive readout electronics and precise sense mode phase matching.

This thesis introduces two ortho-planar MEMS devices that can be used to position microcomponents: the XZ Micropositioning Mechanism and the XYZ Micromanipulator. The displacement and force relationships are presented. The devices were fabricated using surface micromachining processes and the resulting mechanisms were tested. A compliant XYZ Micromanipulator was also designed to reduce backlash and binding. In addition, several other MEMS positioners were fabricated and tested: the Micropositioning Platform Mechanism (MPM), the Ortho-planar Twisting Micromechanism (OTM), and the Ortho-planar Spring Micromechanism (OSM).

Dissertation (Ph.D.)--Worcester Polytechnic Institute.
Keywords: laser beam characteristics; heat transfer; hole profile; MEMS; hole formation; laser micromachining; laser microdrilling; plasma effects; silicon; 304 stainless steel; Fourier theory; lattice-phonon vibration. Includes bibliographical references. (p.379-390)

This thesis presents various integrated antenna solutions for different types of systems and applications, e.g. wireless sensors, broadband handsets, advanced base stations, MEMS-based reconfigurable front-ends, automotive anti-collision radars, and large area electronics. For wireless sensor applications, a T-matched dipole is proposed and integrated in an electrically small body-worn sensor node. Measurement techniques are developed to characterize the port impedance and radiation properties. Possibilities and limitations of the planar inverted cone antenna (PICA) for small handsets are studied experimentally. Printed slot-type and folded PICAs are demonstrated for UWB handheld terminals. Both monolithic and hybrid integration are applied for electrically steerable array antennas. Compact phase shifters within a traveling wave array antenna architecture, on single layer substrate, is investigated for the first time. Radio frequency MEMS switches are utilized to improve the performance of reconfigurable antennas at higher frequencies. Using monolithic integration, a 20 GHz switched beam antenna based on MEMS switches is implemented and evaluated. Compared to similar work published previously, complete experimental results are here for the first time reported. Moreover, a hybrid approach is used for a 24 GHz switched beam traveling wave array antenna. A MEMS router is fabricated on silicon substrate for switching two array antennas on a LTCC chip. A concept of nano-wire based substrate integrated waveguides (SIW) is proposed for millimeter-wave applications. Antenna prototypes based on this concept are successfully demonstrated for automotive radar applications. W-band body-worn nonlinear harmonic radar reflectors are proposed as a means to improve automotive radar functionality. Passive, semi-passive and active nonlinear reflectors consisting of array antennas and nonlinear circuitry on flex foils are investigated. A new stretchable RF electronics concept for large area electronics is demonstrated. It incorporates liquid metal into microstructured elastic channels. The prototypes exhibit high stretchability, foldability, and twistability, with maintained electrical properties.
wisenet

Le but du travail est de montrer la faisabilité du tissage de filament de très faible diamètre (de l'ordre de 10 à 25 -tm) et de matières différentes (cuivre, or, polyester...). Les essais du comportement mécanique (traction, fatigue) du micro filament de cuivre ont montré la possibilité du tissage de ce type du filament à cette échelle. A partir de ces résultats, il est possible d'entrevoir des solutions techniques de tissage pour réaliser des tissus à partir de ces filaments. Ce travail a permis donc de concevoir les différentes parties de la machine de micro tissage : système d'alimentation des fils de chame, système de formation de la foule, système d'insertion du fil de trame, système de mouvement du peigne, système d'appel et de stockage du tissu. Le système de formation de la foule de type Jacquard représente le cœur de la machine à tisser. Il lève un verrou technologique persistant depuis de très nombreuses années. Les résultats prometteurs des micros actionneurs fluidiques ont permis de montrer la faisabilité du micro tissage. Ils ont permis également de valider le procédé de la fabrication d'un bloc des plusieurs actionneurs capable de séparer les filaments de chaîne pour former la foule. Le logiciel de contrôle et de dessin conçu permet à la fois de réaliser des armures et de les compiler en format convenable pour pouvoir les transmettre à la carte de contrôle. Cette dernière permet de contrôler les différentes parties de la machine à tisser.

Micromanufacturing consists of processes for producing structures, devices or systems with feature sizes measured in micrometers. Micromanufacturing began in the mid-1960's with microelectronics fabrication technology. In the 1980's, Micro-Electro-Mechanical Systems (MEMS) began to be developed, in which electrical and mechanical subsystems were integrated at small scales. More recently, Microtechnology-based Energy and Chemical Systems (MECS) have been developed that have led to improved heat and mass transfer in energy and chemical systems. At Oregon State University, new methods to fabricate MECS have been developed. One of the new methods involves microlamination--bonding thin strips of different materials together. This method has generated a high volume and low-cost approach to the production of high-aspect-ratio (height-to-width) structures. Past efforts to make microfloat valves using microlamination methods resulted in an 11:1 diodicity ratio. It was hypothesized that the valve had a ridge of redeposited material around the valve seat caused by the condensation and deposition of ablation ejecta during laser machining. The contribution of this thesis is the creation of a microfloat valve using an Electrochemical Micromachining (EMM) method. EMM methods are known to produce smooth surfaces, free of burrs or any other types of aspirates. Therefore, it was hypothesized that float valves made with EMM methods would improve valve performance. Four steps were involved in the creation of the microfloat valve: lamina formation, laminae registration, laminae bonding and component dissociation. A total of 9 laminae-some of which were made with 304 stainless steel 76.2 ��m thick, others of which were made with 50.8 ��m thick polyimide-made up the microfloat valve. Photolithography and EMM were used to form the lamina. Even though the laminae created by EMM were smaller in size than desired, the machined areas did not have redeposited material, and some areas had straight walls. In laminae registration, a two edge registration method was used. In the laminae bonding step, laminae were bonded by the adhesive method at 248��C under 135 kPa pressure for 13.5 minutes. In the component dissociation step, a capacitor dissociation method that was designed at OSU was used. Upon performance testing, the average diodicity ratio for the EMM valve was 12.45 over the range 0 kPa-450 kPa, indicating improved performance when compared to the Laser Ablation valve-which had an average 11.17 over the range 0 kPa-100 kPa. Microscope examination of valves revealed that statistically significant improvement in valve performance would require refinement of component dissociation methods.
Graduation date: 2000

Chan, Ngai Shing.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.
Includes bibliographical references (leaves 67-70).
Abstracts in English and Chinese.
Abstract --- p.I
摘要 --- p.III
List of Figures --- p.VI
List of Tables --- p.VIII
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Background Information --- p.2
Chapter 1.1.1 --- Project Background --- p.2
Chapter 1.1.2 --- Literature Review --- p.4
Chapter 1.1.3 --- Background on Gear Hobbing --- p.10
Chapter 1.1.4 --- Traditional gear hobbing machines --- p.12
Chapter 2 --- Design and Testing of the MMT system --- p.15
Chapter 2.1 --- Specifications of the MMT system --- p.16
Chapter 2.1.1 --- Overall Configuration --- p.18
Chapter 2.1.2 --- Linear Actuation --- p.18
Chapter 2.1.3 --- Main Spindle Assembly --- p.19
Chapter 2.1.4 --- Tool Plate Assembly --- p.20
Chapter 2.1.5 --- Motion Control --- p.22
Chapter 2.2 --- Main Features --- p.24
Chapter 2.2.1 --- Mechanically Decoupled Gear Hobbing --- p.24
Chapter 2.2.2 --- Single Setup for Non-planar Gears --- p.26
Chapter 2.2.3 --- Quality Assurance by Computer Simulation --- p.27
Chapter 2.3 --- Turning Test --- p.28
Chapter 2.3.1 --- Experiment Results --- p.29
Chapter 2.3.2 --- Tornos' Performance --- p.30
Chapter 2.3.3 --- Estimation of Cutting Force and Workpiece Deflection --- p.32
Chapter 2.4 --- Synchronization Test --- p.33
Chapter 2.4.1 --- Experimental Results --- p.34
Chapter 2.5 --- Gear Hobbing Test --- p.36
Chapter 3 --- Diagnostic Tool: Gear Hobbing Simulation --- p.40
Chapter 3.1 --- Simulation Model --- p.41
Chapter 3.2 --- Simulations with Process Defects --- p.44
Chapter 3.2.1 --- Asynchronous motion between tool and workpiece spindle --- p.44
Chapter 3.2.2 --- Pitch error of the cutter hob --- p.45
Chapter 3.2.3 --- Tool spindle run-out error --- p.47
Chapter 3.2.4 --- Combination of process defects --- p.49
Chapter 3.3 --- Experiment Validation --- p.50
Chapter 4 --- Technical know-hows --- p.55
Chapter 4.1 --- Premature Part Break-off --- p.55
Chapter 4.2 --- Tool Alignment and Centering --- p.58
Chapter 4.2.1 --- Two-turns Aligning Algorithm --- p.59
Chapter 5 --- Conclusion and Future Work --- p.63
References --- p.67
Publication Record --- p.71
Appendix --- p.72