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Metal coating of Fused Silica (FS) Micro-machined Hemispherical Resonator Gyroscopes (micro-HRGs) is necessary to allow for capacitive actuation and detection of motion. Metallization provides electrical conductivity, but reduces the quality factor of resonators. Both effects contribute to sensitivity and noise characteristics of the sensor. In this paper, we considered the metal coating material and thickness, linking the design and fabrication parameters to the gyroscope’s noise performance. We designed and fabricated FS Dual-Shell Gyroscopes (DSGs), a version of micro-HRG, and used it as a test vehicle to study the trade-offs between metallization, quality factor, conductivity, and noise characteristics. We developed an analytical electromechanical model to optimize metal-coating and predict gyroscope performance. The results have been confirmed experimentally. [2022-0052] [ABSTRACT FROM AUTHOR]

This paper introduces a 3-D fused quartz dual-shell microstructure, discussing its design, simulation, fabrication, and instrumentation as a Microelectromechanical System (MEMS) gyroscope. The dual-shell was realized from plastic deformation of fused quartz using triple-stack wafer bonding and high-temperature micro-glassblowing processes. The fabrication process was developed and dual-shell prototypes with different design parameters were fabricated. A Finite Element (FE) model was presented to simulate the deformation of viscous fused quartz during the micro-glassblowing process. The model was utilized to predict the final 3-D geometry from the design process parameters. A modeling framework based on FE simulations was presented for designing the resonators as well as predicting the resonator’s response to transient excitation, such as shock and vibrations. Fused quartz dual-shell resonator prototype with Q-factors as high as 1.83 million and amplitude ringdown time of 120 seconds was demonstrated. An electrode substrate was designed and integrated with the dual-shell resonator for electrostatic excitation and detection of the vibration modes, as well as 3-D packaging and vacuum encapsulation of the sensing element. An open-loop angular rate gyro operation with electrostatic excitation and capacitive detection was demonstrated on the dual-shell resonator. The Allan deviation of zero rate output bias revealed Angle Random Walk (ARW) of $0.058 \deg /\sqrt {hr}$ and in-run bias instability of $0.4 \deg /hr$ without temperature control on the dual-shell resonator gyroscope. The proposed structure can be instrumented to operate as a resonator, a gyroscope, or other vibratory sensors, and is anticipated to have advantages for precision operation in a harsh environment. [ABSTRACT FROM AUTHOR]

This paper presents analysis, design, realization, and experimental demonstration of a bistable switch actuated dynamically utilizing mechanical resonance phenomenon. We demonstrated that if a bistable structure is driven into a resonance near one of its states, it may achieve a large enough amplitude of vibration, sufficient to switch between its stable states. Using energy analysis, we concluded that dynamic switching of bistable structures may provide significant energy advantages over conventional static-switching approaches. To confirm the results, we derived analytically the closed-form actuation conditions guaranteeing switching between the states of a bistable structure and applied these conditions to experimental devices. Micromachined prototypes of dynamically actuated bistable switches were designed, fabricated, and characterized. We demonstrated experimentally that resonant dynamic switching provides energy saving of around 60% at atmospheric pressure with proportional increase in efficiency as the pressure decreases. [2008-0057] Index Terms--Bistability, dynamic snapping, nonlinear resonance.

This paper reports a novel capacitive detection method, called the sideband-ratio (SBR) detection, which is robust to variations of such critical parameters as the nominal capacitance, frequency, and amplitude of the probing voltage and gain of the transimpedance amplifier. The approach constructively utilizes the inherent nonlinearity of paralleilplate sense capacitors in order to measure the amplitude of sinusoidal motion. In the case of parallel-plate detection signal, multiple harmonics exist and each carry information about the amplitude of mechanical motion. The SBR method robustly extracts the amplitude of motion from the ratio of multiple sidebands. This paper presents theoretical background and analysis of this nonlinear measurement method. A real-time measurement algorithm is implemented in software and simulated. Feasibility of the developed approach is demonstrated experimentally. [2006-0292] Index Terms--Automatic calibration, capacitive detection, electromechanical amplitude modulation (EAM), gyroscopes, modulation, parallel plates, resonators, self-calibration, sidebands.

Electrostatic parallel-plate actuators are a common way of actuating microelectromechanical systems, both statically and dynamically. In the static case, the stable actuation voltages are limited by the static pull-in condition, which indicates that the travel range is approximately limited to 1/3 of the initial actuation gap. Under dynamic actuation conditions, however, the stable voltages arc reduced, whereas the travel range can be much extended. This is the case with the dynamic pull-in and the resonant pull-in conditions (RPCs). Using energy analysis, this paper extends the study of pull-in instability to the resonant case and derives the analytical RPC. This condition predicts snapping or pull-in of the structure for a given domain of dc and ac actuation voltages versus quality factor, taking into account the nonlinearities due to large amplitudes of oscillation. Experimental results are presented to validate the analytically derived RPC. [2006-0147] Index Terms--Electrostatic actuation, nonlinear spring, parallel-plate capacitor, pull-in instability, resonators.

A fabrication process for the simultaneous shaping of arrays of glass shells on a wafer level is introduced in this paper. The process is based on etching cavities in silicon, followed by anodic bonding of a thin glass wafer to the etched silicon wafer. The bonded wafers are then heated inside a furnace at a temperature above the softening point of the glass, and due to the expansion of the trapped gas in the silicon cavities the glass is blown into three-dimensional spherical shells. An analytical model which can be used to predict the shape of the glass shells is described and demonstrated to match the experimental data. The ability to blow glass on a wafer level may enable novel capabilities including mass-production of microscopic spherical gas confinement chambers, microlenses, and complex microfluidic networks. [2006-0092] Index Terms--Fabrication, glass, glass blowing, glass bubble, glass shell, microglass sphere, micromachining, spheres, wafer-level manufacturing.

Commercialization of reliable vibratory micromachined gyroscopes for high-volume applications has proven to be extremely challenging, primarily due to the high sensitivity of the dynamical system response to fabrication and environmental variations. This paper reports a novel micromachined gyroscope with two degrees-of-freedom (DOF) sense-mode oscillator that provides inherent robustness against structural parameter variations. The 2-DOF sense-mode oscillator provides a frequency response with two resonant peaks and a flat region between the peaks, instead of a single resonance peak as in conventional gyroscopes. The device is nominally operated in the flat region of the sense-mode response curve, where the amplitude and phase of the response are insensitive to parameter fluctuations. Furthermore, the sensitivity is improved by utilizing dynamical amplification of oscillations in the 2-DOF sense-mode oscillator. Thus, improved robustness to variations in temperature, damping, and structural parameters is achieved, solely by the mechanical system design. Prototype gyroscopes were fabricated using a bulk-micromachining process, and the performance and robustness of the devices have been experimentally evaluated. With a 25 V dc bias and 3 V ac drive signal resulting in 5.8 [micro]m drive-mode amplitude, the gyroscope exhibited a measured noise-floor of 0.64[degrees]/s[square root of Hz] over 50 Hz bandwidth in atmospheric pressure. The sense-mode response in the flat operating region was also experimentally demonstrated to be inherently insensitive to pressure, temperature, and dc bias variations. [1501] Index Terms--Inertial sensor, MEMS gyroscope, micromachined gyroscope, rate sensor.

The limitations of the photolithography-based micromachining technologies defines the upper-bound on the performance and robustness of micromachined gyroscopes. Conventional gyroscope designs based on matching (or near-matching) the drive and sense modes are extremely sensitive to variations in oscillatory system parameters that shift the natural frequencies and introduce quadrature errors. Nonconventional design concepts have been reported that increase bandwidth to improve robustness, but with the expense of response gain reduction. This paper presents a new approach that may yield robust vibratory MEMS gyroscopes with better gain characteristics while retaining the wide bandwidth. The approach is based on utilizing multiple drive-mode oscillators with incrementally spaced resonance frequencies to achieve wide-bandwidth response in the drive-mode, leading to improved robustness to structural and thermal parameter fluctuations. Enhanced mode-decoupling is achieved by distributing the linear drive-mode oscillators radially and symmetrically, to form a multidirectional linear drive-mode and a torsional sense-mode; minimizing quadrature error and zero-rate output. The approach has been implemented on bulk-micromachined prototypes fabricated in a silicon-on-insulator (SOI)-based process, and experimentally demonstrated. [1285] Index Terms--Inertial sensors, micromachined gyroscopes, MEMS, rate sensors.

This paper introduces a batch fabrication method to manufacture Micro-Electro-Mechanical System (MEMS) platforms for 3D integration of sensors spatially-distributed on a 2D plane. In the heart of the concept is a foldable MEMS structure with polymer hinges which is used to support and guide the assembly of the discrete planar sensors by means of folding them into a 3D shape, like origami, providing controlled distribution of sensors in space. Flexible hinges carrying the electrical interconnects are a critical structural element of the platform and material selection study for those is the main focus of this paper. We analyzed different materials for flexible hinges fabrication, including photo-definable polyimide and parylene-C. Three approaches for sensor integration are presented: 1) co-fabrication; 2) sensor drop-in; and 3) transfer bonding. The prototypes of structures with different flexible hinge materials were fabricated and evaluated based on their mechanical flexibility, chemical compatibility, and material outgassing. Parylene-C exhibited similar or better performances compared to polyimide, demonstrating in each of the experiments a higher degree of thermal flexibility up to 350 °C, a superior chemical resistance against hydrofluoric acid, and 2.9 times lower outgassing. [2020-0301] [ABSTRACT FROM AUTHOR]

We present a study on the quantification of energy dissipation of Micro-Electro-Mechanical System (MEMS) resonators. Toroidal Ring Gyroscope (TRG) was used as a platform to conduct the study. The main energy dissipation mechanisms in TRG include viscous air damping, Thermo-Elastic Damping (TED), anchor loss, and surface loss. During our experimental study, these energy dissipation mechanisms were minimized and controlled by venting the encapsulation and actively pumping down to high vacuum, cooling the temperature down to around 123 K, adjusting modal balance by electrostatic tuning, and pre-baking the device at high temperature (425 °C), respectively. At room temperature, the quality factor related to viscous air damping was measured to be 625,000, TED to be 170,000, and anchor loss to be 1,350,000. Finite Element Analysis (FEA) was conducted to support these findings. Relation between the anchor loss and electrostatic tuning was also explored. The effects of moisture-related surface loss have also been demonstrated by monitoring characteristics over a 2-year period of time. High temperature bake-out was proven to be effective in removing the moisture and reducing the surface loss. This paper combines topics that are scattered in literature on identification of energy dissipation mechanisms in kilohertz-range silicon MEMS resonators and presents the topic as a single methodology illustrating how the contribution of each energy dissipation mechanism can be quantified independently. To the best of our knowledge, this study is the first to experimentally quantify all major energy dissipation mechanisms in a kilohertz-range silicon MEMS resonator. [2020-0294] [ABSTRACT FROM AUTHOR]

This paper presents a design process for miniaturized atomic vapor cells using the micro-glassblowing process. It discusses multiple design considerations, including cell geometry, optical properties, materials, and surface coating. The geometry and the optical properties were studied using experimentally verified analytical and Finite Element Models (FEM). The cell construction material and surface coating were the focus of our experimental study on factors that affect the relaxation time (T2) of nuclear spins. We showed that the wafer-level coating process with Al2O3 increased the 131Xe T2 by $3\times $ and by switching from Borosilicate glass (Pyrex) to Aluminosilicate glass (ASG), T2 was improved by $2.5\times $ , for the same species. The improvement in the T2 is projected to reduce the ARW of an NMR gyro and the sensitivity of an NMR magnetometer by $3\times $ with Al2O3 coated cells and by $2.5\times $ with ASG cells. [2019-0158] [ABSTRACT FROM AUTHOR]

In this paper, recent developments in the design and fabrication of micromachined fused quartz hemi-toroidal shells are presented. The fabrication is based on micro glassblowing process, demonstrated to enable the realization of high-Q MEMS resonators and gyroscopes. The design optimization of the shell geometry is performed using parametric finite element analysis. The effect of geometric parameters on the scaling of the resonant frequencies and energy dissipation are discussed. Three variations of the micro-glassblowing process are studied in the paper, concluding that shell resonators with a broad operational frequency range without losing the symmetry and Q-factor are feasible. Finite element models are presented to simulate the presented glassblowing processes, which are used to predict the final geometry of shell resonators accurately. Operational frequency as low as 5 kHz and Q-factor as high as 1.7 million is demonstrated on the fabricated shell resonators. The proposed process modifications demonstrate a low-cost and scalable fabrication of 3D shells for resonators and gyroscopes, which can be used in inertial navigation and timing applications. [2019-0179] [ABSTRACT FROM AUTHOR]

We report on a new design approach for X-Y symmetric resonator, emphasizing the increase in symmetry by localization of the device anchors. The resonator is mechanized as a z-axis rate gyroscope (RG), and the concept is compatible with the rate-integrating gyroscope mechanization. Our approach is based on strategically placing the critical mechanical elements at the center of the resonator structure, to mitigate the effect of fabrication imperfections across the device. We experimentally demonstrated that the design yields a sub-Hz frequency separation between operational modes, which is attributed to the introduced design approach. The high symmetry of the device led to a temperature stability of 50 mHz over 130 °C temperature range. A ring down test demonstrated the Q-factor greater than 330 K. The thermal stability and preliminary characterization results of the gyro in-run stability are presented. [2017-0177] [ABSTRACT FROM AUTHOR]

This paper introduces a batch fabrication method to manufacture micro-electromechanical system (MEMS) components for nuclear magnetic resonance (NMR) atomic sensors, such as NMR gyroscope (NMRG) and NMR magnetometer (NMRM). The components presented are: 1) micro-coils generating the magnetic field with the magnetic field homogeneity of $H=354$ ppm; 2) spherical micro-fabricated atomic cells confining alkali metal and noble gases; 3) micro-heaters keeping the alkali metal in a vapor state while minimizing residual magnetic fields; and 4) origamilike silicon structures with integrated optical reflectors preserving 90.9% of the light polarization. The introduced design utilized a glassblowing process, origamilike folding, and a more traditional MEMS fabrication. We presented an analytical model of imperfections, including errors associated with micro-fabrication of MEMS components. In light of the developed error model, phenomenological dynamic model describing NMR sensors, and experimental evaluation of components, we predicted the effect of errors on performance of NMRG and NMRM. We concluded that with a realistic design, a 5-mrad angular misalignment between coils and folded mirrors, and a 100- $\mu \text{m}$ linear misalignment between folded coils, it would be feasible to achieve an NMRG with ARW 0.1 deg/rt-hr and an NMRM with sensitivity on the order of 10 fT/rt-Hz. [2018-0169] [ABSTRACT FROM AUTHOR]

This paper reports an approach for co-fabrication of silicon-on-insulator (SOI) sensors with low-resistance vertical electrical interconnects in thick (up to 600~\mu \textm ) wafers. The thru-wafer interconnects double-sided (TWIDS) process is based on bottom-up seedless copper electroplating, and allows for voids-free features and high aspect ratio (wafer thickness to copper diameter ratio of 10:1). This work describes the design trade-offs, process flow, and characterization of interconnects. TWIDS technology is compatible with a standard SOI micro-electro-mechanical systems (MEMS) fabrication process and is applicable for micro sensors, such as accelerometers, gyroscopes, resonators, and RF MEMS devices, as well as for the 3-D MEMS assemblies. As a demonstration of potential applications, miniature toroidal ring gyroscopes were fabricated using the TWIDS process. The experimental characterization showed that the low-resistance interconnects with low parasitic losses are suitable for integration with capacitive-detection sensors. In addition, the mechanical stability of the interconnects is discussed in this paper, and a method to enhance structural rigidity by means of filling the insulating gaps with Parylene C is demonstrated. [2017-0179] [ABSTRACT FROM PUBLISHER]

This paper presents a miniature 50 mm3 inertial measurement unit (IMU) implemented using a folded microelectromechanical systems (MEMS) process. The approach is based on wafer-level fabrication of high aspect-ratio single-axis sensors interconnected by flexible hinges and folded into a 3-D configuration, like a silicon Origami [1]. Two different materials for flexible hinges have been explored, including photo-definable polyimide and parylene-C. We report, for the first time, an IMU prototype with seven operational sensors: three accelerometers, three gyroscopes, and a prototype of a reference clock. This paper concludes with the results of experimental characterization of inertial sensors demonstrating the feasibility of the proposed approach for a compact IMU. [2016-0267] [ABSTRACT FROM AUTHOR]

In this paper, we report magnetic neutral loop discharge (NLD) plasma etching of fused silica (FS) and borosilicate glass (BSG), demonstrating high aspect ratio deep etch ( 100~\mu \textm ) with vertical walls (<3° deviation from vertical). This paper for the first time presents the systematic study of FS and BSG deep etching in NLD plasma. Four different masking materials have been explored including metal, amorphous silicon, bonded silicon, and photoresist. Etch parameters were optimized to eliminate unwanted artifacts, such as micro-masking, trenching, and faceting, while retaining a high aspect ratio (up to 7:1 for FS and 8:1 for BSG). In addition, a method for sidewall roughness mitigation based on postfabrication annealing was developed, showing the sidewall roughness reduction from the average roughness ( Ra ) 900 to 85 nm. Further advances in deep plasma etching processes may enable the use of FS and BSG in the fabrication of precision inertial MEMS, micro-fluidic, and micro-optical devices. [2015-0078] [ABSTRACT FROM AUTHOR]

In this paper, we report Q-factor over 1 million on both n = 2 wineglass modes, and high-frequency symmetry (Δf/f ) of 132 ppm on wafer-level microglassblown 3-D fused silica wineglass resonators at a compact size of 7-mm diameter and center frequency of 105 kHz. In addition, we demonstrate for the first time, out-of-plane capacitive transduction on microelectromechanical systems wineglass resonators. High Q-factor is enabled by a high aspect ratio, self-aligned glassblown stem structure, careful surface treatment of the perimeter area, and low internal loss fused silica material. Electrostatic transduction is enabled by detecting the spatial deformation of the 3-D wineglass structure using a new out-of-plane electrode architecture. Out-of-plane electrode architecture enables the use of sacrificial layers to define the capacitive gaps and 10 μm capacitive gaps have been demonstrated on a 7-mm shell, resulting in over 9 pF of active capacitance within the device. Microglassblowing may enable batch-fabrication of high-performance fused silica wineglass gyroscopes at a significantly lower cost than their precision-machined macroscale counterparts. [ABSTRACT FROM AUTHOR]

We demonstrate, for the first time, sub-1 Hz frequency symmetry in micro-glassblown wineglass resonators with integrated electrode structures. A new fabrication process based on deep glass dry etching was developed to fabricate micro-wineglasses with self-aligned stem structures and integrated electrodes. The wineglass modes were identified by electrostatic excitation and mapping the velocity of motion along the perimeter using laser Doppler interferometry. A frequency split (Δf) of 0.15 and 0.2 Hz was demonstrated for n=2 and n=3 wineglass modes, respectively. To verify the repeatability of the results, a total of five devices were tested, three out of five devices showed . Frequency split stayed below 1 Hz for dc bias voltages up to 100 V, confirming that the low frequency split is attributed to high structural symmetry and not to capacitive tuning. High structural symmetry and atomically smooth surfaces (0.23 nm Sa) of the resonators may enable new classes of high performance 3-D MEMS devices, such as rate-integrating MEMS gyroscopes. [ABSTRACT FROM AUTHOR]

North-finding based on micromachined gyroscopes is an attractive possibility. This paper analyzes north-finding methods and demonstrates a measured 4 mrad standard deviation azimuth uncertainty using an in-house developed vibratory silicon MEMS quadruple mass gyroscope (QMG). We instrumented a vacuum packaged QMG with isotropic Q-factor of 1.2 million and Allan deviation bias instability of 0.2^\circ/hr for azimuth detection by measuring the earth's rotation. Continuous rotation (“carouseling”) produced azimuth datapoints with uncertainty diminishing as the square root of the number of turns. Integration of 100 datapoints with normally distributed errors reduced uncertainty to 4 mrad, beyond the noise of current QMG instrumentation. We also implemented self-calibration methods, including in-situ temperature sensing and discrete \pm180^\circ turning (“maytagging” or two-point gyrocompassing) as potential alternatives to carouseling. While both mechanizations produced similar azimuth uncertainty, we conclude that carouseling is more advantageous as it is robust to bias, scale-factor, and temperature drifts, although it requires a rotary platform providing continuous rotation. Maytagging, on the other hand, can be implemented using a simple turn table, but requires calibration due to temperature-induced drifts. \hfill[2012\-0378] [ABSTRACT FROM PUBLISHER]

A fabrication process for the simultaneous shaping of arrays of glass shells on a wafer level is introduced in this paper. The process is based on etching cavities in silicon, followed by anodic bonding of a thin glass wafer to the etched silicon wafer. The bonded wafers are then heated inside a furnace at a temperature above the softening point of the glass, and due to the expansion of the trapped gas in the silicon cavities the glass is blown into three- dimensional spherical shells. An analytical model which can be used to predict the shape of the glass shells is described and demonstrated to match the experimental data. The ability to blow glass on a wafer level may enable novel capabilities including mass-production of microscopic spherical gas confinement chambers, microlenses, and complex microfluidic networks. [ABSTRACT FROM AUTHOR]

We report, for the first time, experimental demonstration of a 3-D spherical shell resonator microelectromechanical systems gyroscope fabricated using wafer-scale glassblowing. The gyroscope utilizes a 1-mm-diameter 10-\mu\m-thick spherical isotropic shell surrounded by eight cofabricated satellite spheres serving as actuation and detection electrodes. To demonstrate functionality of the new device, a four-node wineglass mode at a 945-kHz frequency was utilized as the drive mode of a Coriolis vibratory gyroscope. The input rotation causes the transfer of energy from the drive mode to the sense mode, which is a complementary four-node wineglass mode oriented at a 45^ \circ angle. Sense-mode vibrations were capacitively detected using cofabricated 3-D metal electrodes. Experimental characterization of the spherical shell gyroscope demonstrated a wide linear range of 1000 ^\circ/\s, currently limited only by the experimental setup.\hfill[2011-0327] [ABSTRACT FROM PUBLISHER]