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The Electromechanical Amplitude Modulation (EAM) is frequently used to eliminate feed-through signals between forcer and pick-off electrodes of resonant microstructures. However, there are some undesirable effects of EAM that need to be considered. This work studies the contribution of EAM on dissipation of energy and appeared non-linear dynamics in MEMS Coriolis Vibratory Gyroscopes (CVGs). We presented an analytical model, capturing the effect of AC carrier signal on amplitude-frequency coupling, scale factor instability, and in-run noise performance of CVGs. The effect of EAM on a Dynamically Amplified dual-mass Gyroscope (DAG) was experimentally demonstrated and compared to the simulation results of the analytical model. We concluded that the AC carrier signal in EAM influences the amplitude-frequency couplings along both the drive and sense modes of the gyroscope through modifying the non-linear electrostatic stiffnesses, which was also proven to be one of the dominant sources of both the scale factor nonlinearity and frequency instability in the near-mode-matched DAG, operating in the open-loop rate mode. [ABSTRACT FROM AUTHOR]

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]

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 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]

We report a new silicon Microelectromechanical systems (MEMS) accelerometer based on differential frequency modulation (FM) with experimentally demonstrated thermal compensation over a dynamic temperature environment and \mu g -level Allan deviation of bias. The sensor architecture is based on resonant frequency tracking in a vacuum packaged silicon-on-insulator (SOI) tuning fork oscillator. To address drift over temperature, the MEMS sensor die incorporates two identical tuning forks with opposing axes of sensitivity. Demodulation of the differential FM output from the two simultaneously operated oscillators eliminates common mode errors and provides an FM output with continuous thermal compensation. The first SOI prototype with quality factor of 350000 was built and characterized over a temperature range between 30 °C and 75 °C. Temperature characterization of the FM accelerometer showed less than a 0.5% scale-factor change throughout a temperature range from 30 °C to 75 °C, without any external compensation. This is enabled by an inherently differential frequency output, which cancels common-mode influences, such as those due to temperature. Allan deviation of the differential FM accelerometer revealed a bias instability of 6\,\, \mu \text{g} at 20 s, along with an elimination of any temperature drift due to increases in averaging time. After comparing the measured bias instability with the designed linear range of 20 g, the sensor demonstrates a wide dynamic range of 130 dB. A second design iteration of the FM accelerometer, vacuum-sealed with getter material, was created to maximize Q$ -factor, and thereby frequency resolution. A $Q$ -factor of 2.4 million was experimentally demonstrated, with a time constant of >20 min. [ABSTRACT FROM PUBLISHER]

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]

This paper reports a new approach for design and fabrication of chip-level inertial measurement units (IMUs). The method utilizes a 3-D foldable silicon-on-insulator (SOI) backbone with in-situ fabricated high-aspect-ratio sensors. A planar multisensor unit was fabricated and subsequently folded in a pyramidal shape, forming a compact IMU. Inertial characterization of the sensors integrated on the IMU pyramid was performed at atmospheric pressure. Structural rigidity and sensor axis alignment stability of the folded IMUs have been characterized under various environmental conditions, including vibration, thermal loading, thermal shock, and constant acceleration. The maximum angular misalignment due to variation in environmental conditions between IMU pyramid sidewalls was shown to be less than 4 and 0.2 mrad for epoxy and solder reinforced structures, respectively. Vibration testing revealed no resonances up to 10 kHz in the assembled 3-D structures. Our results confirm feasibility of the fabrication approach. [ABSTRACT FROM PUBLISHER]

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]