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This paper presents the design, fabrication, and characterization of a novel "hinge-shaped" out-of-plane differential accelerometer utilizing nanometer sensing gap (300 nm) electrodes. The increased electromechanical coupling provided by narrow gap allows the design of micro-g accelerometers with high resonant frequency (> 10 kHz), which would extend the operational bandwidth as well...
This paper reports on a theoretical and experimental study of substrate-decoupled three-dimensional micro-shell resonators made of silicon dioxide (SiO2). Design, fabrication and test results of a microscale SiO2 thin-film shallow shell resonator anchored through a hollow cylindrical post is presented. Virtual levitation of the resonator because of the hollow cylinder is explained and the results...
This paper reports on the design and characterization of the first commercially-available tri-axial rotation-rate sensor implemented by the use of substrate-decoupled bulk acoustic wave (SD-BAW) gyroscopes. Owed to their high-frequency of operation (4.3 MHz), these devices exhibit significantly reduced dependencies on environmental stimuli such as vibration and shock. The sensor consists of three...
This paper introduces a ‘high-frequency’ resonant tri-axial tuning fork gyroscope (TFG) with a single-drive mode of operation. The quad-mass device is implemented on a 2×2 mm2 vacuum-packaged die fabricated using the epi-seal process, making this one of the smallest wafer-level packaged 3-axis gyros. In contrast to conventional resonant TFGs, the resonant frequencies are designed to be relatively...
This paper introduces a novel dual-mode actuation and sensing scheme for readout and calibration of axisymmetric Coriolis resonant gyroscopes. The proposed scheme actuates both gyroscope modes simultaneously with the same in-phase excitation, senses both modes concurrently, and utilizes the sum and difference of the sense signals to demonstrate complete cancellation of the gyroscope bias terms, and...
This paper details a center-supported solid disk resonator in <100> single-crystalline-silicon (SCS) that uses a novel substrate decoupling feature to achieve ultra-low dissipation gyroscopic modes with small frequency split. The secondary bulk acoustic wave (BAW) elliptic modes (m = 3) of a 2mm diameter substrate-decoupled disk resonator exhibit quality factor (Q) of ∼1.3 M with 40 ppm frequency...
This paper reports on the design, fabrication and characterization of single proof-mass tri-axial capacitive accelerometers coexisting in a low-pressure environment with high-frequency gyroscopes, for the implementation of monolithic 6-degree-of-freedom inertial measurement units. The accelerometers are designed to operate as quasi-static devices (i.e. non-resonant sensors) in mid vacuum levels (1–10...
This paper presents a gyroscope interface architecture that combines readout and self-calibration functions in a reconfigurable fashion. The phase readout and calibration operation relies on the phase shifts observed at the gyroscope outputs with respect to the applied excitations. The proposed electrostatic calibration obviates the use of any additional moving parts or calibration stage. The significance...
This paper reports on the design, implementation and characterization of triaxial capacitive accelerometers operating in a low-pressure environment (∼1 Torr). Small form-factor devices, with proof-mass area of less than 1mm2, were fabricated on a 40 μm-thick SOI substrate using the HARPSS™ process to attain in-plane and out-of-plane nanoscale capacitive airgaps (∼300 nm). Increased sensitivity and...
The effect of thickness anisotropy on the degenerate elliptical resonance modes of micro-hemispherical shell resonators (μHSRs) created using the thermal oxidation process is investigated. This anisotropy arises from the variation in wet thermal oxide growth according to the exposed crystal planes of the single-crystal-silicon hemispherical mold used to generate the μHSRs. It is shown that, despite...
This paper presents fully-integrated multi-axis piezoelectric-on-silicon kinetic energy harvesters (KEHs) that demonstrate enhanced power output via mechanical frequency upconversion. Mechanical energy is converted to electrical energy by out-of-plane and in-plane devices that are micromachined on the same substrate. The out-of-plane device demonstrates nearly 100× frequency upconversion of 134 Hz...
We present a self-aligned fabrication method developed for three-dimensional (3-D) microscale hemispherical shell resonators with integrated capacitive transducers and a center post for electrical access to the shell. The self-aligned process preserves the axisymmetry for robust, balanced resonators that can potentially reach very high-Q due to suppressed anchor loss. High-Q operation of a thin polycrystalline...
This paper introduces a new approach to self-calibration of Coriolis-based vibratory gyroscopes that does not require the use of any additional moving parts or a calibration stage. Instead, the effect of the Coriolis force on the device is mimicked by the application of a rotating excitation to the device drive and sense modes. This calibration method is based on the theoretical analysis of an equivalent...
This paper reports on the design, fabrication, and characterization of a high-frequency single proof-mass dual-axis gyroscope. The hollow-disk pitch-and-roll resonant gyroscope has electrostatically tunable in-plane and out-of-plane resonance modes to enable mode-matched operation at ∼ 0.9MHz in the presence of process non-idealities such as thickness variations of the SOI wafer. A prototype device...
This work introduces piezo-on-silicon linear acoustic bandgap (LAB) structures, a class of compact 1D micro-scale phononic crystal (PC) which can be directly integrated with micromechanical devices. Finite element simulations with custom-derived dispersion equations predict multiple bandgaps for coupled-ring LAB structures into the GHz region. AlN-on-Si resonator are replaced with coupled-ring LAB...
This paper presents lateral silicon bulk acoustic resonators that are piezoelectrically excited using a thin layer of AlN on their vertical sidewalls. Sputtered AlN coats the sidewalls of a 20 um thick resonator conformally and uniformly, enabling the excitation of width-extensional modes in a suspended silicon microstructure using the longitudinal piezoelectric stress coefficient e33. A motional...
A low-cost, hermetic wafer-level packaging solution with negligible parasitics suitable for MEMS resonators is presented. A glass cap with embedded 50µm diameter vertical single-crystal silicon feedthroughs is anodically bonded in vacuum to an SOI wafer prefabricated with mechanical resonators. This hermetic packaging process provides virtually zero-parasitic-capacitance vertical interconnects. A...
This paper shows improved phase-noise performance of MEMS oscillators when the sustaining amplifier operates a lateral bulk acoustic wave AlN-on-Si resonator in the nonlinear regime. An empirical exponential-series-based model that closely describes the phase noise in nonlinearity is presented, reflecting the increased resonator filter order and the reduced amplifier flicker-noise contribution. An...
This paper demonstrates a dual-mode (DM) oscillator which simultaneously excites the fundamental and third-order modes of a micromachined, piezo-on-silicon bulk acoustic wave (BAW) resonator for real-time self-temperature measurement. By concurrently measuring the temperature coefficient of frequency (TCF) at 30 MHz (f1) and 87 MHz (f3), a beat frequency (fb) with TCF of 162 ppm/°C is extracted. Phase...
This paper reports on the design and characterization of a high-gain tunable transimpedance amplifier (TIA) suitable for gigahertz oscillators that use high-Q lateral micromechanical resonators with large motional resistance and large shunt parasitic capacitance. The TIA consists of a low-power broadband current pre-amplifler combined with a current-to-voltage conversion stage to boost the input current...
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