Effect of structural anisotropy on anchor loss mismatch and predicted case drift in future micro-Hemispherical Resonator Gyros

Sorenson, Logan; Ayazi, Farrokh

doi:10.1109/plans.2014.6851408

Cited by 12 publications

(5 citation statements)

References 12 publications

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“…A lower-bound 'worst-case' value of Q due to anchor loss (Q anchor ) can be estimated for each of the modes by assuming that all the strain energy at the interface is dissipated into the substrate (that is, there are no acoustic reflections) 26,27 . However, this condition is only valid when the dimensions of the substrate are much larger than the wavelength of the acoustic wave generated by the resonator, which is rarely true.…”

Section: Mechanical Reduction Of Anisodampingmentioning

confidence: 99%

Substrate-decoupled, bulk-acoustic wave gyroscopes: Design and evaluation of next-generation environmentally robust devices

Serrano¹,

Zaman²,

Rahafrooz³

et al. 2016

Microsyst Nanoeng

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This paper reports on a new type of high-frequency mode-matched gyroscope with significantly reduced dependencies on environmental stimuli such as temperature, vibration, and shock. A novel stress-isolation system is used to effectively decouple an axis-symmetric bulk-acoustic wave (BAW) vibratory gyro from its substrate, minimizing the effect that external sources of error have on the offset and scale factor of the device. Substrate-decoupled (SD) BAW gyros with a resonance frequency of 4.3 MHz and Q values near 60 000 were implemented using the high aspect ratio poly and single-crystal silicon (HARPSS) process to achieve ultra-narrow capacitive gaps. Wafer-level packaged sensors were interfaced with a customized application-specific integrated circuit (ASIC) to achieve low variations in the offset across temperature (±26°s − 1 from − 40 to 85°C), supreme random-vibration immunity (0.012°s − 1 g RMS − 1 ) and excellent shock rejection. With a scale factor of 800 μV (°s, the SD-BAW gyro system attains a large full-scale range (±1250°s) with a non-linearity of less than 0.07%. A measured angle-random walk (ARW) of 0.39°/√h and a bias instability of 10.5°h − 1 are dominated by the thermal and flicker noise of the integrated circuit (IC), respectively. Additional measurements using external electronics show bias-instability values as low as 3.5°h INTRODUCTIONMicromachined gyroscopes have enabled a myriad of applications that range from basic motion detection for gaming to safety control systems in automobiles 1 . More recently, an increased interest in the use of microelectromechanical system inertial sensors for dead reckoning and pedestrian navigation in handheld electronics has placed stringent requirements on the die size, power consumption, and overall performance of this type of device. To date, most commercially available rate sensors have been designed as low-frequency flexural tuning-fork gyroscopes (TFGs), which are typically sensitive to random vibrations and prone to linear accelerations, such as those experienced under shock. These limitations complicate the use of TFG technology in large-volume, high-end applications, particularly in personal navigation, for which dependencies on fluctuations in the environment translate into long-term drift in the output of the system. Additionally, in recent months, concerns about the high sensitivity of consumer-grade gyroscopes in response to lowfrequency pressure signals that can be used to recover audio have increased as a potential threat for eavesdropping 2 , justifying the need for more environmentally robust rotation sensors.Acceleration suppression mechanisms can be implemented in TFGs to alleviate part of this problem using redundant proof masses that reject shock and vibration as common-mode signals 3 .

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Section: Mechanical Reduction Of Anisodampingmentioning

confidence: 99%

Substrate-decoupled, bulk-acoustic wave gyroscopes: Design and evaluation of next-generation environmentally robust devices

Serrano¹,

Zaman²,

Rahafrooz³

et al. 2016

Microsyst Nanoeng

Self Cite

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“…This work confirmed that the anchor geometry has a significant effect on the Q of these types of resonators. Notably, many other works have widely discussed analytical and numerical models in order to predict the anchor loss and Q of different types of resonators [22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Anchor Loss Reduction in Micro-Electro Mechanical Systems Flexural Beam Resonators Using Trench Hole Array Reflectors

Kazemi,

Nabavi,

Gratuze

et al. 2023

Micromachines

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The quality factor of microelectromechanical resonators is a crucial performance metric and has thus been the subject of numerous studies aimed at maximizing its value by minimizing the anchor loss. This work presents a study on the effect of elastic wave reflectors on the quality factor of MEMS clamped–clamped flexural beam resonators. The elastic wave reflectors are a series of holes created by trenches in the silicon substrate of the resonators. In this regard, four different shapes of arrayed holes are considered, i.e., two sizes of squares and two half circles with different directions are positioned in proximity to the anchors. The impact of these shapes on the quality factor is examined through both numerical simulations and experimental analysis. A 2D in-plane wave propagation model with a low-reflecting fixed boundary condition was used in the numerical simulation to predict the behavior, and the MEMS resonator prototypes were fabricated using a commercially available micro-fabrication process to validate the findings. Notably, the research identifies that half-circle-shaped holes with their curved sides facing the anchors yield the most promising results. With these reflectors, the quality factor of the resonator is increased by a factor of 1.70× in air or 1.72× in vacuum.

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“…The difficulty in fabricating µ-HRGs is the supporting anchor. The height of the support anchor is usually limited by the thickness of the sacrificial layer, which causes large damping [22]. Moreover, the size of the support anchor is usually determined by the etching time of the sacrificial layer, so it cannot be precisely controlled, which limits the accuracy of the µ-HRGs.…”

Section: Introductionmentioning

confidence: 99%

Micro-manufacturing technology of a three-dimensional curved surface diamond structure for gyroscope applications

Zhang

Cao

2019

J. Micromech. Microeng.

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A novel three-dimensional (3D) micro-manufacturing technology of a curved surface diamond structure used for a micro birdbath resonator gyroscope (µ-BRG) with integrated curved electrodes is presented. The integrated curved electrodes with the same curvature as the birdbath shell are embedded using a self-aligned process, which avoids the extra assembly process, ensures the symmetry and improves the driving capacity of the µ-BRG. The capacitive gap is defined by the sacrificial layer, and a uniform and small gap distance (2 µm) between the curved electrodes and the birdbath shell is obtained. The µ-BRGs with a diameter of 1.2 mm and a thickness of 2 µm have been demonstrated by employing borondoped microcrystalline diamond films deposited using hot filament chemical vapor deposition (HFCVD). In this paper, the device structure and basic working principle of the gyroscope are described. The key steps in the fabrication process, such as isotropic wet etching of the bulk silicon for a birdbath mold, photoresist spray-coating for patterning the curved electrodes, and deposition and etching of diamond films, are considered in detail and well solved. The radial deviation of the etched birdbath mold is about 0.31% for the ∼560 µm radius shell and the surface roughness of the birdbath mold is favorable (Rq = 4.933 nm, Ra = 3.945 nm). The key techniques described in this paper can be applied to the fabrication of other 3D micro devices.

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Effect of structural anisotropy on anchor loss mismatch and predicted case drift in future micro-Hemispherical Resonator Gyros

Cited by 12 publications

References 12 publications

Substrate-decoupled, bulk-acoustic wave gyroscopes: Design and evaluation of next-generation environmentally robust devices

Substrate-decoupled, bulk-acoustic wave gyroscopes: Design and evaluation of next-generation environmentally robust devices

Anchor Loss Reduction in Micro-Electro Mechanical Systems Flexural Beam Resonators Using Trench Hole Array Reflectors

Micro-manufacturing technology of a three-dimensional curved surface diamond structure for gyroscope applications

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