·In this paper, the design, implementation and characterization of a continuous time transimpedance-based ASIC for the actuation and sensing of a high-Q MEMS tuning fork gyroscope (TFG) is presented. A T-network transimpedance amplifier (TIA) is used as the front-end for low-noise, sub-atto-Farad capacitive detection. The T-network TIA provides on-chip transimpedance gains of up to 25 MΩ, has a measured capacitive resolution of 0.02 aF/√ Hz at 15 kHz, a wide dynamic range of 104 dB in a bandwidth of 10 Hz and consumes 400 μW of power. The CMOS interface ASIC uses this TIA as the front-end to sustain electromechanical oscillations in a MEMS TFG with motional impedance greater than 10 MΩ. The TFG interfaced with the ASIC yields a two-chip angular rate sensor with measured rate noise floor of2.7°/hr/√Hz, bias instability of 1°/hr and rate sensitivity of 2 mV/°/s. The IC is fabricated in a 0.6-μm standard CMOS process with an area of 2.25 mm 2 and consumes 15 mW.

A 104-dB dynamic range transimpedance-based CMOS ASIC for tuning fork microgyroscopes

In this paper, a novel vibratory optical MEMS gyroscope is proposed, which is composed of an optical sensing system, an electrostatic comb-drive actuator, and a mass-spring system with 2 degrees of freedom and a decoupling frame. The optical sensing system consists of a laser diode light source, a tunable photonic crystal, a photodetector, and integrated waveguides. The sensitive element of the proposed gyroscope has been designed with separated primary and secondary resonance frequencies to increase the operating bandwidth. Simulation results show that the functional characteristics of the proposed gyroscope are as follows: an operating frequency of 1830 Hz, a sense mode resonance frequency of 2330 Hz, an operating bandwidth of 200 Hz, a mechanical sensitivity of 0.14 nm/(°/s), an optical sensitivity of 0.051 nm/(°/s), and a measurement range of ±500 °/s.

Design and Analysis of a Novel MOEMS Gyroscope Using an Electrostatic Comb-Drive Actuator and an Optical Sensing System

This paper presents the design and analysis of a multi degree of freedom (DOF) electro-thermally actuated non-resonant MEMS gyroscope with a 3-DOF drive mode and 1-DOF sense mode system. The 3-DOF drive mode system consists of three masses coupled together using suspension beams. The 1-DOF system consists of a single mass whose motion is decoupled from the drive mode using a decoupling frame. The gyroscope is designed to be operated in the flat region between the first two resonant peaks in drive mode, thus minimizing the effect of environmental and fabrication process variations on device performance. The high gain in the flat operational region is achieved by tuning the suspension beams stiffness. A detailed analytical model, considering the dynamics of both the electro-thermal actuator and multi-mass system, is developed. A parametric optimization is carried out, considering the microfabrication process constraints of the Metal Multi-User MEMS Processes (MetalMUMPs), to achieve high gain. The stiffness of suspension beams is optimized such that the sense mode resonant frequency lies in the flat region between the first two resonant peaks in the drive mode. The results acquired through the developed analytical model are verified with the help of 3D finite element method (FEM)-based simulations. The first three resonant frequencies in the drive mode are designed to be 2.51 kHz, 3.68 kHz, and 5.77 kHz, respectively. The sense mode resonant frequency is designed to be 3.13 kHz. At an actuation voltage of 0.2 V, the dynamically amplified drive mode gain in the sense mass is obtained to be 18.6 µm. With this gain, a capacitive change of 28.11 f F and 862.13 f F is achieved corresponding to the sense mode amplitude of 0.15 μ m and 4.5 μ m at atmospheric air pressure and in a vacuum, respectively.

Design and Analysis of a High-Gain and Robust Multi-DOF Electro-thermally Actuated MEMS Gyroscope

This paper presents the development of an 8-in six-degree-of-freedom (DOF) inertial sensor based on an advanced capacitive inertial sensor fabrication platform. The platform integrates three-axis gyroscopes and three-axis accelerometers on the same chip. The fabricated sensors are vacuum packaged at the wafer level with a polysilicon-based through-silicon interposer (TSI) using the aluminum–germanium eutectic bonding approach. Wafer-level measurement results indicate that a fabrication yield of greater than 92% and a vacuum level of $\sim$ 100 mtorr have been achieved. The fabricated inertial sensors and the customized application-specific integrated circuits are encapsulated in a 5 mm $\times$ 5 mm $\times$ 1.3 mm quad-flat no-leads package using the plastic molding technology. The system-level characterization of the developed six-DOF inertial sensors have been implemented. Several reliability tests conducted according to the relevant JEDEC standards prove that the packaged sensors are highly reliable and robust for a wide range of operating environments.

Development of Six-Degree-of-Freedom Inertial Sensors With an 8-in Advanced MEMS Fabrication Platform

Micro-Electro-Mechanical Systems (MEMS) gyroscopes are inertial sensors for the measurement of angular rates. They have a variety of applications from consumer electronics to drones and the need of stability against environmental fluctuations, such as temperature, is a key factor in order to avoid expensive calibration procedures. Frequency Modulation (FM) has been recently proposed as an innovative working principle for MEMS gyroscopes and as the desired solution in terms of stability against environmental fluctuations. In this paper, the FM working principle is formalized for the three-axial case for the first time and the governing equations are derived both in the idealized case of a point-mass gyroscope and in the real case of a distributed-mass gyroscope. Moreover, the mechanical structure of the first three-axial MEMS FM gyroscope is proposed and studied. Preliminary experimental measurements prove the validity of both the model and the simulations results employed during the design process. The proposed structure overcomes lots of the constraints of the surface micromachining fabrication processes and represents an important step towards the development of a new class of MEMS gyroscopes.

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A new MEMS three-axial frequency-modulated (FM) gyroscope: a mechanical perspective

A fully decoupled z -axis MEMS gyroscope with wide bandwidth and high linearity is presented in this paper. The mechanical structure consists of a dual proof mass, which are mechanically coupled together using a pair of double folded springs. The fully decoupled approach is employed to lower the mechanical cross coupling between the drive mode and sense mode. The gyroscope is fabricated using a simple two-mask process based on a silicon-on-insulator (SOI) substrate with a 30-μm-thick device layer. The electrostatic actuation and capacitive sensing gaps of around 1.1-μm provide an aspect ratio of close to 27. The narrow capacitive gap increases the electromechanical coupling and improves the signal to noise ratio (SNR) of the sensor. The fabricated MEMS gyroscope is vacuum packaged in a ceramic chip carrier in order to minimize the Brownian noise floor for achieving a better performance. A off-the-shelf integrated circuit with the excitation and sensing electronics is hybrid connected to the gyroscope. The MEMS gyroscope system demonstrates a bias instability of 9.6 deg/h, an angular random walk (ARW) of 0.45 deg/ h , a bandwidth of greater than 120 Hz, and a scale-factor nonlinearity of 770 ppm in a full scale range of ±500 deg/s at room temperature.

A dual-mass fully decoupled MEMS gyroscope with wide bandwidth and high linearity

According to various embodiments, there is provided a gyroscope device including: an outer frame; and four cells arranged within the outer frame, each cell of the four cells including: a proof mass arranged at least substantially in a centre region of the cell; and four electrode frames, each electrode frame of the four electrode frames arranged at a corner region of the cell and coupled to a respective side of the proof mass.

Gyroscope devices and methods for fabricating gyroscope devices

Various embodiments may provide a gyroscope. The gyroscope may include a piezoelectric substrate, an excitation transducer configured to generate a surface acoustic wave, and a sensing transducer configured to receive the surface acoustic wave generated by the excitation transducer. The gyroscope may additionally include a mass dot array between the excitation transducer and the sensing transducer, the mass dot array configured to generate a stress on the piezoelectric substrate based on a rotation of said gyroscope upon the surface acoustic wave passing through the mass dot array. The gyroscope may also include a light source, and an optical detector configured to receive one or more light beams generated by the light source to determine the rotation of the gyroscope based on a property of the one or more light beams. The property of the one or more light beams may be variable based on the stress on the piezoelectric substrate.

Geng Li Chua

Papers

A dual-mass fully decoupled MEMS gyroscope with wide bandwidth and high linearity

Gyroscope devices and methods for fabricating gyroscope devices

Gyroscope, methods of forming and operating the same