Babak Vakili Amini

Bio: Babak Vakili Amini is an academic researcher from Georgia Institute of Technology. The author has contributed to research in topics: Capacitive sensing & Gyroscope. The author has an hindex of 15, co-authored 18 publications receiving 851 citations. Previous affiliations of Babak Vakili Amini include Georgia Tech Research Institute & Qualcomm Atheros.

Sub-Micro-Gravity In-Plane Accelerometers With Reduced Capacitive Gaps and Extra Seismic Mass

Abstract: This paper presents a robust fabrication technique for manufacturing ultrasensitive micromechanical capacitive accelerometers in thick silicon-on-insulator substrates. The inertial mass of the sensor is significantly increased by keeping the full thickness of the handle layer attached to the top layer proof mass. High-aspect-ratio capacitive sense gaps are fabricated by depositing a layer of polysilicon on the sidewalls of low aspect- ratio trenches etched in silicon. Using this method, requirements on trench etching are relaxed, whereas the performance is preserved through the gap reduction technique. Therefore, this process flow can potentially enable accelerometers with capacitive gap aspect-ratio values of greater than 40:1, not easily realizable using conventional dry etching equipment. Also, no wet-etching step is involved in this process which in turn facilitates the fabrication of very sensitive motion sensors that utilize very compliant mechanical structures. Sub-micro-gravity in-plane accelerometers are fabricated and tested with measured sensitivity of 35 pF/g, bias instability of 8 mug, and footprint of <0.5 cm2.

A 4.5-mW Closed-Loop $\Delta\Sigma$ Micro-Gravity CMOS SOI Accelerometer

Abstract: In this paper, design, implementation and characterization of a 3-V switched-capacitor (SC) DeltaSigma CMOS interface circuit for the closed-loop operation of a lateral capacitive micro-gravity silicon-on-insulator (SOI) accelerometer is presented The interface circuit is based on a front-end programmable reference-capacitorless SC charge amplifier and a back-end second-order SC DeltaSigma modulator The accelerometer is fabricated through a dry-release high aspect-ratio reduced-gap process By incorporating the low-Q transfer function of the microaccelerometer in a feedback loop, the system's dynamic range is improved by 20 dB, leading to a measured resolution of 4 mug/radicHz and an output dynamic range of 95 dB at 20 Hz The bias instability is 2 to 8 mug for 12 hours The chip is fabricated in the 05-mum standard CMOS process with an area of 225 mm2 The integrated circuit (IC) consumes 45 mW of power

A 2.5-V 14-bit /spl Sigma//spl Delta/ CMOS SOI capacitive accelerometer

Abstract: This paper presents a 2.5-V 14-bit fully differential /spl Sigma//spl Delta/ interface circuit in 0.25-/spl mu/m CMOS technology for a high-resolution silicon-on-insulator capacitive accelerometer fabricated using a simple CMOS-compatible stictionless process. The integrated circuit is based on programmable front-end back-end first-order /spl Sigma//spl Delta/ architecture and provides a 1-bit pulse-width modulated digital output. Using correlated double sampling, the low-frequency noise is suppressed by 10 dB. Capacitive resolution is 22 aF at 75 Hz (resolution bandwidth = 1 Hz), equivalent to 110 /spl mu/g with a dynamic range of 85 dB (14-bit resolution) and a sensitivity of 500 mV/g. The chip occupies 2 mm/sup 2/ and consumes 6 mW.

Micro-gravity capacitive silicon-on-insulator accelerometers

Abstract: In this paper, the implementation and characterization of high-sensitivity in-plane capacitive micro-gravity silicon-on-insulator (SOI) accelerometers with the readout circuitry are presented The devices were implemented in 50 µm thick SOI substrates using a two-mask dry-release process The fabricated accelerometers were interfaced to a low-noise low-power reference-capacitor-less switched-capacitor circuit The integrated circuit (IC) was implemented in a 25 V 025 N-well CMOS process The measured capacitive sensitivity is 03 pF g−1, equivalent to a gain of 075 V g−1 The measured resolution is 11 µg Hz−1/2 at 2 Hz and 02 µg Hz−1/2 at 100 Hz (resolution bandwidth = 1 Hz) The interface IC operates from a single 25 V supply and measures a power consumption of 4 mW with a sampling clock of 100 kHz The core IC die size is 065 mm2

A vibrating beam MEMS accelerometer for gravity and seismic measurements

Abstract: This paper introduces a differential vibrating beam MEMS accelerometer demonstrating excellent long-term stability for applications in gravimetry and seismology The MEMS gravimeter module demonstrates an output Allan deviation of 9 μGal for a 1000 s integration time, a noise floor of 100 μGal/√Hz, and measurement over the full ±1 g dynamic range (1 g = 981 ms−2) The sensitivity of the device is demonstrated through the tracking of Earth tides and recording of ground motion corresponding to a number of teleseismic events over several months These results demonstrate that vibrating beam MEMS accelerometers can be employed for measurements requiring high levels of stability and resolution with wider implications for precision measurement employing other resonant-output MEMS devices such as gyroscopes and magnetometers

The development of micro-gyroscope technology

Abstract: This review reports an overview and development of micro-gyroscope. The review first presents different types of micro-gyroscopes. Micro-gyroscopes in this review are categorized into Coriolis gyroscope, levitated rotor gyroscope, Sagnac gyroscope, nuclear magnetic resonance (NMR) gyroscope according to the working principle. Different principles, structures, materials, fabrications and control technologies of micro-gyroscopes are analyzed. This review compares different classes of gyroscopes in the aspects such as fabrication method, detection axis, materials, size and so on. Finally, the review evaluates the key technologies on how to improve the precision and anti-jamming ability and to extend the available applications of the gyroscopes in the market and patents as well.

The Development of Micromachined Gyroscope Structure and Circuitry Technology

Abstract: This review surveys micromachined gyroscope structure and circuitry technology The principle of micromachined gyroscopes is first introduced Then, different kinds of MEMS gyroscope structures, materials and fabrication technologies are illustrated Micromachined gyroscopes are mainly categorized into micromachined vibrating gyroscopes (MVGs), piezoelectric vibrating gyroscopes (PVGs), surface acoustic wave (SAW) gyroscopes, bulk acoustic wave (BAW) gyroscopes, micromachined electrostatically suspended gyroscopes (MESGs), magnetically suspended gyroscopes (MSGs), micro fiber optic gyroscopes (MFOGs), micro fluid gyroscopes (MFGs), micro atom gyroscopes (MAGs), and special micromachined gyroscopes Next, the control electronics of micromachined gyroscopes are analyzed The control circuits are categorized into typical circuitry and special circuitry technologies The typical circuitry technologies include typical analog circuitry and digital circuitry, while the special circuitry consists of sigma delta, mode matching, temperature/quadrature compensation and novel special technologies Finally, the characteristics of various typical gyroscopes and their development tendency are discussed and investigated in detail

A Mode-Matched Silicon-Yaw Tuning-Fork Gyroscope With Subdegree-Per-Hour Allan Deviation Bias Instability

Abstract: In this paper, we report on the design, fabrication, and characterization of an in-plane mode-matched tuning-fork gyroscope (M2-TFG). The M2-TFG uses two high-quality-factor (Q) resonant flexural modes of a single crystalline silicon mi- crostructure to detect angular rate about the normal axis. Operating the device under mode-matched condition, i.e., zero-hertz frequency split between drive and sense modes, enables a Q -factor mechanical amplification in the rate sensitivity and also improves the overall noise floor and bias stability of the device. The M2 -TFG is fabricated on a silicon-on-insulator substrate using a combination of device and handle-layer silicon etching that precludes the need for any release openings on the proof-mass, thereby maximizing the mass per unit area. Experimental data indicate subdegree-per-hour Brownian noise floor with a measured Allan deviation bias instability of 0.15deg /hr for a 60-mum-thick 1.5 mm X 1.7 mm footprint M2-TFG prototype. The gyroscope exhibits an open-loop rate sensitivity of approximately 83 mV/deg/s in vacuum. [2007-0100].