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

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 lay...

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Bibliographic Details
Published in:Journal of microelectromechanical systems 2007-10, Vol.16 (5), p.1036-1043
Main Authors: Abdolvand, R., Amini, B.V., Ayazi, F.
Format: Article
Language:English
Subjects:
Accelerometer
Accelerometers
Applied sciences
aspect ratio
Dry etching
Electronics
Etching
Etching equipment
Exact sciences and technology
Fabrication
Gaps
Inertial
Instability
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Mechanical instruments, equipment and techniques
Mechanical sensors
Microelectronic fabrication (materials and surfaces technology)
micromechanical
Micromechanical devices
Micromechanical devices and systems
Motion sensors
Physics
Pulp manufacturing
Robustness
Seismic measurements
Seismic phenomena
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Sensors
Silicon on insulator technology
silicon-on-insulator (SOI)
Stability
Trenches
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Summary: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
ISSN:1057-7157
1941-0158
DOI:10.1109/JMEMS.2007.900879