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Proceedings Paper

Area-variable capacitive microaccelerometer with force-balancing electrodes
Author(s): Byeoungju Ha; Byeungleul Lee; Sangkyung Sung; Sangon Choi; Meenam Shinn; Yong-Soo Oh; Ci Moo Song
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Paper Abstract

A surface micromachined accelerometer which senses an inertial motion with an area variation and a force balancing electrodes is developed. The grid-type planar mass of a 7 micrometers thick polysilicon is supported by four thin beams and suspended above a silicon substrate with a 1.5 micrometers air gap. The motion sensing electrodes are formed on the substrate. The sensor is designed as an interdigital rib structure that has a differential capacitor arrangement. The moveable electrodes are mounted on the mass and the pairs of the stationary electrodes are patterned on the substrate. In the accelerometer that has comb-type movable electrodes, the mechanical stress and the electrical pulling effects between a moveable electrodes and the fixed electrodes occur. However this grid-type structure can have a large area variation in a small area relatively without stress and pulling, high sensitivity can be achieved. In order to improve the dynamic rang and a linearity, a pair of comb shape force-balancing electrodes are implemented on both sides of the mass. The force-balancing electrodes are made of the same layer as the mass and anchored on a silicon substrate. When acceleration is applied in the lateral direction, the difference of capacitance results from the area variation between the two capacitors and is measured using a charge amplifier. As AC coupled complimentary pick- off signals are applied in paris of stationary electrodes, the undesirable effects due to temperature and electrical noise are reduced effectively. The accelerometer has a sensitivity of 28mV/g and a bandwidth of DC-120Hz. A resolution of 3mg and a non-linearity of 1.3 percent is achieved for a measurement range of +/- 9 g.

Paper Details

Date Published: 14 November 1997
PDF: 10 pages
Proc. SPIE 3242, Smart Electronics and MEMS, (14 November 1997); doi: 10.1117/12.293548
Show Author Affiliations
Byeoungju Ha, Samsung Advanced Institute of Technology (South Korea)
Byeungleul Lee, Samsung Advanced Institute of Technology (South Korea)
Sangkyung Sung, Seoul National Univ. (South Korea)
Sangon Choi, Samsung Advanced Institute of Technology (South Korea)
Meenam Shinn, Samsung Advanced Institute of Technology (South Korea)
Yong-Soo Oh, Samsung Advanced Institute of Technology (South Korea)
Ci Moo Song, Samsung Advanced Institute of Technology (South Korea)

Published in SPIE Proceedings Vol. 3242:
Smart Electronics and MEMS
Alex Hariz; Vijay K. Varadan; Olaf Reinhold, Editor(s)

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