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Proceedings Paper

Stress-induced warpage and the compensation in a composite micro-accelerometer
Author(s): Gary X. Li; Ron J. Gutteridge; Dan N. Koury; Zhenjun Zhang; Ray M. Roop
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Paper Abstract

Mechanical modeling and analysis have been carried out for a fabricated micro-accelerometer. The sensor is designed with composite polysilicon/silicon nitride tether arms to provide a net overall tensile state. The stress distribution in both polysilicon and silicon nitride films, and the resulting structural deformation, have been calculated. Both experimental results and finite element analysis (FEA) of the complete sensor structure show that a consistent upward deflection of the tether structure exists, which causes an off-set of the suspended poly plate and results in yield loss and sensor performance degradation. This phenomenon is explained by designing, fabricating, and testing two cantilever beams with cross-sections similar to the actual tether structure. Depending on the beam's cross-section dimensions, all the cantilever samples also exhibit upward deflection to varying degrees. Theoretical analysis and FEA simulation are conducted for the cantilever beams, and the results compared with experimental data. An analytical formula is provided to optimize the composite polysilicon/silicon-nitride tether geometry to minimize or eliminate the undesirable stress-induced deflection.

Paper Details

Date Published: 17 September 1996
PDF: 5 pages
Proc. SPIE 2882, Micromachined Devices and Components II, (17 September 1996); doi: 10.1117/12.250697
Show Author Affiliations
Gary X. Li, Motorola (United States)
Ron J. Gutteridge, Motorola (United States)
Dan N. Koury, Motorola (United States)
Zhenjun Zhang, Motorola (United States)
Ray M. Roop, Motorola (United States)

Published in SPIE Proceedings Vol. 2882:
Micromachined Devices and Components II
Kevin H. Chau; Ray M. Roop, Editor(s)

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