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Proceedings Paper

Microfabrication of a wall shear stress sensor using side-implanted piezoresistive tethers
Author(s): Yawei Li; Toshikazu Nishida; David P. Arnold; Mark Sheplak
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Paper Abstract

This paper presents the microfabrication process of a MEMS piezoresistive shear stress sensor for direct, quantitative measurement of time-resolved, fluctuating wall shear stress. The sensor structure integrates shadow side-implanted diffused resistors into the sensor tethers for detecting in-plane deflection. Temperature compensation is achieved by integrating a fixed, dummy Wheatstone bridge adjacent to the active shear stress sensor. The device is fabricated from an SOI wafer using an 8-mask process. A phosphorus blanket implantation forms an n-well to ensure P/N junction isolation. Boron implantation forms a heavily doped Ohmic contact. The tethers and floating element are defined by patterning PECVD oxide via RIE and DRIE. The Si is etched vertically to 8 &mgr;m via DRIE to form the trench for the sidewall implant. The scallops formed on the sidewalls during DRIE are smoothed by hydrogen annealing. After a preamorphization implant, boron is implanted at an oblique angle of 54° to achieve a 5 &mgr;m shadow side-wall implantation. The structure is released from the backside using a combination of DRIE and RIE to etch the silicon, oxide, and nitride layers. Finally, the sensors are annealed in forming gas. Preliminary electrical testing indicates linear, junction-isolated resistors.

Paper Details

Date Published: 6 April 2007
PDF: 11 pages
Proc. SPIE 6529, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2007, 65290D (6 April 2007); doi: 10.1117/12.715797
Show Author Affiliations
Yawei Li, Univ. of Florida (United States)
Toshikazu Nishida, Univ. of Florida (United States)
David P. Arnold, Univ. of Florida (United States)
Mark Sheplak, Univ. of Florida (United States)


Published in SPIE Proceedings Vol. 6529:
Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2007
Masayoshi Tomizuka; Chung-Bang Yun; Victor Giurgiutiu, Editor(s)

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