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Proceedings Paper

Compensating methods of corner undercutting in silicon micromachining
Author(s): Ganru Mao; Suying Yao; Hongwei Qu; Baiying Yu; Weixin Zhang
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Paper Abstract

This paper describes a polysilicon pressure sensor fabricated by silicon micromachining technology. The starting materials of the sensor are (100) orientated monocrystal silicon wafers with double side polishing. The semiconductor integrated circuit process is also used in the testing. The polysilicon piezoresistors are deposited by LPCVD on the thermallygrown oxide film of the silicon wafer. In order to increase sensitivity, a so-called "twin isles" structure has been used. This type of structure consists of a square silicon diaphragm with twin square isles, which are formed by anisotropic etching into the back side of the monocrystal silicon substrate wafer. A main problem in preparation is the convex corner undercutting effect in the etching process. The relationships between the corner undercutting rate and the etching depth in TMAH solution have been obtained experimentally. Two masks of the special pattern are designed to compensate for corner undercutting. 1). A compensating angle bounded by <210< orientation is added to convex corner of twin square isles. The width of the compensation angles depends on the etching depth. 2). A narrow stripe is added to each convex corner along <110< orientation. The length of the narrow stripe depends on the etching depth. The optimized structures of the square diaphragm with twin square isles have been fabricated using the above two methods, respectively. Each method has its own advantages. The fabricated polysilicon pressure sensors have high sensitivity at elevated operation temperature and good accuracy. key words: silicon micromachining, comer undercutting, polysilicon pressure sensor, compensating method.

Paper Details

Date Published: 5 September 1997
PDF: 7 pages
Proc. SPIE 3224, Micromachined Devices and Components III, (5 September 1997); doi: 10.1117/12.284531
Show Author Affiliations
Ganru Mao, Tianjin Univ. (China)
Suying Yao, Tianjin Univ. (China)
Hongwei Qu, Tianjin Univ. (China)
Baiying Yu, Tianjin Univ. (China)
Weixin Zhang, Tianjin Univ. (China)

Published in SPIE Proceedings Vol. 3224:
Micromachined Devices and Components III
Kevin H. Chau; Patrick J. French, Editor(s)

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