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Proceedings Paper

Combined TMAH and HF sacrificial layer etching technique for surface micromachined devices
Author(s): Thomas Lisec; Martin Kreutzer; Beatrice Wenk; Bernd Wagner
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Paper Abstract

This paper presents a two step sacrifical layer etching technique used for the fabrication of surface mciromachined piezoresistive pressure sensors. The sacrificial layer itself is a sandwich structure of a thin polysilicon layer with the underetching channels and a much thicker 'buried' oxide underneath. First the polysilicon part is etched in an aqueous TMAH solution with high etch rates realizing a first shallow cavity. After rinsing, the oxide part is removed in 7:1 buffered HF. Since the oxide is etched now vertically, the process is completed within minutes. Sticking is suppressed successfully and non special drying techniques are required. The whole sensor structures could be passivated by LPCVD or PECVD layers against both etchants. Although the final depth of the cavity is 1 micrometers the sensor structure remains nearly flat. This minimizes technological problems concerning for example the piezoresistor definition or the sealing of the sensor and reduces the noise in the piezoresistor arrangement.

Paper Details

Date Published: 19 September 1995
PDF: 8 pages
Proc. SPIE 2639, Micromachining and Microfabrication Process Technology, (19 September 1995); doi: 10.1117/12.221285
Show Author Affiliations
Thomas Lisec, Fraunhofer-Institut fuer Siliziumtechnologie (Germany)
Martin Kreutzer, Fraunhofer-Institut fuer Siliziumtechnologie (Germany)
Beatrice Wenk, Fraunhofer-Institut fuer Siliziumtechnologie (Germany)
Bernd Wagner, Fraunhofer-Institut fuer Siliziumtechnologie (Germany)

Published in SPIE Proceedings Vol. 2639:
Micromachining and Microfabrication Process Technology
Karen W. Markus, Editor(s)

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