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Proceedings Paper

Monocrystalline Si membranes for pressure sensors fabricated by a novel surface-micromachining process using porous silicon
Author(s): Hans Artmann; Frank Schaefer; Gerhard Lammel; Simon Armbruster; Hubert Benzel; Christoph Schelling; Heribert Weber; Heinz-Georg Vossenberg; Ronald Gampp; Joerg Muchow; Franz Laermer; Stefan Finkbeiner
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Paper Abstract

We developed a novel surface micromachining process to fabricate monocrystalline silicon membranes covering a vacuum cavity without any additional sealing steps. Heart of the process is anodic etching of porous silicon, annealing and epitaxial growth. The porous silicon layer consists of two parts, a starting mesoporous silicon layer with low surface porosity and a nanoporous silicon layer with a high porosity. The following annealing step removes native oxide within the later cavity, and the surface is sealed for the subsequent epitaxial layer deposition. The observed stacking fault density in the epitaxial layer about 1E5 cm-2. The temperature budget of the following ASIC-process leads to a complete transformation of the nanoporous silicon layer into a large cavity. The whole structure can be used as a pressure sensor. The estimated pressure in the cavity is smaller than 1 mbar. First integrated pressure sensors have been fabricated using this process. The sensors show a good linearity over the whole pressure range of 200 mbar to 1000 mbar. This novel process has several advantages compared to already published processes. It is a “MEMS first” process, which means that after the epitaxial growth the surface of the wafer is close to a standard wafer surface. Due to full IC compatibility, standard ASIC processes are possible after the fabrication of the membrane. The use of porous silicon enables a high degree of geometrical freedom in the design of membranes compared to standard bulk micromachining (KOH, TMAH). The monocrystalline membranes can be fabricated with surface micromachining without any additional sealing or backside processing steps.

Paper Details

Date Published: 16 January 2003
PDF: 6 pages
Proc. SPIE 4981, MEMS Components and Applications for Industry, Automobiles, Aerospace, and Communication II, (16 January 2003); doi: 10.1117/12.479564
Show Author Affiliations
Hans Artmann, Robert Bosch GmbH (Germany)
Frank Schaefer, Robert Bosch GmbH (Germany)
Gerhard Lammel, Robert Bosch GmbH (Germany)
Simon Armbruster, Robert Bosch GmbH (Germany)
Hubert Benzel, Robert Bosch GmbH (Germany)
Christoph Schelling, Robert Bosch GmbH (Germany)
Heribert Weber, Robert Bosch GmbH (Germany)
Heinz-Georg Vossenberg, Robert Bosch GmbH (Germany)
Ronald Gampp, Robert Bosch GmbH (Germany)
Joerg Muchow, Robert Bosch GmbH (Germany)
Franz Laermer, Robert Bosch GmbH (Germany)
Stefan Finkbeiner, Robert Bosch GmbH (Germany)

Published in SPIE Proceedings Vol. 4981:
MEMS Components and Applications for Industry, Automobiles, Aerospace, and Communication II
Siegfried W. Janson, Editor(s)

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