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Porous Silicon as a Sacrificial Material for Microstructures Fabrication

Published online by Cambridge University Press:  10 February 2011

M. Morel ,
M. Le Berre ,
V. Lysenko ,
G. Delhomme ,
A. Dittmar  and
D. Barbier
M. Morel
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
M. Le Berre
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
V. Lysenko
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
G. Delhomme
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
A. Dittmar
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
D. Barbier
Affiliation:
L.P.M.-INSA LYON, UMR CNRS 5511, 20 Av. Einstein, 69621 Villeurbanne, France e-mail: [email protected]
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Abstract

Porous silicon (PS) is generated by electrochemical etching in hydrofluoric acid (HF). Recently porous silicon has been applied to micromachining and micro-devices as an alternate material, this material being used as a sacrificial layer. This technology competes with conventional techniques like surface and bulk micromachining regarding its speed, simplicity and reduced costs. A wide range of microstructures and free-standing structures can be fabricated with a large freedom of design in relation to the isotropic behavior of the etching. A sacrificial layer may be realized fast over varying thickness (PS formation rate 45 μm/h compared to silicon bulk micromachining rate 20 μm/h for KOH etching).

This contribution is devoted to the materials aspects of patterning and processing: we will show how basic microstructures (trenches, polysilicon cantilevers, polysilicon free-standing membranes) may be fabricated using a very simple process based on a single photolithography. The important points are the choice of the mask, porous silicon properties as a function of its formation parameters and the choice of the solution removing the sacrificial layer. The morphology and porosity of the porous silicon layers are indeed mainly determined by the electrolyte composition and by the current density for a given substrate type. Optimized conditions (HF 15% and 80 mA/cm2) lead us to an appropriate porous silicon. Finally the applicability of this technology for various microsensors will be underlined.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 605: Symposium MM – Materials Science of Microelectromechanical Systems Devices II , 1999 , 281
Copyright
Copyright © Materials Research Society 2000

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