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Proceedings Paper

Silicon oxide sacrificial layers deposited by pulsed-DC magnetron sputtering for MEMS applications
Author(s): Sheila González-Castilla; Jimena Olivares; Marta Clement; Lucía Vergara; Laura Pulido; Enrique Iborra; Jesús Sangrador
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Paper Abstract

Surface micromachining requires the use of easily-removable sacrificial layers fully compatible with all the materials and technological processes involved. Silicon dioxide films, thermally grown on silicon substrates or deposited by CVD, are commonly used as sacrificial layers in surface micromachining technologies, despite their low lateral etch rate in conventional fluorinate solutions. The development of silicon oxide layers with high etch rates poses a great technological challenge. In this work we have investigated the possibility of obtaining easily removable silicon oxide layers by pulsed-DC magnetron reactive sputtering. We have carried out a comprehensive study of the influence of the deposition parameters (total pressure and gas composition) on the composition, residual stress and lateral etch rate in fluorine wet solutions of the films. This study has allowed to determine the sputtering conditions to deposit, at very high rates (up to 0.1 μm/min), silicon oxide films with excellent characteristics for their use as sacrificial layers. Films with roughness around 5 nm rms, residual stress below 100 MPa and very high etch rate (up to 5 μm/min in the lateral directions), around 70 times greater than for thermal silicon oxide, have been achieved. The structural characteristics of these easily removable silicon oxide layers have been assessed by infrared spectroscopy and atomic force microscopy, which have revealed that the films exhibit some kind of porous structure, related to very specific sputter conditions. Finally, the viability of these films has been demonstrated by using them as sacrificial layer in the fabrication process of AlN-based microresonators.

Paper Details

Date Published: 18 May 2009
PDF: 12 pages
Proc. SPIE 7362, Smart Sensors, Actuators, and MEMS IV, 73620X (18 May 2009); doi: 10.1117/12.821485
Show Author Affiliations
Sheila González-Castilla, Univ. Politécnica de Madrid (Spain)
Jimena Olivares, Univ. Politécnica de Madrid (Spain)
Marta Clement, Univ. Politécnica de Madrid (Spain)
Lucía Vergara, Consejo Superior de Investigaciones Científicas (Spain)
Laura Pulido, Univ. Politécnica de Madrid (Spain)
Enrique Iborra, Univ. Politécnica de Madrid (Spain)
Jesús Sangrador, Univ. Politécnica de Madrid (Spain)

Published in SPIE Proceedings Vol. 7362:
Smart Sensors, Actuators, and MEMS IV
Ulrich Schmid, Editor(s)

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