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Low-Temperature LPCVD MEMS Technologies

Published online by Cambridge University Press:  01 February 2011

Roger T. Howe  and
Tsu-Jae King
Roger T. Howe
Affiliation:
Dept. of EECS and BSAC
Tsu-Jae King
Affiliation:
University of California at Berkeley, Berkeley, CA 94720-1770, U.S.A.
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Abstract

This paper describes recent research on LPCVD processes for the fabrication of high-quality micro-mechanical structures on foundry CMOS wafers. In order to avoid damaging CMOS electronics with either aluminum or copper metallization, the MEMS process temperatures should be limited to a maximum of 450°C. This constraint rules out the conventional polycrystalline silicon (poly-Si) as a candidate structural material for post-CMOS integrated MEMS. Polycrystalline silicon-germanium (poly-SiGe) alloys are attractive for modular integration of MEMS with electronics, because they can be deposited at much lower temperatures than poly-Si films, yet have excellent mechanical properties. In particular, in-situ doped p-type poly-SiGe films deposit rapidly at low temperatures and have adequate conductivity without post-deposition annealing. Poly-Ge can be etched very selectively to Si, SiGe, SiO2 and Si3N4 in a heated hydrogen peroxide solution, and can therefore be used as a sacrificial material to eliminate the need to protect the CMOS electronics during the MEMS-release etch. Low-resistance contact between a structural poly-SiGe layer and an underlying CMOS metal interconnect can be accomplished by deposition of the SiGe onto a typical barrier metal exposed in contact windows. We conclude with directions for further research to develop poly-SiGe technology for integrated inertial, optical, and RF MEMS applications.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 729: Symposium U – MEMS and BioMEMS , 2002 , U5.1
Copyright
Copyright © Materials Research Society 2002

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