A new ultra-hard etch-stop layer for high precision micromachining

In the present work we describe a high-precision fabrication method for silicon micromachining based on a newly developed epitaxial etch-stop. This etch-stop, composed of a silicon-germanium alloy with no boron doping, outperforms traditional boron-doped etch stops in several important and fundament...

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Bibliographic Details
Published inTechnical Digest. IEEE International MEMS 99 Conference. Twelfth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.99CH36291) pp. 205 - 210
Main Authors Borenstein, J.T., Gerrish, N.D., Currie, M.T., Fitzgerald, E.A.
Format Conference Proceeding
LanguageEnglish
Published IEEE 1999
Subjects
Boron alloys
Doping
Epitaxial layers
Etching
Fabrication
Germanium silicon alloys
Micromachining
Silicon alloys
Silicon germanium
Vibrations
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Summary:In the present work we describe a high-precision fabrication method for silicon micromachining based on a newly developed epitaxial etch-stop. This etch-stop, composed of a silicon-germanium alloy with no boron doping, outperforms traditional boron-doped etch stops in several important and fundamental ways. Etch selectivities in a variety of standard etchants compare favorably with those obtained using high-concentration boron diffused and epitaxial layers. Microstructural analysis of the new etch-stop layer demonstrates a significant reduction in defect density relative to boron-doped counterparts. Tuning fork gyroscopes built with the new etch-stop show build dimensions comparable to those fabricated with conventional methods. We propose a band structure model for the etch-stop mechanism that mimics the hole-injection phenomenon often invoked for boron doping, and conclude with a brief discussion of the advantages of this new fabrication technology.
ISBN:0780351940
9780780351943
ISSN:1084-6999
DOI:10.1109/MEMSYS.1999.746810