Title :
A new ultra-hard etch-stop layer for high precision micromachining
Author :
Borenstein, J.T. ; Gerrish, N.D. ; Currie, M.T. ; Fitzgerald, E.A.
Author_Institution :
Charles Stark Draper Lab. Inc., Cambridge, MA, USA
Abstract :
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.
Keywords :
etching; micromachining; semiconductor epitaxial layers; Si; Si-Ge; band structure; fabrication technology; hole injection; silicon micromachining; silicon-germanium alloy epitaxial layer; tuning fork gyroscope; ultra-hard etch-stop layer; Boron alloys; Doping; Epitaxial layers; Etching; Fabrication; Germanium silicon alloys; Micromachining; Silicon alloys; Silicon germanium; Vibrations;
Conference_Titel :
Micro Electro Mechanical Systems, 1999. MEMS '99. Twelfth IEEE International Conference on
Conference_Location :
Orlando, FL, USA
Print_ISBN :
0-7803-5194-0
DOI :
10.1109/MEMSYS.1999.746810