Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-29T09:11:56.607Z Has data issue: false hasContentIssue false
  • English
  • Français

Silicon-Based Epitaxial Films for Mems

Published online by Cambridge University Press:  10 February 2011

E.A. Fitzgerald ,
K.C. Wu ,
M. Currie ,
N. Gerrish ,
D. Bruce  and
J. Borenstein
E.A. Fitzgerald
Affiliation:
Dept. of Materials Science and Engineering, MIT, Cambridge, MA 02139, [email protected]
K.C. Wu
Affiliation:
Dept. of Materials Science and Engineering, MIT, Cambridge, MA 02139, [email protected]
M. Currie
Affiliation:
Dept. of Materials Science and Engineering, MIT, Cambridge, MA 02139, [email protected]
N. Gerrish
Affiliation:
Dept. of Materials Science and Engineering, MIT, Cambridge, MA 02139, [email protected]
D. Bruce
Affiliation:
Dept. of Materials Science and Engineering, MIT, Cambridge, MA 02139, [email protected]
J. Borenstein
Affiliation:
Charles Stark Draper Laboratories, Cambridge, MA 02139
Get access

Abstract

The objective of this work was to develop an improved wet etch-stop technology for silicon micromachining. To establish a reference for process improvement, the diffusion process currently used to fabricate p++ Si:B etch stops was comprehensively investigated. Subsequently, a novel germanium- based epitaxial etch-stop technology was developed.

A range of techniques were used to study p++ silicon layers created by boron diffusion into (001) silicon wafers. The results revealed gradients in boron and lattice constant, as well as a graded three- dimensional dislocation array from lattice-mismatch stress. The gradients in boron concentration and dislocation density can lead to curl in micromachined structures. Although annealing steps can remove the boron gradient, a flat membrane will be a tenuous balance.

Epitaxial films of p++Si:B and strain-compensated p++Si1-xGex:B can remove composition gradients and improve process control. However, it is undesirable to depend on p-type layers doped at levels near the solubility limit to prevent etching. We have therefore developed a unique etch stop created from relaxed SiGe alloys. Etch-stop behavior quite similar to heavily boron-doped silicon has been demonstrated in undoped silicon-germanium. Neither strain nor defects are responsible for the etch-stop behavior. A model is proposed based on energy band structure and a SiOx passivation mechanism.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 518: Symposium N – Microelectromechanical Structures for Materials Research , 1998 , 233
Copyright
Copyright © Materials Research Society 1998

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1 Wu, K.C., Shay, P., Borenstein, J.T., and Fitzgerald, E.A., MRS Symposium Proceedings, Fall 1996.Google Scholar
2 Fitzgerald, E.A., Materials Science Reports 7 (1991) 92–93.Google Scholar
3 Seidel, H., Csepregi, L., Heuberger, A., Baumgartel, H., J. Electrochem. Soc. 137 (1990) 3626–31.Google Scholar
4 Fitzgerald, E. A., Xie, Y.-H., Green, M. L., Brasen, D., Kortan, A.R., Michel, J., Mii, Y.-J., and Weir, B. E., Appl. Phys. Lett. 59, 811 (1991); E.A. Fitzgerald, Y.-H. Xie, D. Monroe, P.J. Silvennan, J.-M. Kuo, A.R. Kortan, F.A. Thiel, B.E. Weir, and L.C. Feldman, J. Vac. Sci. Tech. B 10, 1807 (1992).Google Scholar
5 Palik, E.D., Glembocki, O.J., Heard, I. Jr., J. Electrochem. Soc. 134 (1987) 408.Google Scholar
6 Chen, L.C., Chen, M., Lien, C., Wan, C.C., J. Electrochem. Soc. 142 (1995) 172.Google Scholar