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Thermomechanical response of bare and Al2O3-nanocoated Au/Si bilayer beams for microelectromechanical systems

Published online by Cambridge University Press:  31 January 2011

Ken Gall ,
Michael Hulse ,
Martin L. Dunn ,
Dudley Finch ,
Steven M. George  and
Brian A. Corff
Ken Gall
Affiliation:
Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309
Michael Hulse
Affiliation:
Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309
Martin L. Dunn
Affiliation:
Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309
Dudley Finch
Affiliation:
Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309
Steven M. George
Affiliation:
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309
Brian A. Corff
Affiliation:
Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309
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Abstract

We present results on the thermomechanical behavior of bare and nanocoated gold/polysilicon (Au/Si) bilayer cantilever beams for microelectromechanical system applications. The cantilever beams have comparable thicknesses of the Au and Si layers and thus experience significant out-of-plane curvature due to a temperature change. The experiments focus on the inelastic behavior of the bilayer beams due to thermal holding and thermal cycling. In uncoated Au/Si beams, thermal holding directly after release or thermal cycling both lead to a curvature decrease as a function of time or cycle number, respectively. The drop in curvature during thermal cycling or thermal holding in uncoated beams was not accompanied by a change in the slope of the thermoelastic curvature–temperature relationship. The absolute change in curvature depends on the temperature and the holding time. When holding or cycling to a temperature of 175 °C, the curvature change in uncoated beams is minimal for hold times up to 4500 min or 15,000 cycles. When holding or cycling to temperatures of 200 or 225 °C, the curvature in uncoated beams drops by a factor of three for hold times up to 4500 min or 15,000 cycles. The surface structure induced by long-term holding of uncoated beams shows grooving at the grain boundaries while the surface structure induced by cycling of uncoated beams shows consolidation of the grain boundaries. The Au/Si beams with a conformal 40-nm atomic layer deposition Al2O3 coating show a considerably different response compared to identical Au/Si bare beams subjected to the same thermal histories. The coating completely suppresses decreases in curvature when the beams are held at 225 °C for 4500 min. On the contrary, the coating does not always suppress thermal ratcheting when the beam is cycled from a low temperature to 225 °C. In the coated beams, the drop in curvature due to thermal cycling was accompanied by a change in the thermoelastic slope of the curvature–temperature relationship. Negligible microstructural changes were detected on the Al2O3-coated Au surface after holding or cycling. The results are discussed in light of potential deformation mechanisms and a simple analysis linking the mismatch strain between the layers to the curvature in the beams.

Type
Articles
Information
Journal of Materials Research , Volume 18 , Issue 7 , July 2003 , pp. 1575 - 1587
Copyright
Copyright © Materials Research Society 2003

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References

REFERENCES

1.Miller, D.C., Zhang, W., and Bright, V.M., Sens. Actuators, A 89, 76 (2001).Google Scholar
2.Burns, D.M. and Bright, V.M., Sens. Actuators, A 70, 6 (1998).Google Scholar
3.Go, J.S., Cho, Y.H., Kwak, B.M., and Park, K., Sens. Actuators, A 54, 579 (1996).Google Scholar
4.Chang, C.L. and Chang, P.Z., Sens. Actuators, A 79, 71 (2000).Google Scholar
5.Vickers-Kirby, D.J., Kubena, R.L., Stratton, F.P., Joyce, R.J., Chang, D.T., and Kim, J., in Materials Science of Microelectrome-chanical Systems (MEMS) Devices III, edited by Kahn, H., Boer, M. de, Judy, M., and Spearling, S.M. (Mater. Res. Soc. Symp. Proc. 657, Warrendale, PA, 2001), p. EE2.5.1.Google Scholar
6.Nix, W.D., Metall. Trans. 20A, 2217 (1989).CrossRefGoogle Scholar
7.Stoney, G.G., Proc. Roy. Soc. Lon. A 82, 172 (1909).Google Scholar
8.Thouless, M.D., Gupta, J., and Harper, J.M.E., J. Mater. Res. 8, 1845 (1993).Google Scholar
9.Shen, Y.L. and Suresh, S., Acta Metall. Mater. 43, 3915 (1995).CrossRefGoogle Scholar
10.Thouless, M.D., Rodbell, K.P., and Cabral, C. Jr., J. Vac. Sci. Technol. A 14, 2454 (1996).CrossRefGoogle Scholar
11.Koike, J., Utsunomiya, S., Shimoyama, Y., Maruyama, K., and Oikawa, H., J. Mater. Res. 13, 3256 (1998).Google Scholar
12.Keller, R.M., Baker, S.P., and Arzt, E., Acta Mater. 47, 415 (1999).CrossRefGoogle Scholar
13.Leung, O.S., Munkholm, A., Brennan, S., and Nix, W.D., J App. Phys. 88, 1389 (2000).Google Scholar
14.Weiss, D., Gao, H., and Arzt, E., Acta Mater. 49, 2395 (2001).Google Scholar
15.Vinci, R.P., Forrest, S.A., and Bravman, J.C., J. Mater. Res. 17, 1863 (2002).Google Scholar
16.Harris, K.E. and King, A.H., Acta Mater. 46, 6195 (1998).Google Scholar
17.Vinci, R.P., Cornella, G., and Bravman, J.C., in AIP Conf. Proc. 491, 240 (1999).Google Scholar
18.Owusu-Boahen, K., and King, A.H., Acta Mater. 49, 237 (2001).Google Scholar
19.Spolenak, S., Volkert, C.A., Ziegler, S., Panofen, C., and Brown, W.L. in Dislocations and Deformation Mechanisms in Thin Films and Small Structures, edited by Kraft, O., Schwarz, K.W., Baker, S.P., Freund, L.B., and Hull, R. (Mater. Res. Soc. Symp. Proc. 673, Warrendale, PA, 2001), p. 1.4.1.Google Scholar
20.Zhang, Y. and Dunn, M.L., J. MEMS (in press, 2003).Google Scholar
21.Dunn, M.L., Zhang, Y., and Bright, V.M., J. MEMS 11, 372 (2002).Google Scholar
22.Zhang, Y. and Dunn, M.L., in Proc. MEMS 3, 149 (2001).Google Scholar
23.Gall, K., Dunn, M.L., Zhang, Y., and Corff, B.A., Mech. Mater. (in press).Google Scholar
24.George, S.M., Ott, A.W., and Klaus, J.W., J. Phys. Chem. 100, 13121 (1996).CrossRefGoogle Scholar
25.Koester, D.A., Mahadevan, R., Hardy, B., and Markus, K.W., MUMPs Design Rules, available from http://www.memsrus.com/cronos/svcsrules.html (2001).Google Scholar