Hostname: page-component-76fb5796d-r6qrq Total loading time: 0 Render date: 2024-04-26T15:22:31.803Z Has data issue: false hasContentIssue false

Anelastic Creep Phenomena in Thin Metal Plated Cantilevers for MEMS

Published online by Cambridge University Press:  17 March 2011

Deborah J. Vickers-Kirby
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
Randall L. Kubena
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
Frederic P. Stratton
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
Richard J. Joyce
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
David T. Chang
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
Jinsoo Kim
Affiliation:
Sensors and Materials Laboratory, HRL Laboratories, LLC, 3011 Malibu Canyon Road, Malibu, CA 90265, USA
Get access

Abstract

During the past several years, we have developed high displacement sensitivity tunneling accelerometers using surface micromachining and metal electroplating techniques. These devices consist of a Au tunneling tip fabricated below a 1-2 μm thick metal cantilever beam of electroplated Ni or Au. A thin film of e-beam evaporated Au on the underside of the cantilever serves as the tunneling counter electrode. In operation, a 100mV bias is applied across the tunneling gap. A larger turn-on voltage is also applied between the cantilever and a control electrode, located on the substrate, to deflect the cantilever and maintain a constant tunneling current of 1 or 10 nA. Typical deflections of the end of 100 μm-long and 250 μm-long cantilevers are 0.5μm during operation. We have observed that the turn-on voltage decreases over time for most devices with a larger drop observed for the Au cantilevers. In all cases, the initial decay of the turn-on voltage was almost completely recoverable after the device was turned off for 24 hrs. This decay was not found to be strongly dependent on the magnitude of the tunneling current, but could be significantly reduced by pre-stressing the cantilever before operation. Finally, a vacuum anneal at 100°C influences the measured temperature dependence of the turn-on voltage. The observed effects appear to be consistent with fatigue and creep phenomena in the cantilevers. These effects are reversible at room temperature and are dependent on the stress and temperature history of the devices. A comparison is made between metal plated and all-Si structures.

Type
Research Article
Copyright
Copyright © Materials Research Society 2001

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

REFERENCES

1. Lee, H., Cornella, G., and Braveman, J. C., “Stress Relaxation Of Free-Standing Aluminum Beams For Microelectromechanical Systems Applications”, Appl. Phys. Lett., 76, No. 23, 3415 (2000).Google Scholar
2. Kubena, R.L., Stratton, F.P., Vickers-Kirby, D.J., Joyce, R.J., Chang, D.T., Schimert, T., and Gooch, R.N., “Low-Cost Tunneling Accelerometer Technology for High Dynamic Range Applications,” Position, Location and Navigations Symposium (PLANS) 2000, San Diego, California, Mar. 2000, pp. 522.Google Scholar
3. Kubena, R.L., Atkinson, G.M., Robinson, W.P. and Stratton, F.P., “A New High-Performance Surface-Micromachined Tunneling Accelerometer Fabricated Using Nanolithography,” J. Vac. Sci. Technol. B 14 (6), 4029, (1996).Google Scholar
4. Kubena, R.L., Stratton, F.P., Vickers-Kirby, D.J., Joyce, R.J., Chang, D.T., Schimert, T., and Gooch, R.N., “New Fabrication Techniques for High Dynamic Range Applications,” SPIE Micromachining and Microfabrication Symposium, Santa Clara, CA, Sept. 2000. To be published in SPIE Micromachining and Microfabrication Symposium proceedings, 2001.Google Scholar
5. Nowick, A.S. and Berry, B.S., “Anelastic Relaxation in Crystalline Solids”, (Academic Press 1972).Google Scholar