Time-dependent behavior of thin metal films

Richard P. Vinci, Paul El-Deiry, Seungmin Hyun, and Walter Brown

Department of Materials Science and Engineering, Lehigh University


Introduction

Time-dependent deformation of materials may be recoverable (anelastic/viscoelastic) or permanent (viscoelastic/creep/stress relaxation). This behavior is generally undesirable, but can be controlled to some degree through control of composition and microstructure. These phenomena tend to be stronger in thin metal films than in bulk due to the small scales inherent in thin films.

Characterization of time-dependent thin film behavior is challenging, and customized equipment must often be designed specifically for this purpose.

Sample Images

bulge test geometry

A schematic of a "bulge" specimen geometry used for stress relaxation measurements either under gas pressure or under electrostatic actuation (as shown).

          Al stress relaxation curves
Stress relaxation behavior for 33 nm thick pure Al films as a function of temperature.

 

Goals

Findings 

Related Publications

  1. R.P. Vinci, G. Cornella, J.C. Bravman, Anelastic Effects in Freestanding Al Thin Films, Proc. 5th International Workshop on Stress Induced Phenomena in Metallization, Stuttgart, Germany, June, 1999, pp. 240-8. (Invited)
  2. P. A. El-Deiry and R. P. Vinci, Anelastic Behavior Of Pure Aluminum and Copper Micro-Wires, Mater. Res. Soc. Proc., 695, 2002, p. 159.
  3. S. Hyun, W.L. Brown, and R. P. Vinci, Thickness and temperature dependence of stress relaxation in nanoscale aluminum films, Appl. Phys. Lett., 83 (21), 2003, pp. 4411-13.
  4. N. Barbosa, P. El-Deiry, and R.P. Vinci, Monotonic testing and tension-tension fatigue testing of freestanding Al microtensile Beams, Proc. Mater. Res. Soc. Symp., 2004, U.11.39.1-6.
  5. S. Hyun, W.L. Brown, and R. P. Vinci, Stress relaxation in nanoscale aluminum films, Proc. SPIE, 5343, 2004, 154-162.
  6. P. A. El-Deiry, N. Barbosa III, W. L. Brown, R. P. Vinci, “Effective Modulus and Stress Relaxation of Freestanding Aluminum Microtensile Beams”, submitted to Proc. Mater. Res. Soc., 2004.
  7. S. Hyun, Tejpal K. Hooghan, W.L. Brown, and R.P. Vinci, Linear Viscoelasticity in Aluminum Thin Films, to appear in Appl. Phys. Lett., August 2005.

Portions of this work were performed collaboratively at Lehigh University and Stanford University. Support for Lehigh has been provided by:

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office, Army Research Laboratory, or the U.S. Government.
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Last updated: August 2, 2005