Time-dependent behavior of thin metal films
P. Vinci, Paul El-Deiry, Seungmin Hyun, and Walter Brown
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
Characterization of time-dependent thin film behavior is challenging,
and customized equipment must often be designed specifically for this
A schematic of a "bulge" specimen geometry used for stress
relaxation measurements either under gas pressure or under
electrostatic actuation (as shown).
|Stress relaxation behavior for 33 nm thick pure Al films as
a function of temperature.
- Design and fabrication of apparatus for characterization of
- Characterization of behavior and mechanisms active in sub-micron
- Investigation of the role of anelastic behavior in the "modulus
deficit" often observed in microtensile testing.
- Development of mechanism-based models for time-dependent
behavior, and schemes for increased thin film stability.
- Apparatus has been constructed that allows for time-dependent
testing of thin metal films as thin as 30 nm.
- Anelastic response of thin Al films has been shown to obey the
laws of Linear Viscoelasticity.
- High strain-rate testing of freestanding film (via microtensile
testing) has shown that significant relaxation can occur over 100 msec,
and may account for some of the modulus deficit commonly observed in
slower microtensile tests.
- 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.
- P. A. El-Deiry and R. P. Vinci, Anelastic Behavior Of Pure
Aluminum and Copper Micro-Wires, Mater. Res. Soc. Proc., 695, 2002, p.
- 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.
- 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.
- S. Hyun, W.L. Brown, and R. P. Vinci, Stress relaxation in
nanoscale aluminum films, Proc. SPIE, 5343, 2004, 154-162.
- 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.
- 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
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.
- the U.S. Army Research Office
and U.S. Army Research Laboratory,
Cooperative Agreement Number DAAD19-02-2-0030.
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Last updated: August 2, 2005