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Stress Relaxation in Al–Cu and Al–Si–Cu Thin Films

Published online by Cambridge University Press:  31 January 2011

A. Witvrouw ,
J. Proost ,
Ph. Roussel ,
P. Cosemans  and
K. Maex
A. Witvrouw
Affiliation:
IMEC, Kapeldreef 75, 3001 Leuven, Belgium
J. Proost
Affiliation:
IMEC, Kapeldreef 75, 3001 Leuven, Belgium
Ph. Roussel
Affiliation:
IMEC, Kapeldreef 75, 3001 Leuven, Belgium
P. Cosemans
Affiliation:
LUC, Institute for Materials Research, Materials Physics Division, Universitaire Campus, Wetenschapspark 1, B-3590 Diepenbeek, Belgium
K. Maex
Affiliation:
IMEC, Kapeldreef 75, 3001 Leuven, Belgium
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Abstract

Substrate curvature measurements were used to study stress changes during thermal cycling and isothermal tensile stress relaxation in 800 nm Al–0.5 wt% Cu and Al–1 wt% Si–0.5 wt% Cu films. For both compositions dislocation glide can describe the relaxation data well for temperatures up to 120 °C for Al–Si–Cu and up to 100 °C for Al–Cu. The average activation energy for Al–Si–Cu and Al–Cu is 1.7 ± 0.2 eV and 3.0 ± 0.3 eV, respectively. The athermal flow stress is the same for both and equal to 600 ± 200 MPa. This result is consistent with the obstacles for glide being Al2Cu precipitates, which, in the case of Al–Si–Cu, are fine and can be cut by the dislocations, and, in the case of Al–Cu, are strong and provide Orowan strengthening. Also, the stress changes during thermal cycling in the Al–Cu films are different from those in the Al–Si–Cu films. For Al–Cu films, the room temperature stress decreases after each thermal cycle, while for Al–Si–Cu stress changes during thermal cycling are stable from the second cycle on. These observations are supported by thorough transmission electron microscopy (TEM) studies.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 4 , April 1999 , pp. 1246 - 1254
Copyright
Copyright © Materials Research Society 1999

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