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Creep-controlled Diffusional Hillock Formation in Blanket Aluminum Thin Films as a Mechanism of Stress Relaxation

Published online by Cambridge University Press:  31 January 2011

Deok-Kee Kim ,
William D. Nix ,
Michael D. Deal  and
James D. Plummer
Deok-Kee Kim
Affiliation:
Center for Integrated Systems, Stanford University, Stanford, California 94305
William D. Nix
Affiliation:
Center for Integrated Systems, Stanford University, Stanford, California 94305
Michael D. Deal
Affiliation:
Center for Integrated Systems, Stanford University, Stanford, California 94305
James D. Plummer
Affiliation:
Center for Integrated Systems, Stanford University, Stanford, California 94305
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Abstract

Hillock formation, a stress-induced diffusional relaxation process, was studied in sputter-deposited Al films. The grain sizes in these films were small compared to those in other sputter-deposited Al films, and impurities (O, Ti, W) were incorporated during the preparation of the films. Stress and hardness measurements both indicate that the Al films were strengthened by the small grain size and incorporated impurities. We observed a new type of hillock in these Al thin films after annealing for 2 h at 450 °C in a forming gas ambient. The hillocks were composed of large Al grains created between the substrate and the original Al film with its columnar grain structure, apparently by diffusion from the surrounding area. By modifying the boundary conditions of Chaudhari's hillock formation model [P. Chaudhari, J. Appl. Phy. 45, 4339 (1974)], we have created a new model that can describe the experimentally observed hillocks. Our model seems to explain the experimentally observed abnormal hillock formation and may be applied to other types of hillock formation using different creep laws.

Type
Articles
Information
Journal of Materials Research , Volume 15 , Issue 8 , August 2000 , pp. 1709 - 1718
Copyright
Copyright © Materials Research Society 2000

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References

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