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Residual Stress and Microstructure of Electroplated Cu Film on Different Barrier Layers

Published online by Cambridge University Press:  21 March 2011

Alex A. Volinsky
Affiliation:
Motorola DigitalDNATM Labs, Process and Materials Characterization Lab, Mesa, AZ
Meike Hauschildt
Affiliation:
University of Texas, Materials Science Lab for Interconnect and Packaging, Austin, TX
Joseph B. Vella
Affiliation:
Motorola DigitalDNATM Labs, Process and Materials Characterization Lab, Mesa, AZ
N.V. Edwards
Affiliation:
Motorola DigitalDNATM Labs, Process and Materials Characterization Lab, Mesa, AZ
Rich Gregory
Affiliation:
Motorola DigitalDNATM Labs, Process and Materials Characterization Lab, Mesa, AZ
William W. Gerberich
Affiliation:
University of Minnesota, Dept. of Chem. Eng. and Materials Science, Minneapolis, MN
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Abstract

Copper films of different thicknesses between 0.2 and 2 microns were electroplated on adhesion-promoting TiW and Ta barrier layers on <100> single crystal 6-inch silicon wafers. The residual stress was measured after each processing step using a wafer curvature technique employing Stoney's equation. Large gradients in the stress distributions were found across each wafer. Controlled Cu grain growth was achieved by annealing films at 350 C for 3 minutes in high vacuum. Annealing increased the average tensile residual stress by about 200 MPa for all the films, which is in agreement with stress-temperature cycling measurements.

After aging for 1 year wafer stress mapping showed that the stress gradients in the copper films were alleviated. No stress discrepancies between the copper on Ta and TiW barrier layers could be found. However, X-ray pole figure analysis showed broad and shifted (111) texture in films on a TiW underlayer, whereas the (111) texture in Cu films on Ta is sharp and centered.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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References

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