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Statistical Evaluation of Stressmigration Reliability in Al-Cu Interconnects

Published online by Cambridge University Press:  10 February 2011

D. Jawarani ,
M. Gall ,
C. Capasso ,
J. Müller ,
R. Hernandez  and
H. Kawasaki
D. Jawarani
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
M. Gall
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
C. Capasso
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
J. Müller
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
R. Hernandez
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
H. Kawasaki
Affiliation:
Advanced Products Research and Development Laboratory, Motorola 3501 Ed Bluestein Blvd., Austin, TX 78721, USA
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Abstract

High-resolution resistance measurements of metal stripes have been performed to study void growth during in situ annealing at 180°C. Void growth has been characterized by resistance monitoring over 14,000 hours. During the annealing of Al-lwt%Cu stripes, Cu atoms from solution migrate to grain boundaries to form Al2Cu precipitates leading to a drop in resistance. At the same time, relaxation of tensile stresses in metal stripes takes place in the form of void nucleation and growth, leading to an increase in resistance. The resistance drop due to precipitation was shown to obey Avrami's precipitation kinetics while void growth over this time period obeyed a diffusion-type equation. The resulting equation to describe this physical model was fitted to the measured resistance data. Extrapolation to failure condition (ΔR/R=10%) could therefore be obtained for all the devices under test and plotted on a cumulative probability plot. Using the measured value of activation energy for void growth, stressmigration reliability was then assessed by extrapolation to an operating temperature. Post-mortem microscopy was performed to correlate resistance increase with void density and size in these interconnects. Finite element simulations were performed to calculate resistance increases due to voiding in metal stripes and correlate these with the experimentally obtained data.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 516: Symposium E – Low Dielectric Constant Materials IV , January 1998 , 65
Copyright
Copyright © Materials Research Society 1998

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References

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