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Effect of Poly-Si on Electromigration Behaviors and Microstructure Characteristics of Au Metallization

Published online by Cambridge University Press:  10 February 2011

T. Lee
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
B.R. York
Affiliation:
Materials Laboratory, IBM Corp., 5600 Cottle Rd., San Jose, CA 95193
B. Lindgren
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
H. Kentzinger
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
J. Lee
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
C. Christenson
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
C. Varker
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
K. Evans
Affiliation:
SPS-SCG, Motorola Inc., MD:M544, 2200 W. Broadway Rd., Mesa, AZ 85202
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Abstract

For BJT and MOSFET, poly-Si is the most critical layer used as an emitter to improve the current gain in BJT and as a gate to improve the gate oxide reliability in MOSFET. In both cases, the poly-Si is then connected to the conductor. It is very important to understand how poly-Si affects the microstructure and the electromigration behavior of conductor. NIST test structures (length = 800μ, thickness = 0.7μ, widths = 1, 5, 10 μ) with Au conductor and TiW/TiWN/TiW barrier were used to study the impact of poly-Si. Two groups of samples were used: one with poly-Si under the barrier and the other without poly-Si. Thermal oxide was used to isolate the substrate from the conductor and Si3N4, was used as passivation. DC stress was performed at 175, 200, and 225°C. Microbeam X-ray Diffraction (μ XRD) was used to characterize the microstructure of the TiW barrier and Au metallization layers as a function of line length and width. The data indicates that samples with poly-Si have lower electromigration resistance for Au conductors for all widths and temperatures, with higher initial deformation fault densities on poly-Si.

Type
Research Article
Copyright
Copyright © Materials Research Society 1998

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References

[1] York, B.R., Pfizenmayer, H.L., Lee, C.H., Cames, R.O., MRS Proceedings 1995 Google Scholar
[2] York, B.R., Lee, C.H., to be published 304 Google Scholar