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Effects of Pulse Duration and Polarity on the Electromigration Behavior of Copper Interconnects under Pulsed Current Stress

Published online by Cambridge University Press:  01 February 2011

Meng Keong Lim
Affiliation:
X060016@ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, School of Materials Science and Engineering, Block N4.1, B3-02, Nanyang Avenue, Singapore 639798, Singapore, 639798, Singapore, (65) 6790 4142, (65) 6790 9081
Chee Lip Gan
Affiliation:
CLGan@ntu.edu.sg, Nanyang Technological University, School of Materials Science and Engineering, Block N4.1, 50 Nanyang Avenue, Singapore, 639798, Singapore
Yong Chiang Ee
Affiliation:
eeyc@charteredsemi.com, Chartered Semiconductor Manufacturing Ltd, 60 Woodlands Industrial Park D, Street 2, Singapore, 738406, Singapore
Chee Mang Ng
Affiliation:
ngcm@charteredsemi.com, Chartered Semiconductor Manufacturing Ltd, 60 Woodlands Industrial Park D, Street 2, Singapore, 738406, Singapore
Bei Chao Zhang
Affiliation:
zhangbc@charteredsemi.com, Chartered Semiconductor Manufacturing Ltd, 60 Woodlands Industrial Park D, Street 2, Singapore, 738406, Singapore
Juan Boon Tan
Affiliation:
tanjb@charteredsemi.com, Chartered Semiconductor Manufacturing Ltd, 60 Woodlands Industrial Park D, Street 2, Singapore, 738406, Singapore
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Abstract

Direct current (D.C.) is usually employed to characterize the electromigration reliability of interconnects. However, D.C. characterization techniques might not reflect the actual reliability of interconnects that are carrying pulsed D.C. or A.C. (alternating current) signals during operation. This study investigates the effects of unipolar and bipolar pulsed current on the electromigration lifetime of copper (Cu) interconnects. A series of long period pulsed current (i.e. 2, 16, 32 and 48 hours) were applied to Cu interconnects. Lifetime enhancement is observed when the half-period of pulsed current is shorter than the medium-time-to-failure (t50) of D.C. stressed samples. Minor increase in resistance occurring in-between pulses for unipolar pulsed current stressed samples, and occurrence of damage healing in bipolar pulsed current stressed samples are reasons attributed for the observed enhanced lifetime. We obtained longer MTF when the period of the pulsed current is shorter.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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References

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