Electromigration extrusion kinetics of Cu interconnects

Electromigration lifetime and failure mechanism have been investigated for Cu/low-k interconnects at intermediate interconnect levels. It was observed that extrusion fails occurred mostly before resistance shift fails were detected. The activation energy for extrusion fails was determined to be 1.13...

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Bibliographic Details
Published in2013 IEEE International Reliability Physics Symposium (IRPS) pp. 2C.4.1 - 2C.4.5
Main Authors Lijuan Zhang, Ping-Chuan Wang, Xiao Hu Liu, McLaughlin, P. S., Filippi, R., Baozhen Li, Junjing Bao
Format Conference Proceeding
LanguageEnglish
Published IEEE 01.04.2013
Subjects
activation energy
Anodes
Cathodes
Cu interconnect
current exponent
Electromigration
extrusion
failure mode
Kinetic theory
kinetics
Metals
Resistance
Stress
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Summary:Electromigration lifetime and failure mechanism have been investigated for Cu/low-k interconnects at intermediate interconnect levels. It was observed that extrusion fails occurred mostly before resistance shift fails were detected. The activation energy for extrusion fails was determined to be 1.13 eV, comparable to the value of 0.99 eV for the resistance shift fails. This suggests the same failure mechanism for two failure modes: Cu mass transport primarily along the Cu/cap interface. The current exponent was extracted as 1.48 and 1.36 for extrusion fails and resistance shift fails, respectively. Physical failure analysis confirmed Cu extrusion near the anode and void formation at the cathode. Samples with improved pre-clean process before the cap deposition significantly suppressed EM induced extrusions, indicating a mechanically stronger Cu/cap interface. Furthermore, effective atomic sink at the anode end appeared to reduce the compressive stress buildup during EM, as it also significantly mitigated EM induced extrusion.
ISBN:9781479901128
1479901121
ISSN:1541-7026
1938-1891
DOI:10.1109/IRPS.2013.6531954