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Length Effects on the Reliability of Dual-Damascene Cu Interconnects

Published online by Cambridge University Press:  01 February 2011

F. Wei
Affiliation:
DMSE, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
C. L. Gan
Affiliation:
AMM&NS, Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore 117576
C. V. Thompson
Affiliation:
DMSE, Massachusetts Institute of Technology, Cambridge, MA 02139 USA AMM&NS, Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore 117576
J. J. Clement
Affiliation:
Sandia National Laboratories, Albuquerque, NM 87185
S. P. Hau-Riege
Affiliation:
Intel Corp, Hillsboro, OR 97124, now with LLNL, Livermore, CA 94550
K. L. Pey
Affiliation:
AMM&NS, Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore 117576 Department of Electrical & Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576
W. K. Choi
Affiliation:
AMM&NS, Singapore-MIT Alliance, 4 Engineering Drive 3, Singapore 117576 Department of Electrical & Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576
H. L. Tay
Affiliation:
Institute of Microelectronics, 11 Science Park Road, Singapore 117685
B. Yu
Affiliation:
Institute of Microelectronics, 11 Science Park Road, Singapore 117685
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Abstract

We have carried out experiments on dual-damascene Cu interconnects with different lengths. We find that at short lengths, similar to Al-based interconnects, the reliability of Cubased interconnects improves. Also like Al interconnects, some short Cu segments do not form voids that cause failure before back-stresses prevent the further growth of voids. However, unlike Al-based interconnects, there is no apparent deterministic current-density line-length product (jL) for which all lines are immortal. This is related to the absence of a conducting refractory-metal overlayer in Cu-technology that can shunt current around small voids. Also unlike Al, we find that at long lengths a sub-population of Cu lines is immortal. We propose that this is the result of rupture of the thin refractory metal liner at the base of the dual-damascene Cu vias. As a consequence of this complex behavior, median times to failure and lifetime variations are minimum at intermediate line lengths.

Type
Research Article
Copyright
Copyright © Materials Research Society 2002

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