Statistical Analysis of Electromigration Lifetimes and Void Evolution
- Interconnect and Packaging Group, University of Texas at Austin, PRC/MER, Mail Code, R8650, Austin, TX 78712 (United States)
- CMOS Platform Device Development, Technology Solutions Organization, Freescale Semiconductor, MD K10, 3501 Ed Bluestein Blvd, Austin, TX 78721 (United States)
Electromigration (EM) failure statistics and the origin of the lognormal standard deviation ({sigma}) for Copper (Cu) interconnects have been investigated by analyzing the statistics of EM lifetime and void size distributions at various stages during EM testing. Experiments were performed on 0.18{mu}m wide Cu interconnects with tests terminated after certain amounts of resistance increases, or after a specified test time. Void size distributions of resistance-based, as well as time-based EM tests were obtained using focused ion beam (FIB) microscopy. The lifetime and void size distributions were found to follow lognormal distribution functions. The {sigma} values of EM lifetime and time-based void size distributions decrease with higher percentages of resistance increase, reaching an asymptotic value of {sigma} {approx} 0.14. In contrast, {sigma} values of resistance-based void size distributions are significantly smaller and do not show an obvious dependence on time. The statistics of resistance-based void size distributions can be accounted for by considering geometrical variations of the void shape, while the characteristics of time-based void size distributions require consideration of kinetic aspects of the EM process. The {sigma} values of EM lifetime distributions can be adequately simulated from experimentally obtained void size distributions, including geometrical and experimental factors of the EM experiment as well as kinetic aspects of the mass transport process, such as differences in interface diffusivity between the lines. The variation in diffusivities at the cathode ends of the lines arises from differences in the interface structure as a result of varying Cu grain orientations.
- OSTI ID:
- 20630465
- Journal Information:
- AIP Conference Proceedings, Vol. 741, Issue 1; Conference: 7. international workshop on stress-induced phenomena in metallization, Austin, TX (United States), 14-16 Jun 2004; Other Information: DOI: 10.1063/1.1845841; (c) 2004 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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