Electromigration in Cu(Al) and Cu(Mn) damascene lines
- 1 May 2012
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 111 (9), 093722
- https://doi.org/10.1063/1.4711070
Abstract
The effects of impurities, Mn or Al, on interface and grain boundary electromigration (EM) in Cu damascene lines were investigated. The addition of Mn or Al solute caused a reduction in diffusivity at the Cu/dielectric cap interface and the EM activation energies for both Cu-alloys were found to increase by about 0.2 eV as compared to pure Cu. Mn mitigated and Al enhanced Cu grain boundary diffusion; however, no significant mitigation in Cu grain boundary diffusion was observed in low Mn concentration samples. The activation energies for Cu grain boundary diffusion were found to be 0.74 ± 0.05 eV and 0.77 ± 0.05 eV for 1.5 μm wide polycrystalline lines with pure Cu and Cu (0.5 at. % Mn) seeds, respectively. The effective charge number in Cu grain boundaries Z*GB was estimated from drift velocity and was found to be about −0.4. A significant enhancement in EM lifetimes for Cu(Al) or low Mn concentration bamboo-polycrystalline and near-bamboo grain structures was observed but not for polycrystalline-only alloy lines. These results indicated that the existence of bamboo grains in bamboo-polycrystalline lines played a critical role in slowing down the EM-induced void growth rate. The bamboo grains act as Cu diffusion blocking boundaries for grain boundary mass flow, thus generating a mechanical stress-induced back flow counterbalancing the EM force, which is the equality known as the “Blech short length effect.”Keywords
This publication has 23 references indexed in Scilit:
- Impact of Al in Cu alloy interconnects on electro and stress migration reliabilitiesMicroelectronic Engineering, 2008
- Line Resistance and Electromigration Variations Induced by Hydrogen-Based Plasma Modifications to the Silicon Carbonitride/Copper InterfaceJournal of the Electrochemical Society, 2007
- Recent advances on electromigration in very-large-scale-integration of interconnectsJournal of Applied Physics, 2003
- Size-dependent resistivity of metallic wires in the mesoscopic rangePhysical Review B, 2002
- Electromigration in Cu thin films with Sn and Al cross stripsJournal of Applied Physics, 2001
- Grain boundary self-diffusion in Cu polycrystals of different purityActa Materialia, 1997
- Grain Boundary Diffusion and Electromigration in Cu-Sn Alloy Thin Films and their VLSI InterconnectsDefect and Diffusion Forum, 1997
- Positron annihilation in Cu and dilute CuSb and CuIn alloysJournal of Physics F: Metal Physics, 1986
- Studies of defects at thermal equilibrium and melting in Cu and Ni by positron annihilationJournal of Physics F: Metal Physics, 1977
- The formation energies of a vacancy in pure Cu, Cu-Si, Cu-Ga and Cu- gamma Mn solid solutions by positron annihilationJournal of Physics F: Metal Physics, 1976