The experimentally measured resistivity of Co(0001) and Ru(0001) single crystal thin films, grown on c-plane sapphire substrates, as a function of thickness is modeled using the semiclassical model of Fuchs-Sondheimer. The model fits show that the resistivity of Ru would cross below that for Co at a thickness of approximately 20 nm. For Ru films with thicknesses above 20 nm, transmission electron microscopy evidences threading and misfit dislocations, stacking faults and deformation twins. Exposure of Co films to ambient air, and the deposition of oxide layers of SiO2, MgO, Al2O3 and Cr2O3 on Ru degrade the surface specularity of the metallic layer. However, for the Ru films, annealing in a reducing ambient restores the surface specularity. Epitaxial electrochemical deposition of Co on epitaxially-deposited Ru layers is used as an example to demonstrate the feasibility of generating epitaxial interconnects for back-end of line structures. An electron transport model based on a tight-binding approach is described, with Ru interconnects used an example. The model allows conductivity to be computed for structures comprising large ensembles of atoms (10^5-10^6), scales linearly with system size and can also incorporate defects.
@article{arxiv.2004.00971,
title = {Epitaxial metals for interconnects beyond Cu},
author = {Katayun Barmak and Sameer Ezzat and Ryan Gusle and Atharv Jog and Sit Kerdsongpanya and Asim Khanya and Erik Milosevic and William Richardson and Kadir Sentosun and Amirali Zangiabadi and Daniel Gall and William E. Kaden and Eduardo R. Mucciolo and Patrick K. Schelling and Alan C. West and Kevin R. Coffey},
journal= {arXiv preprint arXiv:2004.00971},
year = {2020}
}
Comments
37 pages, 10 figures, to appear in the Journal of Vacuum Science & Technology A