Electron Scattering at Epitaxial Ni(001) Surfaces

• Published in: IEEE transactions on electron devices 2019-10, Vol.66 (10), p.4326-4330
• Main Authors: Milosevic, Erik, Zheng, Pengyuan, Gall, Daniel
• Format: Article
• Language: English
• Subjects: Alternative metals; back end of line (BEOL); Conductivity; Electrical resistivity; Electrons; Epitaxial growth; Epitaxy; First principles; interconnects; Magnesium oxide; mean-free path; middle of line; Nickel; Oxidation; Pole figures; Predictions; resistivity scaling; Scattering; Size effects; Substrates; surface scattering; Temperature measurement
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2019.2934636

Epitaxial Ni(001) layers are sputter deposited on MgO(001) substrates and their electrical resistivity p measured in situ as a function of thickness dNi = 5-100 nm to quantify the resistivity size effect due to electron surface scattering. X-ray diffraction 8-28 scans, w-rocking curves, and pole figures confirm an epitaxial layer-substrate relationship with Ni[001]II MgO[001] and Ni[100]II MgO[100]. The resistivity is well described with the semiclassical model by Fuchs and Sondheimer and a room-temperature bulk resistivity p o = 7.04 μΩ cm, yielding a bulk electron mean-free path λ = 26 ± 2 and 350 ± 20 nm at 295 and 77 K, respectively. Air exposure causes a resistivity increase by up to 21%, which is attributed to monolayer surface oxidation that results in a transition from 30% specular to completely diffuse electron surface scattering. All measured data are consistent with a temperature-independentproduct po λ = 18.3 × 10 -16 Ωm 2 , which is 4.5 times larger than previously predicted from first-principles, indicating that Ni is less promising as a metal for narrow interconnect lines than those predictions suggest.