Resistivity size effect in tantalum layers
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Authors
Syracuse, Daniel
Issue Date
2024-05
Type
Electronic thesis
Thesis
Thesis
Language
en_US
Keywords
Materials engineering
Alternative Title
Abstract
In situ and ex situ transport measurements at 293 and 77 K on epitaxial Ta(001)/MgO(001) and Ta(110)/Al2O3(112 ̅0) layers with thickness d = 7-350 nm are employed to quantify the anisotropic resistivity size effect in tantalum. X-ray diffraction θ-2θ scans, ω rocking curves, and φ scans indicate a 45° rotated epitaxy for Ta(001)/MgO(001), confirming single crystal layers. In contrast, Ta(110)/Al2O3(112 ̅0) exhibits two domains with different in-plane orientations. The measured resistivity ρ vs d is larger than the Fuchs-Sondheimer prediction at small d ≤ 20 nm, but is well described by a power law with ρ ∝ d¬-2 at both 293 and 77 K. Electron scattering at domain boundaries causes a higher resistivity for Ta(110) than Ta(001) layers, with the resistivity contribution from boundary scattering being proportional to d-1. Comparison of in situ and ex situ measurements after air exposure indicates that surface oxidation results in more pronounced diffuse surface scattering at both the Ta(001) and Ta(110) surfaces. The product of bulk resistivity ρo times electron mean free path λ for Ta is ρoλ = 26.2 × 10-16 Ωm2 for Ta(001)/MgO(001) and ρoλ = 36.7 × 10-16 Ωm2 for Ta(110)/Al2O3(112 ̅0). These values are 4-5× higher than for Cu, indicating that Ta is not a promising conductor for narrow interconnect lines.
Description
May2024
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY