Electron Scattering at Surfaces and Grain Boundaries in Rh Layers

The resistivity size effect in Rh is investigated by quantifying electron scattering at surfaces and grain boundaries in polycrystalline Rh layers with thickness
${d} =9$
–261 nm. Sputter deposition on SiO
₂
/Si(001) at
${T}_{s} =20$
, 350, and 350 °C followed by
in situ
stepwise annealing to 750 °C yields three series of 111-textured Rh layers with increasing average lateral grain sizes
${D}$
. Electron backscatter diffraction (EBSD) maps show that
${D}$
for annealed layers increases with layer thickness from
${D} =89$
to 134 nm, matching the surface morphological lateral correlation length
${{\xi }}=86$
–154 nm measured by atomic force microscopy (AFM).
In situ
transport measurements yield resistivity
${{\rho }}$
versus
${d}$
data, which are described with a combined Fuchs–Sondheimer (FS) and Mayadas–Shatzkes (MS) model and indicate a Rh electron mean free path
${{\lambda }} =9.5$
unboldmath± 0.8 nm and a reflection coefficient
${R} =0.41$
unboldmath± 0.05 for grain boundaries characterized by a rotation about the
$\langle 111\rangle $
axis. As-deposited layers have considerably smaller grains, leading to a threefold and sixfold increase in
${{\rho }}$
above the bulk value for
${d} =10$
nm and
${T}_{s} =350$
and 20 °C, respectively. The overall results indicate a conductance benefit of Rh versus Cu for narrow interconnect lines and reveal the importance of Rh processing to achieve a large (>10 nm) grain size, which is essential to realize the conductivity advantage.