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 SiO2/Si(001) at T-s = 20 , 350, and 350 degrees C followed by in situ stepwise annealing to 750 degrees 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 +/- 0.8 nm and a reflection coefficient R = 0.41 +/- 0.05 for grain boundaries characterized by a rotation about the <111> 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 degrees 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.

Automated summary

The resistivity size effect in Rh has been investigated by studying electron scattering at surfaces and grain boundaries. The results show that Rh has better conductivity than Cu for narrow interconnect lines, and achieving large grain size is essential for realizing the conductivity advantage.