First-principles evaluation of resistance contributions in Ruthenium interconnects for advanced technology nodes

Resistance contribution within Ruthenium (Ru) interconnects, used in middle-of-the line and back-end-of- the line process in an integrated circuit, are evaluated using first-principles density functional theory based transport calculations using the non-equilibrium Green’s function. Three prominent scattering mechanisms impurity scattering, interface/surface scattering and grain-boundary reflections are studied systematically. The results are compared with available resistivity data from literature. The calculated reflection coefficients (R) for the symmetric-tilt grain boundaries lie in the range of 0.38 to 0.51, indicating the grain boundary reflections can significantly enhance the metal resistivity within Ru interconnects. These grain boundary reflection coefficients are in good agreement with hardware data and a fit to the measured resistivity data predicts an average reflection coefficient of 0.51 for Ru interconnect, using Mayadas-Shatzkes model. The results obtained provide useful physical insights into Ru grain-boundary reflections and can be used to classify the metals for advanced interconnect technology.