Numerical evaluation of grain boundary electron scattering in molybdenum thin films: A critical analysis for advanced interconnects

Abstract

We present a methodology for numerically evaluating grain boundary scattering in polycrystalline molybdenum (Mo) thin films. Two types of Mo films (an epitaxially grown (110)-single-crystal film and a <110>-fiber-textured polycrystalline thin film) were sputter-deposited under identical conditions on a lattice-matched (11 (2) over bar0)-Al2O3 substrate and an amorphous glass substrate, respectively. This indicates equal background scattering (phonon and impurity scattering) for the two types. Further, the selected film thickness (236 nm) significantly exceeds Mo's inherent electron mean free path (11.2 nm), rendering surface scattering contributions negligible. The resistivity difference is therefore attributed to the grain boundary scattering. Using the Mayadas-Shatzkes model and an average grain size of 80.9 +/- 2.8 nm (measured from a statistically significant number of grains (747)), the grain-boundary reflection coefficient for Mo films was determined to be 0.48 nm. The presented methodology, not limited to Mo, is expected to serve as a reliable analytical approach for advanced interconnects.