This work investigates the temperature and composition dependencies of Cu diffusion in tantalum nitride (TaNx) thin films. This study also measured the concentration profile of Cu using Auger electron spectroscopy. Also investigated herein are the morphology and the crystalline microstructure of tantalum nitride films using atomic force microscopy, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction, respectively. Lattice and grain boundary diffusivities were extracted from the concentration profile using the Whipple analysis of grain boundary diffusion, after annealing samples at temperatures between 500 and 800 degrees C. Analysis results indicated that the Whipple model correlates well with experimental results.