Comparative study of HfNx and Hf–Ge–N copper diffusion barriers on Ge

Abstract

The diffusion barrier properties of HfNx and Hf–Ge–N thin films for Cu metallization on Ge are examined. The diffusion barrier films were deposited by reactive sputtering on p-Ge (001) single crystal substrates with varying thicknesses. Cu thin films were then deposited in situ on the diffusion barrier. The multilayer film structure was subsequently annealed in an Ar atmosphere. X-ray diffraction was used to determine the film crystallinity and identify intermetallic phases due to reactions involving the film and substrate. The HfNx and Hf–Ge–N diffusion barrier films remained amorphous for annealing temperatures up to 700°C. At thickness of 50nm, the HfNx films showed superior diffusion barrier properties as compared to Hf–Ge–N based on the appearance of secondary phases due to reactions and changes in the Cu morphology. These results suggest that HfNx is an effective barrier material for Cu integration on Ge.