A comparative study of the diffusion barrier properties of TiN and ZrN

Abstract

The usefulness of Ti/TiN and Zr/ZrN bilayers as low resistivity contacts and diffusion barriers between doped silicon and aluminium was examined. The metal nitride layers were formed by reactive sputtering from elemental targets in Ar-N 2 mixtures. Analytical results obtained using Rutherford backscattering spectroscopy (RBS) showed that the as-deposited layers were stoichiometric. X-ray diffactometry revealed that the as-deposited films were polycrystalline. The respective RBS spectra showed that no detectable intermixing occured between aluminium and silicon after heat treatment up to 550°C for 30 min for either combinations. Furthermore, RBS analysis indicated that arsenic implanted in the silicon was snow ploughed during the formation of zirconium silicide, which is essential for the formation of low resistivity ohmic contacts. In contrast, arsenic was observed to diffuse through the titanium silicide layer during its formation. Finally, the possibility of in situ deposition of a multilayered structure of Zr/ZrN/Al and the formation of zirconium silicide during the post-metal anneal without aluminium-silicon intermixing was examined.