Silicon reaction of TiNx diffusion barriers at high temperatures

Abstract

TiNx diffusion barriers have been deposited onto n-Si wafers by reactive sputtering in a N2+Ar atmosphere, with a nitrogen content varying in the 0%–25% range. The relative composition of the as-deposited films was examined by Rutherford backscattering spectroscopy (RBS) and Auger electron spectroscopy (AES) analysis yielding a TiNx composition between x=0.8 and x=1.2, respectively. The near stoichiometric samples were thermally annealed at temperatures between 600 and 900 °C in vacuum and N2 atmosphere. Films with composition TiN1.1 and TiN0.9 present very good behavior as barrier layers against the Si diffusion and a very low reactivity with the Si substrate. When the nitrogen content in the as-deposited films decreases, the films lose their barrier properties. For the TiN0.8 samples, Si diffusion through the films is observed after annealing in vacuum at temperatures of 600 °C and above. However, when the heat treatment is carried out in a N2 atmosphere an improvement in the barrier characteristics and reactivity with the Si at the interface was observed.