Jitu,
     What are you using the Tantallum Nitride as a barrier against.  If
copper there are lots of technical papers on the efficiency of these and
other barrier layers. There are good papers on 200 Angstrom thick layers
of Ta,TaN,Ti,etc.  There are newer papers on silane as a barrier layer
only 10 to 20 angstroms thick.
  Bill Moffat