Plasma-enhanced atomic layer deposition of TaN thin films using tantalum-pentafluoride and N-2/H-2/Ar plasma

Abstract

TaN thin films were grown by plasma-enhanced atomic layer deposition using tantalum-pentafluoride (TaF5) as the metal precursor and N-2/H-2/Ar plasma as the reducing agent at a temperature of 350 degrees C. When the source pulse time exceeded 1.5 s, the thickness per cycle of TaN thin films was saturated at 0.41 angstrom/cycle and the resistivity was about 610 mu Omega cm. Under this condition, the TaN thin films had a high density (14.6 g/cm(3)), which was very close to the theoretical value (15.8 g/cm(3)), and fluorine or hydrogen impurities were below detection limit. The resistivity and N/Ta ratio of the TaN thin films increased with the plasma time, and did not saturate. In addition, increasing the N-2/H-2 ratio induced a sudden rise in the resistivity, which was related to the formation of a Ta3N5 phase. This dielectric phase was reduced by lowering the N-2/H-2 ratio. In addition, when H-2 plasma post-treatment was applied to the deposition process, the resistivity of the TaN thin films was reduced to 400 mu Omega cm. (c) 2006 The Electrochemical Society.