Tantalum nitride (TaNx) atomic layer deposition (ALD) was performed using sequential exposures of (tert-butylimido)tris(diethylamido) tantalum (TBTDET) and either hydrazine (N2H4) or ammonia (NH3). X-ray reflectivity studies demonstrated that hydrazine consistently yielded TaNx films with larger growth rates and higher densities than the TaNx films grown using ammonia. The TaNx ALD growth rate of 0.62 angstrom per cycle using hydrazine was higher than the growth rate obtained using ammonia over the temperature range from 150-250 degrees C. Quartz crystal microbalance measurements were also used to confirm the TaNx ALD growth rates and to verify the self-limiting behavior of each reactant. Hydrazine yielded a TaNx density of 10.1 g/cm(3) at 225 degrees C that was significantly greater than the highest density of 8.3 g/cm(3) obtained at 225 degrees C with ammonia. In situ resistivity measurements on the TaNx ALD films grown using hydrazine at 225 degrees C obtained resistivities of similar to 1 x 10(5) mu ohm cm at 225 degrees C and similar to 4 x 10(4) mu ohm cm after annealing to 450 degrees C. The surface species and reaction products during the sequential exposures of TBTDET and hydrazine at 225 degrees C were examined using Fourier transform infrared spectroscopy and quadrupole mass spectrometry. These studies allowed a growth mechanism to be proposed for TaNx ALD using TBTDET and hydrazine. (c) 2008 The Electrochemical Society.