A new process was developed for deposition of the tungsten nitride at moderate substrate temperatures (350-400 °C). The tungsten source bis (tert-butylamido)bis(tertbutylimido) tungsten, (tBuNH)2(tBuN)2W, reacts with ammonia in a low-pressure CVD reactor. Growth rates ranged from about 0.6 to 4.1 nm per minute. The stoichiometry of the films varied from WN1.2O1.7 to WN1.6o0.25, depending mainly on deposition temperature. The films are amorphous by X-ray diffraction, and smooth by scanning electron microscopy. Step coverage is nearly 100% in vias with an aspect ratio of 6:1 for films deposited at 400 °C or lower. Barriers 45 nm thick resist diffusion of copper up to temperatures of 600 °C. Adhesion is strong to all substrates tested, including silicon, silicon dioxide, soda-lime glass, glassy carbon, aluminum and stainless steel. This new halogen-free process avoids halogen contamination of films and corrosion of equipment. Uniformity of thickness and stoichiometry are readily achieved. This process is a promising method for forming copper diffusion barriers in future generations of microelectronics.