Ta(Al)N(C) thin films were deposited by the atomic layer deposition technique using or and as precursors and as an additional reducing agent. For comparison TaN thin films were deposited also from and with and without Zn. The films were analyzed by means of the time-of-flight elastic recoil detection analysis, energy dispersive X-ray spectroscopy, X-ray diffraction, and standard four-point probe method. The deposition temperature was varied between 250 and 400°C. The films contained aluminum, carbon, hydrogen, and chlorine impurities. The chlorine content decreased drastically as the deposition temperature was increased. The film deposited at 400°C contained less than 4 atom % chlorine and also had the lowest resistivity, 1300 μΩ cm. The barrier properties of the Cu/Ta(Al)N(C)/Si structure were studied by using sheet resistance and X-ray diffraction measurements. © 2001 The Electrochemical Society. All rights reserved.