NbTiN thin films deposited by hybrid HiPIMS/DC magnetron co-sputtering

Nb1 - xTixNy thin films (with 0 <= x <= 1 and 0.85 <= y <= 1.15) were deposited from Nb and Ti metallic targets using a hybrid process combining high-power impulse magnetron sputtering (HiPIMS) and DC magnetron sputtering (DCMS) techniques. Two series of Nb1-xTixNy films were deposited in which the HiPIMS mode was applied either to the Nb or to the Ti target while the second target (Ti or Nb) was operated in DCMS mode. The HiPIMS generator was operated at a fixed time-average power of 100 W (5 W cm(-2)) with a pulse-width of 50 mu s and a repetition frequency of 1000 Hz whereas the DC power applied to the second target was varied from 0 to 90 W to adjust the relative contents of Ti or Nb in the films. Depositions were performed in an Ar + N-2 atmosphere at a total pressure of 0.5 Pa. The substrate temperature was fixed at 250 degrees C and the sample holder was biased at -50 V. The films were characterized by XRD, SEM, EDS, nanoindentation, optical and electrical measurements. All the ternary films crystallize in the fcc NaCl-type of the structure. The films exhibit a dense columnar structure and their hardness values increase from 26 for TiN to 35 GPa for NbN. The optical properties of the Nb1 - xTixNy films progressively evolve from those of the fcc-NbN to those of the fcc-TiN as the Ti content x increases from 0 to 1. The room temperature resistivity value decreases from about 300 mu Omega cm (for NbN0.99) down to 25 mu Omega cm (for TiN0.98) as x increases from 0 to 1. In contrast to that, Nb1 - xTixNy films deposited under similar deposition conditions using DCMS exhibit open columnar structure, low hardness values (15 to 22 GPa), high electrical resistivity in the range of 200-360 mu Omega cm, and optical properties without clear correlation with the chemical composition of the films. The peculiar physical properties of these films, compared with those obtained by the hybrid process, are mainly attributed to their open columnar morphology. (C) 2015 Elsevier B.V. All rights reserved.