High-power impulse magnetron sputter deposition of TiB_x thin films: Effects of pulse length and peak current density

We report on a systematic study of the effect of pulse length (ton = 25 - 200 mu s), and peak target current density (JT,peak = 0.25 - 2.0 A /cm2) during HiPIMS deposition of AlB2-phase TiBx thin films from a TiB2 target at a pressure of pAr = 1.33 Pa (10 mTorr) and substrate temperature T-s = 500 C-degrees. All films are under-stoichiometric with B/Ti = 1.36-1.89, with the higher values corresponding to longer pulses and higher JT,peak values. While the deposition flux, including both ions and neutrals, in general increases with increasing ton and JT,peak, the Ti+ ion flux saturates, resulting in the higher B/Ti values under these conditions. Thus, the relative amount of Ti ionization, and the degree to which these ions are guided toward the substrate by magnetic fields, are main modulators determining the composition of TiBx thin films.