  The effect of applying a positive voltage pulse (Urev = 10 - 150 V) directly
after the negative high power impulse magnetron sputtering (HiPIMS) pulse
(bipolar HiPIMS) is investigated for the reactive sputter deposition of TiN
thin films. Energy-resolved mass spectroscopy analyses are performed to gain
insight in the effect on the ion energy distribution function of the various
ions. It is demonstrated that the energy of a large fraction of the ions can be
tuned by a reverse target potential and gain energy corresponding to the
applied Urev. Microscopy observations and x-ray reflectometry reveal
densification of the films which results in an increase in the film hardness
from 23.9 to 34 GPa as well as an increase in compressive film stress from 2.1
GPa to 4.7 GPa when comparing conventional HiPIMS with bipolar HiPIMS (Urev =
150 V).
