Angle-resolved evolution of the composition of Cr-Al-C thin films deposited by sputtering of a compound target

The composition of multi-element thin films deposited by magnetron sputtering of a compound target may significantly differ from the target composition. Differences in the sputter emission characteristics (angle and energy distributions) and transport of the sputtered species through the gas phase for different elements were shown to be responsible for this phenomenon (Neidhardt et al 2008 J. Appl. Phys. 104 063304). The evolution of the composition of Cr-Al-C thin films deposited by magnetron sputtering of a compound target is investigated as a function of the deposition pressure. The pressure was varied from 0.2 to 3.0 Pa, corresponding to a pressure-distance product range 1.4-21.0 Pa cm. Additionally, the influence of the angle between the target normal and the line between the target and the substrate on the composition is investigated in the range 0 degrees-67.5 degrees. Good agreement between the experimental data and an extended Monte Carlo model based on dynamic (TRIDYN) and static transport of ions in matter (TRIM) simulations is observed for a ternary compound target with a mass ratio of the target constituents of up to 4.3. Furthermore, the influence of the surface binding energies (SBEs) of the target constituents on the thin-film composition is discussed. The simulations indicate that scattering within the collision cascades in a compound target rather than the SBEs determine the character of the angular distribution functions of the sputtered species and, consequently, the thin-film composition. The extended Monte Carlo model employed here predicts variations in composition between the compound target and the as-deposited thin films as the pressure-distance product and the angular orientation of the film with respect to the substrate are varied.