Infrared thermography-assisted detection of surface alteration during plasma cleaning and implications on subsequently deposited magnetron sputtered films

In this work, we report on anisotropic surface alteration of aluminium (AA2024 Alclad) and steel (M2) substrates by plasma cleaning using pulsed DC voltage. It is found by means of thermography and scanning electron microscopy that the ion bombardment leads to formation of cone-shaped structures in the region near the edge while the topography in the centre of the samples stays almost unaffected. In case of aluminium substrates, the cones arise from sputtering and redeposition of aluminium oxide whereas in case of high-speed steel they emerge due to different sputtering yields of the base material and the embedded carbides. There is some evidence that these cones strongly affect the size and density of growth defects (hillocks) in subsequent deposited films. Furthermore, the effect of parameters like table voltage and gas pressure on the temperature distribution is shown illustrating the potential of thermography as a powerful tool to optimise the parameters of plasma etching and film deposition.