Effects of plasma non-homogeneity on the physical properties of sputtered thin films

The plasma generated in a two-target closed field unbalanced magnetron sputtering system for thin film deposition is characterized by means of Hall probes and cylindrical Langmuir probes as a function of the position inside the vacuum system. The plasma potential, electron density and temperature profiles in different locations are measured by two diagnostic systems equipped with cylindrical Langmuir probes. The plasma non-homogeneity due to the presence of magnetic field gradients is evaluated. In order to test the effects of measured plasma non-homogeneity on the physical properties of sputter-deposited coatings, several substrates are put inside the chamber in regions characterized by different plasma density and plasma potential. The composition, microstructure and morphology of TiNx films grown onto these substrates are then studied by means of nuclear techniques (RBS, n-RBS, NRA, ERDA), X-ray diffraction (XRD) and secondary electron microscopy (SEM). The mechanical properties are determined by micro-scratch test and nanoindentation and correlated to the local plasma parameters.