Spatially-resolved spectroscopic optical emission of dc-magnetron sputtering discharges in argon-nitrogen gas mixtures

The spatially-resolved spectroscopic optical emission of various lines of a dc-magnetron sputtering discharge (with cylindrical symmetry) is studied. The discharge works with an aluminium-based alloy cathode. Ar-N-2 gas mixtu res are used. Emission lines corresponding to the cathode (Al) and the gas discharge species (Ar, N-2, N-2(+), N) are considered. The three-dimensiona l emission profiles, I(r, z), of the lines are measured, where r is the dis tance from the centre of the cathode and z is the height from the cathode. I(r, z) profiles are studied as a function of the total pressure, the gas c omposition and the electrical power. In order to compare the results, I(r, z) profiles are fitted with an empirical analytical function. It turns out that the three-dimensional emission profiles of the various lines behave di fferently. The results are understood by taking into account the motion of electrons in our measured magnetic field distribution and the role of elect rons in populating the upper levels of the optical transitions.