DC magnetron discharges in argon-nitrogen gas mixtures have been characterized by optical emission spectroscopy (OES). Optical lines from the cathode species (aluminium) and the gas mixture (argon, nitrogen) have been measured at constant total pressure, as a function of the gas mixture composition and electrical power. The experimental data are compared with results of a theoretical plasma model which solves self-consistently the Boltzmann equation for electrons and the kinetic equations for aluminium, argon, molecular and atomic nitrogen states. The emission intensity variations of plasma species have been analysed versus the nitrogen relative concentration and electrical power and compared with calculated populations of emitting species with a satisfactory agreement. The variation of aluminium density versus the nitrogen concentration has been deduced by using the Al * line intensity and excitation rates given by the model.
A plasma model of a dc magnetron glow discharge of an Ar-N 2 mixture, with an aluminium target, is extended in order to explicitly include plasma-surface interactions. Theoretical results are compared with experimental data from optical emission spectroscopy of Al. The effect of the nitrogen concentration is studied. The theoretical calculation trends are in good agreement with the experimental results. The present work allows (1) the theoretical evaluation of the concentration of sputtered Al species and (2) the evaluation of the relative roles of the sputtering mechanisms and the contribution of the various species.
By means of dc-reactive sputtering, it is possible to vary the stoichiometry of deposited zirconium nitrides, by varying the molar fraction of N2 in an Ar–N2 gas mixture. In order to understand the origin of this effect, a theoretical model of reactive sputtering is devised. It is based on the study of reaction kinetics taking place at the surfaces of the cathode and the chamber walls. In fitting the model with experimental data, it turns out that one has to introduce the roles of Ar, N2, and N species. For reactive sputtering of ZrNz films, a good fit is obtained when it is assumed that the molar fraction of N is constant when the molar fraction of N2 increases up to about 75% (under our experimental conditions). Above this concentration of N2, the concentration of N has to increase. By the analysis of the theoretical model, general scaling laws between experimental parameters (current, pressure, and areas of the cathode and the chamber walls) are easily obtained.
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 mixtures are used. Emission lines corresponding to the cathode (Al) and the gas discharge species (Ar, N 2 , N + 2 , N) are considered. The three-dimensional emission profiles, I (r, z), of the lines are measured, where r is the distance 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 composition 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 differently. The results are understood by taking into account the motion of electrons in our measured magnetic field distribution and the role of electrons in populating the upper levels of the optical transitions.
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