Echtzeit-in-situ-Messung der Oberflächenbelegung einer Magnetron-Kathode bei der reaktiven Sputter-Abscheidung

Reactive Sputtering is a widely used technique in processing of thin compound films. Such films can be sputtered from metal targets, which are comparatively cost efficient. Also the fact that sputtering from metal targets can ccur in the dc mode reduces the cost of the sputtering equipment. To keep the deposition process stable, its necessary to know the effects of target poisoning including its hyteresis behavior. The aim of this work was to nvestigate the evolution of reactive gas coverage on a titanium magnetron target surface, by real time, in-situ ion beam analysis during magnetron sputtering. A cylindrical 2 inch magnetron was used for reactive sputtering of TiN. It was operated in an Ar/N₂ gas mixture at achamber pressure of about 3∙10^-3 mbar. The argon/nitrogen flux ratio was variated between 0 and 20%. The nitrogen concentration on the target was determinated using the ¹⁴N(d, α)¹²C, nuclear reaction at a deuterium beam energy of 1.8 MeV. Depending on the adjusted nitrogen flow the target incorporation varies between 0 and about 1∙10¹⁶ N∙cm^-2. Further the expected hysteresis behaviour ofnitrogen partial pressure, target voltage and nitrogen concentration at increasing/decreasing nitrogen gas flow is confirmed. The lateral distribution of nitrogen was measured across the diameter of target surface. In the zone of higher erosion (the "race track") the nitrogen concentration is 50% lower than in the middle or the edge of the target. A deposition zone in the center of the target could not be detected. By increasing the nitrogen flow into the chamber a saturation in nitrogen content in the target was found at an Ar/N₂ flow ratio of about 10%. Assuming nitrogen implantation with a depth of 2.5 nm under the influence of typical target voltage during magnetron sputtering, this saturation is at a concentration value where stoichiomtric TiN is formed. Within the precision of the measurements, a mobile fraction of nitrogen could not determined. The concentration in the target remains unchanged after switching off the magnetron.