Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

Simulation of the cathode spot dynamics in vacuum arc discharges

: Rackwitz, N.

ECMI Newsletter 26 (1999), S.15-19
ISSN: 1013-9338
Fraunhofer IWS ()
Bogentechnologie; PVD

The commercial production of thin coatings in the micrometer or submicrometer range relies on PVD technologies (physical vapour deposition). One important PVD method makes use of an arc discharge under high vacuum conditions that generates a highly ionized plasma of cathodic material. The plasma condenses on a substrate that is placed in front of the cathode and forms a functional or decorative layer. The electrical discharge in vacuum is carried by theformation of so called cathode spots that concentrate the discharge energy in areas of only a few hundred 5m in diameter. This well known but in detail not sufficiently unterstood phenomenon exhibits a highly nonlinear dynamic behavior that leads to a rapid spot motion and to spontanous spot splitting and extinction events. Due to the high complexityof the inner spot processes, these outer spot dynamics are described only by phenomenological concepts (see [1], a work that still features the current point of view). The spot movement is related to important process conditions, i.e. droplet emission, long term target erosion patterns, and homogenity of the layer thickness on large substrates. Due to the in uence of magnetic felds on the spot motion it is possible to construct arc steering devices based on magnetic felds that are capable of optimizing the coating process with respect to the above listed conditions [2]. In order to better understand the cathode spot behaviour in magnetic felds and to efficiently construct and operate steering devices, work for a diploma thesis has been carried out at the department of mathematics of the TU Dresden and at the Fraunhofer Institute for material and beam technology (IWS) in Dresden on modelling and on computer simulation of the spot dynamics and the further calculation of the target erosion patterns and substrate located processes. The aim was to reduce production costs by increasing the target life time, simulation of new steering device designs, and low cost interactive staff training. The simulation model for the spot dynamics we introduce here could be shown to point out the signifcant features of the actual spot dynamics in magnetic felds. Especially the sensitiveness of the long term behaviour of the spot motion on extern felds was demonstrated.