Plasma State Control of Reactive Sputter Processes

Nonlinear reactive sputter processes are indispensable for the deposition of functional thin film layers. As the coating process is driven by a low pressure plasma the plasma state affects the thin film properties. The process behavior has specific properties. It is unstable, one specific input value can lead to different values of the plasma state and the same plasma state can be achieved by different input values. This unstable and ambiguous behavior requires a control system, which consists of a stabilizing controller, an estimation unit and a feedforward controller. In this paper, a design method for the plasma state control based of an input/output-model is proposed. Experiments show the effectiveness of the proposed control method.