Control-oriented modeling and feedback control of reactive sputtering

This thesis investigates the nonlinear reactive sputter process in a novel way: both from the control-theoretical side and from the plasma-physical side.
The plasma behavior is explicitly considered for the process modeling and for the design of the control system to establish steady-state plasma conditions. By use of one of the presented control systems an unstable operation point of the process can be stabilized, which enables high deposition speed and a stoichiometric thin film subject to steady-state plasma conditions. In this framework, the plasma state is either defined by the self-bias voltage or the electron density. The application of the Multipole Resonance Probe allows to control the electron density as a quantity that directly characterizes the plasma state.
Experimental results validate the applicability of the developed models and of the developed control systems for various process conditions. Algorithms summarize the steps for the model identification as well as for the control system design. In addition, the technical components of the experimental set-up and dominant process drifts that occur are described in detail.