Controllability Analysis of Reactive Magnetron Sputtering Process

Reactive magnetron sputtering deposition is one of the major established techniques for deposition of both metallic and nonmetallic thin films on various substrates; it is a very nonlinear process, and exhibits hysteresis behavior with respect to the reactive gas flow. This nonlinearity is characterized by a sudden change in sputtering rate and fraction of compound formation. Most of the problems encountered in the preparation of compound films by reactive sputtering are due to the hysteresis effect. The industrial applications request high rate deposition processes. To meet this demand, it is necessary to have a very good control system of such processes and to ensure a stable sputtering in the transition mode by using closed loop reactive gas control. Therefore, the controllability analysis is an important issue. The aim of this paper is to study the controllability of reactive sputtering process, especially in the transition region; a simple mathematical model based on Berg's original proposal is used. Analysis results show that the reactive magnetron sputtering process shows unstable behavior in the transition region and it is a controllable process.