Dynamic simulation of process control of the reactive sputter process using two seperate targets and experimental results

Recently, the control of reactive sputter processes has been dynamically simulated by integrating the Larsson differential equations. This was done by employing a fast Runge-Kutta step control algorithm, allowing simulation of reactive sputtering with more than 100-fold real time speed on a standard PC [1]. A simple PID-algorithm was implemented to simulate the process control via reactive gas flow at fixed current and the process control via current at fixed reactive gas flow. With respect to multi target processes and in-line vacuum coating machines the dynamic simulation was extended to simulate the process behavior of two separate targets A and B, which were coupled by the oxygen partial pressure. From these simulations strategies to adjust different target states of processes A and B can be obtained. In general, the processes A and B influcence each other in a complex manner, especially in the unstable transition mode, which is proposed for economic high rate processes. However, it turns out that both processes can be adjusted simultaneously also within the unstable transition mode at any desired combination of the two target states. To validate the simulation results, experimental results of process control involving two targets carried out in a batch coater are presented