Parallel DSMC Gasflow Simulation of an In-Line Coater for Reactive Sputtering

Abstract

There is an increasing demand for high precision coatings on large areas via in-line reactive sputtering, which requires advanced process control techniques. Thus, an improved theoretical understanding of the reactive sputtering process kinetics is mandatory for further technical improvement. We present a detailed Direct Simulation Monte Carlo (DSMC) gas flow model of an in-line sputtering coater for large area architectural glazing. With this model, the pressure fluctuations caused by a moving substrate are calculated in comparison with the experiment. The model reveals a significant phase shift in the pressure fluctuations between the areas above the center and the edges of the substrate. This is a geometric effect and is e. g. independent of the substrate travelling direction. Consequently, a long sputtering source will observe pressure fluctuations at its center and edges, which are out of phase.

For a heuristic model of the reactive sputtering process, we show that in certain cases a two-dimensional model treatment is sufficient for predicting the film thickness distribution on the moving substrate. In other cases, a strong phase shift between averaged pressure fluctuations and reactive sputtering process response is observed indicating that a threedimensional model treatment is required for a realistic simulation of the in-line deposition process.