Michael Muecke, Christian Heinrich, Buhler Leybold Optics Alzenau, Germany
The roll-to-roll production of complex multilayers by sputtering presents unique opportunities for various products. The number of available process compartments is limited compared to large inline coaters (e.g. architectural glass coaters). The primary parameter to adjust the individual layer thickness or coating speed is the process power.
In reactive sputtering, large changes in process power will cause a drift of the working point, leading to variations in the sputter rate and, consequently, in the optical properties. It is essential to maintain a well-defined process state to enable a robust thickness control over a wide process range.
In this work, an automated procedure is presented that determines the dependence of the working-point voltage on the applied power while operating the process in voltage. As a result, normalized sputter rates and layer uniformity across the web width are maintained, leading to stable optical properties.
The validity of the procedure is demonstrated using a multilayer coating application produced on an industrial large-scale roll-to-roll sputtering system.