Eliminating short and long term drifts in reactive sputter coating of glass

Dermot Monaghan, Victor Bellido-Gonzalez, Benoit Daniel, Sarah Powell, John Counsell
Gencoa Ltd

This paper introduces the concept of combining fast and slow feedback control with measured plasma properties in order to maintain a systems operation at optimum level with enhanced up-time and reduced energy costs. Plasma emission monitoring (PEM) for fast feedback control is typically used when maintaining a reactive sputtering process in high rate transition mode. Slow feedback can be used to determine the state of the system and measure drifts in plasma properties with time and provide the appropriate corrections or operator warnings. The slow feedback is ‘condition monitoring’ and helps to predict maintenance cycles and failure of the plasma process. This results in products within the given specifications. In order to provide a more robust PEM response from the process an ex-situ method is illustrated that used the plasma within a typical Penning vacuum measurement gauge to provide the process information. This can be used as a stand-alone signal or in combination with in-situ PEM measurements to enhance the suite of possible ‘sensors’ used to decide on the direction and maintenance of the process.

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