Target voltage monitoring
A convenient sensor from the process is the target voltage output from the magnetron power supply. This can be used for some material combinations as a stand-alone signal or in addition to a secondary signal such as PEM. Successful materials for this type of sensor are silicon and aluminium oxides and nitrides.
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Plasma emission sensor - narrow bandpass filter
The visual light from the plasma contains information of all the species present via the optical emission spectrum. To monitor the intensity of any element in the plasma a narrow band-pass filter can be used to only allow the wavelength of light through of the material or gas of interest.
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Plasma emission sensor - CCD spectrometer
The plasma light can be captured by a CCD type spectrometer which provides a universal picture of the process. For control purposes the wavelengths of interest are electronically filtered and input to the controller. This type of tool is more flexible, however the integration time of the spectrometer slows down the feedback speed compared to the ‘edge’ filter method above.
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Lambda sensor - O2 probe
The Lambda sensor is an oxygen ‘sniffer’ which provides a direct signal of the oxygen concentrations present in the vacuum. The Gencoa Lambda sensor provides a robust signal with good response speeds. Like PEM, it can provide information from multiple monitoring zones down the target length.
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