The Plasma Matrix is used to clean soda lime glass for the fabrication of CdS/CdTe and CIGS thin film solar cells. Substrates are typically 1 inch2 glass with a 1 mm or 4 mm thickness for the CdTe and CIGS solar cells, respectively. The fabrication of high efficiency photovoltaic devices requires that the substrate surface is extremely clean and free of contaminants (e.g. dust and grease). Therefore, prior to the glass being loaded in to the Plasma Matrix, the glass is cleaned with acetone and isopropanol solvents. The substrate is positioned vertically in the chamber using an in-house made sample tray to ensure the cleaning of both sides of the glass. The sample tray also allows for multiple substrates to be cleaned concurrently. Removal of any residual organic material is conducted by bombarding the surface with ionized molecules in the Plasma Matrix. No additional gas supplies are required, as the machine uses ambient air as the source of the ionized molecules. The RF magnetron generator operates with a power of 96 W and DC bias voltage of 390 V at room temperature. The Plasma Matrix reaches a vacuum of 4,7×10-1 mbar in under 90 s, and the glass is sufficiently clean for thin film deposition after only 10 minutes.
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