Cleaning of an Optical Filter

ToF-SIMS was used to monitor the cleaning efficiency during the production of an optical filter. In an initial experiment, surface spectrometry was used to identify the nature of contaminants present on the sample before and after the final cleaning step. The analysis clearly identified a contamination by triglycerides and dodecylbenzenesulfonate salts before the cleaning. The amount of both was greatly reduced after the final drop-and-wipe cleaning with acetone.

However, mass spectrometry without localization did not give the full picture. Therefore, in a second experiment, ToF-SIMS imaging in macro scan mode (i.e. imaging of the chemical composition on large areas, in this case 60 x 60 mm2) was performed. Dodecylbenzenesulfonate salt was still detected in localized spots. Other compounds like smaller oxygen-containing hydrocarbon fragments were also detected with inhomogeneous distributions. Therfore, ToF-SIMS analysis revealed that the conventional drop-and-wipe method as a final cleaning step was not performing efficiently.

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