Time resolved detection of particle contamination during thin film deposition

Particle contamination is a limiting factor for the quality of multilayer thin films, and to evaluate this effect, coated optics are typically subjected to an ex situ inspection. However, to identify the generation mechanisms of particles during the deposition process, it is necessary to record data in situ. In this work we report on a camera based detection method for time resolved particle measurements during plasma deposition processes. We analyze silicon substrates in the vacuum coating chamber by means of dark field illumination to reach high sensitivity to small defects on the substrate surface. We show camera images of the substrate, which document the evolution of particle contamination during the deposition process, and compare the results to microscopy. By providing a cost-efficient monitoring strategy, we take the steps towards an identification of particle sources in the vacuum chamber.