Optimizing large area homogeneity for Ion beam sputtering thin film deposition: A multifaceted approach

Manufacturing coatings with precise spectral features and the required spatial homogeneity is challenging for extreme large substrates of about 2 m in diameter. Here, a digital twin model is presented that supports the new process development significantly to coat substrates of this size with high precision, suitable for interference coatings. Recent demands for these large optics originate from astronomy with large telescopes such as the Extreme Large Telescope (ELT). Since the established manufacturing processes do not scale efficiently with the substrate size, more effort is necessary to produce coatings with a thickness precision of about 1 % or better for single layers, which is often specified for high-quality interference coatings. Therefore, a novel concept for an ion beam sputtering plant with a moving ion source/target carrier is developed. The digital twin model combines several simulation methods in the virtual coater framework. Within this model, a method for determining the required movement track of the carrier is developed, which can then be easily transferred to experimental tests. Further atomistic simulations by molecular dynamics facilitate estimations of structural differences in the lateral dimension that mainly originate from parasitic sputtering. Also the findings are compared to preliminary experimental results.