Thermal stability of nanolayers for EUV optics

This thesis focuses on investigations of the thermal stability of nanolayers composed of Si, Mo, and Ru, with a particular emphasis on the optical lifetime of Extreme Ultraviolet (EUV) mirrors and ultra-thin membranes, known as pellicles. By studying the phenomenon of dewetting at the nanometer and atomic scales, we aim to understand the breakup of layered structures into agglomerates. Combining our research with a proactive approach, we explore potential solutions to address these challenges.
In this study, we examine the thermal evolution of ultra-thin nanolayers, including elemental Mo and Ru, as well as bilayers of Ru on top of Mo on Si(100) substrates with a native oxide. Our findings reveal that incorporating Mo as an interlayer between the Ru capping layer and the substrate significantly enhances the wetting properties of the Ru layer. Additionally, we demonstrate that the sputter deposition technique, commonly used in the industry, can readily achieve an amorphous arrangement for the binary metal alloy of Mo and Ru. Compared to traditional, polycrystalline films, these amorphous films exhibit superior smoothness.
Our investigation shows that the amorphous alloy films possess unexpectedly good thermal stability, making them a promising material for various applications. This research contributes to the understanding of nanolayer behavior under high-temperature conditions and presents potential avenues for optimizing the performance of EUV mirrors and pellicles.