| dc.description.abstract | Extreme ultraviolet (EUV) reflectors require exceptionally high reflectivity. However, during usage, contaminants can reduce reflectivity, significantly affecting production yield. To maintain high-quality reflectors, it is essential to remove carbon contamination, tin contamination, surface oxidation layers, and etching debris. This can be achieved by cleaning the mirror surface with hydrogen ions. Prolonged hydrogen ion bombardment can cause bubbles on the mirror surface, leading to damage and reduced reflectivity. Therefore, this paper investigates the effects of hydrogen ion bombardment on EUV mirror capping layers.
In this study, a B4C/Mo/B4C/Si multilayer film was deposited on a Si substrate using an ion beam sputtering machine. The ion beam voltage and current for each material were fixed. Surface roughness was analyzed using an Atomic Force Microscope, and preliminary film thickness was determined with an X-Ray Reflectivity. Cross-analysis was performed using a High-Resolution Scanning Transmission Electron Microscope. By adjusting the deposition time, higher reflectivity was achieved. Measurements using an EUV Reflectometer showed a reflectivity of 51.6% at a 19° incident angle.
Due to the high-energy radiation exposure during the operation of EUV lithography machines, the capping layer can be contaminated, leading to surface oxidation and hydrogen bubbles during cleaning. Literature indicates that oxide capping layers exhibit good oxidation resistance and hydrogen resistance. Therefore, in this study, an oxide capping layer was deposited on the mirror surface using an Atomic Layer Deposition system after the reflector was completed. The mirrors were subjected to hydrogen ion bombardment at a fixed voltage and current for various durations. Scanning Electron Microscopy, Atomic Force Microscopy, and High-Resolution Transmission Electron Microscopy were used to measure and analyze the surface morphology, roughness, and cross-sectional conditions of the mirrors. | en_US |