Liquid Tin Droplet Generator in Laser-Produced Plasma Extreme Ultraviolet Source: A Review

The 13.5-nm extreme ultraviolet (EUV) light radiated by laser-produced tin droplet plasma is successfully used in manufacturing integrated circuits with critical dimensions (CDs) below 7 nm. As a vital component in the EUV source, the tin droplet generators (DGs) are comprehensively investigated. We focus on the principle, mechanical structure, and performance parameters of tin DG from aspects of industrial manufacturing and scientific research. Moreover, we analyzed the existing droplet control schemes and droplet synchronization technology for long-term laser-droplet alignment. Finally, the potential development direction for tin droplet targets is summarized.