The development progress of the high power LPP-EUV light source using a magnetic field

We report the status of the CO2-Sn-LPP (Laser-produced-plasma) EUV light source development at Gigaphoton. It is the high power 13.5nm light source solution for the manufacturing of semiconductor pattern below 7nm. Our unique and original technologies are; a combination of a pulsed CO2 laser with Sn droplets, dual wavelength laser application and Sn debris mitigation with a magnetic field. Providing high EUV power with high operation availability is a requirement for the EUV light source system. With above technologies, we have demonstrated a collector mirror reflectivity degradation rate of less than -0.5%/Bp at an average power of 125W at IF during a week of operation. We also achieved an inband power of 270W under dose-controlled operation and demonstrated a power scalability up to 365W. To achieve higher availability, we improved the two main factors that limit the operation availability, that are the lifetime of the collector mirror and of the droplet generator. The mirror lifetime is determined by the reflectivity degradation of the multilayer coating, due to hydrogen blistering, oxidation, as well as sputtering, implantation, and deposition by Sn ions, Sn atoms, and Sn fragments. Since our magnetic mitigation scheme works effectively for lower energy ions, we developed advanced pre-pulse laser irradiation to suppress the generation of high-energy ions from the Sn plasma without loss of the high EUV Conversion Efficiency of ~6%. We are also developing a new long-lifetime droplet generator with an inline Tin feed feature, that extends the lifetime of our droplet generators.