High-brightness LDP source for EUVL mask inspection

The Laser-assisted Discharge-produced Plasma (LDP) EUV source has been developed as a light source for actinic mask inspection and is currently deployed in the field. As the EUVL process is used more in the mass-production process, the requirement for EUV source for mask inspection is required more. LDP source enables the generation of high brightness with relatively large EUV plasma to fulfill these requirements. Ushio LDP source has overcome various issues specialized from LDP source and realized high reliability 24/7 based operation with high brightness maintained. In this paper, we address the followings: (1) LDP source configuration and its monitoring system, (2) Features of LDP source for inspection purposes, (3) Recent availability in the field, (4) Improvement of source stability and cleanliness, and (5) Roadmap of source availability.