High-brightness extreme-ultraviolet light sources are required for mask inspections and metrology, including mask blank inspection, actinic pattern inspection, and aerial image measurement system to improve yield and lower cost of ownership. Laser-produced plasma (LPP) light sources have the highest potential to achieve the brightness requirements for all the range of mask inspection tools currently foreseen. High brightness of LPP sources (100 to 1000 W/mm2 sr) is the result of a smaller source size ( ∼ 0.1 mm) than that of competing technologies. Since brightness is inversely proportional to the area of the source, smaller source size corresponds with greater brightness and hence greater inspection throughput.
At the Laboratory for Energy Conversion of ETH Zurich, a fully operational continuous-running multi-kHz LPP light source has been developed over the last five years and is now undergoing system optimization. Adlyte, a spin-off of ETH Zurich, is working with industry leaders to commercialize this LPP source. Individual subsystem configuration and the physical boundary conditions and limitations that affect power, brightness, stability, and lifetime management are discussed. This integrated system produces a measured brightness of 259 W/mm2 sr. Outlook for the future growth and integration of the source in high-volume manufacturing tools is then discussed.