Extreme ultraviolet sources based on gas jets

Summary form only given. EUV lithography is the principle application for the gas jet source. To maximize EUV lithographic printing speed, efficient collection of emitted source power with multilayer-coated condenser optics is necessary. Motivated by the need to maximize condenser lifetimes for reliability and lower cost, the interaction of the gas jet plasma with these nearby optical surfaces has been studied. Initial experiments revealed that multilayer mirrors placed 10 cm from the plasma retained 90% of their original reflectance after an exposure of 1×10⁸ plasma pulses; an improvement of a factor of >200 compared with the best solid targets. The mechanisms of reflectance loss and methods for reducing it will be discussed