Compact 13.5-nm free-electron laser for extreme ultraviolet lithography

Optical lithography has been actively used over the past decades to produce more and more dense integrated circuits. To keep with the pace of the miniaturization, light of shorter and shorter wavelength was used with time. The capabilities of the present 193-nm UV photolithography were expanded time after time, but it is now believed that further progress will require deployment of extreme ultraviolet (EUV) lithography based on the use of 13.5-nm radiation. However, presently no light source exists with sufficient average power to enable high-volume manufacturing. We report here the results of a study that shows the feasibility of a free-electron laser EUV source driven by a multiturn superconducting energy-recovery linac (ERL). The proposed 40×20m2 facility, using MW-scale consumption from the power grid, is estimated to provide about 5 kW of average EUV power. We elaborate the self-amplified spontaneous emission (SASE) option, which is presently technically feasible. A regenerative-amplifier option is also discussed. The proposed design is based on a short-period (2–3 cm) undulator. The corresponding electron beam energy is about 0.5–1.0 GeV. The proposed accelerator consists of a photoinjector, a booster, and a multiturn ERL.