Tabletop storage ring MIRRORCLE extreme ultraviolet lithography source

Abstract

Advances of tabletop electron storage rings for generating a brilliant extreme ultraviolet (EUV) or soft x-ray beam are discussed. An electron storage ring called MIRRORCLE-20SX currently provides a stored beam current with an average of 3 A, a 1-minute lifetime, 15 ms radiation damping time, and a beam size of about 3 × 3 mm 2 . We generate EUV by a thin-film target placed in the electron orbit. Photons in the wavelength around 13.9 nm is generated by an Si thin film, and 4.3 nm by a diamond-like carbon (DLC) film placed in the circulating electron beam. It is known from previous experimental studies that the mechanism of EUV emission is a synchrotron Cherenkov radiation (SCR). The observed photon power is 14 W∕sr by the DLC film. We report that SCR is suitable for EUV lithography (EUVL) because the spectrum is monochromatic, the radiation angular spread is as narrow as 20 × 5 mrad 2 , and the emitter size can be 0.01 × 3 mm 2 . An optimized EUV source for lithography based on the tabletop synchrotron is proposed.