Application of a Theory for Generation of Soft X-Ray by Storage Rings and Its Use For X-Ray Lithography

A theory has been developed for generation of soft X‐ray transition radiation (TR) by storage ring synchrotrons. It takes into consideration that the dielectric constant of the TR target material is a complex number, utilizes an explicit expression for the number of passes of an injected electron through the target, and describes more precisely the absorption of TR in the target. Such TR can be used for performing X‐ray lithography (XRL), and therefore a formula is included for the sensitivity of the photoresist used in XRL. TR targets for XRL can be optimized, based on finding a maximum of the resist sensitivity. Application of this theory to optimization of Mg target shows that a target containing only one Mg foil, with a thickness of about 245 nm is the best Mg target, for performing XRL by our storage ring synchrotron MIRRORCLE‐20SX.