Thermo-correction of quasi-static optical distortions for EUV lithography

Now optical reducing systems for extreme ultraviolet projection lithography are being actively developed. Optical elements of these systems are required to be of super-high optical quality. For systems operating in the 13-nm wavelength range, their optical distortions should not exceed 1 nm in magnitude. Manufacturing of such elements with super-high optical quality requires large financial injections. In this report, we consider how to use thermal deformation of an optical element exposed to light for improvement of optical quality of the element. It is shown, in particular, that residual quasi-static large-scale (20% of diameter of the element) optical distortions, about 15 nm in magnitude, can be compensated with the proposed technique down to 0.5 nm (i.e. ≈ λ 0 /20 - λ 0 /30 for EUV).