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

摘要

Now optical reducing systems for extreme ultraviolet projection lithography are being actively developed. Opticalelements of these systems are required to be of super-high optical quality. For systems operating in the 1 3-nmwavelength range, their optical distortions should not exceed 1 nm in magnitude. Manufacturing of such elements withsuper-high optical quality requires large financial injections. In this report, we consider how to use thermal deformationof an optical element exposed to light for improvement of optical quality of the element. It is shown, in particular, thatresidual quasi-static large-scale (20 % of diameter of the element) optical distortions, about 15 nm in magnitude, can becompensated with the proposed technique down to 0.5 nm (i.e. A/2O -X/3O for EUV).