Flare in extreme ultraviolet lithography: metrology, out-of-band radiation, fractal point-spread function, and flare map calibration

摘要

The critical role of flare in extreme ultraviolet u0001EUVu0002 lithogra-nphy is well known. In this work, the implementation of a robust flarenmetrology is discussed, and the proposed approach is qualified both innterms of precision and accuracy. The flare measurements are comparednto full-chip simulations using a simplified single fractal point-spread func-ntion u0001PSFu0002, and the parameters of the analytical PSF are optimized byncomparing the simulation output to the experimental results. After flarenmap calibration, the matching of simulation and experiment in the flarenrange from 4 to 12% is quite good, clearly indicating an offset of aboutn3%. The origin of this offset is attributed to the presence of DUV light. Annexperimental estimate of the DUV component is found in good agree-nment with the predicted value.