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Phase-shifting effect of EUV masks with various absorber thicknesses has been studied both by simulations and experiments. In EUV lithography, masks with 180 phase shifting absorber work like embedded attenuated phase-shifting masks. At 66nm thickness of TaN/TaON absorber, 180 degree phase shifting can be achieved in theory. Based on the experiments, we observed that the true180 degree phase shifting can be achieved with absorber thickness between 66 and 76 nm. In this paper, phase shifting impact of the various thickness absorbers has been characterized. Imaging performance of masks with 51 nm, 66 nm and 76 nm thick absorber has been experimentally compared. The process window of various thickness absorber masks are rigorously studied.

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A multilayer coating of Mo∕Si is usually used for space science in the spectral range of extreme ultraviolet, especially for He-II (30.4nm) radiation, because it is highly stable under vacuum and atmosphere. The fairly high reflectivity of 15%–20% is achieved. But the space science community needs a higher reflective coating at 30.4nm for the future satellite missions. In this work, we report the design of a multilayer, consisting of a pair of Mg and SiC, and its fabrication, and result of the reflectance.

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