Extreme ultraviolet (EUV) microscopy is invaluable for the development of EUV photomasks, providing detailed information for the creation of new mask processes, and reliable feedback for comparison with printing studies. The SHARP microscope at Lawrence Berkeley National Laboratory is dedicated to photomask research. It was developed with forward-looking specifications that make it well suited to the emulation of current EUV lithography tools and a variety of possible future directions. Some recent examples include (1) the demonstration of imaging with 4x numerical aperture values up to 0.625, measuring patterns with feature sizes down to 30-nm half-pitch, created with a tin-based photoresist serving as the absorber. (2) The emulation of complex, free-form illuminators used in source-mask optimization, including grayscale pupil fills. (3) Point by point phase measurement from aerial image measurements using several techniques. (4) Direct observation of non-telecentric, through-focus imaging effects that arise from the angular-dependence of the mask’s multilayer coating properties. In addition, we are preparing to extend SHARP imaging to include anamorphic optics, an emerging area of EUV lithography research.
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Kenneth A. Goldberg ; Markus P. Benk ; Antoine Wojdyla ; David G. Johnson and Alexander P. Donoghue
New ways of looking at masks with the SHARP EUV microscope
", Proc. SPIE 9422, Extreme Ultraviolet (EUV) Lithography VI, 94221A (March 16, 2015); doi:10.1117/12.2175553; http://dx.doi.org/10.1117/12.2175553