Earlier work has been done on double exposures that exposed in the same resist a horizontal grating with x-dipoles and subsequently a vertical grating with y dipoles, without intermediate process steps. This yielded a high contrast image in resist at k1 <0.3.1 We show that an equivalent result can be achieved in a single exposure with a single mask, at admittedly high dose. We investigate the process parameters and the related mask tolerances, and find a non-intuitive result for the mask pattern that yields an optimized image at given mask specifications. Finally, we investigate the extension of this technique to EUV through simulations and experiments.
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Martin Burkhardt, Yongan Xu, Hsinyu Tsai, Alexander Tritchkov, Jörg Mellmann, "Ultimate 2D resolution printing with negative tone development," Proc. SPIE 9780, Optical Microlithography XXIX, 97800E (15 March 2016);