Title:
High sensitivity nonchemically amplified molecular resists based on photosensitive dissolution inhibitors
High sensitivity nonchemically amplified molecular resists based on photosensitive dissolution inhibitors
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Author(s)
Lawson, Richard A.
Tolbert, Laren M.
Henderson, Clifford L.
Tolbert, Laren M.
Henderson, Clifford L.
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Abstract
A new class of nonchemically amplified molecular resists has been made based on the use of photosensitive protecting groups. The deprotection during exposure converts a dissolution inhibiting compound into a dissolution promoter. The key benefit of the use of molecular resists in this application is that they can exhibit a sharp solubility transition with relatively low levels of deprotection. Two different inhibiting compounds were made that use a 2-nitrobenzyl protecting group; NBnDCh, an aliphatic molecular resist based on deoxycholic acid, and NBnHPF, based on an aromatic molecular resist containing two phenol groups. Blending these compounds with a calixarene dissolution promoter allowed the contrast and sensitivity of the resist formulations to be tuned. Contrast ratios as high as 27 and deep ultraviolet (DUV) sensitivities between 150 and 400 mJ/cm2 were obtained using NBnDCh. NBnHPF based systems not only showed somewhat lower contrasts but also exhibited much lower clearing doses of only 60 mJ/cm2 and smaller. One particular NBnHPF formulation possessed a sensitivity of 10 mJ/cm2 and a contrast of 8.3, and it was even possible to formulate one resist with an extremely low dose-to-clear value of only 1 mJ/cm2. Such low dose-to-clear values in nonchemically amplified resists have, to the authors’ knowledge, not been reported before. The Dill C parameter for each of the two systems was quantified using Fourier transform infrared spectroscopy. The sensitivity of the NBnHPF systems was found to be very good because they undergo a solubility transition at 75 mol % inhibitor; this means that some formulations only need 0.5% photoconversion to pattern. Despite the excellent DUV sensitivity of these systems, it was found that they do not possess high sensitivity when exposed using extreme ultraviolet or e-beam exposure sources.
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2010-11
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