Application of Plasmask R resist and the DESIRE process to lithography at 248 nm

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Plasmask resist and its associated dry development process called DESIRE constitute one product which has incorporated surface imaging for lithography at 436 and 366 nm. Based on its performance at these wavelengths, Plasmask 150U resist is predicted to have a resolution limit of ∼0.3 μm at 248 nm with a 0.38 NA lens. Using best focus exposures of 1.5-μm thick films we have examined a variety of factors that influence the resolution and sensitivity of Plasmask 150U resist at 248 nm. These include standard processing steps as well as silylation with hexmethyldisilazane, plasma development conditions and equipment, and various descum techniques. Processing without a descum step resolved 75° profile, 0.3 μm line and space patterns at high exposure doses, but always afforded a grassy residue. Use of Ar sputter etching to remove ∼2200 Å from unexposed areas prior to plasma development afforded vertical profile 0.3-μm resolution patterns with no grassy residue.