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In this study, the top coating (TC) resist and new top coating free (TCF) resist at the condition of immersion patterning
process have been evaluated and compared in the respect of leaching rate, process margins and immersion related defects.
The 55nm of dense L/S patterns are defined by using immersion process. The leaching rates of TCF resist are
investigated for the different conditions of baking temperatures and leaching times. Their measurements have been done
for the cation and anion dissociated from PAG under the conditions of unexposed and exposed areas. The cation leaching
rate of new TCF resist is 1.4 × E-13 mol/cm2.sec at the unexposed area. It is lower than the spec suggested by ASML.
From the leaching data, it is confirmed that the TCF resist can apply for the patterning without top coating material. The
process margins of TCF resist are slightly wider than those of TC resist in the respect of depth of focus and energy
latitude. And the top loss of TC resist and TCF resist are 20nm and 8nm, respectively after development process. The
immersion related defects are also investigated for these resists. The defect map of TCF resist shows much fewer defects
than those of TC resist. The immersion related defect of TCF resist is not founded among the patterns and the number of
micro-bridge defect is fewer than 5. The defect level of TCF resist is more stabilized by optimizations of chemical
structure of resist and process. From the experimental results, it is confirmed that the TCF resist is available to apply for
device production of sub-55nm technology. Especially, the application of TCF resist can reduce the process step of top
coating and also make the improvement of through-put with cost of ownership in process. Therefore, the TCF resist
should be progressively studied and applied for device production in the respect of improvement of device property and
process simplification.
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