Size Dependence of Quick Cavity Filling Behavior in Ultraviolet Nanoimprint Lithography Using Pentafluoropropane Gas

Rapid bubble elimination using pentafuoropropane (CFH2CH2CF3, HFC-245fa, CAS No. 460-3-1) condensing gas is one of the most promising methods to realize ultrahigh-speed ultraviolet nanoimprint lithography (UV-NIL). In this study, we investigated the shrinkage behaviors and elimination time of bubbles for different cavity sizes and resist thicknesses by employing a UV-NIL stepper with a real-time monitoring system. As predicted, a smaller cavity size resulted in a faster filling. Unlike the prediction from an analysis model based on Stefan's equation, a nonlinear decrease in bubble elimination time was observed in accordance with the decrease in cavity size (area). Instead, a linear relationship between bubble elimination time and cavity width was found for a certain range of cavity widths (W). In the cavity width, range from 25 to 340 µm, bubble elimination time was almost proportional to cavity width and could be defined as 0.00145×W(s). When the cavity width was 25 µm, the complete filling time was less than 0.033 s, indicating the potential to realize a ultrahigh-throughput nanopatterning process. Regarding the effect of initial resist thickness on a bubble shrinkage behavior, bubble elimination time tended to increase with the decrease in resist thickness.