Size dependence of quick cavity filling behavior in ultraviolet nanoimprint lithography using pentafluoropropane gas

Rapid bubble elimination using pentafuoropropane (CFH₂CH ₂CF₃, 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 mm, bubble elimination time was almost proportional to cavity width and could be defined as 0:00145 ×W (s). When the cavity width was 25 mm, 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.