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

Rapid bubble elimination using pentafuoropropane (CFH 2 CH 2 CF 3 , 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...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 49; no. 6; pp. 06GL06 - 06GL06-5
Main Authors Youn, Sung-Won, Hiroshima, Hiroshi, Takahashi, Masaharu, Maeda, Ryutaro
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.06.2010
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Summary:Rapid bubble elimination using pentafuoropropane (CFH 2 CH 2 CF 3 , 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 \mbox{$\mu$m}, bubble elimination time was almost proportional to cavity width and could be defined as $0.00145\times W$ (s). When the cavity width was 25 \mbox{$\mu$m}, 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.
Bibliography:(Color online) (a) Schematic diagram of the quartz mold. (b) Optical microscopy image of a surface of a sample quartz mold. (Color online) (a) Schematic of nanoimprint stepper and microscope for real-time observation. (b) Photo of UV nanoimprint stepper with microscope system for real-time observation of bubble shrinkage. (Color online) Bubble shrinkage behaviors for different-sized cavities as a function of imprinting time; (a) $A = 160000$ \mbox{$\mu$m} 2 , $W = 400$ \mbox{$\mu$m}, (b) $A = 115600$ \mbox{$\mu$m} 2 , $W = 340$ \mbox{$\mu$m}, (c) $A = 22500$ \mbox{$\mu$m} 2 , $W = 150$ \mbox{$\mu$m}, (d) $A = 10000$ \mbox{$\mu$m} 2 , $W = 100$ \mbox{$\mu$m}, (e) $A = 5625$ \mbox{$\mu$m} 2 , $W = 75$ \mbox{$\mu$m}, (f) $A = 2500$ \mbox{$\mu$m} 2 , $W = 50$ \mbox{$\mu$m}, (g) $A = 625$ \mbox{$\mu$m} 2 , $W = 25$ \mbox{$\mu$m}. Optical microscope images were taken during imprinting by a real-time monitoring system. (Color online) Optical microscope images of checkered patterns with different cavity sizes fabricated by UV-NIL under pentafuoropropane flow of 2500 sccm: (a) $W = 340$ \mbox{$\mu$m}; $A = 115600$ \mbox{$\mu$m} 2 ; complete filling time, 0.5 s; (b) $W = 25$ \mbox{$\mu$m}; $A = 625$ \mbox{$\mu$m} 2 ; complete filling time, 0.033 s. Schematic drawings showing simplified cavity filling behavior of resin: (a) before contact between mold and resist, (b) mold sinking into a depth of d from the initial resist level and the resulting bubble. Bubble elimination time as a function of cavity area ($A$). (Color online) Bubble elimination time as a function of cavity width ($W$). Relationship between initial resist thickness and bubble elimination time. The quartz mold ($W = 150$ \mbox{$\mu$m}) with a pattern height of 93 nm was used for experiments.
ISSN:0021-4922
1347-4065
DOI:10.1143/JJAP.49.06GL06