Facile wide-scale defect detection of UV-nanoimprinted resist patterns by fluorescent microscopy

The occurrence of resist pattern defects in UV nanoimprinting with a spincoated resin thin film on a silicon wafer was studied by fluorescent microscopy using a fluorescent UV-curable liquid resin causing radical photopolymerization. The generation of nonfill defects with a surface-modified silica mold with submicrometer line cavities was compared between UV nanoimprinting atmospheres of air and pentafluoropropane. It was visualized in a rapid and nondestructive manner that nonfill defects were hardly induced by UV nanoimprinting under easily condensable pentafluoropropane atmosphere, while nonfill defects owing to bubble trap and resin adhesion to a mold surface were observed in the case of UV nanoimprinting under air atmosphere. The fluorescent microscopy using the fluorescent UV-curable resin was useful for mold inspection whether or not the submicrometer-scale mold cavities were partially filled with the resin. To investigate a resolution limit to nonfill defect, the authors examined a pattern pitch and a space width for convex resist line patterns in the line width range of 80-3000 nm with various ratios of space width to line width. Linear analysis of fluorescence intensity using fluorescent microscope images revealed that line pattern pitches with a space width of 0.30 μm could be detected by fluorescent microscopy. The 0.30 μm space width was almost consistent with a value calculated according to a Sparrow resolution limit.