میکروسکوپ فلورسانس برای کنترل کیفیت در لیتوگرافی nanoimprint

Fluorescence microscopy is introduced as a low cost quality control process for nanoimprint lithography. To depict imprinted structures down to 1 μm lateral size and to detect residues down to 100 nm lateral size, the standard printable polymer mr-I8000 is labelled with less than 0.1 wt.% fluorescent dye. Three different types of stamps are used to determine the dependence of the shape and size of stamp features in a series of imprints. The quality of a stamp is given by the sticking polymer residues per unit area. Fluorescence light images as well as visible light images are analysed. Changes in the area of the stamp covered with polymer as a function of the number of imprints is summarised in a statistical process chart. Adhesion was artificially induced in order to observe self cleaning of virgin stamps. They were detected and monitored, suggesting that this method is a suitable technique for quality control and that it could be easily adapted to the nanoimprint process.

In recent years nanoimprint lithography (NIL) has been developed as a low cost method for the fabrication of nanoscaled patterns. Nanoimprint lithography is a parallel process in which a structured stamp is pressed into a soft or softened polymer layer [1] and [2]. Due to its projected reliability, throughput and low cost nanoimprint lithography is seen an alternative to conventional nanometer scale patterning technologies like, e.g. electron beam lithography. Prints on 6″ wafers [3] and master for nanostructures down to 10 nm [4] have been demonstrated. To become a real alternative on industrial scale it is necessary to combine the process of NIL with a reliable and fast quality control routine to guarantee both the quality of the stamp and the quality of the imprint. Generally, scanning electron microscopy (SEM) and atomic force microscopy are used to evaluate the quality of prints or the status of the stamp. In this investigation, fluorescence microscopy has been the method of choice for nanoscale quality control because it opens ways to circumvent the resolution limit to access quality information. The status of a stamp depends on the amount of fluorescent polymer residues on its surface. These residues can be detected using a CCD-technology coupled to the fluorescence microscope.

Fluorescence microscopy is a quick and easy tool to evaluate stamp and imprint quality when a fluorescence labelled polymer is used. Since the experimental set-up allows a non-contact assessment of the whole stamp surface without additional sample preparation, serial measurements are performed easily. This measurement technique may facilitate NIL inspections and process control in the future.