Using NanoImprinting for Optics Applications

Nanoimprint lithography [1][2][3] is a verified production technology for a variety of applications, from creating microlenses [4] to use in the production of vertical-cavity surface-emitting lasers (VCSELs) [5].

Nanoimprint is executed on the wafer-scale in most of these applications. Roller-based nanoimprint has been suggested very early on for larger areas [6]. Roll-to-roll based nanoimprint [7][8][9] has undergone several developments. However, in the case of roll-to-plate NIL utilizing rigid substrates, much less have been refined.

To solve the limitations of large-area nanoimprinting on opaque and rigid substrates, Stensborg has developed roll-to-plate nanoimprint tools based on light-curing. It is established on Stensborg's patented concept [10] and includes a translucent cylinder and a substrate translation stage. A translucent imprinting template can be connected to the cylinder. Inside the rotatable cylinder,  an optical engine is placed which cures the curable substrate material. The optical engine emits light, which is directed to the nip. The nip is the place where the imprinting template and the substrate material meet.

The roll-to-plate nanoimprinting tools that are currently produced and installed manage substrates with sizes of up to 30 x 60 cm2 and plate thickness of up to 10 mm. The imprinting speed can vary from 1 to 10 meters per minute. Slot die coating and inkjet printing equipment are options that can be installed to include coating abilities for large areas.

Stensborg has performed initial imprinting tests. To carry out these investigations, a primed glass substrate was fixed onto the granite substrate table. A polymer foil was attached to the glass substrate and a light-curable imprint material was applied with slot die coating.

Linescan (Profilometer) of a roll-to-plate imprinted micro optical test structure, feature height approximately 45 µm, period approximately 100 µm.

Figure 1. Linescan (Profilometer) of a roll-to-plate imprinted micro optical test structure, feature height approximately 45 µm, period approximately 100 µm. Image Credit: Stensborg

Linescan (AFM) of a roll-to-plate imprinted holographic test structure, feature height approximately 350 nm, period approximately 880 nm.

Figure 2. Linescan (AFM) of a roll-to-plate imprinted holographic test structure, feature height approximately 350 nm, period approximately 880 nm. Image Credit: Stensborg 

Characteristics with a broad variety of dimensions were replicated successfully. Figure 1 shows a line scan of a micro-optical test structure, and a line scan of a test-hologram is shown in Figure 2.

Optical micrograph of a hologram test pattern corresponding to Figure 2.

Figure 3. Optical micrograph of a hologram test pattern corresponding to Figure 2. Image Credit: Profaktor 

Photograph of the roller during imprinting with a printing plate mounted to the roller.

Figure 4. Photograph of the roller during imprinting with a printing plate mounted to the roller. Image Credit: Profaktor 

The period of the features along with the height vary by multiple orders of magnitude. A standard imprinted hologram structure is demonstrated in Figure 3. An image of the device throughout nanoimprinting, including the imprinting template, can be seen in Figure 4.

Due to the material combinations that were evaluated, the separation was very effective. It was not necessary to adhere the polymer foils on the glass substrate to enable effective separation following the imprinting.

Imprinting plates produced from a light-curable resin material or light-curable PDMS were used along with X29 imprinting resist from Stensborg. In both combinations, the separation was instant, so the foil isolated itself from the imprinting plate.

Stensborg will publish additional imprinting results with a larger range of micro- and nanoscale characteristics, and also the further results from a large area coating of light-curable materials.

Acknowledgments

Produced from materials originally authored by L. Yde1, L. Lindvold1, J. Stensborg1, T. Voglhuber2, H. Außerhuber2, S. Wögerer2, T. Fischinger2, M. Mühlberger2, and W. Hackl3from Stensborg1, PROFACTOR GmbH2 and Forster Verkehr- und Werbetechnik GmbH3.

References and Further Reading

[1] Chou, S.Y., et al., J Vac Sci Technol B 14 (1996) 4129.
[2] Haisma, J., et al. J Vac Sci Technol B 14 (1996), 4124.
[3] Schift, H., J Vac Sci Technol B26 (2008) 458.
[4] Heptagon, (accessed 4.4.2016)
[5] Verschuuren, M.A., presented at NNT2011
[6] Tan, H., et al,. J Vac Sci Technol B 16 (1998) 3926.
[7] Thesen, M.W., et al. Microel Eng 123 (2014) 121.
[8] Ahn, S.H., et al., Advanced Materials 20 (2008) 2044.
[9] John, J., et al., Nanotechnology 24 (2013) 505307.
[10] Lindvold, L., Stensborg, J., Rasmussen, T., EP 1150843 B2Lindvold, L., Stensborg, L.Yde., GB1814552.4

This information has been sourced, reviewed and adapted from materials provided by Stensborg.

For more information on this source, please visit Stensborg.

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