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Characterizing the degradation of PDMS stamps in nanoimprint lithography

: Tucher, N.; Höhn, O.; Hauser, H.; Müller, C.; Bläsi, B.


Microelectronic engineering 180 (2017), pp.40-44
ISSN: 0167-9317
Journal Article
Fraunhofer ISE ()
Solarzellen - Entwicklung und Charakterisierung; Photovoltaik; Silicium-Photovoltaik; Neuartige Photovoltaik-Technologien; Oberflächen - Konditionierung; Passivierung; Lichteinfang; Photonenmanagement; lithography; up-scaling; replication; lifetime; force microscopy

Within this work we investigate the lifetime of soft PDMS stamps as a critical parameter for the up-scaled fabrication of microstructures via nanoimprint lithography. We propose the characterization of the PDMS hardness as a suitable parameter for the stamp degradation. The increasing hardness for a larger number of imprints is attributed to resist diffusion into the PDMS volume and possibly subsequent cross-linking. Force-distance measurements with an atomic force microscope were applied to demonstrate for two acrylic materials that a lower average molecular weight leads to a faster degradation. Using a temperature-assisted UV-imprint process with an epoxy material (SU-8 2002) enabled more than 100 imprints without measurable degradation due to the complex molecular structure which we assume to reduce the resist diffusion. This can be a key development towards a higher stamp lifetime and finally an industrial realization of NIL.