Nanoimprint lithography

Nanophotonics and photonic integrated circuits are modern concepts to increase the functionality and density of photonic devices, epecially nanophotonic structures, such as plasmonic components and photonic crystals require lithography processes that are able to reach feature sizes of few nanometers. One attractive method for low cost nanopatterning is nanoimprint lithography (NIL). The investment in NIL equipment is modest which makes it available even for small research laboratories and companies. The resolution of this technique is good and so far it has been shown to be especially suitable for patterning photonic devices.

The NIL process is a mechanical replication process where a surface relief from a template is embossed on a thin polymer layer on the substrate. Two versions of NIL are typically employed: the first is based on thermal embossing of thermoplast polymers and the second is based on transparent stamps and UV-curable polymers. We use a method utilizing spin coating of the substrate with UV-curable resists (UV-NIL).

The materials used in the process need to be carefully selected. The master template and in some cases the stamp itself need to be coated with an anti-adhesion layer to improve their separation. The stamp can be soft, e.g. made of polydimethylsiloxane (PDMS) or hard, e.g. made of Ormostamp (Micro resist technology GmbH) or quartz.