NNT 2015 – Napa (California)

Thermal nanoimprint lithography (T-NIL) makes use of the thermomechanical properties of thermoplastic polymers. Crucial for pattern transfer and applications is that its mechanical, optoelectronic, chemical properties are not altered as a result of the NIL process. We compare the effects of T-NIL and pulsed-NIL (p-NIL) on the mechanical properties of PMMA, looking at possible effects such as local polymer densification by reduction of free-volume, residual birefringence by orientation of polymer chains and flow-induced crystallization and degradation through high mechanical pressure or shear. These effects would be expected to be more pronounced in the case of Pulsed-NIL in which much higher temperatures are attained. We report here the effects of T-NIL on the Young’s modulus at the surface of a nanoimprinted PMMA film, by using the PeakForce QNMTM mode available in the Bruker Dimension Icon AFM.

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Developing the capability of originating large-area truly seamless patterns from small size dies by nanoimprint lithography in a Step & Repeat (S&R) mode would represent an key milestone and an asset for several industrial applications. The availability of such technology would simplify the fabrication of both periodic (e.g. extended gratings of uninterrupted lines) and aperiodic continuos pattern of nanostructures up to square meters areas. However, in spite of the efforts, this goal has not been achieved yet by thermal-NIL nor by UV-NIL. In particular, in the case of thermal-NIL it is almost unavoidable that, while nanoimprinting a field, the already imprinted pattern in the surrounding areas relax (polymer reflow) due to unconstrained propagation of heat. We demonstrate here that Pulsed-NIL technology presented at the past NNT conference in Kyoto, has the potential to achieve continuous patterning in a Step & Repeat process.

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