Relaxation of structures made by Nanoimprint Lithography
Un article de Surface du verre et interfaces.
Fabien Roberrini - Jérémie Teisseire - Etienne Barthel - Elin Sondergard
Relaxation of PMMA structures
Nano-Imprint Lithography (NIL) is a powerful technique for surface texturation at nanoscale size. It uses direct impression of stamp, usually on thermoplastic polymers films, resulting in a strong potential for large area, low cost texturation.
However, due to the nanoscale size of structures, the Laplace Pressure plays an active role on their stability. This effect is particularly pronounced with soft materials as polymers near or above their glass transition temperature (Tg) where the material flow is possible. This issue can have a very important impact on process like step and repeat or roll to roll used to make large patterned area.
Indeed NIL is often applied to thin films and the slowing down of the flow due to confinment is a primary concern. So we focalise our study on the impact of confinement on the dynamics of material flow during the NIL. We work on PMMA thin films with different thicknesses in order to measure by AFM the evolution of structures's profil during annealing.
Optical measurement
To follow the relaxation of structures during the annealing should give many advantages. For that aim, we are developing an in-situ optical set-up based on the diffraction of a laser beam on a printed grating in a thin film. The objective is to measure the intensity of diffracted order (-1, 0 and 1) to follow the evolution of the height of structures during annealing.
We want to observe in-situ the impact of confinement on relaxation time with a model material (PMMA). Besides, we search to analyse the relaxation of a reactive material like sol-gel (see Nanostructuration by sol-gel embossing).