Polymer Films’ Residual Stress Attenuation from the Supramolecular Complexation with Ultra-Small Nanoparticles for High Resolution Nanoimprint Lithography

Abstract

Nanoimprint lithography (NIL) has been broadly applied in the fabrication of nano-patterned polymer films for cost-efficiency and high through-put; however, the intrinsic tradeoff between mechanical strength and residual stress of polymer films significantly limits the NIL resolution while the harsh processing conditions limit its versatile applications to different substrates. Herein, 1 nm metal oxide cluster, phosphotungstic acid (PTA), is used to complex with polyvinyl alcohol (PVA) for high-resolution NIL that can be operated at large-scale and mild conditions. The ultra-small size of PTA enables dense supramolecular interaction with PVA for the diminished crystallinity and accelerated chain dynamics that help relax the residual stress during film casting. Meanwhile, the PTAs serve as supramolecular crosslinkers for the increased modulus of the films (ca. 2 GPa), providing promising dimensional stability required for high-resolution NIL. Simple casting the aqueous blend on a master mold successfully gives a residual stress-free film with sub-2 nm resolution at wafer scale (>100 cm²). The mild processing at ambient condition permits broad NIL applications to diverse substrates, e.g., integrated circuit chips, compact discs, PET nano gratings and even delicate bio-surfaces.