Photocurable Silsesquioxane-Based Formulations as Versatile Resins for Nanoimprint Lithography

Abstract

Methacrylate octafunctionalized silsesquioxane (SSQMA) was shown to be an ideal material with high performance for ultraviolet (UV)-based nanoimprint lithography (NIL). The total viscosity of SSQMA-based formulations was adjusted to between 0.8 and 50 cP by incorporating low-viscosity acrylic additives, making the formulations suitable for UV-based NIL. The cured SSQMA-based formulations showed numerous desirable characteristics, including low volumetric shrinkage (4%), high Young's modulus (2.445-4.272 GPa), high resistance to oxygen plasma, high transparency to UV light, and high resistance to organic/aqueous media, as a functional imprint material for UV-based NIL and step-and-flash imprint lithography (SFIL). Using both techniques, the SSQMA-based formulations were easily transferred to relief structures with excellent imprint fidelity and minimal residual thickness. Formulations containing 50% SSQMA (wt %) were able to reproduce high-aspect-ratio nanostructures with aspect ratios as high as 4.5 using bilayer SFIL. Transparent rigiflex molds and hard replica molds with sub-50-nm size features were reproducibly duplicated by using UV-NIL with the SSQMA-based resin. Nanostructures with feature sizes down to 50 nm were successfully reproduced using these molds in both UV- and thermal-NIL processes. After repeating 20 imprinting cycles at relatively high temperature and pressure, no detectable collapse or contamination on the replica surface was observed. These properties of the SSQMA-based resins make them suitable as inexpensive and convenient components in all NIL processes that are based on physical contact.