Study of the behaviour of monomers in thermal nanoimprint lithography

Abstract

Thermoplastics are commonly used in thermal nanoimprint lithography (NIL) but their high viscosity leads to inhomogeneities of residual thickness in patterns with various densities. Monomers exhibit low viscosity and are imprinted easily and polymerized with UV–NIL processes. These monomers can be also used for thermal NIL. We have imprinted A-POSS material which is spontaneously polymerized at 170 °C. The inorganic part of this monomer is interesting for pattern transfer and for permanent applications. Thermal properties of this molecule are presented in this paper. It is shown that polymerization occurs at 170 °C, and that the viscosity is 1330 mPa s at ambient temperature. Imprint experiments have demonstrated that A-POSS flows over larger surfaces during imprint step, compared to thermoplastics. Patterns with different densities have been studied and different filling regimes have been observed depending on material viscosity. They are induced by a competition between material flow and mold deformation. Finally, we imprinted some nanoelectrodes simultaneously with millimetric large connection pads, and it was demonstrated that complete filling was obtained with monomers whereas this was not possible with thermoplastics.