Morphology of nanoimprinted polyimide films fabricated via a controlled thermal history

Abstract

Fabricating nanopatterns on polyimide (PI) films directly by nanoimprint lithography (NIL) is difficult owing to the high glass transition temperature (Tg). In this study, a nanopatterned PI film was successfully obtained by nanoimprinting poly(amic acid) (PAA) film and curing it afterward. Differential scanning calorimetry, thermogravimetry and dynamic mechanical analysis were carried out to study the state of thermal molecular motion in PAA thick films that have the same content of residual solvent as the PAA thin films used in NIL. The thermal and dynamic mechanical behaviors of PI thick films were studied for comparison. An appropriate nanoimprinting process was proposed based on an understanding of the thermal and dynamic mechanical properties of PAA and PI films. Atomic force microscopy showed that the line pattern was transferred without distortion from the PAA film to the PI film, even though a larger shrinkage took place during the hard baking. The surface of polyimide (PI) film was successfully patterned by nanoimprinting poly(amic acid) (PAA) film and then hard baking. An appropriate nanoimprinting process was established through the study of the thermal and dynamic mechanical properties of PAA and PI film. Atomic force microscopy revealed that line pattern was transferred from silicon mold to PI film successfully and the nanostructures remain undamaged even though a larger shrinkage took place during the hard baking.