Pattern replication of 100 nm to millimeter-scale features by thermal nanoimprint lithography

The aim of this work is to demonstrate the ability of nanoimprint lithography (NIL) to replicate patterns having feature sizes ranging from nanoscale to millimeter scale. The pattern replication process includes NIL on PMMA, PMMA RIE, metal liftoff and then silicon RIE for final pattern transfer. A tri-layer resist scheme was employed to facilitate the liftoff. We studied systematically the dependence of the maximum duplicable feature size on imprint temperature, pressure and time, which shows good agreement with a simple squeeze flow model. The maximum duplicable feature size also depends on PMMA molecular weight and the amount of PMMA RIE. For example, with NIL at 200 °C and 20 bar for 20 min and PMMA etching of 180 nm, we duplicated 1.3 mm square pattern without defects using 12 kg/mol PMMA. Such amount of PMMA RIE leads to the nanoscale grating line-width increase of 18 nm.