A novel processing procedure for T/UV-NIL with negative tone resists

Abstract

The use of a conventional negative tone resist, like SU-8, for UV nanoimprint lithography (UV-NIL) allows the exploitation of the wide knowledge available for this material from micromechanical applications for nanoimprint. For this purpose a novel processing procedure is defined. SU-8 is used as a spin-coated layer; it is first flood-exposed and then thermally imprinted, the imprint simultaneously serving as the post exposure bake required for the cross-linking of the material. By an evaluation of the residual layer height obtained after imprint the changes of the material properties upon exposure and upon temperature treatment are investigated. An optimized T/UV-NIL processing sequence is defined for SU-8 in terms of a two-step process, where, after flood exposure, the imprint is performed at 50^oC followed by heating to 100^oC and cross-linking, within the non-transparent Si stamp.