High resolution soft mold for UV-curing nanoimprint lithography using an oxygen insensitive degradable material

Abstract

Soft nanoimprint lithography has been developed to overcome the disadvantages of conventional nanoimprint lithography based on rigid molds. Hybrid nanoimprint-soft lithography mold is an efficient strategy to improve the resolution of soft nanoimprint because a rigid UV-curable material is used as the structural layer. In this paper, the authors design a novel UV-curable material for hybrid soft mold fabrication, which is degradable under mild acidic conditions and insensitive to oxygen during photopolymerization. The material comprises an acid-degradable cross-linker, 2,10-diacryloyloxymethyl-1,4,9,12-tetraoxaspiro[4.2.4.2] tetradecane, and an acyrlated polysiloxane, poly[(mercaptopropyl)methylsiloxane]. Oxygen sensitivity of acrylate groups during UV curing is avoided due to the cross-linking mechanism based on thiol-ene chemistry. The cured material can be decomposed into linear chains through the cleavage of acid-labile ketal links and dissolved in organic solvent when heated in an acidic solution. The material possesses necessary properties for mold fabrication and imprinting, including low shrinkage (about 5%), high modulus (1.4 GPa), high thermal stability, high UV transparency and stability in normal environment. Furthermore, since the cured material is degradable in acidic media, the stained master can be renewed in a mild condition. Various nanoscaled patterns are fabricated on planar and curved substrates via UV-nanoimprint when the same material is used as a patterning layer.