Easy release of mold in imprint lithography using ion-beam-irradiated photoresist surface

We demonstrate the successful release of a mold from an ion-beam-irradiated photoresist film without pattern destruction in nano-imprint lithography. A stripe-patterned V-shaped groove was used as a mold for the imprinting. The photoresist containing mainly novolac resin was used. The surface of the photoresist was modified by irradiating it with 100 keV argon ions with varying ion doses. It is found that the success rate of release increases with the increase of ion dose without any deformation of the transferred structure. It is also found that the modification of the photoresist surface can shorten the imprinting time. These improvements of the release and imprinting characteristics are caused by the existence of a stiffened layer at the photoresist surface produced by the ion-beam irradiation. We also demonstrate step-and-repeat imprinting using this technique.