Clearing residual resist in nanoimprint lithography by multi-mask

When UV-Nanoimprint Lithography(NIL) is used in manufacturing gratings of Distributed Feedback Laser Diodes(DFB LDs),the resist often turns into a high polymer after curing and can not be eliminated completely.To eliminate the residual resist,a multi-mask layer process was demonstrated.In this process,a 50 nm SiO2 hard mask was deposited between the wafer and the UV-curable resist and then traditional nanoimprint lithography based on soft stamp UV-imprinting was executed.Following that,the Inductively Coupled Plasma(ICP) dry etching was used to transfer the pattern on the substrate.Finally,it was rinsed with Buffered Oxide Etchant(BOE)for a few seconds.The effect of etching time on the duty ratio of grating was explored and the grating morphologies processed by traditional method and proposed method were compared.A scanning electron microscope image of rinsed grating shows that the grating with about 240 nm pitch and 82 nm depth offers a clean surface and a good feature.Therefore.The proposed method not only can eliminate the residual resist effectively but also can avoid the morphologic damage.