Penetration of Residual Layer in Nanoimprint Lithography by Direct Oxidation of Photocatalytic Film

INTRODUCTION The demand for the practical use of the nanoimprint lithography (NIL) has risen for the miniaturization in two-dimensional micro/nano fabrication technology. Photolithography is now used widely, however, has a few of difficulties such as the high equipment cost and the diffraction limit. NIL, in which a resist on a substrate is patterned by mechanical pressing a nanostructured mold, is expected to be a post-technology of photolithography [1]. However, in order to use NIL practically, there is a problem of residual layer. Residual layer is the part of resist which is remained in the convex part of mold by the viscosity in arranging resist by the nanoimprint. Then the process of O2-plasma etching is needed to remove residual layer in processing the substrate and this process causes a side etching. Figure 1 shows the schematic that the side etching prevents the miniaturization, which means pattern destruction because etching can not be completely anisotropy i.e., the resist is etched not only vertically but also horizontally. Here we propose the method of penetration of residual layer in NIL, which uses the oxidation of the titanium dioxide (TiO2) under UV irradiation for the penetration of the residual layer.