Evaluation Method of "Formablity" in Nano/Micro Processing and Its Application to Inprint Lithography

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An idea of "formability" which stands for fundamental possibility of forming and is independent of existing forming methods has been proposed. This idea can be used to evaluate how much the effort to develop a new forming technique for producing new products has practical possibility. In this study, we have developed a method of qualitative and quantitative evaluation of the "formability" in nano/micro processing and we have applied it to inprint lithography that is expected to be one of the new forming methods in the next generation. The application has clarified theoretical possibility and limits of the new method as follows :(1)"Formability" in inprint lithography consists of mold releasability and transferability. Mold releasability is, semi-quantitatively, classified into three levels depending on interfaces where separation begins : separation between mold/resin, separation between resin/resin and separation between resin/base. The basic factors for mold releasability are the ratio of cohesive energy of resin-mold to base-resin and the aspect ratio of a shape to be formed. Quantitatively, mold release is possible when the ratio of cohesive energy of resin-mold to base-resin is less than or equal to 1. However, in case of large aspect ratio, the ratio of cohesive energy should be decreased for condition of good mold release, because the ratio is in inverse proportion to the aspect ratio.(2)Transferability is, semi-quantitatively, classified into three levels based on the degree of deformation of resin after mold release. This transferability depends on the energy ratio (B/A) and the aspect ratio (E/D), where 'A' is cohesive energy of resin, 'B' is cohesive energy between resin and mold, and (E/D) is the aspect ratio of a shape to be formed. Quantitative condition for good transferability is(E/D)【less than or equal】-4×(B/A)+3,while for(E/D)【greater than or equal】-4×(B/A)+4,transfer from mold to resin is impossible.