| The research work presented in this thesis focuses on three topics: (1) studies of a critical step of nanoimprint lithography (NIL), the dynamic process of filling liquid resist into the imprint gap (2) development of novel nanofabrication approaches for 1D and 2D nanostructures and (3) self-improvement of pre-fabricated nanostructures through various Self Perfection by Liquefaction (SPEL) processes.The first part describes an innovative approach of filling the liquid resist in NIL gap, which directly affects NIL results and therefore attracts much attention. Recently dispensing-based NIL has been developed [8] in order to further reduce the system cost and achieve step-and-repeat NIL in the atmosphere. But it suffers from air bubble defects formed by feature pinning and the circling of residual air by the merge of multiple resist droplets. These air bubbles could stay in the resist for a long time and seriously affect the imprint quality. Thus we develop a novel approach of filling liquid resists into the air gap between the structured mold and the substrate based on capillary flow assisted by electrohydrodynamic (EHD) force. Our results have shown that the use of EHD force could result in a smooth and continuous flow, greatly reducing the chance of trapping air.The second part explores the feasibility of self-assembled systems as tools for nanofabrication. The principal objective is to guide a self-assembled process in such a manner so as to produce lithographic templates appropriate for subsequent device development. We were able to manufacture 65-nm-half-pitch gratings over large scale (cm2) via Fracture Induced Structuring (FIS) in which a thin homopolymer film fractures into periodic grating lines when confined between two rigid substrates. An overview of the experiments is presented. In addition, we explored the limit of FIS grating period and pushed it to 70 nm. Finally, we further develop Lithography Guided FIS as an innovative approach to make 2D integrated nanopatterns.In the last part, we tried to overcome the bottleneck in the nanofabrication---templates with sub-10-nm feature size. We developed various SPEL treatments, which could desirably reshape the pre-fabricated structures. High aspect-ratio grating lines have been achieved with smooth surface. Sub-10-nm lines/trenches have been demonstrated. By integrating the top-down lithography patterning techniques with this bottom-up approach, more complicated 3D mirco/nanostructures have been fabricated.Finally, we provide a brief summary of the work and possible directions for the future in chapter 6. |
