Wearable electronic device and flexible electronics formed a potential market in the recent years. Circuit fabrication on non-flat surface becomes more and more important to the industry. The nano-patterning technology is the foundation of all the high performance electronics. High resolution nano-structures in the electronic components not only provide a higher calculation speed but also lower the energy consumption of the device. Current processes for high resolution nano-patterning, like UV-lithography and E-beam lithography are only applicable to flat Si wafers surface. Making nano-feature on non-flat substrate is still a big challenge in this field. And the traditional lithography system requires high cost in facility set up because the process is sensitive to temperature fluctuati...[ Read more ]

Wearable electronic device and flexible electronics formed a potential market in the recent years. Circuit fabrication on non-flat surface becomes more and more important to the industry. The nano-patterning technology is the foundation of all the high performance electronics. High resolution nano-structures in the electronic components not only provide a higher calculation speed but also lower the energy consumption of the device. Current processes for high resolution nano-patterning, like UV-lithography and E-beam lithography are only applicable to flat Si wafers surface. Making nano-feature on non-flat substrate is still a big challenge in this field. And the traditional lithography system requires high cost in facility set up because the process is sensitive to temperature fluctuation and vibration. In order to make breakthrough in new generation consumer electronic devices, there is a demand for high-precision low cost nano-patterning technology which can be applied to both Si wafer and flexible substrates.

Nanoimprint lithography (NIL), which is based on the mechanical embossing principle, is a promising process to produce high resolution nano-patterns. However, the application of NIL is limited by the yield and resolution.

This thesis develops a low cost and high resolution nano-patterning process, which is suitable for both rigid and flexible substrate material. The process is based on roller type ultraviolet nanoimprint lithography (UV-RNIL). By using UV-curable polymer resist, room temperature and low pressure nano-patterning process was achieved. The application of flexible soft molds in the UV-NIL made the conformal contact with large area non-flat substrate surface become possible. The nano-patterns in the soft mold were duplicated from pre-patterned Si master mold by simply casting. Roller type printing machine was used to gradually apply the imprint force over the entire patterning area. A de-molding-free UV-NIL process was demonstrated by using a water dissolvable polymer (polyvinyl alcohol) for soft mold fabrication. Micro and nano-scale patterns can be transferred together within a single process cycle. The separation of imprint and curing process leads to a high printing speed and high product throughput. Si wafer and Polyethylene terephthalate (PET) film were tested as substrates material. Measurement from both SEM and AFM showed that high fidelity nano-pattern with feature size down to 30 nm were transferred by the process.

The thesis study the relationship between the defects and process parameters. The efficiency of NIL is improved by minimizing the mold distortion and the delamination. The process avoided the potential defects caused by the mechanical de-molding, and achieve a high yield of high resolution nano-pattern transfer. A near zero residual layer thickness was achieved in the proposed NIL process, which is ideal for further cleaning room processing.

A multi-scale simulation method, which can predict the adhesion force at the de-molding interface in UV NIL system, is worked out in this study. The simulation can calculate interfacial stress at nano-scale by molecular dynamics. And it is linked to macro-scale finite element model to simulate the mechanical de-molding process. The result is able to be tested and verified by the standard thin film peel-off experiment.