Abstract:

This thesis investigates the nanoimprint pressing methods, real-time monitoring and parameter control, and process optimizations and developments, aimed at moving nanoimprint lithography one step closer to becoming a suitable production technology with low cost, high throughput and high yield for the future nanostructure engineering.

The first part of the thesis focuses on the nanoimprint instrumentation. The advantages of a novel pressing method - air cushion press (ACP) is first discussed, including ultra-uniform pressure distribution and pattern uniformity, high throughput and yield, and the protection of molds and substrates. The ACP principle is used for all subsequent discussions throughout the thesis. The development and implementation of a non-destructive real-time nanoimprint monitoring method - real-time imprint monitoring using scattering-of-light (RIMS) is then discussed. RIMS serves a real need of nanoimprint lithography, and can be used for process monitoring, nanoscale material behavior study and investigating the effects of various nanoimprint conditions. It can also be used for automatic imprint parameter control for advanced nanoimprint machines.

The second part of the thesis focuses on the nanoimprint process optimizations and developments. With tools developed based on principles discussed in the first part, we get more insights about how to optimize the process parameters which can be achieved either manually or automatically. A novel nanoimprint process---thermally assisted photo-nanoimprint lithography (TAP-NIL) is presented and the process can improve the resist flow while at the same time retaining the desired post-imprint process properties of the resist. Finally, the nanoimprint process developments for fabricating subwavelength antireflective structures (SAS) are discussed. The fabrication processes are based on the unique 3D patterning capability of nanoimprint lithography. Fabricated structures demonstrate high performance over a broad wavelength range with a large angular tolerance. The possible application of SAS to waveguides is also explored.