The fidelity of pattern transfer in lithography relies on how much we can control the integrity of resist films and patterns throughout the process. It is necessary to avoid undesired instability and defects of the resist films in order to ensure the accuracy of the design. This thesis aims to investigate the instability and the surface morphology of polymer films....[ Read more ]

The fidelity of pattern transfer in lithography relies on how much we can control the integrity of resist films and patterns throughout the process. It is necessary to avoid undesired instability and defects of the resist films in order to ensure the accuracy of the design. This thesis aims to investigate the instability and the surface morphology of polymer films.

Spin coating is the most widely used technique to prepare polymer films. Unfortunately, surface patterns are often obtained in spin coated films. Consensus remains elusive till now regarding the formation of these surface patterns. In this thesis, the effects of solvents and substrates on the stability and the surface morphology of polymer thin films have been systematically studied. The stability and the surface morphology were found to depend on the competition of polymer-substrate and solvent-substrate interactions. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles were used to determine the distribution of end groups along the depth of the films. A high concentration of bromine end groups at the interface helps to prevent dewetting of films. An increase in the solvent-substrate interactions, which inhibited any contact between the polymer and the substrate, promoted dewetting of films. The addition of nanoparticles was able to suppress dewetting of films. The distribution of the nanoparticles along the depth of the films was obtained by ToF-SIMS depth profiling. The suppression of dewetting was attributed to the surface segregation of the nanoparticles because of their low-surface-tension surface coating. The structure of surface patterns was revealed by ToF-SIMS 3D microanalyses. For the first time, the surface patterns were unambiguously shown to be hollow rather than solid. Moreover, the structural parameters of the surface patterns were estimated from the retrospectively reconstructed depth profiles.

In addition, the effects of temperature and plasma treatment on the morphology of polymer films were also investigated in this thesis.