Kwantummechanische modellering van de interactie tussen extreem ultraviolet licht en materie

For many decades, progress in the electronics industry has been, and is still, driven by the miniaturization of integrated circuits (ICs). Besides getting smaller the circuit designs are also getting more and more complex. Creating the patterns to realize these circuits on a chip is performed by using photolithography. In photolithography a chemical photoresist is irradiated by laser light in the desired pattern. After washing away the non-reacted residue, the layer below the areas that are not protected by the reacted photoresist can be etched to form the desired pattern. The wavelength of the laser light ultimately restricts how small the dimensions of the printed patterns can be made. To produce the patterns of the next generation electronics we will need to use 13nm laser light. This light has an energy of 90eV and does not directly interact with the valence electrons, which participate in chemical bonding, but first with much more strongly bound core electrons. Working at these high energies, therefor, makes for a much more complex chemistry. Developing a better understanding of this chemistry is essential to enable the next generation of electronic devices. To investigate photoresist chemistry at EUV energies, imec has built a new lab, the AttoLab. At the AttoLab, the spectroscopic properties of the photoresists can be followed starting from only tens of attoseconds after the interaction with an EUV pulse. Changes in the various spectra indicate the occurrence of a reaction step or any other change in the material. However, determining what happened at the atomic level from the spectra alone is far from trivial. By comparing the measured spectra to results from quantum chemical calculations we can assign certain states of the material to specific spectra and so understand which reactions take place. Performing these calculations, making the comparisons, and modeling the full process will eventually develop the much-needed understanding of what happens in EUV photoresists and is the topic of this PhD. project. In this project theoretical methods for the study of light-matter interactions upon EUV radiation will be developed and implemented. These interactions involve both the excitation by the initial EUV pump and subsequent IR and optical UPS and XPS probe pulses. The reference materials will be chosen as systems of increasing complexity: single molecules in the gas phase, molecular crystals, pure reference polymer systems, and blend reference polymer systems. The benchmarking will be in close collaboration with the experimental AttoLab team. Finally, this modelling will be used to improve understanding of electron migration causing the chemical degradation processes upon EUV irradiation. Ultimately these improved insights will help the rationalization and control of EUV photolithography processes.