(95w) Small Molecule Segregation in Thin Polymer Films with Implications in Immersion Lithography
The purpose of this research was to study the effect that immersion has on the segregation of small molecules in thin polymethyl methacrylate (PMMA) films. In particular, anthracene, trioctylamine (TOA), and triphenylsulfonium perfluoro-1-butanesulfonate (TPS-PFBS) were used due to their implications in immersion lithography. Near Edge X-ray Adsorption Fine Structure (NEXAFS) spectroscopy was utilized to make the surface measurements necessary to study to the segregation of the different molecules within the PMMA films and from the resulting spectra the data could be examined qualitatively as well as quantitatively. Neat PMMA films and PMMA films containing the desired small molecule were immersed in water containing the small molecule and pure water, respectively. By doing this it was shown that for the model system, PMMA/anthracene, it is more favorable for anthracene to leach out of a PMMA/anthracene film into pure water than for anthracene to leach into a neat PMMA film from solution. The same result was also observed for the PMMA/TOA and PMMA/TPS-PFBS systems. The PMMA/TPS-PFBS system was studied the most extensively, immersions in TOA solutions were performed and also the effect of ultraviolet exposure was studied. No effect was seen when UV treatment was done before immersion versus after immersion. However, when the neat PMMA films were immersed in TPS-PFBS and then exposed to UV light there was much more TPS-PFBS present than when the PMMA/TPS-PFBS films were immersed in pure water and then exposed. This result is the opposite of what was observed previously when there was no UV exposure involved. Also, the PMMA/TPS-PFBS films that were immersed in TOA showed that it was more favorable for TOA to leach into the films than for anthracene to do so.