PHOTOSENSITIVE SALT DISTRIBUTION IN POLYMER-FILMS STUDIED BY F-19 MULTIPLE-QUANTUM NMR

In this work, the dispersion of triphenylsulfonium metal-fluoride salts in polymer films modeling chemically amplified resist systems has been characterized by solid-state F-19 multiple-quantum nuclear magnetic resonance (MQ-NMR). Previously, this technique has been used to characterize H-1 distributions on a length scale of approximately 20 angstrom in various materials. In agreement with differential scanning calorimetry, metal-fluoride salts were shown to be immiscible with the nonpolar polymers poly(n-butyl methacrylate) (PnBMA) and poly-(isobutyl methacrylate) (PiBMA), with no indication of individual salt molecules solubilized within the polymer matrix. Metal-fluoride salts in poly(methyl methacrylate) (PMMA) were observed to be dispersed on a molecular scale even at a salt loading of 20% w/w. Although observed by electron microscopy, evidence of larger aggregates is absent in the MQ-NMR data of the salt/PMMA films, indicating that these aggregates represent a small fraction of the total salt in these films. In addition, unlike electron microscopy, MQ-NMR is nondestructive with respect to the photosensitive salt and polymers comprising resist systems.