  We report on the near edge X-ray absorption fine structure (NEXAFS)
spectroscopy of hybrid organic-inorganic resists. These materials are
nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized
from organically modified precursors and transition metal alkoxides by a
sol-gel route and designed for ultraviolet, extreme ultraviolet and electron
beam lithography. The experiments were conducted using a scanning transmission
X-ray microscope (STXM) which combines high spatial-resolution microscopy and
NEXAFS spectroscopy. The absorption spectra were collected in the proximity of
the carbon edge (~ 290 eV) before and after in situ exposure, enabling the
measurement of a significant photo-induced degradation of the organic group
(phenyl or methyl methacrylate, respectively), the degree of which depends on
the configuration of the ligand. Photo-induced degradation was more efficient
in the resist synthesized with pendant phenyl substituents than it was in the
case of systems based on bridging phenyl groups. The degradation of the methyl
methacrylate group was relatively efficient, with about half of the initial
ligands dissociated upon exposure. Our data reveal that the such dissociation
can produce different outcomes, depending on the structural configuration.
While all the organic groups were expected to detach and desorb from the resist
in their entirety, a sizeable amount of them remain and form undesired
byproducts such as alkene chains. In the framework of the materials synthesis
and engineering through specific building blocks, these results provide a
deeper insight into the photochemistry of resists, in particular for extreme
ultraviolet lithography.
