We synthesized several new monomers with an acid-cleavable protective group and investigated their deprotection
reactions. Polymers were prepared using these monomers, and their thermal properties and dissolution rates were
investigated. The acidic reactivity of protective groups of these monomers was evaluated using a method we developed.
The activation energies [Ea(experimental)] calculated using reaction rate constants were found to correlate to some extent
with the activation energies [Ea(calculated)] calculated from MOPAC. The dissolution rates of some polymers containing
similar protective groups as structures were measured. The dissolution rates were related to the polarity and molecular
volume (MV) of the decomposed products of protective groups.
Characteristic matrix method was applied to study the anomalous Quartz-Crystal-Microbalance (QCM) data such as
sequential peaks of resonance frequency and impedance. The formation of swelling layer was found to cause the broad
peak of resonance frequency at the beginning of development. An impedance peak followed the frequency peak when
the rigidity of the swelling layer decreased to ca. 105 Pa due to absorption of the developer. Constant thickness of a
swelling layer makes double sets of sequential peaks in frequency and impedance. Continuous changes in swelling layer
thickness caused a single set of peaks during development. A fast data-acquisition system for QCM was set up and
showed the sampling time of 1 kHz with the accuracy of 0.5 nm. It gives good and precise information for resist of large
dissolution rate and interface region between resist and substrate.
In recent years, ArF lithography has required a half-pitch size (DRAM) of 45 nm or less. To achieve the
requirement, line edge roughness (LER) is recognized as one of the most serious problems in lithography today,
because LER directly degrades device characteristics and affects system performances. Although the uniformity of
polymer film is important for reducing LER, little is known about polymer morphology after coating. In this study, we
observed the surface of poly(methacrylate) samples after coating with AFM tapping mode and found specific
morphology in the phase images for the first time (the height image was flat).
We report effects of methacrylates with polar group on resist performance determined by Quartz crystal microbalance (QCM) method. We found that high composition ratio of mevalonic lactone methacrylate accelerates dissolution of the resist film, which is suitable for high resolution resist. In addition, dissolution rate of the resist film depends on the structure of polar monomer. Also, a difference of swelling depending on the structure of polar monomer was observed in a low exposure dose. We think that the polymer polarity and acid dissociation energy of pendant group were influential to these phenomena. This information is also useful to develop new materials for ArF lithography.