As resist feature sizes and film thicknesses continue to shrink in dimension, a number of resist
feature size and film thickness dependent effects are being observed in the lithographic performance
of high resolution photoresists. In order to understand these phenomena, a better understanding of
the physiochemical behavior of complex multi-component organic resist thin films is needed. As a
first step in that direction, a series of model photoresists were studied in an effort to begin to
understand the thermophysical properties of such multi-component thin films. The influence of
photoacid generator (PAG) loading and PAG chemistry on the glass transition behavior using the
model photoresists was studied. A thermal flow experiment was used to characterize an "apparent
glass transition temperature" of the resist thin films as a function of PAG type and loading. These
results were compared to traditional glass transition measurements made on the same resist
compositions using differential scanning calorimetry (DSC). The two methods, namely DSC and the
thermal flow measurement, yielded very different results depending on the type of PAG used.
Further studies using ToF SIMS to profile the distribution of PAG in the resist thin films revealed
that the two PAGs focused on in this work, a triphenylsulfonium triflate (TPS.OTF) and a
triphenylsulfonium nonaflate (TPS.ONF), exhibited very different distribution behavior in resist thin
films. In the case of TPS.OTF, the PAG was observed to show a depletion region near the resistsubstrate
interface while the TPS.ONF PAG was relatively homogeneously distributed in the resist
thin films. In the case of TPS.ONF, it was also the resist system which showed very different
thermophysical behavior when comparing the glass transition temperature measured using DSC to
the thermal flow temperature measurement. This work points out the fact that component
distribution and thin film effects must be carefully considered in interpreting and analyzing the
behavior of multi-component thin films.
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