As resist feature sizes and film thicknesses continue to shrink in dimension, a number of resistfeature size and film thickness dependent effects are being observed in the lithographic performanceof high resolution photoresists. In order to understand these phenomena, a better understanding ofthe physiochemical behavior of complex multi-component organic resist thin films is needed. As afirst step in that direction, a series of model photoresists were studied in an effort to begin tounderstand the thermophysical properties of such multi-component thin films. The influence ofphotoacid generator (PAG) loading and PAG chemistry on the glass transition behavior using themodel photoresists was studied. A thermal flow experiment was used to characterize an "apparentglass transition temperature" of the resist thin films as a function of PAG type and loading. Theseresults were compared to traditional glass transition measurements made on the same resistcompositions using differential scanning calorimetry (DSC). The two methods, namely DSC and thethermal 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 revealedthat the two PAGs focused on in this work, a triphenylsulfonium triflate (TPS.OTF) and atriphenylsulfonium nonaflate (TPS.ONF), exhibited very different distribution behavior in resist thinfilms. In the case of TPS.OTF, the PAG was observed to show a depletion region near the resist-substrate interface while the TPS.ONF PAG was relatively homogeneously distributed in the resistthin films. In the case of TPS.ONF, it was also the resist system which showed very differentthermophysical behavior when comparing the glass transition temperature measured using DSC tothe thermal flow temperature measurement. This work points out the fact that componentdistribution and thin film effects must be carefully considered in interpreting and analyzing thebehavior of multi-component thin films.
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