Understanding defects in ultrathin polymer films is of great importance to the microelectronics industry. We have taken the approach of trying to understand factors in polymer mobility by changes in glass transition temperature (Tg) and dewetting behavior. Incorporating fullerite into polystyrene (PS) films increased Tg relative to pure films. Photocrosslinkable PS showed a linear decrease in Tg with decreasing film thickness. Pyrene end-tagged polystyrene (PS-Py) and PS (both Mw = 4k) were compared on glass and gold substrates. Fluorescence data gave evidence of a higher probability of pyrene groups in proximity to the gold interface. This change in spatial distribution would be related to increases in Tg and suppression of dewetting for PS-Py films on gold.
We have used ellipsometry to study the glass transition temperature (Tg) of thin films (thicknesses 4-300 nm) of monodisperse polystyrene (PS-M), polydisperse polystyrene (PS-P), and a Shipley photoresist base polymer (SBP) with and without photoacid generator (PAG) on silicon substrates. For films less than 40 nm thick, Tg values decreased with respect to their bulk values for PS-M and SBP films. Films containing PAG exhibited further reduction of Tg values as predicted by the Fox equation to within experimental error.