Approach toward environmental stabilization of chemical amplification resists

A molecular design for stabilization of chemical amplification resists toward airborne contamination is described, which is based on our observation that glass transition temperatures (Tg) primarily govern the absorption of N-methylpyrrolidone (NMP) vapor in thin polymer films. Employing the meta-isomer (Tg=85 °C) of poly(t-butoxycarbonyloxystyrene) (PBOCST) to replace the para-isomer (Tg=130°C) in the IBM's tBOC resist has proved the validity of our Tg theory in NMP uptake measurements as well as in negative lithographic imaging. Furthermore, the use of a meta-isomer to lower Tg for better annealing has been shown to be also useful in decreasing NMP absorption in aqueous base developable,. positive copolymer resists, providing increased contamination resistance. We believe that annealing of resist films to minimize free volume plays a key role in environmental stabilization of chemical amplification resists. © 1993, The Society of Photopolymer Science and Technology(SPST). All rights reserved.