Fundamental Aspects of Norbornene-Maleic Anhydride Co-and Terpolymers for 193 nm Lithography: Polymerization Chemistry and Polymer Properties

摘要

Radical co- and terpolymerizations of norbomene (NB) derivatives and maleic anhydride :MA) were in situ monitored in dioxane-d~8 at elevated temperatures by 'H nuclear magnetic resonance (NMR) spectroscopy. The 5-substitution on norbomene reduces the [)olymerization rate. The endo and e."o isomers of t-butyl norbomene-5-carboxylate are incorporated in the polymer at the same rate. In terpolymerization involving methacrylic monomers (t-butyl methacrylate, methacrylic acid), the third homopolymerizable monomer is much more rapidly incorporated in the p-olymer, with the ratio ofNB to MA in :he polymer significantly deviating from III. This observation indicates that the ;ommonly believed chain transfer (CT) mechanism is unfounded. In contrast. acrylic acid ind t-butyl acrylate are more uniformly incorporated in the terpolymer. Another evidence igainst the CT polymerization was obtained by applying the mercury method to analyze he monomer reactivities using gas chromatography. UV absorption of MA-NB polymers it 193 nm tends to be fairly high, which is a compounded effect of modest intrinsic ibsorption of the anhydride structure itself and a significant contribution from the polymer ~nd group. The anhydride ring can undergo hydrolysis during development when the natrix is polar enough to allow aqueous base penetration, which could enhance the ievelopment contrast but the anhydride hydrolysis could lower the storage stability.