Synthesis of Narrow Molecular Weight Distribution Norbornene-Lactone Functionalized Polymers by Nitroxide-Mediated Polymerization: Candidates for 193-nm Photoresist Materials

One hundred ninety three-nanometer candidate photoresist materials were synthesized by nitroxide-mediated polymerization (NMP). Statistical copolymerizations of 5-methacryloyloxy-2,6-norboranecarbolactone (NLAM) with 5–10 mol% of controlling co-monomers (which are necessary for controlled polymerizations of methacrylates by NMP with the initiator used) in the feed, such as styrene (ST), p-acetoxystyrene (AcOST), 2-vinyl naphthalene (VN) and pentafluorostyrene (PFS), using the unimolecular BlocBuilder® initiator in 35 wt% dioxane solution at 90 °C were performed. As little as 5 mol% controlling comonomer in the feed was demonstrated to be sufficient to lead to linear evolution of number average molecular weight with respect to conversion up to 50%, and the resulting copolymers had dispersities of ~1.3 in most cases, an attractive feature for reducing line width roughness (LWR) in photoresists. The copolymers generally showed relatively low absorbance at 193 nm, comparable to other 193-nm candidate photoresists reported previously, despite the inclusion of a small amount of the styrenic co-monomers in the copolymer.