Abstract
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.
Highlights
Nitroxide-mediated polymerization (NMP), a type of controlled radical polymerization (CRP), combines the practicality of conventional free radical polymerization with the good microstructural control usually associated with living polymerizations, like ionic polymerization [1,2]
The molecular weights were determined by calibration with linear narrow molecular weight distribution poly(methyl methacrylate) (PMMA) standards, and the Gel permeation chromatography (GPC) was equipped with a differential refractive index (RI 2410) detector
Well-defined random candidate copolymers rich in NLAM for 193 nm photoresists were synthesized for the first time by NMP at 90 °C in 1,4 dioxane solution with BlocBuilder® as the unimolecular initiator
Summary
Nitroxide-mediated polymerization (NMP), a type of controlled radical polymerization (CRP), combines the practicality of conventional free radical polymerization with the good microstructural control usually associated with living polymerizations, like ionic polymerization [1,2]. There are three basic requirements that all 193-nm (the current standard wavelength in the photolithography industry) resists have to satisfy: high optical transparency at 193 nm, good etch resistance and thermal stability to withstand high temperature processing conditions that are used in manufacturing [53,54] Due to their high carbon contents, polymers with alicyclic units, such as the adamantyl and isobornyl groups, have been shown to have high etching durability [55,56]. The copolymerization kinetics of NLAM with different controlling comonomers, i.e., p-acetoxystyrene (AcOST), styrene (ST), 2-vinyl naphthalene (VN) and pentafluorostyrene (PFS), was investigated, and the absorption properties of the NLAM-rich copolymers were studied This latter part is essential, as the methacrylate requires a controlling co-monomer for BlocBuilder-mediated NMP, which is often a styrenic, which can absorb at wavelengths near 193 nm.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
