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

Abstract

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. OPEN ACCESSPolymers 2014, 6 566

Synthesis of Narrow Molecular Weight Distribution Copolymers for ArF Photoresist Materials by Nitroxide Mediated Polymerization

“…The statistical copolymerizations of GBLMA/HAMA/MAMA with small amounts of ST as controlling comonomer (experiments termed GHM/ST) were done by NMP using BlocBuilder as the initiator in 35 wt% 1,4 dioxane solution at 90 °C (with a ratio of 10 mol% free SG1 nitroxide initially relative to the BlocBuilder). The ratio of GBLMA, HAMA, and MAMA in the initial mixture was matched to the compositions used previously in RAFT terpolymerizations, which in turn were selected based on their favorable lithographic properties . The composition of the copolymers was determined as follows.…”

“…The ratio of GBLMA, HAMA, and MAMA in the initial mixture was matched to the compositions used previously in RAFT terpolymerizations, [6] which in turn were selected based on their favorable lithographic properties. [53] The composition of the copolymers was determined as follows. For GBLMA: These initial experiments with ST comonomer were done to examine the effect of different target degrees of polymerization at complete conversion on the polymerization.…”

Nitroxide‐mediated polymerization of adamantyl‐functional methacrylates for 193 nm photoresists

“…The hydroxyl group of HAMA aids in the solubility and stability of the polymer. MAMA is particularly sensitive to 193 nm light, and improves the etching resolution (chemical amplification) . In photolithography, feature reproduction depends on the photoresist polymer's properties.…”

“…No attempts have however been made to use nitroxide mediated polymerization (NMP) for methacrylic‐based photoresist resins with the exception of 5‐methacryloxy‐2,6, norboranecarbolactone (NLAM) . This is likely due to the notion that NMP is only applicable to a certain set of monomers.…”

“…This lack of discolouration is important, as the polymers need to be transparent for the UV‐irradiation to be effective. Usually, the controlling co‐monomer is a styrenic and 2,3,4,5,6‐pentafluorostyrene (PFS) was chosen as the controlling monomer as it was found to have low absorption in the range near 193 nm and would thus not interfere with the photolithography process . Further, it has potential to be useful in immersion lithography due to the low surface energy of the fluorinated groups .…”