Dendritic Polyphenol with an Improved Glass Transition Temperature for Microelectronic Applications

In this study, we report the synthesis of a dendritic polyphenol characterized by a high glass transition temperature (Tg), comparable to that of poly(4-hydroxystyrene). Although the molecule (DP8) was designed to have a molecular weight as low as 1169 g/mol with eight hydroxyl groups, it exhibited a Tg of ca. 160 °C along with a stable amorphous nature when prepared from the trityl chloride structural motif. The beneficial effect of its high Tg was revealed when DP8 was converted to an acid-labile derivative, DP8-tBOC, with tert-butoxycarbonyl (tBOC) protective moieties. Compared to its smaller counterpart based on six hydroxyl units, DP8-tBOC could survive at higher temperatures, with a slower acid diffusion rate under proton injection conditions. These characteristics enabled the formation of 130 nm thick, 50 nm wide patterns in a lithographic experiment using a focused electron beam. As a versatile building block, DP8 was also derivatized into a fluoroalkylated molecule, DP8-PPVE, which produced 50 nm-sized features under electron-beam lithographic conditions. These results demonstrate the strong potential of the low-molecular-weight, high-Tg DP8 molecule as an extreme UV resist platform for high-resolution microlithography.