Positive- and Negative-Tone CVD Polyacrylic Electron-Beam Resists Developable by Supercritical CO2

Resist layers sensitive to electron-beam (e-beam) exposure and developable in supercritical carbon dioxide (scCO2) can be synthesized by initiated CVD (iCVD), resulting in an all-dry lithographic process. The low energy and low temperatures of the iCVD method permit the retention of the irradiation-sensitive pendent organic functional groups, and the incorporation of the fluorinated acrylates needed for increased solubility in scCO2. Negative-tone contrast is realized through crosslinking of the epoxy group of glycidyl methacrylate (GMA) when copolymerized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA). The Fineman-Ross equation describes the systematic tuning and random nature of the composition of these iCVD films. Positive-tone contrast with non-swelling 300 nm features was achieved through the anhydride-stabilized chain-scission reactions in post-annealed iCVD copolymers of methacrylic acid (MAA) and perfluoroalkyl ethyl methacrylate (PFEMA). The CF3 end groups in PFEMA contribute to higher scCO2 solubility than DFHA, allowing development of PFEMA copolymers with lower content of fluorine-containing component at milder condition than DFHA copolymers.