Polymer Chain Configurations in Constrained Geometries: Ultrathin Films for Microlithography

摘要

Ultrathin (0.9 -15.3 nm) poly(methyl methacrylate) (PMMA) films prepared by the Langmuir-Blodgett (LB) technique have been explored as high resolution electron beam resists. One eighth micron lines-and-spaces patterns have been achieved by using a Perkin Elmer MEBES I pattern generation system as the exposure tool. The etch resistance of films with thicknesses greater than 4.5 nm is sufficient to allow patterning of chromium film suitable for photomask fabrication. Monolayer PMMA films containing 5 mol% pyrenedodecanoic acid (PDA) as a probe were prepared by transfer to the substrate at different surface pressures and characterized by fluorescence spectroscopy. The ratio of excimer to monomer emission intensity has a maximum value at 10 dyn/cm, which may be related to a structural rearrangement in the film. Intrinsic bilayer PMMA films prepared at 1 and 19 dyn/cm have also been examined by transmission electron microscopy. The wrinkle-like surface topography observed in the 19 dyn/cm sample and not in the 1 dyn/cm sample suggests that the structure in the LB PMMA film depends upon the transfer pressure. Polymethyl methacrylate. (mjm)