The lithographic effect of electron beam on poly(methyl methacrylate) in a scanning electron microscope: Minimization of line width by the dose and beam current

摘要

AbstractThe lithographic effect of electron beam in line exposures in scanning electron microscopy (SEM) on poly(methyl methacrylate) (PMMA) was evaluated using the line width in a film deposited on a silicium substrate and from the line profiles in a PMMA plate. It was found that the effect of the dose on dimensions of the exposed structures in line exposures is not unambiguous, in contrast to area exposures, but that at constant dose and beam width the line dimensions increase with beam current. Sensitivity in line exposures (line sensitivity) is smaller than in area exposures (area sensitivity). The effect of beam current on the line width increases with decreasing dose; at doses close to line sensitivity it is the strongest. The increasing effect of a beam on the polymer with increasing current at constant dose is explained through the increasing range of thermal degradation due to exposure. A qualitative explanation is based on simplified calculations of the thermal conditions in the resist film during and after the exposure.