Pattern placement imprecision due to charging of the workpiece is believed
to be a significant contribution to the total positional error in electron
beam lithography. In an earlier work, Liu et al. [J. Vac. Sci. Technol. B 1
3, 1979 (1995)] reported that the surface potential of exposed resist could
be negative or positive according to the resist thickness and the electron
energy. In that work the authors were constrained to use a flood beam. In
this study, we report a new independent approach using a Kelvin probe elect
rometer to measure the surface potential after exposure by a focused beam.
There is a qualitative agreement with the earlier work in that the surface
potential tends to be less positive at lower electron energies and for thic
ker resists. We observed positive surface potentials at 10 and 20 keV beam
irradiation. This positive charging is much more evident in polybutene sulf
one than in UV5. (C) 1999 American Vacuum Society. [S0734-211X(99)09906-0].