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For nearly all relevant applications of e-beam lithography the resolution and pattern quality requirements are
approaching or exceeding the limits of the available process. On one hand, for shrinking feature dimensions, the e-beam
proximity effect and process effects such as photo acid diffusion limit the pattern contrast and process window. On the
other hand, e-beam process related parasitic effects such as shot noise, fogging, developer loading, heating, charging, and
inhomogeneous bake introduce some significant errors. Even though e-beam tool and process tool suppliers continue to
implement new or improve current strategies to avoid or correct these effects, the amount of residual errors requires
some reasonable e-beam process window, in particular for high end applications.
For some patterns the undersize-overdose approach (SIZE) improves the pattern fidelity and process window. However,
for patterns with high fill factors this approach increases the overall deposited electron dose, which due to the increased
backscattering diminishes or even eliminates the advantages. The geometrically induced dose correction (GIDC) method
overcomes this issue by combining the SIZE concept with a short range framing technique, which reduces the deposited
dose in large filled pattern areas.
This paper provides a comparison of the standard, SIZE, and GIDC correction approaches for 1D test patterns as well as
production patterns. For a broad comparison, patterns were printed onto negative and positive chemically amplified
resists and on wafer and mask substrates using a Vistec SB352HR variable shape e-beam writer. Both wafers were also
etched.
The outcome of the study is that the SIZE and GIDC approaches often outperform the standard proximity effect
correction. For dense patterns, GIDC still provides a better pattern quality and process window, while the SIZE approach
suffers from the increased overall deposited electron dose and clearly falls behind GIDC in terms of process window.
Further it was shown that the lowering of the dose in inner areas due to GIDC does not impact the etch resistance.
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